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<p>NEURORADIOLOGY SIGNS</p><p>Notice</p><p>Medicine is an ever-changing science. As new research and clinical experience broaden</p><p>our knowledge, changes in treatment and drug therapy are required. The authors and</p><p>the publisher of this work have checked with sources believed to be reliable in their</p><p>efforts to provide information that is complete and generally in accord with the standards</p><p>accepted at the time of publication. However, in view of the possibility of human error</p><p>or changes in medical sciences, neither the authors nor the publisher nor any other party</p><p>who has been involved in the preparation or publication of this work warrants that the</p><p>information contained herein is in every respect accurate or complete, and they disclaim</p><p>all responsibility for any errors or omissions or for the results obtained from use of the</p><p>information contained in this work. Readers are encouraged to confi rm the information</p><p>contained herein with other sources. For example and in particular, readers are advised</p><p>to check the product information sheet included in the package of each drug they plan to</p><p>administer to be certain that the information contained in this work is accurate and that</p><p>changes have not been made in the recommended dose or in the contraindications for</p><p>administration. This recommendation is of particular importance in connection with new</p><p>or infrequently used drugs.</p><p>Mai-Lan Ho, MD</p><p>Fellow in Neuroradiology</p><p>University of California, San Francisco</p><p>San Francisco, California</p><p>Ronald L. Eisenberg, MD, JD</p><p>Professor of Radiology</p><p>Beth Israel Deaconess Medical Center</p><p>Harvard Medical School</p><p>Boston, Massachusetts</p><p>NEURORADIOLOGY</p><p>SIGNS</p><p>New York Chicago San Francisco Athens Lisbon Madrid</p><p>Mexico City Milan New Delhi Singapore Sydney Toronto</p><p>Copyright © 2014 by McGraw-Hill Education. All rights reserved. Except as permitted under the United States Copyright Act of 1976, no part of this</p><p>publication may be reproduced or distributed in any form or by any means, or stored in a database or retrieval system, without the prior written permission of</p><p>the publisher.</p><p>ISBN: 978-0-07-180433-2</p><p>MHID: 0-07-180433-1</p><p>The material in this eBook also appears in the print version of this title: ISBN: 978-0-07-180432-5,</p><p>MHID: 0-07-180432-3.</p><p>eBook conversion by codeMantra</p><p>Version 1.0</p><p>All trademarks are trademarks of their respective owners. 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Neither McGraw-Hill Education nor its licensors shall be liable to you or anyone else for</p><p>any inaccuracy, error or omission, regardless of cause, in the work or for any damages resulting therefrom. McGraw-Hill Education has no responsibility for</p><p>the content of any information accessed through the work. Under no circumstances shall McGraw-Hill Education and/or its licensors be liable for any indirect,</p><p>incidental, special, punitive, consequential or similar damages that result from the use of or inability to use the work, even if any of them has been advised of</p><p>the possibility of such damages. This limitation of liability shall apply to any claim or cause whatsoever whether such claim or cause arises in contract, tort or</p><p>otherwise.</p><p>http://www.mhprofessional.com</p><p>About the Authors</p><p>Mai-Lan Ho, MD, is a Fellow in Neuroradiology at the University of California,</p><p>San Francisco. She completed her residency in diagnostic radiology at Beth Israel</p><p>Deaconess Medical Center, Harvard Medical School; as well as chemical engineering</p><p>training at Stanford University and Massachusetts Institute of Technology. Dr. Ho is</p><p>the recipient of several prestigious radiology awards including the William W. Olmsted</p><p>Editorial Fellowship for Trainees, Roentgen Resident/Fellow Research Award, and</p><p>Bracco Diagnostics Research Resident Grant from the Radiological Society of North</p><p>America; Lucy Frank Squire Award from the American Association for Women</p><p>Radiologists; and Stephen A. Kieffer Award from the Eastern Neuroradiological</p><p>Society.</p><p>Ronald L. Eisenberg, MD, JD, is a Professor of Radiology at Beth Israel Deaconess</p><p>Medical Center, Harvard Medical School. He earned his medical degree from the</p><p>University of Pennsylvania, and residency training at Massachusetts General Hospital</p><p>and the University of California, San Francisco. Dr. Eisenberg is an internationally</p><p>renowned radiologist who has authored 21 books in radiology, including the 1984</p><p>Atlas of Signs in Radiology and the 1994 Skull and Spine Imaging: An Atlas of</p><p>Differential Diagnosis. He is also Section Editor of the “Pattern of the Month” series</p><p>for the American Journal of Roentgenology.</p><p>This page intentionally left blank</p><p>Dedication</p><p>To my parents, Huong and Sa Ho, for their love and support;</p><p>David Hackney and Hugh Curtin, for their wisdom and guidance;</p><p>and Jeff Petrella, for his friendship and inspiration</p><p>— Mai-Lan Ho</p><p>To Zina, Avlana, and Cherina</p><p>— Ronald L. Eisenberg</p><p>This page intentionally left blank</p><p>Foreword</p><p>It is my pleasure to introduce Neuroradiology Signs, the fi rst comprehensive</p><p>multimodality guide to signs in neuroimaging. The idea for this text came from</p><p>Dr. Mai-Lan Ho, currently a Fellow in Neuroradiology at the University of</p><p>California, San Francisco. Inspired by the Radiology “Signs in Imaging” series, she</p><p>began compiling a database of imaging signs as part of her residency training at Beth</p><p>Israel Deaconess Medical Center, Harvard Medical School. Noticing the scarcity</p><p>of literature specifi c to neuroradiology, she teamed up with Dr. Ron Eisenberg,</p><p>author of the original 1984 Atlas of Signs in Radiology. Together they developed the</p><p>concept for this book, which consists of over 440 spectacular CT, MR, angiography,</p><p>radiography, ultrasound, and nuclear medicine cases. The text is organized into</p><p>subspecialty chapters with high-resolution radiologic images, full-color photos,</p><p>imaging fi ndings, differential diagnosis, discussion, and up-to-date references.</p><p>Neuroradiology Signs should benefi t any student, resident, or fellow (or staff!)</p><p>wishing to review imaging features and pathology of the brain, head and neck, and</p><p>spine. This is a perfect boards study aid, as well as a great reference</p><p>ngers”). This is thought to represent perivenular infl ammation along the courses</p><p>of the medullary veins, and is both sensitive and specifi c for MS. Isolated cerebral</p><p>plaques remote from the ependymal veins are known as “Steiner splashes.” The</p><p>differential includes other demyelinating diseases, such as acute hemorrhagic</p><p>leukoencephalitis (Weston-Hurst syndrome), in which linear areas of periventricular</p><p>hemorrhage may be identifi ed on SWI MR. Another possibility is vasculitis, which</p><p>can be associated with perivenular enhancement and multifocal infarcts.</p><p>References:</p><p>Horowitz AL, Kaplan RD, Grewe G, et al. The ovoid lesion: a new MR observation in patients with</p><p>multiple sclerosis. AJNR Am J Neuroradiol. 1989;10(2):303-305.</p><p>Tan IL, van Schijndel RA, Pouwels PJ, et al. MR venography of multiple sclerosis. AJNR Am J</p><p>Neuroradiol. 2000;21(6):1039-1042.</p><p>DAWSON FINGERS, OVOID</p><p>Modality:</p><p>MR</p><p>Dimple 35</p><p>FINDINGS:</p><p>Axial contrast-enhanced T1-weighted MR shows a right frontal lobe lesion with</p><p>peripheral enhancement and focal medial evagination (arrow), as well as surrounding</p><p>vasogenic edema.</p><p>DIAGNOSIS:</p><p>Abscess</p><p>DISCUSSION:</p><p>Cerebral abscesses may result from penetrating trauma, surgery, direct spread of</p><p>adjacent infection, or hematogenous dissemination. Various bacterial, fungal, and</p><p>parasitic pathogens have been described. The time for formation of a mature abscess</p><p>ranges from two weeks to a few months. Organized abscesses demonstrate a smooth</p><p>peripheral enhancing rim of fi brous collagen. This tends to be slightly thinner on the</p><p>ventricular side than along the cortical margin, possibly due to differences between</p><p>white and gray matter perfusion. Over time, the abscess may evaginate or “dimple”</p><p>toward the ventricular margin. If untreated, there is risk of intraventricular rupture</p><p>with ependymal spread of infection, which greatly increases morbidity and mortality.</p><p>Reference:</p><p>Loevner LA, Yousem DM. Brain Imaging: Case Review Series, 2nd ed. St Louis, MO: Mosby, 2008.</p><p>DIMPLE</p><p>Modalities:</p><p>CT, MR</p><p>36 Chapter 1: Adult and General Brain</p><p>FINDINGS:</p><p>Axial contrast-enhanced T1-weighted MR shows a lobulated enhancing left</p><p>perirolandic mass with surrounding vasogenic edema. Following steroid treatment,</p><p>there is complete resolution of the mass (dotted circle).</p><p>DIFFERENTIAL DIAGNOSIS:</p><p>• CNS lymphoma</p><p>• Tumefactive demyelination</p><p>DISCUSSION:</p><p>Primary central nervous system lymphoma (PCNSL) occurs in immunocompromised</p><p>patients and immunocompetent individuals after the fi fth decade. The most common</p><p>type is non-Hodgkin B-cell lymphoma. Due to tumor hypercellularity, lesions are</p><p>typically hyperdense on CT and hypointense on T2-weighted MR, with reduced</p><p>diffusion. The enhancement pattern is homogeneous and solid in immunocompetent</p><p>patients, but more heterogeneous and ring-enhancing in immunocompromised</p><p>patients. Lesions can be multifocal and involve the brain parenchyma, vessels,</p><p>ependyma, and meninges. Lymphoma responds dramatically to steroids and radiation</p><p>therapy, often disappearing completely on immediate posttreatment imaging (“ghost</p><p>tumor”). However, this is generally followed by recurrence and systemic involvement</p><p>within 3 years. Recent studies suggest a minimum of 5-year follow-up to screen for</p><p>disease relapse. Granulomatous and demyelinating diseases can regress with steroids,</p><p>but have a different clinical presentation and imaging appearance. Tumors other</p><p>than lymphoma may decrease in size because of reduced infl ammation and edema,</p><p>but should not disappear completely.</p><p>References:</p><p>Bromberg JE, Siemers MD, Taphoorn MJ. Is a “vanishing tumor” always a lymphoma? Neurology.</p><p>2002;59(5):762-764.</p><p>Okita Y, Narita Y, Miyakita Y, et al. Long-term follow-up of vanishing tumors in the brain:</p><p>how should a lesion mimicking primary CNS lymphoma be managed? Clin Neurol Neurosurg.</p><p>2012;114(9):1217-1221.</p><p>DISAPPEARING/GHOST/VANISHING TUMOR, SENTINEL LESION</p><p>Modalities:</p><p>CT, MR</p><p>FINDINGS:</p><p>Axial contrast-enhanced T1-</p><p>weighted MR shows a right</p><p>corona radiata mass (arrow) with</p><p>complete rim enhancement.</p><p>DIFFERENTIAL DIAGNOSIS:</p><p>• Metastasis</p><p>• Abscess</p><p>• Glioblastoma multiforme</p><p>• Radiation necrosis</p><p>• CNS lymphoma</p><p>(if immunocompromised)</p><p>• Toxoplasmosis</p><p>(if immunocompromised)</p><p>DISCUSSION:</p><p>The classic mnemonic for ring-enhancing lesions is “MAGIC DR L”: metas tasis,</p><p>abscess, glioblastoma multiforme, infarct (subacute), contusion, demyelinating</p><p>disease, radiation necrosis, and lymphoma. Metastases are often multiple and</p><p>centered at the gray-white junction, with variable internal necrosis that can yield a</p><p>ring-enhancing pattern. Organized abscesses have smooth rim enhancement with</p><p>internal reduced diffusion. GBM shows a thick irregular rim with heterogeneous</p><p>internal enhancement. Infarcts rarely demonstrate ring enhancement, unless</p><p>located in the deep gray matter. Contusions infrequently have ring enhancement,</p><p>and may show susceptibility from internal hemorrhage. Tumefactive demyelination</p><p>demonstrates “incomplete ring” enhancement along the active (leading) edge of</p><p>disease, and nonenhancement of the inactive (trailing) edge. Radiation necrosis</p><p>has variable enhancement patterns, with encephalomalacia creating a “soap-</p><p>bubble” appearance. In immunocompromised patients, the two ring-enhancing</p><p>lesions suggest CNS lymphoma or toxoplasmosis. Treatment is often empiric,</p><p>but additional imaging studies that can aid in diagnosis are thallium-201 SPECT</p><p>(increased uptake in lymphoma, decreased in toxoplasmosis), MR spectroscopy</p><p>(increased choline in lymphoma, decreased in toxoplasmosis), and MR</p><p>perfusion (centrally increased cerebral blood volume in lymphoma, decreased in</p><p>toxoplasmosis).</p><p>References:</p><p>Chang L, Cornford ME, Chiang FL, et al. Radiologic-pathologic correlation. Cerebral toxoplasmosis</p><p>and lymphoma in AIDS. AJNR Am J Neuroradiol. 1995;16(8):1653-1663.</p><p>Smirniotopoulos JG, Murphy FM, Rushing EJ, et al. Patterns of contrast enhancement in the brain</p><p>and meninges. Radiographics. 2007;27(2):525-551.</p><p>DONUT/DOUGHNUT, RIM, RING</p><p>Modalities:</p><p>CT, MR</p><p>Donut/Doughnut, Rim, Ring 37</p><p>38 Chapter 1: Adult and General Brain</p><p>FINDINGS:</p><p>Axial contrast-enhanced T1-</p><p>weighted MR shows a</p><p>hypointense mass extending</p><p>from the right frontal horn to</p><p>the subcortical white matter.</p><p>There are faint internal foci</p><p>of enhancement (arrows).</p><p>DIFFERENTIAL DIAGNOSIS:</p><p>• Oligodendroglioma</p><p>• Oligoastrocytoma</p><p>DISCUSSION:</p><p>Oligodendroglioma is a glial</p><p>neoplasm that typically</p><p>affects males in the fourth</p><p>to seventh decades. The</p><p>World Health Organization</p><p>classifi es oligo dendroglioma</p><p>into well-differentiated and</p><p>anaplastic types. In addition,</p><p>mixed gliomas can occur,</p><p>with the most common being</p><p>oligoastrocytoma (oligo dendrocytes and astrocytes). The most frequent location</p><p>is the frontal lobe, followed by the temporal lobe. Lesions tend to be superfi cial</p><p>with involvement of the cortex and/or subcortical white matter, often producing</p><p>scalloping of the overlying calvarium. Margins are generally well-circumscribed, and</p><p>internal contents are T2-hyperintense and multilocular with a “bubbly” appearance.</p><p>Internal “dotlike” or “lacy” enhancement is a characteristic feature, though some</p><p>lesions may not enhance at all. The presence of contrast enhancement indicates a</p><p>higher tumor grade and worse patient prognosis. Other imaging features include</p><p>calcifi cation and occasional hemorrhage.</p><p>Reference:</p><p>Koeller KK, Rushing EJ. From the archives of the AFIP: Oligodendroglioma and its variants: radiologic-</p><p>pathologic correlation. Radiographics. 2005;25(6):1669-1688.</p><p>DOTLIKE, LACY</p><p>Modality:</p><p>MR</p><p>Dove Tail 39</p><p>FINDINGS:</p><p>Axial contrast-enhanced T1-weighted MR shows an enhancing left cavernous sinus/</p><p>sellar mass that encases and narrows the cavernous ICA. There is dural extension</p><p>anteriorly along the left sphenoid wing and posteriorly along the tentorium cerebelli</p><p>(arrow).</p><p>DIFFERENTIAL DIAGNOSIS:</p><p>• Meningioma</p><p>• Lymphoma</p><p>• Granulomatous disease</p><p>DISCUSSION:</p><p>Cavernous sinus meningiomas may extend</p><p>posteriorly along the dura with smooth</p><p>bulging of the tentorium cerebelli, giving a “dove’s tail” appearance. Lymphoma</p><p>and granulomatous disease can occasionally involve the tentorium, but tend to</p><p>have a more infi ltrative growth pattern. Other primary and metastatic tumors</p><p>in this location usually have a more tumefactive appearance with resultant mass</p><p>effect.</p><p>Reference:</p><p>Grossman RI and Yousem DM. Neuroradiology: The Requisites, 2nd ed. St. Louis, MO: Mosby, 2003.</p><p>DOVE TAIL</p><p>Modalities:</p><p>CT, MR</p><p>40 Chapter 1: Adult and General Brain</p><p>FINDINGS:</p><p>Axial T2-weighted MR shows a hooked appearance of the central sulci enclosing the</p><p>motor hand regions (arrows).</p><p>DIAGNOSIS:</p><p>Normal central sulcus</p><p>DISCUSSION:</p><p>The central sulcus is an important landmark of the brain that separates the frontal</p><p>and parietal lobes, as well as the primary motor and somatosensory cortex. The</p><p>midportion of the central sulcus is focally indented by the posterior precentral</p><p>gyrus, which resembles the upside-down Greek letter omega (Ω) in the axial plane,</p><p>and sigma (ς) in the sagittal plane. When a double gyrus is present, the appearance</p><p>mimics the letter epsilon (ε). In normal brains, these fi ndings are highly accurate and</p><p>reproducible landmarks for the motor hand region.</p><p>References:</p><p>Caulo M, Briganti C, Mattei PA, et al. New morphologic variants of the hand motor cortex as seen</p><p>with MR imaging in a large study population. AJNR Am J Neuroradiol. 2007;28(8):1480-1485.</p><p>Yousry TA, Schmid UD, Alkadhi H, et al. Localization of the motor hand area to a knob on the</p><p>precentral gyrus: a new landmark. Brain. 1997;120(pt 1):141-157.</p><p>DUCKY BREAST, EPSILON, KNOB, KNEE, REVERSE OMEGA, SIGMOID HOOK</p><p>Modalities:</p><p>CT, MR</p><p>FINDINGS:</p><p>Axial contrast-enhanced T1-</p><p>weighted MR shows diffuse</p><p>enhancement of the dura mater</p><p>(arrows).</p><p>DIFFERENTIAL DIAGNOSIS:</p><p>• Intracranial hypotension</p><p>• Infl ammation/infection</p><p>• Malignancy</p><p>• Idiopathic hypertrophic</p><p>pachymeningitis</p><p>DISCUSSION:</p><p>The dura mater (pachymeninges)</p><p>include the periosteum of the</p><p>inner table of the skull and</p><p>its meningeal refl ections (falx</p><p>cerebri, tentorium cerebelli, and</p><p>cavernous sinuses). Normally,</p><p>the dura enhances mildly and discontinuously. Thick linear pachymeningeal</p><p>enhancement can be seen in intracranial hypotension (CSF hypovolemia), which</p><p>leads to secondary vasocongestion and interstitial edema in the dura mater.</p><p>This condition may be idiopathic (spontaneous intracranial hypotension) or</p><p>secondary to lumbar puncture or trauma. Noncontrast FLAIR MR sequences are</p><p>also effective for identifying pachymeningeal thickening and subdural effusions/</p><p>hematomas in CSF hypotension. Thin linear dural enhancement is a common</p><p>fi nding in postoperative patients. Focal or diffuse dural enhancement has been</p><p>described in various other infl ammatory, autoimmune, infectious, and neoplastic</p><p>conditions. When no primary cause is identifi ed, the condition is known as idiopathic</p><p>hypertrophic pachymeningitis.</p><p>References:</p><p>Smirniotopoulos JG, Murphy FM, Rushing EJ, et al. Patterns of contrast enhancement in the brain</p><p>and meninges. Radiographics. 2007;27(2):525-551.</p><p>Tosaka M, Sato N, Fujimaki H, et al. Diffuse pachymeningeal hyperintensity and subdural effusion/</p><p>hematoma detected by fl uid-attenuated inversion recovery MR imaging in patients with spontaneous</p><p>intracranial hypotension. AJNR Am J Neuroradiol. 2008;29(6):1164-1170.</p><p>DURAL/PACHYMENINGEAL ENHANCEMENT</p><p>Modalities:</p><p>CT, MR</p><p>Dural/Pachymeningeal Enhancement 41</p><p>42 Chapter 1: Adult and General Brain</p><p>FINDINGS:</p><p>Axial contrast-enhanced T1-weighted MR shows a right middle cranial fossa mass</p><p>with dural thickening along the greater sphenoid wing (arrows). There is posterior</p><p>displacement of the right temporal gyri.</p><p>DIFFERENTIAL DIAGNOSIS:</p><p>• Meningioma</p><p>• Other dural masses</p><p>DISCUSSION:</p><p>The presence of a “dural tail” (dural thickening and enhancement contiguous</p><p>with an intracranial mass) is classic for meningioma. This fi nding is most apparent</p><p>on contrast-enhanced T1-weighted MR, and seen in about 60% of cases. The</p><p>pathophysiology is not completely understood, but may relate to microscopic tumor</p><p>invasion and/or reactive meningeal changes. Occasionally, other extra-axial and</p><p>peripherally located intra-axial lesions can also involve the dura. The possibilities</p><p>are wide and include metastasis, lymphoma, plasmacytoma, chloroma, glioma, nerve</p><p>sheath tumors, pituitary lesions, infl ammatory/granulomatous/histiocytic diseases,</p><p>infection, primary bone tumors, and vascular abnormalities.</p><p>References:</p><p>Guermazi A, Lafi tte F, Miaux Y, et al. The dural tail sign—beyond meningioma. Clin Radiol.</p><p>2005;60(2):171-188.</p><p>Wallace EW. The dural tail sign. Radiology. 2004;233(1):56-57.</p><p>DURAL TAIL, FLARE, MENINGEAL</p><p>Modalities:</p><p>CT, MR</p><p>Empty Light Bulb, Halo, Hollow Skull, Hot Nose 43</p><p>FINDINGS:</p><p>• Posterior planar 99mTc-HMPAO scan shows complete absence of tracer uptake in</p><p>the brain (asterisk), with surrounding uptake in the scalp.</p><p>• Anterior planar image shows increased uptake in the nose (arrow) and facial soft</p><p>tissues.</p><p>DIAGNOSIS:</p><p>Brain death</p><p>DISCUSSION:</p><p>Accurate diagnosis of brain death is critical prior to discontinuing life support in a</p><p>comatose patient, particularly when organ donation is being considered. Clinical</p><p>examination is only reliable in the absence of hypothermia, barbiturates, sedatives, and</p><p>hypnotics. If the diagnosis is unclear, a nuclear medicine brain scan can be performed</p><p>with technetium-99m ethyl cysteinate dimer (99mTc-ECD), hexamethylpropylene</p><p>amine oxime (99mTc-HMPAO), or diethylene triamine pentaacetic acid (99mTc-DTPA).</p><p>HMPAO and ECD are preferred, being lipophilic agents that selectively cross the</p><p>blood-brain barrier and are taken up by the brain parenchyma. Initial dynamic fl ow</p><p>images are acquired in the anterior projection, followed by delayed static blood pool</p><p>images in anterior, posterior, and lateral projections. Brain death is diagnosed when</p><p>there is complete absence of tracer uptake within the cranium on all images. Care</p><p>must be taken to distinguish no fl ow from very slow fl ow within the cerebral arteries</p><p>and/or veins. Occlusion of the ICAs prevents blood infl ow to the brain, with increased</p><p>collateral fl ow to the ECAs. This results in increased uptake of the nasopharyngeal</p><p>soft tissues and scalp, producing the “hot nose” and “hollow skull” signs. In adults, a</p><p>scalp band or tourniquet can be used to decrease scalp activity that might be confused</p><p>for intracranial uptake. If the patient’s head is resting on a fi rm surface, focal scalp</p><p>compression may produce a photopenic defect known as the “halo” sign.</p><p>References:</p><p>Abdel-Dayem HM, Bahar RH, Sigurdsson GH, et al. The hollow skull: a sign of brain death in Tc-99m</p><p>HM-PAO brain scintigraphy. Clin Nucl Med. 1989;14(12):912-916.</p><p>Huang AH. The hot nose sign. Radiology. 2005;235(1):216-217.</p><p>EMPTY LIGHT BULB, HALO, HOLLOW SKULL, HOT NOSE</p><p>Modality:</p><p>NM</p><p>44 Chapter 1: Adult and General Brain</p><p>FINDINGS:</p><p>Axial CT shows a rounded</p><p>hyperdense pineal mass with central</p><p>calcifi cation (arrow).</p><p>DIAGNOSIS:</p><p>Pineal germ cell tumor</p><p>DISCUSSION:</p><p>The differential for pineal region</p><p>solid masses is wide and includes</p><p>pineal parenchymal tumor, germ</p><p>cell tumor, metastasis, glioma,</p><p>lymphoma, neuroendocrine tumor,</p><p>meningioma, and vascular lesions.</p><p>Clinical symptoms include Parinaud</p><p>syndrome (upward gaze palsy), headache, and ataxia. To determine whether a lesion</p><p>is pineal or parapineal in origin, images should be reviewed to identify the pineal</p><p>gland (if visible) and surrounding structures: internal cerebral veins (superior),</p><p>midbrain tectum (anterior), cerebellar vermis (inferior), and tentorial incisura</p><p>(posterior). In adults, physiologic calcifi cation aids in identifi cation of the pineal</p><p>gland. For true pineal masses, the pattern of calcifi cation is helpful: germ cell tumors</p><p>tend to grow around and “engulf” preexisting pineal calcifi cations, whereas pineal</p><p>parenchymal tumors disrupt and peripherally disperse</p><p>(“explode”) calcifi cations.</p><p>Types of germ cell tumors include germinoma, teratoma, embryonal carcinoma,</p><p>endodermal sinus (yolk sac) tumor, and choriocarcinoma. Germinomas, which</p><p>are characteristically seen in young males, appear hyperdense on CT with avid</p><p>homogeneous enhancement. They can be multifocal with additional lesions in the</p><p>suprasellar region (“bifocal germinoma”), basal ganglia, and thalami. Tumors are</p><p>exquisitely sensitive to radiation and/or chemotherapy, often resolving completely</p><p>after treatment. When a pineal malignancy is diagnosed, the entire neuraxis should</p><p>be imaged to assess for leptomeningeal spread of disease.</p><p>Reference:</p><p>Smith AB, Rushing EJ, Smirniotopoulos JG. From the archives of the AFIP: lesions of the pineal</p><p>region: radiologic-pathologic correlation. Radiographics. 2010;30(7):2001-2020.</p><p>Modalities:</p><p>CT, MR</p><p>ENGULFED CALCIFICATION</p><p>Entrapment, Trapped Ventricle 45</p><p>FINDINGS:</p><p>Axial T2-weighted MR shows a cystic mass in the left atrium (arrow), with</p><p>asymmetric dilation of the left occipital horn.</p><p>DIFFERENTIAL DIAGNOSIS:</p><p>• Intraventricular mass</p><p>• Intraventricular adhesions</p><p>• Extraventricular mass</p><p>DISCUSSION:</p><p>“Trapped” ventricle refers to isolated ventricular dilation caused by blockage of</p><p>cerebrospinal fl uid outfl ow, and represents a focal form of obstructive hydrocephalus.</p><p>Causes include prior surgery, trauma, or infection with residual adhesions;</p><p>intraventricular neoplasms or cysts; and extraventricular lesions causing asymmetric</p><p>mass effect. The lateral ventricles are most commonly affected, but rare entrapment</p><p>of the third or fourth ventricles can also occur.</p><p>References:</p><p>Kuiper EJ, Vandertop WP. Trapped third ventricle. Acta Neurochir (Wien). 2001;143(11):1169-1172.</p><p>Maurice Williams RS, Chokesy M. Entrapment of the temporal horn: a form of focal obstructive</p><p>hydrocephalus. J Neurol Neurosurg Psychiatry. 1986;49:238-242.</p><p>ENTRAPMENT, TRAPPED VENTRICLE</p><p>Modalities:</p><p>CT, MR</p><p>46 Chapter 1: Adult and General Brain</p><p>FINDINGS:</p><p>Sagittal FLAIR MR shows subcallosal hyperintense foci (arrows) separated by</p><p>normal ependyma.</p><p>DIAGNOSIS:</p><p>Multiple sclerosis</p><p>DISCUSSION:</p><p>Multiple sclerosis (MS) is a chronic demyelinating disorder characterized by spatial</p><p>and temporal heterogeneity. On thin-section sagittal FLAIR MR, there is irregularity</p><p>of the ependymal stripe on the undersurface of the corpus callosum. Two or more</p><p>rounded hyperintense “dots” are seen, with intervening normal ependymal “dashes.”</p><p>Lesions are not oriented perpendicular to the ependyma, in contrast to subcallosal</p><p>striations and Dawson fi ngers. This fi nding has been shown to be highly sensitive</p><p>and specifi c for detection of early MS, particularly in younger patients.</p><p>Reference:</p><p>Lisanti CJ, Asbach P, Bradley WG Jr. The ependymal “Dot-Dash” sign: an MR imaging fi nding of</p><p>early multiple sclerosis. AJNR Am J Neuroradiol. 2005;26(8):2033-2036.</p><p>EPENDYMAL DOT-DASH</p><p>Modality:</p><p>MR</p><p>État Criblé, Honeycomb, Swiss Cheese 47</p><p>FINDINGS:</p><p>Axial FLAIR MR shows numerous cystic spaces throughout the brain, particularly</p><p>the high convexity white matter and corpus callosum (arrow).</p><p>DIFFERENTIAL DIAGNOSIS:</p><p>• Dilated Virchow-Robin spaces</p><p>• Mucopolysaccharidosis</p><p>• Multiple sclerosis</p><p>• Lacunar infarcts</p><p>DISCUSSION:</p><p>Virchow-Robin (VR) spaces are interstitial fl uid-containing spaces that surround</p><p>vessels as they course from the subarachnoid space into the brain parenchyma.</p><p>Small VR spaces are normally seen at imaging, and increase in size and number</p><p>with advancing age. Dilated VR spaces are seen in three typical locations: type I,</p><p>basal ganglia (lenticulostriate arteries); type II, high convexities (perforating</p><p>medullary arteries); and type III, midbrain (collicular arteries). Diffusely enlarged</p><p>VR spaces yield the “état criblé” appearance (French for “tissue riddled with holes”</p><p>or “sievelike state”). This may be seen with the mucopolysaccharidoses, in which</p><p>enzyme defi ciencies disable breakdown of glycosaminoglycans (GAG). The VR</p><p>spaces are dilated by accumulated GAG, producing a “cribriform” appearance of</p><p>the white matter, corpus callosum, and basal ganglia. Toxic intracellular substrates</p><p>also lead to cerebral atrophy and gliosis. Multiple sclerosis can show diffuse</p><p>punctate (5 mm), fewer, and less symmetric in distribution.</p><p>References:</p><p>Achiron A, Faibel M. Sandlike appearance of Virchow-Robin spaces in early multiple sclerosis: a novel</p><p>neuroradiologic marker. AJNR Am J Neuroradiol. 2002;23(3):376-380.</p><p>Kwee RM, Kwee TC. Virchow-Robin spaces at MR imaging. Radiographics. 2007;27(4):1071-1086.</p><p>ÉTAT CRIBLÉ, HONEYCOMB, SWISS CHEESE</p><p>Modalities:</p><p>CT, MR</p><p>48 Chapter 1: Adult and General Brain</p><p>Modalities:</p><p>CT, MR</p><p>FINDINGS:</p><p>Axial and sagittal CT show a large irregular pineal mass with peripheral calcifi cations</p><p>(arrows).</p><p>DIAGNOSIS:</p><p>Pineal cell tumor</p><p>DISCUSSION:</p><p>The differential for pineal region solid masses is wide and includes pineal parenchymal</p><p>tumor, germ cell tumor, metastasis, glioma, lymphoma, neuroendocrine tumor,</p><p>meningioma, and vascular lesions. Clinical symptoms include Parinaud syndrome</p><p>(upward gaze palsy), headache, and ataxia. To determine whether a lesion is pineal or</p><p>parapineal in origin, images should be reviewed to identify the pineal gland (if visible)</p><p>and surrounding structures: internal cerebral veins (superior), midbrain tectum</p><p>(anterior), cerebellar vermis (inferior), and tentorial incisura (posterior). In adults,</p><p>physiologic calcifi cation aids in identifi cation of the pineal gland. For true pineal</p><p>masses, the pattern of calcifi cation is helpful: germ cell tumors tend to grow around</p><p>and “engulf” preexisting pineal calcifi cations, whereas pineal parenchymal tumors</p><p>disrupt and peripherally disperse (“explode”) calcifi cations. Pineal parenchymal</p><p>tumors are derived from pinealocytes with varying degrees of differentiation.</p><p>Histologically, they are classifi ed as pineocytoma [WHO grade I], pineal parenchymal</p><p>tumor of intermediate differentiation (PPTID) [WHO grade II-III], papillary tumor</p><p>of the pineal region (PPTR) [WHO grade II-III], and pineoblastoma (primitive</p><p>neuroectodermal tumor of pineal gland) [WHO grade IV]. Lower-grade tumors are</p><p>smaller, well-defi ned, and slowly growing, while higher-grade tumors appear larger,</p><p>heterogeneous, and locally invasive. Pineoblastoma can be seen in patients with</p><p>ocular retinoblastoma (“trilateral” retinoblastoma), along with suprasellar PNET</p><p>(“quadrilateral” retinoblastoma). When a pineal malignancy is diagnosed, the entire</p><p>neuraxis should be imaged to assess for leptomeningeal spread of disease.</p><p>Reference:</p><p>Smith AB, Rushing EJ, Smirniotopoulos JG. From the archives of the AFIP: lesions of the pineal</p><p>region: radiologic-pathologic correlation. Radiographics. 2010;30(7):2001-2020.</p><p>EXPLODED CALCIFICATION</p><p>FINDINGS:</p><p>Axial T2-weighted MR shows</p><p>hyperintense globus pallidi with</p><p>hypointense rims (arrows).</p><p>DIFFERENTIAL DIAGNOSIS:</p><p>• Pantothenate kinase–associated</p><p>neurodegeneration</p><p>• Other extrapyramidal parkinso-</p><p>nian disorders</p><p>DISCUSSION:</p><p>Neurodegeneration with brain iron</p><p>accumulation (NBIA), previously</p><p>known as Hallevorden-Spatz</p><p>syndrome, refers to a spectrum</p><p>of pediatric neurodegenerative</p><p>disorders characterized by</p><p>abnormal iron deposition in the</p><p>basal ganglia. Symptoms begin in childhood with progressive extrapyramidal</p><p>dysfunction causing rigidity, dystonia, impaired postural refl exes, and progressive</p><p>dementia. Pantothenate kinase–associated neurodegeneration (PKAN) is the most</p><p>common subtype of NBIA (NBIA1), and is caused by mutations in the pantothenate</p><p>kinase 2 (PANK2) gene. On T2-weighted and SWI MR, the globus pallidi</p><p>demonstrate high signal intensity with a hypointense rim (“eye of the tiger” sign).</p><p>Histologically, this corresponds to central gliosis and vacuolization with surrounding</p><p>iron deposition. This imaging fi nding is highly effective for distinguishing NBIA</p><p>patients with the PANK2 mutation from mutation-negative patients. However, other</p><p>extrapyramidal parkinsonian disorders such as corticobasal degeneration, early-</p><p>onset levodopa-responsive parkinsonism, and progressive supranuclear palsy can</p><p>have similar imaging fi ndings, and clinical correlation is crucial for diagnosis.</p><p>References:</p><p>Guillerman RP. The eye-of-the-tiger sign. Radiology. 2000;217(3):895-896.</p><p>Savoiardo M, Halliday WC, Nardocci N, et al. Hallervorden-Spatz disease: MR and pathologic</p><p>fi ndings. AJNR Am J Neuroradiol. 1993;14(1):155-162.</p><p>Modality:</p><p>MR</p><p>EYE OF THE TIGER</p><p>Eye of the Tiger 49</p><p>50 Chapter 1: Adult and General Brain</p><p>FINDINGS:</p><p>Axial T2-weighted MR of the midbrain shows high signal throughout the tegmentum,</p><p>sparing the red nuclei (thick arrows) and periaqueductal gray (thin arrow). Low signal</p><p>is seen in the substantia nigra and cerebral peduncles.</p><p>DIFFERENTIAL DIAGNOSIS:</p><p>• Wilson disease</p><p>• Leigh disease</p><p>• Glutaric aciduria type 1</p><p>DISCUSSION:</p><p>Wilson disease, or hepatolenticular degeneration, is an autosomal recessive disorder</p><p>caused by mutations in the Wilson disease protein (ATP7B) gene on chromosome 13.</p><p>This interferes with normal copper metabolism, resulting in pathologic accumulation</p><p>of copper and other heavy metals in the central nervous system, liver, kidneys,</p><p>and heart. On T2-weighted MR, the “face of the giant panda” refers to abnormal</p><p>high signal in the midbrain tegmentum; preserved normal signal in the red nuclei</p><p>(“eyes”), lateral pars reticulata of the substantia nigra (“ears”), and periaqueductal</p><p>gray (“nose”); and hypointensity of the superior colliculi (“mouth”). Diffuse</p><p>symmetric T2 hyperintensities in the subcortical white matter, internal and external</p><p>capsules (“bright claustrum” sign), basal ganglia, and thalami can also be seen and</p><p>are thought to represent edema or gliosis. The differential diagnosis includes other</p><p>metabolic disorders, such as Leigh disease and glutaric aciduria type 1.</p><p>References:</p><p>Prashanth LK, Sinha S, Taly AB, et al. Do MRI features distinguish Wilson’s disease from other early</p><p>onset extrapyramidal disorders? An analysis of 100 cases. Mov Disord. 2010;25(6):672-678.</p><p>Schott JM. A neurological MRI menagerie. Pract Neurol. 2007;7:186-190.</p><p>Modality:</p><p>MR</p><p>FACE OF THE GIANT PANDA, PANDA MIDBRAIN</p><p>FINDINGS:</p><p>Axial T2-weighted MR of the pons shows hypointensity of the central tegmental</p><p>tracts (thick arrows) and brachia conjunctivum. The fourth ventricle appears</p><p>normally hyperintense with a central fl ow void (thin arrow).</p><p>DIAGNOSIS:</p><p>Wilson disease</p><p>DISCUSSION:</p><p>Wilson disease, or hepatolenticular degeneration, is an autosomal recessive disorder</p><p>caused by mutations in the Wilson disease protein (ATP7B) gene on chromosome</p><p>13. This interferes with normal copper metabolism, resulting in pathologic</p><p>accumulation of copper and other heavy metals in the central nervous system, liver,</p><p>kidneys, and heart. On T2-weighted MR, the “face of the miniature panda” sign</p><p>refers to abnormal high signal within the pontine tegmentum; normal signal in</p><p>the cerebral peduncles (“ears”), hypointensity of the medial longitudinal fasciculi,</p><p>central tegmental tracts (“eyes”), and superior cerebellar peduncles (“cheeks”); and</p><p>hyperintense fl uid signal within the aqueduct of Sylvius and fourth ventricle (“nose</p><p>and mouth”). The combination of this sign with the “face of the giant panda” sign is</p><p>termed the “double panda” sign, and is virtually pathognomonic for Wilson disease.</p><p>Diffuse symmetric T2 hyperintensities in the subcortical white matter, internal and</p><p>external capsules (“bright claustrum” sign), basal ganglia, and thalami can also be</p><p>seen, and are thought to represent edema or gliosis.</p><p>References:</p><p>Jacobs DA, Markowitz CE, Liebeskind DS, et al. The “double panda sign” in Wilson’s disease.</p><p>Neurology. 2003;61(7):969.</p><p>Prashanth LK, Sinha S, Taly AB, et al. Do MRI features distinguish Wilson’s disease from other early</p><p>onset extrapyramidal disorders? An analysis of 100 cases. Mov Disord. 2010;25(6):672-678.</p><p>Modality:</p><p>MR</p><p>FACE OF THE MINIATURE PANDA, PANDA CUB</p><p>Face of the Miniature Panda, Panda Cub 51</p><p>52 Chapter 1: Adult and General Brain</p><p>FINDINGS:</p><p>Sagittal T1-weighted MR</p><p>shows distended midbrain</p><p>(thick arrow) and inferior</p><p>migration of the brainstem</p><p>with fl attening of the pons</p><p>against the clivus (thin arrow).</p><p>The pituitary gland is also</p><p>distended.</p><p>DIAGNOSIS:</p><p>Intracranial hypotension</p><p>DISCUSSION:</p><p>Intracranial hypotension can</p><p>be caused by idiopathic,</p><p>degenerative, traumatic, and</p><p>iatrogenic etiologies. Dural</p><p>tears in the brain or spine</p><p>cause continuous loss of fl uid,</p><p>resulting in cerebrospinal fl uid</p><p>hypovolemia. The Monro-</p><p>Kellie doctrine states that in a</p><p>closed compartment, the total volume of brain, blood, and CSF must remain constant.</p><p>As a result, the high-capacitance venous system becomes engorged with blood. The</p><p>deep cerebral structures and brainstem become swollen (“fat midbrain”), refl ecting</p><p>mild diffuse vasogenic edema. There is fl attening of the pons against the clivus with</p><p>effacement of the prepontine and interpeduncular cisterns. The entire brain migrates</p><p>inferiorly with low-lying brainstem, cerebellar tonsils, third ventricle, optic chiasm,</p><p>mammillary bodies, and splenium. Patients may present with orthostatic headaches,</p><p>cranial neuropathies, nausea/vomiting, and fatigue. Strategies for identifying the</p><p>site of leakage include radionuclide cisternography and conventional, CT, or MR</p><p>myelography. Once identifi ed, the leak can be repaired by epidural blood patch,</p><p>percutaneous fi brin glue injection, or surgery.</p><p>References:</p><p>Hadizadeh DR, Kovács A, Tschampa H, et al. Postsurgical intracranial hypotension: diagnostic and</p><p>prognostic imaging fi ndings. AJNR Am J Neuroradiol. 2010;31(1):100-105.</p><p>Savoiardo M, Minati L, Farina L, et al. Spontaneous intracranial hypotension with deep brain swelling.</p><p>Brain. 2007;130(pt 7):1884-1893.</p><p>FAT/SAGGING/SWELLING MIDBRAIN</p><p>Modalities:</p><p>CT, MR</p><p>Feathery, Soap Bubble, Spreading Wavefront, Swiss Cheese 53</p><p>FEATHERY, SOAP BUBBLE, SPREADING WAVEFRONT, SWISS CHEESE</p><p>FINDINGS:</p><p>Axial contrast-enhanced T1-</p><p>weighted MR shows a ring-</p><p>enhancing lesion in the right</p><p>corona radiata with ill-defi ned</p><p>peripheral enhancement</p><p>(arrows).</p><p>DIAGNOSIS:</p><p>Radiation necrosis</p><p>DISCUSSION:</p><p>Radiation necrosis refers</p><p>to degradation of brain</p><p>tissue following therapeutic</p><p>irradiation for intracranial</p><p>tumors (especially high-grade</p><p>gliomas and metastases),</p><p>arteriovenous malforma tions,</p><p>and head and neck cancers.</p><p>There is characteristic “soap</p><p>bubble” or “Swiss cheese” enhancement, refl ecting internal necrosis. The enhancing</p><p>margins gradually blend in with surrounding brain, producing a “feathery” or</p><p>“spreading wavefront” appearance. In the setting of treated tumor (particularly</p><p>high-grade glioma), local recurrence and radiation necrosis are notoriously diffi cult</p><p>to distinguish. Useful imaging studies include MR diffusion (reduced in recurrence,</p><p>normal or increased in necrosis), CT/MR perfusion (increased in recurrence,</p><p>decreased in radiation necrosis), MR spectroscopy (elevated choline-to-creatine and</p><p>choline-to-NAA ratios in recurrence, reduced major metabolites and lactate peak in</p><p>radiation necrosis), thallium-201 SPECT (increased uptake in recurrence, decreased</p><p>in radiation necrosis), and 18F-FDG PET (increased metabolism in recurrence,</p><p>decreased in radiation necrosis).</p><p>References:</p><p>Caroline I, Rosenthal MA. Imaging modalities in high-grade gliomas: pseudoprogression, recurrence,</p><p>or necrosis? J Clin Neurosci. 2012;19(5):633-637.</p><p>Mullins ME, Barest GD, Schaefer PW, et al. Radiation necrosis versus glioma recurrence: conventional</p><p>MR imaging clues to diagnosis. AJNR Am J Neuroradiol. 2005;26(8):1967-1972.</p><p>Shah R, Vattoth S, Jacob R, et al. Radiation necrosis in the brain: imaging features and differentiation</p><p>from tumor recurrence. Radiographics. 2012;32(5):1343-1359.</p><p>Modalities:</p><p>CT, MR</p><p>54 Chapter 1: Adult and General Brain</p><p>FINDINGS:</p><p>Axial</p><p>CT shows mixed edema and hemorrhage in the bilateral inferior frontal (thick</p><p>arrow) and right anterior temporal (thin arrow) lobes.</p><p>DIAGNOSIS:</p><p>Hemorrhagic contusions</p><p>DISCUSSION:</p><p>Cerebral contusions are caused by low-velocity direct head trauma. Coup injuries</p><p>occur at the site of impact, whereas contrecoup injuries are caused by inertial force</p><p>transmission to the opposite side. Confl uent areas of edema in the inferior frontal</p><p>and anterior temporal lobes are the result of impaction against the cribriform plate</p><p>and sphenoid wings. Petechial hemorrhages refl ect traumatic shearing of small</p><p>vessels and may be seen at the gray-white junction, deep gray matter, brainstem, and</p><p>periventricular regions. On CT, the combination of hypodense edema and hyperdense</p><p>hemorrhage produces a “salt and pepper” appearance. Small simple contusions may</p><p>normalize on follow-up imaging, whereas large and severe contusions progress to</p><p>encephalomalacia. Late complications include attention, emotion, and memory</p><p>defi cits.</p><p>Reference:</p><p>Kurland D, Hong C, Aarabi B, et al. Hemorrhagic progression of a contusion after traumatic brain</p><p>injury: a review. J Neurotrauma. 2012;29(1):19-31.</p><p>FLECKED, MOTTLED, SALT AND PEPPER</p><p>Modality:</p><p>CT</p><p>Gelatinous Pseudocysts, Soap Bubble 55</p><p>FINDINGS:</p><p>Axial T2-weighted MR shows clustered cystic lesions in the bilateral basal ganglia</p><p>and cerebellar dentate nuclei (arrows).</p><p>DIAGNOSIS:</p><p>Cryptococcosis</p><p>DISCUSSION:</p><p>Cryptococcus neoformans is an encapsulated fungus found in soil contaminated</p><p>by bird excreta. It is the most common fungal infection of the CNS, and the</p><p>third most common in AIDS patients. In immunocompromised individuals,</p><p>hematogenous spread from the lungs to the central nervous system results in</p><p>CNS cryptococcosis (torulosis). Three patterns of disease have been identifi ed:</p><p>parenchymal granulomas (cryptococcomas or torulomas), gelatinous pseudocysts,</p><p>and meningitis. Gelatinous pseudocysts represent dilated perivascular (Virchow-</p><p>Robin) spaces fi lled with infl ammatory cells and mucoid material produced by</p><p>fungal capsules. These predominate in the basal ganglia, thalami, midbrain,</p><p>cerebellum, and periventricular regions. There is high T2 and variable T1 signal,</p><p>depending on the mucin content of cysts. Depending on the degree of immune</p><p>competency, associated edema and enhancement may be present. Early treatment</p><p>with intravenous antifungals is crucial to minimize morbidity and mortality.</p><p>References:</p><p>Andreula CF, Burdi N, Carella A. CNS cryptococcosis in AIDS: spectrum of MR fi ndings. J Comput</p><p>Assist Tomogr. 1993;17(3):438-441.</p><p>Smith AB, Smirniotopoulos JG, Rushing EJ. From the archives of the AFIP: central nervous system</p><p>infections associated with human immunodefi ciency virus infection: radiologic-pathologic correlation.</p><p>Radiographics. 2008;28(7):2033-2058.</p><p>GELATINOUS PSEUDOCYSTS, SOAP BUBBLE</p><p>Modalities:</p><p>CT, MR</p><p>56 Chapter 1: Adult and General Brain</p><p>FINDINGS:</p><p>Coronal contrast-enhanced T1-weighted MR shows leptomeningeal enhancement in</p><p>the right parietal lobe (arrow).</p><p>DIFFERENTIAL DIAGNOSIS:</p><p>• Infectious/infl ammatory meningitis</p><p>• Vascular conditions</p><p>• Leptomeningeal carcinomatosis</p><p>DISCUSSION:</p><p>Enhancement of the arachnoid and pia mater refl ects breakdown of the blood-</p><p>brain barrier, with subsequent contrast leak age from vessels into cerebrospinal</p><p>fl uid. Common etiologies include infectious or infl ammatory meningitis, vascular</p><p>conditions, and leptomeningeal carcinomatosis. Bacterial (pyogenic) and viral</p><p>(aseptic) meningitis demonstrate smooth linear leptomeningeal enhancement.</p><p>Fungal, tuberculous, and other granulo matous (chronic) meningitides demonstrate</p><p>more nodular enhancement with a pre dilection for the basilar cisterns. Vascular</p><p>etiologies include acutely reperfused or subacute arterial infarction, posterior</p><p>reversible leukoencephalopathy, vasculitis, and vasodilation associated with</p><p>migraine or seizures. Typically, the subjacent cortex is also involved. Metastases</p><p>from CNS primaries, breast, lung, melanoma, and lymphoma can diffusely involve</p><p>the meninges. Infl ammation secondary to prior surgery or subarachnoid hemorrhage</p><p>can occasionally produce leptomeningeal enhancement.</p><p>Reference:</p><p>Smirniotopoulos JG, Murphy FM, Rushing EJ, et al. Patterns of contrast enhancement in the brain</p><p>and meninges. Radiographics. 2007;27(2):525-551.</p><p>GYRIFORM, LEPTOMENINGEAL ENHANCEMENT, SERPENTINE</p><p>Modalities:</p><p>CT, MR</p><p>Hockey Stick, Pulvinar 57</p><p>FINDINGS:</p><p>Axial T2-weighted MR shows</p><p>symmetric increased signal in the</p><p>dorsomedial (thin arrows) and</p><p>pulvinar nuclei (thick arrows) of</p><p>both thalami.</p><p>DIAGNOSIS:</p><p>Creutzfeldt-Jakob disease</p><p>DISCUSSION:</p><p>Creutzfeldt-Jakob disease (CJD)</p><p>is a rapidly progressing and fatal</p><p>dementia caused by prions, which</p><p>are misfolded proteins that cannot</p><p>be broken down by the body and</p><p>subsequently convert their correctly</p><p>folded counterparts. Subtypes of</p><p>CJD include classical/sporadic</p><p>(sCJD), inherited/familial (fCJD), variant (vCJD), and iatrogenic/acquired. vCJD,</p><p>or “mad cow disease,” was fi rst described in the 1990s and linked to eating beef</p><p>contaminated with bovine spongiform encephalopathy (BSE). Most cases have</p><p>occurred in the United Kingdom, with a younger age of onset and longer duration</p><p>of disease than in sCJD. On MR, there is rapidly progressive signal abnormality</p><p>of the basal ganglia, thalami, and cerebral cortex. Symmetric T2 hyperintensities</p><p>and reduced diffusion can be seen in the pulvinar and dorsomedial nuclei of the</p><p>thalamus (“hockey stick” appearance), caudate heads, putamina, globus pallidi,</p><p>insulae, cingulate cortex, and periaqueductal gray matter. Occasionally, intrinsic</p><p>T1 shortening may be present, which is thought to represent deposition of prion</p><p>proteins. In the late stages, there is massive loss of brain tissue that produces a</p><p>“spongiform” or “Swiss cheese” appearance.</p><p>References:</p><p>Collie DA, Summers DM, Sellar RJ, et al. Diagnosing variant Creutzfeldt-Jakob disease with the</p><p>pulvinar sign: MR imaging fi ndings in 86 neuropathologically confi rmed cases. AJNR Am J</p><p>Neuroradiol. 2003;24(8):1560-1569.</p><p>Young GS, Geschwind MD, Fischbein NJ, et al. Diffusion-weighted and fl uid-attenuated inversion</p><p>recovery imaging in Creutzfeldt-Jakob disease: high sensitivity and specifi city for diagnosis. AJNR Am</p><p>J Neuroradiol. 2005;26(6):1551-1562.</p><p>Modality:</p><p>MR</p><p>HOCKEY STICK, PULVINAR</p><p>58 Chapter 1: Adult and General Brain</p><p>FINDINGS:</p><p>Sagittal FLAIR MR shows</p><p>midbrain atrophy with concave</p><p>superior margin (thin arrow)</p><p>and deep inter peduncular fossa</p><p>(thick arrow). The pons and</p><p>medulla are normal in size.</p><p>DIAGNOSIS:</p><p>Progressive supranuclear palsy</p><p>DISCUSSION:</p><p>Progressive supranuclear palsy</p><p>(Steele-Richardson-Olszewski</p><p>syndrome), an adult-onset</p><p>neurodegenerative dis order,</p><p>is the most common cause</p><p>of parkinsonism following</p><p>Parkinson disease. Symptoms</p><p>include dementia, postural</p><p>instability, and vertical supranuclear gaze palsy. There is selective atrophy of</p><p>the midbrain tectum and tegmentum, with fl attened or concave margins and a</p><p>deep interpeduncular fossa. On sagittal images, the “hummingbird” sign refers</p><p>to midbrain atrophy juxtaposed with normal pons and medulla. On axial images,</p><p>the “Mickey Mouse” or “morning glory” sign is produced by midbrain atrophy</p><p>with preserved cerebral peduncles. Focal hypometabolism on PET gives rise to the</p><p>“pimple” sign. Findings may be diffi cult to distinguish from age-related volume</p><p>loss and other dementing disorders, and correlation with clinical symptoms is</p><p>crucial for diagnosis.</p><p>References:</p><p>Botha H, Whitwell JL, Madhaven A, et al. The pimple sign of progressive supranuclear palsy syndrome.</p><p>Parkinsonism Relat Disord. 2013 Nov 4. [Epub ahead of print]</p><p>Gröschel K, Kastrup A, Litvan I, et al. Penguins and hummingbirds: midbrain atrophy in progressive</p><p>supranuclear palsy. Neurology. 2006;66(6):949-950.</p><p>Modalities:</p><p>CT, MR</p><p>HUMMINGBIRD, PENGUIN</p><p>Hyperdense Falx, Hyperdense Tentorium 59</p><p>Modality:</p><p>CT</p><p>FINDINGS:</p><p>Axial</p><p>CT shows a left holohemispheric subdural hematoma that extends superiorly</p><p>along the falx cerebri and inferiorly along the tentorium cerebelli (arrows).</p><p>DIAGNOSIS:</p><p>Subdural hematoma</p><p>DISCUSSION:</p><p>Subdural hematomas (SDHs) are bleeds between the dura mater and arachnoid</p><p>mater. These are caused by shear stress on bridging veins due to rotational and/or</p><p>linear forces, resulting in low-pressure bleeding. In very young, elderly, and alcoholic</p><p>patients, the presence of enlarged subdural spaces predisposes to SDH with minimal</p><p>head trauma. Symptoms include gradually increasing headache and confusion. At</p><p>imaging, SDH is typically crescentic in appearance, outlining the cerebral convexities</p><p>and tracking along dural refl ections (falx cerebri and tentorium cerebelli). A small</p><p>SDH may present as subtle hyperdense thickening of the falx or tentorium, which</p><p>can be easily missed. The differential for hyperdensity in the subdural space includes</p><p>infectious (subdural empyema), infl ammatory, and neoplastic etiologies, which can</p><p>readily be distinguished on contrast-enhanced images.</p><p>Reference:</p><p>Brant WE, Helms C. Fundamentals of Diagnostic Radiology, 3rd ed. Baltimore: Lippincott Williams</p><p>and Wilkins, 2012.</p><p>HYPERDENSE FALX, HYPERDENSE TENTORIUM</p><p>60 Chapter 1: Adult and General Brain</p><p>Modality:</p><p>MR</p><p>FINDINGS:</p><p>Axial T2-weighted and SWI MR show bilateral putaminal atrophy with</p><p>T2-hypointense signal. There is linear hyperintensity along the lateral putaminal</p><p>margins (arrows).</p><p>DIAGNOSIS:</p><p>Multiple system atrophy, parkinsonian subtype</p><p>DISCUSSION:</p><p>Multiple system atrophy (MSA) is an adult-onset neurodegenerative disease</p><p>characterized by parkinsonism, autonomic failure, cerebellar ataxia, and pyramidal</p><p>signs. Classifi cation is based on the predominant clinical characteristics and includes</p><p>MSA-P (parkinsonian) or striatonigral degeneration (SND), MSA-C (cerebellar)</p><p>or olivopontocerebellar atrophy (OPCA), and MSA-A (autonomic) or Shy-Drager</p><p>syndrome (SDS). MSA-P shows selective atrophy and mineralization of the putamina,</p><p>with T2-hypointense and T1-hyperintense signal. On T2-weighted and FLAIR MR,</p><p>the putamina appear abnormally hypointense with a residual hyperintense rim. There</p><p>is linearization of the lateral margins, producing a “slitlike” appearance. Findings</p><p>may be diffi cult to distinguish from age-related changes and other dementing</p><p>disorders, and correlation with clinical symptoms is crucial for diagnosis.</p><p>References:</p><p>Ito S, Shirai W, Hattori T. Putaminal hyperintensity on T1-weighted MR imaging in patients with the</p><p>Parkinson variant of multiple system atrophy. AJNR Am J Neuroradiol. 2009;30(4):689-692.</p><p>Lee JY, Yun JY, Shin CW, et al. Putaminal abnormality on 3-T magnetic resonance imaging in early</p><p>parkinsonism-predominant multiple system atrophy. J Neurol. 2010;257(12):2065-2070.</p><p>HYPERINTENSE RIM, PUTAMINAL HYPERINTENSITY, SLITLIKE</p><p>Knife Blade/Edge 61</p><p>FINDINGS:</p><p>Axial T2-weighted MR shows</p><p>selective atrophy of the frontal and</p><p>temporal lobes, with enlargement</p><p>of the Sylvian fi ssures and sharp</p><p>pointed gyri (arrows).</p><p>DIAGNOSIS:</p><p>Frontotemporal lobar degeneration</p><p>DISCUSSION:</p><p>Frontotemporal lobar degeneration</p><p>(FTLD) refers to a spectrum of</p><p>neurodegenerative disorders char-</p><p>acterized by selective, progressive</p><p>atrophy of the frontal and temporal</p><p>lobes. This has been linked to</p><p>tissue deposition of abnormally</p><p>aggregated proteins including</p><p>phosphorylated tau protein, transactive response DNA-binding protein 43 (TDP-</p><p>43), and fused in sarcoma (FUS) protein. 25-40% of cases are familial, with</p><p>autosomal dominant inheritance in 10-20%. The three clinically defi ned subtypes</p><p>of FTLD are frontotemporal dementia (Pick disease or behavioral variant, bvFTD),</p><p>semantic dementia (SD), and progressive non-fl uent aphasia (PNFA). Alternate</p><p>presentations include extrapyramidal symptoms and motor neuron disease,</p><p>producing clinical overlap with corticobasal degeneration (CBD) and progressive</p><p>supranuclear palsy (PSP). At imaging, there is characteristic enlargement of the</p><p>Sylvian fi ssures, widening of sulci, and pointed “knife-edge” gyri. Findings may</p><p>be diffi cult to distinguish from age-related volume loss and other dementing</p><p>disorders, and correlation with clinical symptoms is crucial for diagnosis.</p><p>References:</p><p>Lindberg O, Ostberg P, Zandbelt BB, et al. Cortical morphometric subclassifi cation of frontotemporal</p><p>lobar degeneration. AJNR Am J Neuroradiol. 2009;30(6):1233-1239.</p><p>Warren JD, Rohrer JD, Rossor MN. Clinical review. Frontotemporal dementia. BMJ. 2013 Aug 6;</p><p>347:f4827.</p><p>Modalities:</p><p>CT, MR</p><p>KNIFE BLADE/EDGE</p><p>62 Chapter 1: Adult and General Brain</p><p>FINDINGS:</p><p>Axial contrast-enhanced T1-weighted MR shows multiple periventricular and</p><p>subependymal masses involving the left frontal horn, atrium, septum pellucidum,</p><p>and splenium with patchy contrast enhancement (arrows).</p><p>DIAGNOSIS:</p><p>Primary CNS lymphoma</p><p>DISCUSSION:</p><p>Primary central nervous system lymphoma (PCNSL) occurs in immunocompromised</p><p>patients and immunocompetent individuals after the fi fth decade. The most common</p><p>type is non-Hodgkin B-cell lymphoma. Due to tumor hypercellularity, lesions are</p><p>typically hyperdense on CT and hypointense on T2-weighted MR, with reduced</p><p>diffusion. In immunocompetent patients, lymphoma demonstrates mild patchy</p><p>enhancement with a “lamb’s wool” appearance. Lesions can be multifocal and</p><p>involve the brain parenchyma, vessels, ependyma, and meninges.</p><p>References:</p><p>Slone HW, Blake JJ, Shah R, et al. CT and MRI fi ndings of intracranial lymphoma. AJR Am J</p><p>Roentgenol. 2005;184(5):1679-1685.</p><p>Smirniotopoulos JG, Murphy FM, Rushing EJ, et al. Patterns of contrast enhancement in the brain</p><p>and meninges. Radiographics. 2007;27(2):525-551.</p><p>LAMB WOOL</p><p>Modalities:</p><p>CT, MR</p><p>Lenticular 63</p><p>FINDINGS:</p><p>Axial CT shows a right temporal tip epidural hematoma (arrow).</p><p>DIAGNOSIS:</p><p>Epidural hematoma</p><p>DISCUSSION:</p><p>Epidural hematomas (EDHs) are bleeds located between the skull and dura mater.</p><p>These are caused by major trauma with skull fractures producing lacerations of</p><p>the meningeal arteries (usually MMA), or less commonly the dural venous sinuses.</p><p>Classically, patients have a lucid interval, followed by rapid loss of consciousness as</p><p>the high-pressure bleed begins to compress intracranial structures. At imaging, EDH</p><p>has a “lenticular” appearance that is constrained by the cranial sutures. Prompt</p><p>surgical intervention is critical for minimizing morbidity and mortality.</p><p>Reference:</p><p>Brant WE, Helms C. Fundamentals of Diagnostic Radiology, 3rd ed. Baltimore: Lippincott Williams</p><p>and Wilkins, 2012.</p><p>LENTICULAR</p><p>Modalities:</p><p>CT, MR</p><p>64 Chapter 1: Adult and General Brain</p><p>FINDINGS:</p><p>Sagittal T1-weighted MR</p><p>shows the cerebellar tonsils</p><p>extending below the foramen</p><p>magnum (arrow).</p><p>DIFFERENTIAL DIAGNOSIS:</p><p>• Tonsillar ectopia</p><p>• Chiari I malformation</p><p>• Intracranial hypotension</p><p>• Tonsillar herniation</p><p>DISCUSSION:</p><p>The cerebellar tonsils are</p><p>normally located above the</p><p>foramen magnum, but may</p><p>be at or slightly below this</p><p>level. Tonsillar ectopia is a</p><p>normal variant in which the</p><p>tonsils are located within 5</p><p>mm of the foramen magnum,</p><p>without other anatomic abnormalities. In Chiari I malformation, the tonsils have</p><p>a peglike confi guration and are displaced over 3 to 5 mm below the foramen</p><p>magnum. There may be associated cervicomedullary kinking and obstruction of</p><p>CSF outfl ow, which can result in syringohydromyelia. In intracranial hypotension</p><p>(CSF hypovolemia), there is downward sagging of the entire brain, including the</p><p>cerebellar tonsils. Associated fi ndings include venous engorgement, brainstem</p><p>and pituitary edema, and subdural effusions. Intracranial hypertension causes</p><p>crowding of intracranial structures, which in severe cases can lead to tonsillar</p><p>herniation.</p><p>Reference:</p><p>Barkovich AJ, Wippold FJ, Sherman JL, et al. Signifi cance of cerebellar tonsillar position on MR.</p><p>AJNR Am J Neuroradiol. 1986;7(5):795-799.</p><p>LOW LYING TONSILS</p><p>Modalities:</p><p>CT, MR</p><p>Mickey Mouse, Morning Glory</p><p>65</p><p>FINDINGS:</p><p>Axial FLAIR MR shows midbrain atrophy with concave lateral margins of the</p><p>tegmentum (arrows). The cerebral peduncles are normal in size.</p><p>DIAGNOSIS:</p><p>Progressive supranuclear palsy</p><p>DISCUSSION:</p><p>Progressive supranuclear palsy (Steele-Richardson-Olszewski syndrome), an adult-</p><p>onset neurodegenerative disorder, is the most common cause of parkin sonism</p><p>following Parkinson disease. Symptoms include dementia, postural instability,</p><p>and vertical supranuclear gaze palsy. There is selective atrophy of the midbrain</p><p>tegmentum and tectum, with fl attened or concave margins and a deep interpeduncular</p><p>fossa. On axial images, the “Mickey Mouse” or “morning glory” sign is produced</p><p>by midbrain atrophy with preserved cerebral peduncles. On sagittal images, the</p><p>“hummingbird” sign refers to midbrain atrophy juxtaposed with normal pons and</p><p>medulla. Focal hypometabolism on PET gives rise to the “pimple” sign. Findings</p><p>may be diffi cult to distinguish from age-related volume loss and other dementing</p><p>disorders, and correlation with clinical symptoms is crucial for diagnosis.</p><p>References:</p><p>Adachi M, Kawanami T, Ohshima H, et al. Morning glory sign: a particular MR fi nding in progressive</p><p>supranuclear palsy. Magn Reson Med Sci. 2004;3(3):125-132.</p><p>Botha H, Whitwell JL, Madhaven A, et al. The pimple sign of progressive supranuclear palsy syndrome.</p><p>Parkinsonism Relat Disord. 2013 Nov 4. [Epub ahead of print]</p><p>Modalities:</p><p>CT, MR</p><p>MICKEY MOUSE, MORNING GLORY</p><p>66 Chapter 1: Adult and General Brain</p><p>FINDINGS:</p><p>Coronal CT shows ballooning of the lateral (arrows) and third ventricles.</p><p>DIAGNOSIS:</p><p>Internal hydrocephalus</p><p>DISCUSSION:</p><p>Cerebrospinal fl uid is produced in the choroid plexus of the ventricles, circulates</p><p>continuously through the brain and spinal cord, and is reabsorbed by arachnoid</p><p>granulations and/or lymphatic channels. Hydrocephalus refers to increased CSF</p><p>accumulation in the brain, either internal (within ventricles) or external (within</p><p>subarachnoid spaces). External hydrocephalus refers to enlarged subarachnoid</p><p>spaces with normal-sized ventricles. This is a benign condition of infancy that</p><p>resolves spontaneously by 2 years of age. Internal hydrocephalus may be produced</p><p>by obstructive (noncommunicating) or nonobstructive (communicating) causes.</p><p>In noncommunicating hydrocephalus, there is blockage of fl ow within the</p><p>ventricular system, with continued upstream CSF production causing progressive</p><p>dilation. In communicating hydrocephalus, the ventricular system is patent, but</p><p>CSF overproduction or impaired absorption by arachnoid granulations results in</p><p>increased CSF volume. Characteristic ballooning of the lateral ventricles creates</p><p>a “Mickey Mouse ears” appearance. Clinical symptoms depend on the time</p><p>course and severity of disease. Ventricular drainage or shunt placement can serve</p><p>as a temporizing measure, but defi nitive treatment requires identifi cation and</p><p>correction of the underlying cause. True hydrocephalus should be distinguished</p><p>from cerebral atrophy (“hydrocephalus ex vacuo”), in which parenchymal volume</p><p>loss is responsible for diffuse enlargement of the CSF spaces.</p><p>Reference:</p><p>Brant WE, Helms C. Fundamentals of Diagnostic Radiology, 3rd ed. Baltimore: Lippincott Williams</p><p>and Wilkins, 2012.</p><p>MICKEY MOUSE EARS</p><p>Modalities:</p><p>CT, MR</p><p>Mount Fuji, Peaking 67</p><p>FINDINGS:</p><p>Axial CT shows bifrontal pneumocephalus and subdural fl uid collections. There is</p><p>compression of the frontal lobes and widening of the interhemispheric space (arrow).</p><p>DIFFERENTIAL DIAGNOSIS:</p><p>• Postsurgical pneumocephalus</p><p>• Tension pneumocephalus</p><p>DISCUSSION:</p><p>Pneumocephalus is a normal fi nding after surgery or trauma with violation of the dural</p><p>space. Progressive air accumulation can develop because of a ball-valve mechanism,</p><p>producing mass effect on adjacent brain. An important sign of tension pneumocephalus</p><p>is compression and separation of the frontal lobes, resembling the double-peaked</p><p>silhouette of Mount Fuji. The presence of gas within the interhemispheric space</p><p>indicates that air pressure exceeds the surface tension of cerebrospinal fl uid between</p><p>the frontal lobes. Tension pneumocephalus is a neurosurgical emergency requiring</p><p>immediate decompression.</p><p>Reference:</p><p>Michel SJ. The Mount Fuji sign. Radiology. 2004;232(2):449-450.</p><p>MOUNT FUJI, PEAKING</p><p>Modality:</p><p>CT</p><p>68 Chapter 1: Adult and General Brain</p><p>FINDINGS:</p><p>Sagittal contrast-enhanced T1-weighted MR shows a mixed solid and cystic mass</p><p>with scalloping of the inner table of the calvarium (arrow), transdural invasion, and</p><p>invagination into the frontal lobe.</p><p>DIFFERENTIAL DIAGNOSIS:</p><p>• Hemangiopericytoma</p><p>• Atypical meningioma</p><p>• Metastasis</p><p>DISCUSSION:</p><p>Hemangiopericytomas (formerly known as angioblastic meningiomas) are extraaxial</p><p>tumors composed of pericytes of Zimmerman, the smooth muscle cells surrounding</p><p>capillaries. The classic imaging appearance is a mixed solid/cystic mass with avid</p><p>heterogeneous enhancement, fl ow voids refl ecting hypervascularity, narrow dural</p><p>attachment, and erosion of the overlying calvarium. When intraparenchymal invasion</p><p>occurs through the relatively small dural attachment, it creates a “mushroom”</p><p>appearance. In contrast, meningiomas appear more homogeneous, often calcify, have</p><p>a broad dural base, and produce bony hyperostosis rather than erosion. Atypical</p><p>meningiomas have a more irregular appearance, with the extradural variant involving</p><p>the calvarium and subcutaneous tissues. Intra-axial invasion is rare and suggests</p><p>malignant transformation; the broad dural attachment usually produces a “pannus”</p><p>rather than “mushroom” appearance. Metastases may also behave aggressively with</p><p>dural, calvarial and/or parenchymal invasion.</p><p>References:</p><p>Chiechi MV, Smirniotopoulos JG, Mena H. Intracranial hemangiopericytomas: MR and CT features.</p><p>AJNR Am J Neuroradiol. 1996;17(7):1365-1371.</p><p>New PF, Hesselink JR, O’Carroll CP, Kleinman GM. Malignant meningiomas: CT and histologic</p><p>criteria, including a new CT sign. AJNR Am J Neuroradiol. 1982;3(3):267-276.</p><p>Tokgoz N, Oner YA, Kaymaz M, et al. Primary intraosseous meningioma: CT and MRI appearance.</p><p>AJNR Am J Neuroradiol. 2005;26(8):2053-2056.</p><p>MUSHROOM, PANNUS</p><p>Modalities:</p><p>CT, MR</p><p>FINDINGS:</p><p>Anterior planar In-111 DTPA</p><p>cisternogram shows expected</p><p>ascent of radiopharmaceutical</p><p>from the intrathecal injection site</p><p>to the cerebral convexities, with no</p><p>ventricular refl ux. This results in</p><p>normal tracer accumulation within</p><p>the interhemispheric (thick arrow)</p><p>and sylvian (thin arrows) cisterns.</p><p>DIAGNOSIS:</p><p>Normal cisternogram</p><p>DISCUSSION:</p><p>Radionuclide cisternography</p><p>involves intra thecal injection of</p><p>a radiolabeled pharma ceutical</p><p>(usually indium-111 diethylene</p><p>triamine pentaacetic acid) with</p><p>sequential imaging to evaluate CSF</p><p>fl ow. In a normal patient, tracer</p><p>ascends up the spinal column to</p><p>the level of the basal cisterns by</p><p>1 hour, the frontal poles and sylvian</p><p>fi ssures by 2-6 hours, the cerebral</p><p>convexities by 12 hours, and the</p><p>sagittal sinus by 24 hours. Normal</p><p>activity in the interhemispheric</p><p>and sylvian cisterns creates the standard “trident” appearance. Tracer does not</p><p>normally enter the ventricular system, because physiologic fl ow of CSF is in the</p><p>opposite direction.</p><p>Reference:</p><p>Mettler FA, Guiberteau MJ. Essentials of Nuclear Medicine Imaging, 5th ed. St Louis, MO: Saunders,</p><p>Elsevier, 2006.</p><p>(NEPTUNE) TRIDENT, TRIUMVIRATE</p><p>Modality:</p><p>NM</p><p>(Neptune) Trident, Triumvirate 69</p><p>70 Chapter 1: Adult and General Brain</p><p>FINDINGS:</p><p>Axial T2-weighted MR shows multifocal encephalomalacia with cortical irregularity</p><p>(arrows) and subcortical hyperintensities.</p><p>DIAGNOSIS:</p><p>Sneddon syndrome</p><p>DISCUSSION:</p><p>Sneddon syndrome is a noninfl ammatory arteriopathy causing cerebrovascular</p><p>disease, livedo reticularis or livedo racemosa, and hypertension. Most cases are</p><p>idiopathic, but a familial form of the disease exists with autosomal dominant</p><p>inheritance. Antiphospholipid antibodies are positive in 50% of cases. Patients</p><p>suffer from vasospastic</p><p>episodes, transient ischemic attacks, strokes, and early-</p><p>onset dementia. Small and medium-sized vessels are affected, with asymmetric</p><p>multifocal cortical/subcortical infarcts. Nuclear medicine SPECT, CTP, or MRP</p><p>studies may facilitate early diagnosis, identifying underperfused areas of brain prior</p><p>to the development of irreversible infarcts. In late-stage disease, there is multifocal</p><p>encephalomalacia with subcortical white matter signal abnormalities and irregular</p><p>volume loss of the overlying cortex (“nibbled cortex”).</p><p>References:</p><p>Karagülle AT, Karada D, Erden A, et al. Sneddon’s syndrome: MR imaging fi ndings. Eur Radiol.</p><p>2002;12(1):144-146.</p><p>Menzel C, Reinhold U, Grünwald F, et al. Cerebral blood fl ow in Sneddon syndrome. J Nucl Med.</p><p>1994;35(3):461-464.</p><p>NIBBLED CORTEX</p><p>Modalities:</p><p>NM, CT, MR</p><p>Notch 71</p><p>FINDINGS:</p><p>Coronal contrast-enhanced T1-weighted MR shows a left temporal enhancing mass</p><p>with multiple peripheral indentations (arrows).</p><p>DIAGNOSIS:</p><p>CNS lymphoma</p><p>DISCUSSION:</p><p>Primary central nervous system lymphoma (PCNSL) occurs in immunocompromised</p><p>patients and immunocompetent individuals after the fi fth decade. The most common</p><p>type is non-Hodgkin B-cell lymphoma. Due to tumor hypercellularity, lesions are</p><p>typically hyperdense on CT and hypointense on T2-weighted MR, with reduced</p><p>diffusion. The enhancement pattern is homogeneous and solid in immunocompetent</p><p>patients, but more heterogeneous and ring-enhancing in immunocompromised</p><p>patients. Lesions can be multifocal and involve the brain parenchyma, vessels,</p><p>ependyma, and meninges. The “notch” sign has recently been described and refers</p><p>to abnormally deep depressions of lesion margins. This is a rare but highly specifi c</p><p>fi nding that effectively distinguishes PCNSL from other primary and metastatic</p><p>brain tumors.</p><p>References:</p><p>Slone HW, Blake JJ, Shah R, et al. CT and MRI fi ndings of intracranial lymphoma. AJR Am J</p><p>Roentgenol. 2005;184(5):1679-1685.</p><p>Zhang D, Hu LB, Henning TD, et al. MRI fi ndings of primary CNS lymphoma in 26 immunocompetent</p><p>patients. Korean J Radiol. 2010;11(3):269-277.</p><p>NOTCH</p><p>Modalities:</p><p>CT, MR</p><p>72 Chapter 1: Adult and General Brain</p><p>FINDINGS:</p><p>Axial T2-weighted MR shows hyper intense signal within the central pons, sparing</p><p>the corticospinal tracts (arrows) and peripheral pons.</p><p>DIAGNOSIS:</p><p>Osmotic demyelination syndrome</p><p>DISCUSSION:</p><p>Osmotic demyelination syndrome (ODMS), formerly classifi ed into central</p><p>pontine myelinolysis (CPM) and extrapontine myelinolysis (EPM), refers to acute</p><p>demyelination caused by rapid changes in serum osmolality. The classic presentation</p><p>is an alcoholic, hyponatremic patient who undergoes rapid correction of serum</p><p>sodium levels, resulting in massive fl uid effl ux from the brain into the serum.</p><p>Symmetric T2-hyperintense signal and reduced diffusion are seen in the central pons,</p><p>basal ganglia, and/or cerebral white matter. Mild injury produces signal abnormality</p><p>in the median raphe and basis pontis, with a bilobed (“bat wing”) or triangular</p><p>(“trident”) morphology. More profound injury affects the entire pons with relative</p><p>sparing of the tegmentum, corticobulbar, and corticospinal tracts (“owl/snake eyes”</p><p>appearance). In the subacute period, signal changes improve or resolve completely.</p><p>The differential for central pontine T2 hyperintensity includes infarction, neoplasm,</p><p>demyelination, infection, metabolic disorders, and radiation. However, combined</p><p>fi ndings of CPM and EPM are essentially pathognomonic for ODMS.</p><p>References:</p><p>Chua GC, Sitoh YY, Lim CC, et al. MRI fi ndings in osmotic myelinolysis. Clin Radiol. 2002;57(9):</p><p>800-806.</p><p>Ho VB, Fitz CR, Yoder CC, et al. Resolving MR features in osmotic myelinolysis (central pontine and</p><p>extrapontine myelinolysis). AJNR Am J Neuroradiol. 1993;14(1):163-167.</p><p>Modality:</p><p>MR</p><p>OWL/SNAKE EYES</p><p>Periventricular Hyperintensity/Hypodensity 73</p><p>Modalities:</p><p>CT, MR</p><p>FINDINGS:</p><p>Axial FLAIR MR shows multiple T2-hyperintense foci in the periventricular white</p><p>matter (arrows). There is diffuse enlargement of ventricles and sulci.</p><p>DIFFERENTIAL DIAGNOSIS:</p><p>• Normal aging</p><p>• Vasculopathy</p><p>• Demyelinating disease</p><p>• Dementia</p><p>• Hydrocephalus</p><p>DISCUSSION:</p><p>Foci of CT hypodensity/MR hyperintensity in the white matter are known as</p><p>leukoaraiosis, and are common incidental fi ndings at imaging. They increase</p><p>proportionally with patient age, cerebral atrophy, and vascular risk factors.</p><p>At pathology, these foci are found to consist of dilated perivascular spaces, myelin</p><p>pallor, and/or gliosis. Periventricular signal abnormalities greater than expected</p><p>for patient age should raise the question of other pathologies such as vasculopathy,</p><p>demyelinating disease, dementia, and hydrocephalus with transependymal fl ow</p><p>of CSF.</p><p>References:</p><p>Debette S, Markus HS. The clinical importance of white matter hyperintensities on brain magnetic</p><p>resonance imaging: systematic review and meta-analysis. BMJ. 2010;341:c3666.</p><p>Matsusue E, Sugihara S, Fujii S, et al. White matter changes in elderly people: MR-pathologic</p><p>correlations. Magn Reson Med Sci. 2006;5(2):99-104.</p><p>PERIVENTRICULAR HYPERINTENSITY/HYPODENSITY</p><p>74 Chapter 1: Adult and General Brain</p><p>Modalities:</p><p>XR, MR</p><p>FINDINGS:</p><p>• Coronal contrast-enhanced T1-weighted MR shows an enhancing planum</p><p>sphenoidale mass (thick arrow). There is enlargement and hyperaeration of the</p><p>sphenoid sinuses (thin arrows).</p><p>• Coronal CT in a different patient shows a sylvian fi ssure arachnoid cyst (asterisk).</p><p>There is hyperaeration of the sphenoid sinuses and right anterior clinoid process</p><p>(arrow).</p><p>DIFFERENTIAL DIAGNOSIS:</p><p>• Meningioma</p><p>• Arachnoid cyst</p><p>DISCUSSION:</p><p>Pneumosinus dilatans refers to abnormal dilatation of one or more paranasal sinuses</p><p>without bone destruction, hyperostosis, or mucosal thickening. This most commonly</p><p>affects the frontal sinus, followed by the sphenoid, ethmoid, and maxillary sinuses.</p><p>The mechanism is unknown, but proposed etiologies include ball-valve obstruction,</p><p>dural tethering, aerobic infection, mucocele discharge, and hormonal dysregulation.</p><p>Pneumosinus dilatans has been described in conjunction with meningioma,</p><p>arachnoid cyst, meningocele, nerve sheath tumors, sinonasal polyposis, Dyke-</p><p>Davidoff-Masson syndrome, fi bro-osseous dysplasia, hydrocephalus, and trauma.</p><p>Diffuse involvement of the paranasal sinuses and mastoid air cells is known as</p><p>pneumosinus dilatans multiplex, and is associated with mental retardation and</p><p>craniofacial malformations. Spontaneous pneumocephalus can occur after minimal</p><p>trauma. Other types of sinus air cysts include hypersinus, sinus enlargement</p><p>contained within normal boundaries; pneumocele, sinus enlargement with bone</p><p>thinning/erosion; and pneumatocele, subperiosteal air along the sinus wall.</p><p>Reference:</p><p>Teh BM, Hall C, Chan SW. Pneumosinus dilatans, pneumocoele or air cyst? A case report and literature</p><p>review. J Laryngol Otol. 2012;126(1):88-93.</p><p>PNEUMOSINUS DILATANS</p><p>Pseudo-Subarachnoid Hemorrhage 75</p><p>Modality:</p><p>CT</p><p>FINDINGS:</p><p>Axial noncontrast CT shows</p><p>diffuse cerebral edema with</p><p>apparent hyperdensity throughout</p><p>the subarachnoid space (arrows).</p><p>DIFFERENTIAL DIAGNOSIS:</p><p>• Cerebral edema</p><p>• Meningitis</p><p>• Leptomeningeal carcinomatosis</p><p>• Intracranial hypotension</p><p>• Prior contrast administration</p><p>DISCUSSION:</p><p>Increased attenuation in the</p><p>subarachnoid spaces and basal</p><p>cisterns does not always represent</p><p>subarachnoid hemorrhage. In dif-</p><p>fuse cerebral edema, the brain</p><p>parenchyma is diffusely hypodense</p><p>with loss of gray-white distinction. Increased intracranial pressure causes</p><p>displacement of cerebrospinal fl uid from the subarachnoid spaces, as well as</p><p>engorgement of superfi cial veins, yielding a dense appearance of the leptomeninges</p><p>(“pseudo-subarachnoid hemorrhage” sign). The MR correlate of this fi nding</p><p>is known as the “FLAIR hyperintensity” sign. Other processes that affect the</p><p>subarachnoid space include meningitis (proteinaceous fl uid), leptomeningeal</p><p>carcinomatosis (tumor cells), and prior contrast administration</p><p>(intrathecal</p><p>or intravascular). Intracranial hypotension can produce superfi cial venous</p><p>engorgement in the pachymeninges and/or leptomeninges.</p><p>References:</p><p>Given CA 2nd, Burdette JH, Elster AD, et al. Pseudo-subarachnoid hemorrhage: a potential imaging</p><p>pitfall associated with diffuse cerebral edema. AJNR Am J Neuroradiol. 2003;24(2):254-256.</p><p>Lang JL, Leach PL, Emelifeonwu JA, et al. Meningitis presenting as spontaneous subarachnoid</p><p>haemorrhage (pseudo-subarachnoid haemorrhage). Eur J Emerg Med. 2013;20(2):140-141.</p><p>Schievink WI, Maya MM, Tourje J, Moser FG. Pseudo-subarachnoid hemorrhage: a CT-fi nding in</p><p>spontaneous intracranial hypotension. Neurology. 2005;65(1):135-137.</p><p>PSEUDO-SUBARACHNOID HEMORRHAGE</p><p>76 Chapter 1: Adult and General Brain</p><p>FINDINGS:</p><p>Axial DWI MR shows reduced</p><p>diffusion in the central</p><p>(arrows) and lateral splenium.</p><p>The ventral and dorsal layers</p><p>of the corpus callosum are</p><p>relatively preserved.</p><p>DIAGNOSIS:</p><p>Marchiafava-Bignami disease</p><p>DISCUSSION:</p><p>Marchiafava-Bignami disease</p><p>typically occurs in chronic</p><p>alcoholics with severe</p><p>malnutrition. Defi ciency of</p><p>the vitamin B complex results</p><p>in degeneration of the corpus</p><p>callosum. This fi rst involves</p><p>the body, followed by the</p><p>genu and splenium. Other</p><p>affected areas include the anterior/posterior commissures, corticospinal tracts,</p><p>brachia pontis, and hemispheric white matter. On MR, the corpus callosum</p><p>appears T2-hyperintense and T1-hypointense. Preferential involvement of the</p><p>central layer, with relative sparing of the dorsal and ventral layers, creates a</p><p>“sandwich” appearance. In the acute phase, there may be reduced diffusion and</p><p>peripheral enhancement. In the chronic phase, lesions necrose and cavitate. Other</p><p>processes that can affect the corpus callosum include infarction, demyelination,</p><p>and trauma (diffuse axonal injury). However, these entities have disparate clinical</p><p>presentations and do not typically produce a “layered” appearance.</p><p>References:</p><p>Arbelaez A, Pajon A, Castillo M. Acute Marchiafava-Bignami disease: MR fi ndings in two patients.</p><p>AJNR Am J Neuroradiol. 2003;24(10):1955-1957.</p><p>Ménégon P, Sibon I, Pachai C, et al. Marchiafava-Bignami disease: diffusion-weighted MRI in corpus</p><p>callosum and cortical lesions. Neurology. 2005;65(3):475-477.</p><p>SANDWICH</p><p>Modality:</p><p>MR</p><p>Satellite 77</p><p>FINDINGS:</p><p>Coronal contrast-enhanced T1-weighted MR shows a heterogeneously enhancing</p><p>right subinsular mass. There is a second focus of enhancement (arrow) superior to</p><p>and separate from the dominant lesion.</p><p>DIFFERENTIAL DIAGNOSIS:</p><p>• Glioblastoma multiforme</p><p>• Metastases</p><p>• Abscesses</p><p>DISCUSSION:</p><p>“Satellite” foci refer to smaller lesions adjacent to, but separate from, a primary</p><p>mass. Glioblastoma multiforme, which shows an aggressive and infi ltrative growth</p><p>pattern, is the most common primary brain tumor with this appearance. Metastases</p><p>can present as multiple discrete masses throughout the brain. Daughter abscesses</p><p>may develop adjacent to a parent abscess, but are usually contiguous and evolve</p><p>rapidly over time with progressive organization and rim enhancement.</p><p>Reference:</p><p>Dobelbower MC, Burnett OL III, Nordal RA, et al. Patterns of failure for glioblastoma multiforme</p><p>following concurrent radiation and temozolomide. J Med Imaging Radiat Oncol. 2011;55(1):77-81.</p><p>SATELLITE</p><p>Modalities:</p><p>CT, MR</p><p>78 Chapter 1: Adult and General Brain</p><p>FINDINGS:</p><p>Sagittal FLAIR MR shows hyperintense signal and scalloped morphology (arrow) of</p><p>the corpus callosum.</p><p>DIAGNOSIS:</p><p>Decompressed chronic hydrocephalus</p><p>DISCUSSION:</p><p>Chronic hydrocephalus produces ventriculomegaly with elevation of the corpus</p><p>callosum. Following CSF drain or shunt placement, the corpus callosum rapidly</p><p>descends away from the rigid falx cerebri. The dorsal body of the corpus callosum</p><p>can develop a “scalloped” appearance, refl ecting tethering by pericallosal artery</p><p>branches to the overlying cingulate cortex. T2-hyperintense, T1-hypointense MR</p><p>signal changes have been suggested to represent biomechanical compression, edema,</p><p>ischemia, and/or demyelination.</p><p>References:</p><p>Lane JI, Luetmer PH, Atkinson JL. Corpus callosal signal changes in patients with obstructive</p><p>hydrocephalus after ventriculoperitoneal shunting. AJNR Am J Neuroradiol. 2001;22(1):158-162.</p><p>Numaguchi Y, Kristt DA, Joy C, et al. Scalloping deformity of the corpus callosum following ventricular</p><p>shunting. AJNR Am J Neuroradiol. 1993;14(2):355-362.</p><p>SCALLOPED</p><p>Modalities:</p><p>CT, MR</p><p>Slit Ventricles 79</p><p>FINDINGS:</p><p>Axial T2-weighted MR shows</p><p>diminutive lateral ventricles</p><p>(arrows). There is effacement</p><p>of the subarachnoid spaces with</p><p>gyral remodeling of the inner</p><p>table, indicating chronically</p><p>increased intracranial pressure.</p><p>DIFFERENTIAL DIAGNOSIS:</p><p>• Increased intracranial pressure</p><p>• Excessive CSF removal</p><p>DISCUSSION:</p><p>The Monro-Kellie doctrine states</p><p>that the brain, CSF, and blood</p><p>are in volume equilibrium within</p><p>the fi xed cranial compartment.</p><p>Causes of increased intracranial</p><p>pressure including pseudotumor</p><p>cerebri (idiopathic intracranial hypertension), supratentorial masses, and cerebral</p><p>edema can force out CSF from the ventricles, producing a “slitlike” appearance.</p><p>Other imaging features of increased intracranial pressure include effacement of the</p><p>subarachnoid spaces, empty sella, papilledema, venous pseudostenosis, and calvarial</p><p>remodeling. The cavernous sinuses, Meckel caves, and cranial nerve meati may be</p><p>narrowed in the acute phase, but can expand in the chronic phase due to transmitted</p><p>CSF pulsations. In patients who undergo lumbar puncture, ventricular drainage,</p><p>or shunting, the cranial compartment is no longer isolated from the external</p><p>environment. Excessive CSF removal can also cause a slit ventricle appearance in</p><p>these cases. In patients with indwelling ventricular shunts, the combination of new-</p><p>onset mental status changes, slit ventricles on imaging, and abnormally low CSF</p><p>pressures is diagnostic of shunt malfunction.</p><p>References:</p><p>Bruce DA, Weprin B. The slit ventricle syndrome. Neurosurg Clin N Am. 2001;12(4):709-717, viii.</p><p>Degnan AJ, Levy LM. Narrowing of Meckel’s cave and cavernous sinus and enlargement of the optic</p><p>nerve sheath in pseudotumor cerebri. J Comput Assist Tomogr. 2011;35(2):308-312.</p><p>SLIT VENTRICLES</p><p>Modalities:</p><p>CT, MR</p><p>80 Chapter 1: Adult and General Brain</p><p>FINDINGS:</p><p>• Axial CT shows diffuse cerebral and cerebellar edema (asterisk) with upward</p><p>transtentorial herniation. There is a triangular appearance of the quadrigeminal</p><p>plate cistern with compression of the posterolateral margins of the midbrain</p><p>(arrows).</p><p>• Axial CT in a different patient shows hemorrhage and edema within the</p><p>cerebellar vermis (thin arrow). Upward transtentorial herniation compresses the</p><p>posterolateral margins of the midbrain (thick arrows).</p><p>DIAGNOSIS:</p><p>Ascending transtentorial herniation</p><p>DISCUSSION:</p><p>Cerebral herniation is a response to increased intracranial pressure caused by</p><p>hemorrhage, edema, and/or mass lesions. The Monro-Kellie doctrine states that</p><p>in a closed compartment, the total volume of brain, blood, and CSF must remain</p><p>constant. Types of cerebral herniation include subfalcine (cingulate); transalar</p><p>(sphenoid); transtentorial (uncal, central); cerebellar (tonsillar, foramen magnum);</p><p>and external (transcalvarial, extracranial). Transtentorial herniation refers to</p><p>herniation across the tentorium cerebelli. Descending (downward) transtentorial</p><p>herniation occurs in the setting of supratentorial mass effect, and is more common.</p><p>Upward (ascending) transtentorial herniation occurs secondary to posterior fossa</p><p>mass effect. There is effacement of the quadrigeminal plate cistern (“triangle” or</p><p>“square” appearance), compression of the posterolateral midbrain (“spinning top”</p><p>appearance), and fl attening of the third ventricle. Cerebral herniation is an urgent</p><p>imaging fi nding that should be addressed with prompt correction of the underlying</p><p>cause. Additional strategies for lowering intracranial pressure include mannitol</p><p>diuresis,</p><p>ventriculostomy placement, and decompressive craniectomy.</p><p>References:</p><p>Laine FJ, Shedden AI, Dunn MM, et al. Acquired intracranial herniations: MR imaging fi ndings. AJR</p><p>Am J Roentgenol. 1995;165(4):967-973.</p><p>Osborn AG, Heaston DK, Wing SD. Diagnosis of ascending transtentorial herniation by cranial</p><p>computed tomography. AJR Am J Roentgenol. 1978;130(4):755-760.</p><p>SPINNING TOP, SQUARE, TRIANGLE</p><p>Modalities:</p><p>CT, MR</p><p>Star 81</p><p>FINDINGS:</p><p>Axial CT shows hyperdense material within the suprasellar cistern.</p><p>DIAGNOSIS:</p><p>Subarachnoid hemorrhage</p><p>DISCUSSION:</p><p>The suprasellar cistern is a CSF–fi lled space located inferior to the hypothalamus and</p><p>superior to the sella turcica. It contains the optic chiasm, pituitary infundibulum, and</p><p>circle of Willis. The boundaries of the suprasellar cistern include the interhemispheric</p><p>fi ssure anteriorly; the unci laterally; and the pons and cerebral peduncles posteriorly.</p><p>It is shaped like a fi ve-pointed star at the level of the pons, and a six-pointed star at</p><p>the level of the cerebral peduncles. Apparent hyperdensity in the suprasellar cistern</p><p>indicates subarachnoid hemorrhage or its mimics (diffuse cerebral edema, basilar</p><p>meningitis, leptomeningeal carcinomatosis, prior contrast administration). Loss of</p><p>the normal star appearance can occur with transtentorial herniation.</p><p>Reference:</p><p>Chen R, Zhang S, Zhang W, et al. A comparative study of thin-layer cross-sectional anatomic</p><p>morphology and CT images of the basal cistern and its application in acute craniocerebral traumas.</p><p>Surg Radiol Anat. 2009;31(2):129-138.</p><p>STAR</p><p>Modalities:</p><p>CT, MR</p><p>82 Chapter 1: Adult and General Brain</p><p>FINDINGS:</p><p>Axial CT shows a mixed-density mass (arrow) with multiple punctate calcifi cations</p><p>in the left cerebellar hemisphere and vermis.</p><p>DIFFERENTIAL DIAGNOSIS:</p><p>• Dermoid/epidermoid</p><p>• Vascular malformation</p><p>DISCUSSION:</p><p>Punctate “stippled” calcifi cations are seen in a variety of benign and malignant brain</p><p>lesions, most classically dermoid/epidermoid cysts. These are congenital ectodermal</p><p>inclusion cysts lined by squamous epithelium (epidermoid) and varying amounts</p><p>of hair, sebaceous, and sweat glands (dermoid). Calcifi cation is also common in</p><p>vascular lesions, including cavernomas and arteriovenous malformations. Primary</p><p>and metastatic brain tumors (breast, lung, thyroid, osteosarcoma, chondrosarcoma)</p><p>can also calcify, but the calcifi cations are usually coarser and more confl uent.</p><p>References:</p><p>Smirniotopoulos JG, Chiechi MV. Teratomas, dermoids, and epidermoids of the head and neck.</p><p>Radiographics. 1995;15(6):1437-1455.</p><p>Vilanova JC, Barceló J, Smirniotopoulos JG, et al. Hemangioma from head to toe: MR imaging with</p><p>pathologic correlation. Radiographics. 2004;24(2):367-385.</p><p>STIPPLED</p><p>Modality:</p><p>CT</p><p>Subdural Effusions 83</p><p>Modalities:</p><p>CT, MR</p><p>FINDINGS:</p><p>Axial T2-weighted MR shows</p><p>bilateral holohemispheric</p><p>subdural fl uid collections</p><p>(arrows).</p><p>DIFFERENTIAL DIAGNOSIS:</p><p>• Intracranial hypotension</p><p>• Subdural empyemas</p><p>• Subdural hygromas</p><p>• Subdural hematomas</p><p>DISCUSSION:</p><p>Intracranial hypotension</p><p>can be caused by idiopathic,</p><p>degenerative, traumatic,</p><p>and iatrogenic etiologies.</p><p>Dural tears in the brain or</p><p>spine cause continuous loss</p><p>of fl uid, resulting in CSF</p><p>hypovolemia. The Monro-</p><p>Kellie doctrine states that in</p><p>a closed compartment, the total volume of brain, blood, and CSF must remain</p><p>constant. As the pressure within the intracranial compartment decreases, the brain</p><p>migrates inferiorly, with distension of veins and CSF spaces overlying the cerebral</p><p>convexities. Other types of subdural collections include subdural empyemas</p><p>(infection), subdural hygromas (CSF), and subdural hematomas (blood). Clinical</p><p>presentation and correlation with other MR sequences (FLAIR, SWI, contrast-</p><p>enhanced T1) should enable distinction of these various etiologies.</p><p>References:</p><p>Tosaka M, Sato N, Fujimaki H, et al. Diffuse pachymeningeal hyperintensity and subdural effusion/</p><p>hematoma detected by fl uid-attenuated inversion recovery MR imaging in patients with spontaneous</p><p>intracranial hypotension. AJNR Am J Neuroradiol. 2008;29(6):1164-1170.</p><p>Wetterling T, Rama B. Differential diagnosis of subdural effusions. Rontgenblatter. 1989;42(12):</p><p>508-514.</p><p>SUBDURAL EFFUSIONS</p><p>84 Chapter 1: Adult and General Brain</p><p>FINDINGS:</p><p>Axial T2-weighted and DWI MR show T2 hyperintensity and reduced diffusion</p><p>throughout the cortex and subcortical white matter, exaggerating the normal gray-</p><p>white distinction.</p><p>DIAGNOSIS:</p><p>Hypoxic-ischemic encephalopathy</p><p>DISCUSSION:</p><p>Severe hypoxic-ischemic encephalopathy results in globally reduced diffusion</p><p>throughout the cortex and subcortical white matter. The gray matter, which is</p><p>eight times more metabolically active than the white matter, is more susceptible to</p><p>injury and undergoes diffuse cortical laminar necrosis. On other MR sequences,</p><p>the gray-white matter distinction is preserved or may even be accentuated. In the</p><p>subacute period, worsening edema becomes more apparent on T2/FLAIR images,</p><p>with pseudonormalization on DWI.</p><p>References:</p><p>McKinney AM, Teksam M, Felice R, et al. Diffusion-weighted imaging in the setting of diffuse</p><p>cortical laminar necrosis and hypoxic-ischemic encephalopathy. AJNR Am J Neuroradiol.</p><p>2004;25(10):1659-1665.</p><p>Wijdicks EF, Campeau NG, Miller GM. MR imaging in comatose survivors of cardiac resuscitation.</p><p>AJNR Am J Neuroradiol. 2001;22(8):1561-1565.</p><p>SUPERNORMAL, SUPERSCAN, WHITE CEREBRUM</p><p>Modality:</p><p>MR</p><p>Tadpole 85</p><p>FINDINGS:</p><p>Sagittal T1-weighted MR</p><p>shows severe cervico medullary</p><p>atrophy (arrows) with normal</p><p>midbrain and pons.</p><p>DIAGNOSIS:</p><p>Adult-onset Alexander disease</p><p>DISCUSSION:</p><p>Alexander disease is a</p><p>fatal, autosomal dominant</p><p>neurodegenerative disorder</p><p>caused by mutations in the</p><p>GFAP gene on chromosome</p><p>17q21. This results in</p><p>pathologic formation of</p><p>Rosenthal fi bers, astrocytic</p><p>inclusions of long-chain fatty</p><p>acids that lead to myelin</p><p>destruction. Infantile (less than</p><p>2 years), juvenile (4 to 10 years),</p><p>and adult-onset (over 12 years)</p><p>forms have been described,</p><p>with later presentations</p><p>demonstrating less severe and</p><p>slower progression of disease.</p><p>At imaging, the infantile form</p><p>usually shows frontal lobe white matter abnormalities with macrocephaly. The</p><p>juvenile form typically has nodular brainstem lesions and periventricular “garlands.”</p><p>The adult form is characterized by a “tadpole” brainstem with selective atrophy of</p><p>the medulla oblongata and cervical cord.</p><p>References:</p><p>Namekawa M, Takiyama Y, Honda J, et al. Adult-onset Alexander disease with typical “tadpole”</p><p>brainstem atrophy and unusual bilateral basal ganglia involvement: a case report and review of the</p><p>literature. BMC Neurol. 2010;10:21.</p><p>van der Knaap MS, Naidu S, Breiter SN, et al. Alexander disease: diagnosis with MR imaging. AJNR</p><p>Am J Neuroradiol. 2001;22(3):541-552.</p><p>Modalities:</p><p>CT, MR</p><p>TADPOLE</p><p>86 Chapter 1: Adult and General Brain</p><p>FINDINGS:</p><p>Axial CT shows bilateral subdural fl uid collections isodense to gray matter (arrows),</p><p>obscuring the normal sulci and gyri.</p><p>DIAGNOSIS:</p><p>Isodense subdural hematomas</p><p>DISCUSSION:</p><p>Subdural hematomas (SDHs) are bleeds between the dura mater and arachnoid</p><p>mater. These are caused by shear stress on bridging veins due to rotational and/or</p><p>linear forces, with low-pressure bleeding. At imaging, SDH is typically crescentic in</p><p>appearance, tracking along the cerebral convexities. Acute bleeds ( 3 weeks) liquefy</p><p>and become hypodense to gray matter. In the subacute stage, hemorrhage may be</p><p>isodense and diffi cult to distinguish from gray matter. Acute bleeds in patients with</p><p>anemia can also appear iso- to hypodense. On CT, this results in nonvisualization</p><p>of the normal sulci/gyri with displacement from the inner table. With MR, subdural</p><p>hematomas are readily distinguished from subjacent brain.</p><p>Reference:</p><p>Brant WE, Helms C. Fundamentals of Diagnostic Radiology, 3rd ed. Baltimore: Lippincott Williams</p><p>and Wilkins,</p><p>book for any</p><p>clinician wishing to refresh or expand their differential diagnosis in neuroimaging.</p><p>William P. Dillon, MD</p><p>Elizabeth A. Guillaumin Professor of</p><p>Radiology, Neurology and Neurosurgery</p><p>Executive Vice-Chair and Chief of Neuroradiology</p><p>Department of Radiology and Biomedical Imaging</p><p>University of California, San Francisco</p><p>San Francisco, California</p><p>This page intentionally left blank</p><p>Preface</p><p>We have always been fascinated by imaging patterns ranging from pathognomonic</p><p>“Aunt Minnie” lesions to key fi ndings with focused differential diagnoses. The</p><p>identifi cation of a specifi c imaging sign can dramatically alter a radiologist’s</p><p>impression of a case and help clinch the diagnosis. In many cases, it is recognition of</p><p>these fi ne details that distinguishes very good readers from truly great ones.</p><p>With this book, we aim to fi ll a relative void in the literature with a review of over</p><p>440 signs in neuroradiology across the modalities of computed tomography, magnetic</p><p>resonance, angiography, radiography, ultrasound, and nuclear medicine. The book</p><p>is divided into seven chapters: (1) Adult and General Brain; (2) Pediatric Brain;</p><p>(3) Head, Neck, and Orbits; (4) Vascular; (5) Skull and Facial Bones; (6) Vertebrae;</p><p>and (7) Spinal Cord and Nerves. All cases have been reviewed by subspecialty</p><p>experts, and are presented in a comprehensive yet concise fashion.</p><p>In each chapter, signs are listed on separate pages and organized in alphabetical</p><p>order for the convenience of the reader. Each section includes imaging fi ndings,</p><p>differential diagnosis, discussion, and key references. Furthermore, color photos</p><p>clarify the etymology of each sign. This novel feature makes the learning process more</p><p>enjoyable, while also providing “real-world” visual correlation. Imaging modalities</p><p>for each sign are listed in order of increasing complexity. Readers can refer to the</p><p>ACR Appropriateness Criteria® for evidence-based guidelines regarding the most</p><p>suitable imaging examination in a given clinical scenario. For easy reference, the</p><p>index at the end of the book is organized in three ways: by sign, diagnosis, and</p><p>modality.</p><p>We have designed this book for a wide audience including general and subspecialty</p><p>neuroradiologists, neuroradiology fellows, and radiology residents; as well as</p><p>neurologists, surgeons, primary care physicians, technologists, and medical students.</p><p>As such, it is a handy reference for the bookshelf or reading room, and very high-</p><p>yield material for board examinations. We hope that you have as much fun reading</p><p>our book as we did writing it!</p><p>— Mai-Lan Ho, MD</p><p>— Ronald L. Eisenberg, MD, JD</p><p>This page intentionally left blank</p><p>Acknowledgments</p><p>This project would not have been possible without the help of Michael Weitz and</p><p>Brian Kearns at McGraw-Hill, Saloni Narang at Thomson Digital, and our fabulous</p><p>section editors and contributors. I am grateful to Wikipedia and Microsoft Offi ce</p><p>Online for their vast collections of open-source stock photography.</p><p>To my mother, Huong, and father, Sa: thank you for your eternal love and</p><p>understanding. Your support helped me get through all those late-night writing</p><p>sessions! My chemical engineering professor, Channing Robertson: thanks for</p><p>believing in me and encouraging me to think “outside the box.” To Claire Anderson:</p><p>you introduced me to radiology, and thus changed my life forever. Nahum Goldberg:</p><p>thanks for discovering me and giving me a chance to be part of something greater.</p><p>To Alex Bankier: I could not have asked for a better advisor and confi dant—together</p><p>we made the Scholar’s Track! Jonny Kruskal and Debbie Levine: thank you for your</p><p>exemplary mentorship throughout my residency. David Hackney: I owe much of my</p><p>success to you, and value your opinion above all. Hugh Curtin: what can I say that</p><p>hasn’t already been said? You’re a living legend, and like a father to me. Gul Moonis,</p><p>Rafael Rojas, Rafeeque Bhadelia, and Jim Wu: you are talented, inspirational, and</p><p>genuine “friends of the resident.” Jeff Petrella: thank you for your selfl ess advice</p><p>and clarity of insight. A continually positive force in my life, you always bring out</p><p>the best in me. And fi nally, I would like to acknowledge all my fantastic teachers,</p><p>colleagues, and friends at UCSF and our exceptional leader, Bill Dillon, who is the</p><p>“quintessential” academic neuroradiologist and a true visionary!</p><p>— Mai-Lan Ho, MD</p><p>This page intentionally left blank</p><p>Section Editors</p><p>Rafeeque Bhadelia, MD</p><p>Clinical Director and Associate Professor</p><p>in Neuroradiology</p><p>Beth Israel Deaconess Medical Center</p><p>Harvard Medical School</p><p>Boston, Massachusetts</p><p>Daniel T. Ginat, MD, MS</p><p>Assistant Professor in Neuroradiology</p><p>University of Chicago</p><p>Chicago, Illinois</p><p>Amy F. Juliano, MD</p><p>Instructor in Radiology</p><p>Massachusetts Eye and Ear Infi rmary</p><p>Harvard Medical School</p><p>Boston, Massachusetts</p><p>Gul Moonis, MD</p><p>Assistant Professor in Neuroradiology</p><p>Beth Israel Deaconess Medical Center</p><p>Massachusetts Eye and Ear Infi rmary</p><p>Harvard Medical School</p><p>Boston, Massachusetts</p><p>Jared A. Narvid, MD</p><p>Clinical Instructor in Neuro-Interventional</p><p>Radiology</p><p>University of California, San Francisco</p><p>San Francisco, California</p><p>Sanjay P. Prabhu, MBBS, MRCPCH, FRCR</p><p>Assistant Professor in Neuroradiology</p><p>Director of Advanced Image Analysis Laboratory</p><p>Children’s Hospital Boston</p><p>Harvard Medical School</p><p>Boston, Massachusetts</p><p>Rafael Rojas, MD</p><p>Assistant Professor in Neuroradiology</p><p>Beth Israel Deaconess Medical Center</p><p>Harvard Medical School</p><p>Boston, Massachusetts</p><p>Jim S. Wu, MD</p><p>Assistant Professor in Musculoskeletal Imaging</p><p>Beth Israel Deaconess Medical Center</p><p>Harvard Medical School</p><p>Boston, Massachusetts</p><p>Contributors</p><p>Larry Barbaras, BS</p><p>Senior Programmer and Analyst in Radiology</p><p>Beth Israel Deaconess Medical Center</p><p>Harvard Medical School</p><p>Boston, Massachusetts</p><p>A. James Barkovich, MD</p><p>Chief of Pediatric Neuroradiology</p><p>University of California, San Francisco</p><p>San Francisco, California</p><p>Cynthia T. Chin, MD</p><p>Professor in Neuroradiology and Neurosurgery</p><p>Director of Precision Spine and Peripheral</p><p>Nerve Center</p><p>University of California, San Francisco</p><p>San Francisco, California</p><p>Hugh D. Curtin, MD</p><p>Chair of Radiology</p><p>Massachusetts Eye and Ear Infi rmary</p><p>Harvard Medical School</p><p>Boston, Massachusetts</p><p>Kevin J. Donohoe, MD</p><p>Assistant Professor in Nuclear Medicine</p><p>Beth Israel Deaconess Medical Center</p><p>Harvard Medical School</p><p>Boston, Massachusetts</p><p>Christopher F. Dowd, MD</p><p>Professor in Neuro-Interventional Radiology,</p><p>Neurological Surgery, Neurology,</p><p>and Anesthesia and Perioperative Care</p><p>University of California, San Francisco</p><p>San Francisco, California</p><p>Christine M. Glastonbury, MBBS</p><p>Professor in Neuroradiology,</p><p>Otolaryngology-Head and Neck Surgery,</p><p>and Radiation Oncology</p><p>University of California, San Francisco</p><p>San Francisco, California</p><p>David B. Hackney, MD</p><p>Chief of Neuroradiology</p><p>Assistant Dean for Faculty Development</p><p>Beth Israel Deaconess Medical Center</p><p>Harvard Medical School</p><p>Boston, Massachusetts</p><p>Mary G. Hochman, MD, MBA</p><p>Chief of Musculoskeletal Imaging</p><p>Beth Israel Deaconess Medical Center</p><p>Harvard Medical School</p><p>Boston, Massachusetts</p><p>Jason M. Johnson, MD</p><p>Clinical Instructor in Neuroradiology</p><p>University of California, San Francisco</p><p>San Francisco, California</p><p>Michael Larson, MFA</p><p>Media Specialist in Radiology</p><p>Beth Israel Deaconess Medical Center</p><p>Harvard Medical School</p><p>Boston, Massachusetts</p><p>Deborah Levine, MD</p><p>Chief of Obstetric and Gynecologic Ultrasound</p><p>Vice Chair for Academic Affairs in Radiology</p><p>Beth Israel Deaconess Medical Center</p><p>Harvard Medical School</p><p>Boston, Massachusetts</p><p>William A. Mehan Jr., MD</p><p>Assistant Professor in Neuroradiology</p><p>Tufts Medical Center</p><p>Boston, Massachusetts</p><p>J. Anthony Parker, MD, PhD</p><p>Associate Professor in Nuclear Medicine</p><p>Beth Israel Deaconess Medical Center</p><p>Harvard Medical School</p><p>Boston, Massachusetts</p><p>A. Suresh Reddy, MD</p><p>Chief of Interventional Neuroradiology</p><p>Beth Israel Deaconess Medical Center</p><p>Harvard Medical School</p><p>Boston, Massachusetts</p><p>Ammar Sarwar, MD</p><p>Fellow in Interventional Radiology</p><p>2012.</p><p>THICK CORTEX</p><p>Modality:</p><p>CT</p><p>Zebra 87</p><p>FINDINGS:</p><p>Axial T2-weighted MR shows hypointense hemosiderin outlining the pons (thick</p><p>arrow), temporal tips, and cerebellar folia (thin arrows).</p><p>DIFFERENTIAL DIAGNOSIS:</p><p>• Posterior fossa hemorrhage</p><p>• Superfi cial siderosis</p><p>DISCUSSION:</p><p>In the adult, posterior fossa hemorrhage can be caused by traumatic, iatrogenic,</p><p>ischemic, vascular, and neoplastic (particularly metastases and hemangioblastoma)</p><p>etiologies. This produces a characteristic streaky appearance of blood outlining</p><p>the cerebellar folia (“zebra” sign), which is hyperintense on CT in the acute phase,</p><p>and hypointense on T2-weighted and SWI MR in the chronic phase. Subarachnoid</p><p>hemorrhage anywhere along the neuraxis leads to superfi cial siderosis, in which</p><p>hemosiderin is deposited along the surface of the brain, spinal cord, and nerves. On</p><p>T2-weighted MR, linear hypointense signal outlines the brain and spinal cord, often</p><p>with associated demyelination and gliosis.</p><p>References:</p><p>Figueiredo EG, de Amorim RL, Teixeira MJ. Remote cerebellar hemorrhage (zebra sign) in vascular</p><p>neurosurgery: pathophysiological insights. Neurol Med Chir (Tokyo). 2009;49(6):229-233; discussion</p><p>233-234.</p><p>Kumar N, Cohen-Gadol AA, Wright RA, et al. Superfi cial siderosis. Neurology. 2006;66(8):1144-1152.</p><p>ZEBRA</p><p>Modalities:</p><p>CT, MR</p><p>This page intentionally left blank</p><p>89</p><p>2 CHAPTER TWO</p><p>PEDIATRIC BRAIN</p><p>ABSENT BUTTERFLY, MONOVENTRICLE</p><p>FINDINGS:</p><p>Fetal US, axial plane, shows a large monoventricle (asterisk) with absence of normal</p><p>choroid plexus. The thalami are also fused.</p><p>DIAGNOSIS:</p><p>Alobar holoprosencephaly</p><p>DISCUSSION:</p><p>Holoprosencephaly refers to a spectrum of congenital malformations in which the</p><p>embryonic forebrain (prosencephalon) fails to separate completely. Based on the</p><p>degree of midline fusion, these are classifi ed as alobar, semilobar, lobar, and middle</p><p>interhemispheric variant (syntelencephaly). The alobar variant is the most severe,</p><p>with holospheric cortical fusion; absent corpus callosum, septum pellucidum, and</p><p>falx cerebri; single monoventricle; and fusion of the basal ganglia and thalami. On</p><p>prenatal US, failure to identify the normal “butterfl y” appearance of hyperechoic</p><p>choroid plexus within the paired lateral ventricles is an early harbinger of</p><p>holoprosencephaly.</p><p>References:</p><p>Hahn JS, Barnes PD. Neuroimaging advances in holoprosencephaly: refi ning the spectrum of the</p><p>midline malformation. Am J Med Genet C Semin Med Genet. 2010;154C(1):120-132.</p><p>Sepulveda W, Dezerega V, Be C. First-trimester sonographic diagnosis of holoprosencephaly: value of</p><p>the “butterfl y” sign. J Ultrasound Med. 2004;23(6):761-765; quiz 766-767.</p><p>Modalities:</p><p>US, CT, MR</p><p>90 Chapter 2: Pediatric Brain</p><p>ABSENT POSTERIOR LIMB, 1-2-3-4</p><p>FINDINGS:</p><p>• Axial T1-weighted MR shows markedly increased signal in the bilateral basal</p><p>ganglia (thick arrows) and thalami. There is loss of the normal T1-hyperintense</p><p>signal in the posterior limbs of the internal capsules (thin arrows).</p><p>• Axial ADC MR shows reduced diffusion in the basal ganglia and thalami (arrows).</p><p>DIAGNOSIS:</p><p>Hypoxic-ischemic encephalopathy, term infant</p><p>DISCUSSION:</p><p>In the term infant, hypoxic-ischemic encephalopathy (HIE) manifests differently than</p><p>in older children and adults. Although US and CT can be used for screening, MR is</p><p>the modality of choice for diagnosing HIE. After 37 weeks of gestational age, normal</p><p>myelination involves the dorsal portion of the posterior limb of the internal capsule</p><p>(PLIC) and ventrolateral nucleus of the thalamus, which appear T1-hyperintense</p><p>and T2-hypointense. Severe HIE is caused by sudden total loss of oxygenation,</p><p>which injures metabolically active structures including the putamina, globus pallidi,</p><p>thalami, hippocampi, corticospinal tracts, lateral geniculate nuclei, and sensorimotor</p><p>cortex. The constellation of fi ndings has been termed the “1-2-3-4” sign and includes</p><p>T1-hyperintense signal in the basal ganglia and thalami, loss of T1 signal in the</p><p>PLIC (“absent posterior limb” sign), and reduced diffusion. ADC data should always</p><p>be reviewed because the high T2 values of unmyelinated tissue can mask diffusion</p><p>changes on DWI. On MR spectroscopy, an elevated choline-to-creatine ratio,</p><p>decreased NAA, and lactate peak may be present. More profound hypoxia can cause</p><p>diffuse gray and white matter injury. Partial HIE occurs with prolonged incomplete</p><p>loss of oxygenation and results in parasagittal cortical/subcortical watershed injury.</p><p>References:</p><p>Heinz ER, Provenzale JM. Imaging fi ndings in neonatal hypoxia: a practical review. AJR Am J</p><p>Roentgenol. 2009;192(1):41-47.</p><p>Huang BY, Castillo M. Hypoxic-ischemic brain injury: imaging fi ndings from birth to adulthood.</p><p>Radiographics. 2008;28(2):417-439.</p><p>Modality:</p><p>MR</p><p>Angel Wing, Triple Peak 91</p><p>ANGEL WING, TRIPLE PEAK</p><p>FINDINGS:</p><p>Axial T2-weighted MR shows inferior herniation of the cerebellar hemispheres (thin</p><p>arrows), wrapping laterally around the pons (thick arrow).</p><p>DIAGNOSIS:</p><p>Chiari II malformation</p><p>DISCUSSION:</p><p>The Chiari II malformation is a complex congenital anomaly consisting of small</p><p>posterior fossa, inferior displacement of the cerebellum and brainstem, and</p><p>lumbosacral myelomeningocele. The cerebellar hemispheres wrap laterally around</p><p>the pons and extend into the cerebellopontine angles, forming a “triple peak”</p><p>appearance. Other characteristic imaging signs of Chiari II malformation include</p><p>beaked tectum, cervicomedullary kink, wide incisura with towering cerebellum, and</p><p>fenestrated falx with interdigitating gyri. In the Chiari III malformation, there is also</p><p>an occipital or high cervical encephalocele.</p><p>Reference:</p><p>Naidich TP, Pudlowski RM, Naidich JB. Computed tomographic signs of Chiari II malformation,</p><p>II: midbrain and cerebellum. Radiology. 1980;134(2):391-398.</p><p>Modalities:</p><p>CT, MR</p><p>92 Chapter 2: Pediatric Brain</p><p>Modalities:</p><p>US, MR</p><p>ANGULAR, POINT, SQUARE, TRIANGLE</p><p>FINDINGS:</p><p>Fetal US, coronal and axial planes, show dilated lateral ventricles with an angular</p><p>morphology (thin arrows) and pointed occipital horns (thick arrows).</p><p>DIFFERENTIAL DIAGNOSIS:</p><p>• Fetal Chiari malformation</p><p>• Spinal dysraphism</p><p>DISCUSSION:</p><p>Accurate diagnosis of fetal neural tube defects is crucial for guiding further imaging</p><p>evaluation, genetic workup, and prenatal counseling. The Chiari II malformation</p><p>is a complex congenital deformity involving small posterior fossa and lumbosacral</p><p>myelomeningocele. Infratentorial abnormalities can be diffi cult to detect in early</p><p>pregnancy. Before 24 weeks of gestational age, there is characteristic pointing</p><p>and posterior displacement of the occipital horn (“too-far-back” ventricle). After</p><p>24 weeks, the occipital horns become increasingly dilated and angular, with various</p><p>geometric appearances depending on the severity of the malformation. Fetal MR</p><p>may help to further characterize the spectrum of anatomic abnormalities.</p><p>References:</p><p>Callen AL, Filly RA. Supratentorial abnormalities in the Chiari II malformation, I: the ventricular</p><p>“point.” J Ultrasound Med. 2008;27(1):33-38.</p><p>Fujisawa H, Kitawaki J, Iwasa K, et al. New ultrasonographic criteria for the prenatal diagnosis of</p><p>Chiari type 2 malformation. Acta Obstet Gynecol Scand. 2006;85(12):1426-1429.</p><p>Angular, Fan, Scalloped, Triangle 93</p><p>FINDINGS:</p><p>Axial T2-weighted MR shows multifocal periventricular hyperintensities (thin</p><p>arrows). There is ex vacuo dilation of the lateral ventricles, with irregular contours</p><p>(thick arrows).</p><p>DIAGNOSIS:</p><p>Periventricular leukomalacia</p><p>DISCUSSION:</p><p>In premature infants, the periventricular white matter is most susceptible to hypoxic</p><p>injury because it is supplied by ventriculopetal penetrating arteries from the cortical</p><p>surface. Periventricular leukomalacia (PVL) is the most common preterm brain</p><p>injury, manifesting with periventricular white matter changes that appear echogenic</p><p>on US, hypodense on CT, and hyperintense on T2-weighted MR. Localized venous</p><p>infarctions produce “fan” or “triangle”-shaped</p><p>abnormalities, refl ecting the vascular</p><p>borderzones in this age group. After 2-6 weeks, the white matter begins to involute,</p><p>causing ex vacuo dilation of the ventricles with an “angular” or “scalloped”</p><p>morphology. End-stage PVL is characterized by cystic encephalomalacia (“Swiss</p><p>cheese” brain) with severe white matter loss and ventriculomegaly.</p><p>References:</p><p>Chao CP, Zaleski CG, Patton AC. Neonatal hypoxic-ischemic encephalopathy: multimodality imaging</p><p>fi ndings. Radiographics. 2006;26(Suppl 1):S159-S172.</p><p>Nakamura Y, Okudera T, Hashimoto T. Vascular architecture in white matter of neonates: its</p><p>relationship to periventricular leukomalacia. J Neuropathol Exp Neurol. 1994;53(6):582-589.</p><p>Modalities:</p><p>US, CT, MR</p><p>ANGULAR, FAN, SCALLOPED, TRIANGLE</p><p>94 Chapter 2: Pediatric Brain</p><p>Modalities:</p><p>US, CT, MR</p><p>FINDINGS:</p><p>Axial and coronal T2-weighted MR show fusion of the cerebral cortex (arrows) and</p><p>thalami across the midline. There is a monoventricular cavity that communicates</p><p>widely with a dorsal cyst.</p><p>DIAGNOSIS:</p><p>Alobar holoprosencephaly</p><p>DISCUSSION:</p><p>Holoprosencephaly refers to a spectrum of congenital malformations in which</p><p>the embryonic forebrain (prosencephalon) fails to separate completely. Based on</p><p>the degree of midline fusion, these are classifi ed as alobar, semilobar, lobar, and</p><p>middle interhemispheric variant (syntelencephaly). The alobar variant is the most</p><p>severe, with holospheric cortical fusion; absent corpus callosum, septum pellucidum,</p><p>and falx cerebri; and fusion of the basal ganglia and thalami. There is a single</p><p>“crescent”-shaped monoventricle that communicates widely with a dorsal cyst.</p><p>The surrounding dysmorphic brain parenchyma has an appearance that is variably</p><p>described as “ball,” “boomerang,” “cup,” “horseshoe,” or “pancake”-shaped.</p><p>Holoprosencephaly should be distinguished from hydranencephaly caused by</p><p>bilateral ICA occlusion in utero. In this condition, diffuse cortical destruction is</p><p>present, but the posterior fossa and thalami are normal.</p><p>Reference:</p><p>Hahn JS, Barnes PD. Neuroimaging advances in holoprosencephaly: refi ning the spectrum of the</p><p>midline malformation. Am J Med Genet C Semin Med Genet. 2010;154C(1):120-132.</p><p>BALL, BOOMERANG, CRESCENT, CUP, HORSESHOE, PANCAKE</p><p>Banana, Tight Posterior Fossa 95</p><p>Modalities:</p><p>US, MR</p><p>BANANA, TIGHT POSTERIOR FOSSA</p><p>FINDINGS:</p><p>Fetal US, axial plane, shows hypoplastic posterior fossa with cerebellar hemispheres</p><p>(arrows) wrapping around the brainstem.</p><p>DIFFERENTIAL DIAGNOSIS:</p><p>• Fetal Chiari malformation</p><p>• Spinal dysraphism</p><p>DISCUSSION:</p><p>Accurate diagnosis of fetal neural tube defects is crucial for guiding further imaging</p><p>evaluation, genetic workup, and prenatal counseling. The Chiari II malformation</p><p>is a complex congenital deformity involving small posterior fossa and lumbosacral</p><p>myelomeningocele. Before 24 weeks of gestational age, the posterior fossa shows a</p><p>“banana” confi guration with cerebellar hemispheres wrapping around the posterior</p><p>brainstem, due to downward traction on the spinal cord. After 24 weeks, the</p><p>cerebellum descends further below the foramen magnum and is not well seen at US</p><p>(“vanishing cerebellum”). Fetal MR may help to further characterize the spectrum</p><p>of anatomic abnormalities.</p><p>References:</p><p>Ando K, Ishikura R, Ogawa M, et al. MRI tight posterior fossa sign for prenatal diagnosis of Chiari</p><p>type II malformation. Neuroradiology. 2007;49(12):1033-1039.</p><p>Boltshauser E, Schneider J, Kollias S, et al. Vanishing cerebellum in myelomeningocoele. Eur J Paediatr</p><p>Neurol. 2002;6(2):109-113.</p><p>Nicolaides KH, Campbell S, Gabbe SG, et al. Ultrasound screening for spina bifi da: cranial and</p><p>cerebellar signs. Lancet. 1986;2(8498):72-74.</p><p>96 Chapter 2: Pediatric Brain</p><p>Modalities:</p><p>CT, MR</p><p>BAT WING, BEAK, DOUBLE POINT</p><p>FINDINGS:</p><p>Axial T2-weighted MR shows dilated frontal horns with notching along the lateral</p><p>walls (thick and thin arrows), due to prominent caudate heads.</p><p>DIAGNOSIS:</p><p>Chiari II malformation</p><p>DISCUSSION:</p><p>The Chiari II malformation is a complex congenital anomaly consisting of small</p><p>posterior fossa, inferior displacement of the cerebellum and brainstem, and</p><p>lumbosacral myelomeningocele. The frontal horns of the lateral ventricles are dilated</p><p>and assume a “double pointed” or “bat wing” appearance, refl ecting indentation</p><p>of the lateral walls by prominent caudate nuclei. Other characteristic imaging signs</p><p>of Chiari II malformation include beaked tectum, cervicomedullary kink, wide</p><p>incisura with towering cerebellum, and fenestrated falx with interdigitating gyri. In</p><p>the Chiari III malformation, there is also an occipital or high cervical encephalocele.</p><p>Reference:</p><p>Naidich TP, Pudlowski RM, Naidich JB. Computed tomographic signs of the Chiari II malformation,</p><p>III: ventricles and cisterns. Radiology. 1980;134(3):657-663.</p><p>Bat Wing, Bull/Ram/Steer Horn, Candelabra, Crescent, Moose Head, Trident, Viking Helmet 97</p><p>BAT WING, BULL/RAM/STEER HORN, CANDELABRA, CRESCENT, MOOSE HEAD,</p><p>TRIDENT, VIKING HELMET</p><p>FINDINGS:</p><p>Coronal T2-weighted MR shows absent corpus callosum with widely separated and</p><p>curvilinear frontal horns (arrows).</p><p>DIAGNOSIS:</p><p>Callosal agenesis</p><p>DISCUSSION:</p><p>Dysgenesis of the corpus callosum is caused by abnormalities in neural development</p><p>between 12 and 18 weeks of gestation. The sequence of formation is largely ventral to</p><p>dorsal, beginning with the genu and progressing through the anterior body, posterior</p><p>body, splenium, and rostrum. In callosal agenesis, there is complete absence of the</p><p>normal crossing white matter tracts. Instead, nondecussating white matter fi bers</p><p>known as Probst bundles course anteroposteriorly along the medial edges of the</p><p>lateral ventricles. The lateral ventricles assume a parallel orientation, with narrow</p><p>curvilinear frontal horns that are widely separated (“bull horn” confi guration) and</p><p>dilated occipital horns (colpocephaly). Without crossing fi bers to displace and invert</p><p>them, the cingulate gyri remain everted and the cingulate sulcus is unformed. Other</p><p>imaging signs of callosal agenesis include high-riding third ventricle, radiating gyri,</p><p>and “keyhole” temporal horns.</p><p>References:</p><p>Atlas SW. Magnetic Resonance Imaging of the Brain and Spine. 4th ed, vol. 1. Philadelphia: Wolters</p><p>Kluwer; 2008.</p><p>Barkovich AJ, Raybaud C. Pediatric Neuroimaging. 5th ed. Philadelphia: Wolters Kluwer; 2011.</p><p>Modalities:</p><p>US, CT, MR</p><p>98 Chapter 2: Pediatric Brain</p><p>Modalities:</p><p>US, CT, MR</p><p>BAT WING, RECTANGLE, UMBRELLA</p><p>FINDINGS:</p><p>• Axial T2-weighted MR shows absent cerebellar vermis with apposition of the</p><p>cerebellar hemispheres and pointed roof of the fourth ventricle (arrow).</p><p>• Sagittal T1-weighted MR shows angular bulging of the roof of the fourth ventricle</p><p>(arrows) in the region of the absent vermis.</p><p>DIAGNOSIS:</p><p>Joubert syndrome-related disorders</p><p>DISCUSSION:</p><p>Joubert syndrome–related disorders (JSRD), or cerebello-oculo-renal disorders, are</p><p>autosomal recessive disruptions of midbrain-hindbrain development with associated</p><p>ocular, facial, hepatic, renal, and digital anomalies. Hypoplasia of the cerebellar</p><p>vermis results in dilation of the fourth ventricle and bulging of its roof, creating a</p><p>“rectangular” appearance on sagittal images. Just below the pontomesencephalic</p><p>junction, there is notching of the fourth ventricular roof between the cerebellar</p><p>hemispheres. This is best appreciated on axial images, and yields the “bat wing”</p><p>or “umbrella” appearance. Other imaging signs of JSRD include the “molar tooth”</p><p>appearance of the midbrain and “bullet” third ventricle.</p><p>References:</p><p>Alorainy IA, Sabir S, Seidahmed MZ, et al. Brain stem and cerebellar fi ndings in Joubert syndrome.</p><p>J Comput Assist Tomogr. 2006;30(1):116-121.</p><p>Brancati F, Dallapiccola B, Valente EM. Joubert syndrome and related disorders. Orphanet J Rare Dis.</p><p>2010;5:20.</p><p>Boxcar Ventricles 99</p><p>FINDINGS:</p><p>Coronal T2-weighted MR shows absent septum pellucidum and squared lateral</p><p>ventricles (arrows).</p><p>DIFFERENTIAL DIAGNOSIS:</p><p>• Septo-optic dysplasia</p><p>• Holoprosencephaly</p><p>DISCUSSION:</p><p>Septo-optic dysplasia, also known as de Morsier syndrome, is a congenital anomaly</p><p>that may represent a forme fruste of lobar holoprosencephaly. Classic fi ndings are</p><p>optic nerve hypoplasia, absent septum pellucidum, and hypothalamic-pituitary</p><p>dysfunction. Midline defects result in closely apposed lateral ventricles with a</p><p>squared (“boxcar”) appearance. Two subsets of disease have been identifi ed, based</p><p>on the presence or absence of schizencephaly. Patients with schizencephaly (“septo-</p><p>optic dysplasia plus”) tend to have less severe midline defects. Patients without</p><p>schizencephaly exhibit diffuse white matter hypoplasia, resulting in ventriculomegaly</p><p>with squaring of the frontal horns. The olfactory bulbs may also be absent (Kallmann</p><p>syndrome). In true holoprosencephaly, incomplete separation of forebrain structures</p><p>can also yield a “boxcar” appearance of the frontal horns, with more severe midline</p><p>and facial abnormalities.</p><p>Reference:</p><p>Barkovich AJ, Fram EK, Norman D. Septo-optic dysplasia: MR imaging. Radiology. 1989;171(1):</p><p>189-192.</p><p>Modalities:</p><p>US, CT, MR</p><p>BOXCAR VENTRICLES</p><p>100 Chapter 2: Pediatric Brain</p><p>Modalities:</p><p>US, CT, MR</p><p>FINDINGS:</p><p>• Coronal T1-weighted MR shows a hyperintense mass (thin arrow) in the anterior</p><p>interhemispheric fi ssure with chemical shift artifact along the inferior margin. There</p><p>is associated callosal dysgenesis with abnormal confi guration of the frontal horns.</p><p>• Coronal T2-weighted MR shows susceptibility along the lateral margins of the</p><p>mass (thick arrows), compatible with calcifi cation.</p><p>DIAGNOSIS:</p><p>Pericallosal lipoma, tubulonodular subtype</p><p>DISCUSSION:</p><p>Intracranial lipoma is thought to result from abnormal persistence of the meninx</p><p>primitiva, the mesenchymal precursor to the meninges. Normally, the inner meninx</p><p>is resorbed between weeks 8 and 10 of gestation and gives rise to the subarachnoid</p><p>cisterns. When residual meninx is present, it differentiates into lipomatous tissue</p><p>and can interfere with normal growth. Pericallosal lipomas are the most common,</p><p>and may be tubulonodular or curvilinear in morphology. Tubulonodular lipomas are</p><p>large round or cylindrical masses, usually greater than 1-2 cm in diameter. They arise</p><p>earlier in development and are usually located along the genu, with peripheral</p><p>calcifi cations producing a “bracket” sign on coronal images. There is a high rate</p><p>of associated malformations including callosal dysgenesis, sincipital encephaloceles,</p><p>and migration/gyration anomalies. Curvilinear lipomas are thin ribbonlike masses</p><p>that typically curve around the splenium. They arise later in development, with</p><p>no or mild associated anomalies. Lipomas appear echogenic on US, hypodense on</p><p>CT, hyperintense on T1-weighted MR, and variably hyperintense on T2-weighted</p><p>MR. Identifi cation of chemical shift artifact and signal dropout on fat-suppressed</p><p>sequences is diagnostic.</p><p>References:</p><p>Tart RP, Quisling RG. Curvilinear and tubulonodular varieties of lipoma of the corpus callosum: an</p><p>MR and CT study. J Comput Assist Tomogr. 1991;15(5):805-810.</p><p>Truwit CL, Barkovich AJ. Pathogenesis of intracranial lipoma: an MR study in 42 patients. AJR Am</p><p>J Roentgenol. 1990;155(4):855-864; discussion 865.</p><p>BRACKET</p><p>Bright Rim, Hyperintense Ring 101</p><p>FINDINGS:</p><p>Axial FLAIR MR shows a</p><p>peripheral left temporo-occipital</p><p>mass with hyper intense rim</p><p>(arrow).</p><p>DIAGNOSIS:</p><p>Dysembryoplastic neuroepithelial</p><p>tumor</p><p>DISCUSSION:</p><p>Dysembryoplastic neuroepithelial</p><p>tumors (DNETs) are benign, slow-</p><p>growing neuroepithelial tumors</p><p>arising from cortical or deep gray</p><p>matter. Patients are typically male</p><p>and under age 20. The temporal</p><p>lobe is the most common location,</p><p>followed by the frontal lobe. Simple DNETs are T2-hyperintense multiseptated</p><p>“bubbly” masses with little vasogenic edema, enhancement, or mass effect. On</p><p>FLAIR MR, there is nulling of the cystic components of tumor with a characteristic</p><p>“bright rim,” which may be complete or incomplete. Pathologically, this corresponds</p><p>to peripheral loose neuroglial elements, and suggests residual or recurrent tumor in</p><p>the postoperative setting. Complex DNETs have varying amounts of solid tissue</p><p>and low-level enhancement. Lesions typically have a wedge-shaped morphology,</p><p>in which the apex points toward the ventricle, and the outer surface extends</p><p>to cortex with remodeling of the inner table. Associated cortical dysplasia is</p><p>common. Other pediatric cystic tumors include ganglioglioma (GGL), pleomorphic</p><p>xanthoastrocytoma (PXA), and juvenile pilocytic astrocytoma (JPA), which tend</p><p>to be associated with mural nodules. In GGLs, edema is rare and calcifi cation is</p><p>common. PXAs tend to be larger and produce dural tails without skull erosion.</p><p>When supratentorial, JPAs are usually adjacent to the third ventricle.</p><p>References:</p><p>Koeller KK, Henry JM. From the archives of the AFIP: superfi cial gliomas: radiologic-pathologic</p><p>correlation. Armed Forces Institute of Pathology. Radiographics. 2001;21(6):1533-1556.</p><p>Parmar HA, Hawkins C, Ozelame R, et al. Fluid-attenuated inversion recovery ring sign as a marker</p><p>of dysembryoplastic neuroepithelial tumors. J Comput Assist Tomogr. 2007;31(3):348-353.</p><p>Modality:</p><p>MR</p><p>BRIGHT RIM, HYPERINTENSE RING</p><p>102 Chapter 2: Pediatric Brain</p><p>FINDINGS:</p><p>• Axial FLAIR MR shows multiple hyperintense, mildly expansile lesions in the</p><p>bilateral basal ganglia (thin arrows) and thalami (thick arrows).</p><p>• Axial contrast-enhanced T1-weighted MR shows no appreciable enhancement.</p><p>DIAGNOSIS:</p><p>Neurofi bromatosis type I</p><p>DISCUSSION:</p><p>Neurofi bromatosis type I (NF1), also known as von Recklinghausen disease, is the</p><p>most common phakomatosis. Caused by a mutation in the NF1 gene on the long</p><p>arm of chromosome 17, it is transmitted with autosomal dominant inheritance. At</p><p>least two of the following diagnostic criteria must be present to make the diagnosis:</p><p>café-au-lait spots, multiple or plexiform neurofi bromas, axillary or inguinal</p><p>freckling, optic gliomas, Lisch nodules (iris hamartomas), osseous abnormalities</p><p>(sphenoid dysplasia, long bone thinning and pseudoarthrosis), and a fi rst-degree</p><p>relative with NF1. On MR, 30% to 60% of patients demonstrate T2-hyperintense</p><p>foci with predilection for the basal ganglia, cerebellum, and brainstem. Known as</p><p>unidentifi ed bright objects (UBOs), these are considered benign hamartomas and</p><p>correlate histologically with spongiform myelinopathy (myelin vacuolization with</p><p>edema). Higher UBO burden is associated with cognitive dysfunction, though most</p><p>lesions regress with age. Children with large numbers and volumes of UBOs should</p><p>undergo regular imaging surveillance, given the increased risk of both benign and</p><p>malignant CNS tumors. Lesion enlargement and/or contrast enhancement are</p><p>suspicious imaging features that raise concern for neoplastic transformation.</p><p>References:</p><p>Gutmann DH, Aylsworth A, Carey JC, et al. The diagnostic evaluation and multidisciplinary</p><p>management of neurofi bromatosis 1 and neurofi bromatosis 2. JAMA. 1997;278(1):51-57.</p><p>Mentzel HJ, Seidel J, Fitzek C, et al. Pediatric brain MRI in neurofi bromatosis type I. Eur Radiol.</p><p>2005;15(4):814-822.</p><p>Modality:</p><p>MR</p><p>BRIGHT SPOTS, UNIDENTIFIED BRIGHT OBJECTS</p><p>Bubbly, Feathery, Soap Bubble, Swiss Cheese 103</p><p>FINDINGS:</p><p>Axial T2-weighted MR shows a</p><p>multiloculated hyperintense mass</p><p>in the right perirolandic region</p><p>(arrow).</p><p>DIAGNOSIS:</p><p>Dysembryoplastic neuroepithelial</p><p>tumor</p><p>DISCUSSION:</p><p>Dysembryoplastic neuroepithelial</p><p>tumors (DNETs) are benign, slow-</p><p>growing neuroepithelial tumors</p><p>arising from cortical or deep</p><p>gray matter. Patients are typically</p><p>male and under age 20. The</p><p>temporal lobe is the most</p><p>common location, followed by</p><p>the frontal lobe. Simple DNETs</p><p>are T2-hyperintense multiseptated “bubbly” masses with little vasogenic edema,</p><p>enhancement, or mass effect. On FLAIR MR, there is nulling of the cystic components</p><p>of tumor with a characteristic “bright rim,” which may be complete or incomplete.</p><p>Pathologically, this corresponds to peripheral</p><p>loose neuroglial elements, and suggests</p><p>residual or recurrent tumor in the postoperative setting. Complex DNETs have</p><p>varying amounts of solid tissue and low-level enhancement. Lesions typically have</p><p>a wedge-shaped morphology, in which the apex points toward the ventricle, and</p><p>the outer surface extends to cortex with remodeling of the inner table. Associated</p><p>cortical dysplasia is common. Other pediatric cystic tumors include ganglioglioma</p><p>(GGL), pleomorphic xanthoastrocytoma (PXA), and juvenile pilocytic astrocytoma</p><p>(JPA), which tend to be associated with enhancing mural nodules. In GGLs, edema</p><p>is rare and calcifi cation is common. PXAs tend to be larger and produce dural tails</p><p>rather than skull erosion. When supratentorial, JPAs are usually adjacent to the third</p><p>ventricle.</p><p>References:</p><p>Fernandez C, Girard N, Paz Paredes A, et al. The usefulness of MR imaging in the diagnosis of</p><p>dysembryoplastic neuroepithelial tumor in children: a study of 14 cases. AJNR Am J Neuroradiol.</p><p>2003;24:829-834.</p><p>Koeller KK, Henry JM. From the archives of the AFIP: superfi cial gliomas: radiologic-pathologic</p><p>correlation. Armed Forces Institute of Pathology. Radiographics. 2001;21(6):1533-1556.</p><p>Modalities:</p><p>CT, MR</p><p>BUBBLY, FEATHERY, SOAP BUBBLE, SWISS CHEESE</p><p>104 Chapter 2: Pediatric Brain</p><p>FINDINGS:</p><p>Axial FLAIR MR shows a deep interpeduncular fossa with dorsal pointing of the</p><p>third ventricle (arrow).</p><p>DIAGNOSIS:</p><p>Joubert syndrome–related disorders</p><p>DISCUSSION:</p><p>Joubert syndrome–related disorders (JSRD), or cerebello-oculo-renal disor ders, are</p><p>autosomal recessive disruptions of midbrain-hindbrain development with associated</p><p>ocular, facial, hepatic, renal, and digital anomalies. Lack of decussation of the superior</p><p>cerebellar peduncles within the midbrain results in deepening of the interpeduncular</p><p>fossa, with elongation of the third ventricle posteriorly (“bullet” appearance). Other</p><p>imaging signs of JSRD include the “molar tooth” appearance of the midbrain, “bat-</p><p>wing” fourth ventricle, and vermian dysplasia.</p><p>References:</p><p>Alorainy IA, Sabir S, Seidahmed MZ, et al. Brain stem and cerebellar fi ndings in Joubert syndrome.</p><p>J Comput Assist Tomogr. 2006;30(1):116-121.</p><p>Brancati F, Dallapiccola B, Valente EM. Joubert syndrome and related disorders. Orphanet J Rare Dis.</p><p>2010;5:20.</p><p>Modalities:</p><p>CT, MR</p><p>BULLET</p><p>Bullet/Heart/Towering Cerebellum, Tentorial Pseudotumor 105</p><p>Modalities:</p><p>CT, MR</p><p>BULLET/HEART/TOWERING CEREBELLUM, TENTORIAL PSEUDOTUMOR</p><p>FINDINGS:</p><p>Axial and coronal T2-weighted MR show a widened incisura, with the cerebellum</p><p>herniating superiorly (thick arrows) above the tentorium and wrapping laterally</p><p>around the midbrain (thin arrows).</p><p>DIAGNOSIS:</p><p>Chiari II malformation</p><p>DISCUSSION:</p><p>The Chiari II malformation is a complex congenital anomaly consisting of small</p><p>posterior fossa and lumbosacral myelomeningocele. Hypoplasia of the tentorium</p><p>cerebelli produces a wide incisura, through which the cerebellum can herniate</p><p>superiorly (“towering cerebellum”). Other characteristic imaging signs of Chiari II</p><p>malformation include beaked tectum, cervicomedullary kink, and fenestrated falx</p><p>with interdigitating gyri. In the Chiari III malformation, there is also an occipital or</p><p>high cervical encephalocele.</p><p>References:</p><p>el Gammal T, Mark EK, Brooks BS. MR imaging of Chiari II malformation. AJR Am J Roentgenol.</p><p>1988;150(1):163-170.</p><p>Naidich TP, Pudlowski RM, Naidich JB. Computed tomographic signs of Chiari II malformation,</p><p>II: midbrain and cerebellum. Radiology. 1980;134(2):391-398.</p><p>106 Chapter 2: Pediatric Brain</p><p>Modalities:</p><p>US, CT, MR</p><p>BUMPY, COBBLESTONE, NODULAR, PEBBLE, VERRUCOUS</p><p>FINDINGS:</p><p>Axial T2-weighted MR shows dysplastic gyri and sulci with a micronodular</p><p>appearance of the cortex, most pronounced in the frontal lobes (arrows).</p><p>DIAGNOSIS:</p><p>Lissencephaly, type II</p><p>DISCUSSION:</p><p>Congenital brain malformations with incomplete cortical sulcation include agyria</p><p>(no gyri), pachygyria (broad gyri), and lissencephaly (underdeveloped gyri).</p><p>Lissencephaly can be divided into type I (classic) and type II (cobblestone) types.</p><p>Type I lissencephaly results from undermigration, while type II lissencephaly results</p><p>from overmigration of neuroblasts and glial cells into the subarachnoid space during</p><p>development. In type II lissencephaly, a thinned multinodular cortex (“cobblestone”</p><p>appearance) and thickened meninges are seen, often in an anterior distribution.</p><p>There is an association with muscular dystrophy–like syndromes. From most to</p><p>least severe, these are Walker-Warburg syndrome (WWS), muscle-eye-brain disease</p><p>(MEB), and Fukuyama congenital muscular dystrophy (FCMD). Associated ocular</p><p>hypoplasia, midline anomalies, and hydrocephalus may be present.</p><p>References:</p><p>Abdel Razek AA, Kandell AY, Elsorogy LG, et al. Disorders of cortical formation: MR imaging</p><p>features. AJNR Am J Neuroradiol. 2009;30(1):4-11.</p><p>Pilz DT, Quarrell OW. Syndromes with lissencephaly. J Med Genet. 1996;33(4):319-323.</p><p>Butterfly 107</p><p>Modalities:</p><p>CT, MR</p><p>BUTTERFLY</p><p>FINDINGS:</p><p>• Axial FLAIR MR shows symmetric hyperintensity within the periatrial white</p><p>matter and splenium (arrow).</p><p>• Axial contrast-enhanced T1-weighted MR shows peripheral enhancement along</p><p>the areas of FLAIR signal abnormality (arrows).</p><p>DIAGNOSIS:</p><p>Adrenoleukodystrophy</p><p>DISCUSSION:</p><p>Adrenoleukodystrophy (ALD) is an X-linked hereditary leukoencephalopathy</p><p>caused by mutations in the ABCD1 peroxisomal protein, which is responsible</p><p>for β-oxidation of very long chain fatty acids (VLCFAs). Most patients are young</p><p>males, but there are additional subtypes of disease that affect neonates, adolescents,</p><p>and adults. Accumulation of VLCFAs is toxic to the brain and causes symmetric</p><p>demyelination of the splenium and periatrial white matter, producing a “butterfl y”</p><p>appearance. Demyelination progresses from central to peripheral, with characteristic</p><p>enhancement along the leading edges. Less commonly, disease involves the frontal</p><p>lobes, genu, cerebellum, and/or brainstem. There is also dysfunction of the adrenal</p><p>cortex and testicular Leydig cells, yielding Addison disease and gonadal insuffi ciency.</p><p>References:</p><p>Cheon JE, Kim IO, Hwang YS, et al. Leukodystrophy in children: a pictorial review of MR imaging</p><p>features. Radiographics. 2002;22(3):461-476.</p><p>Kim JH, Kim HJ. Childhood X-linked adrenoleukodystrophy: clinical-pathologic overview and MR</p><p>imaging manifestations at initial evaluation and follow-up. Radiographics. 2005;25(3):619-631.</p><p>108 Chapter 2: Pediatric Brain</p><p>FINDINGS:</p><p>Coronal T2-weighted MR shows absent cerebellar vermis with apposition of the</p><p>cerebellar hemispheres, separated by a thin CSF cleft (arrow).</p><p>DIAGNOSIS:</p><p>Joubert syndrome–related disorders</p><p>DISCUSSION:</p><p>Joubert syndrome–related disorders (JSRD), or cerebello-oculo-renal disor ders, are</p><p>autosomal recessive disruptions of midbrain-hindbrain development with associated</p><p>ocular, facial, hepatic, renal, and digital anomalies. There is vermian hypoplasia with</p><p>enlarged cisterna magna, creating a CSF-fi lled notch between the apposed cerebellar</p><p>hemispheres (“buttock” sign). Other imaging signs of JSRD include the “molar tooth”</p><p>appearance of the midbrain and “bat-wing” fourth ventricle. Another condition</p><p>involving vermian aplasia is rhombencephalosynapsis, in which the cerebellar</p><p>hemispheres and deep nuclei are fused across midline with no intervening cleft.</p><p>References:</p><p>Alorainy IA, Sabir S, Seidahmed MZ, et al. Brain stem and cerebellar fi ndings in Joubert syndrome.</p><p>J Comput Assist Tomogr. 2006;30(1):116-121.</p><p>Brancati F, Dallapiccola B, Valente EM. Joubert syndrome and related disorders. Orphanet J Rare Dis.</p><p>2010;5:20.</p><p>Modalities:</p><p>US, CT, MR</p><p>BUTTOCK</p><p>Candle Guttering/Wax 109</p><p>FINDINGS:</p><p>Axial T2-weighted MR</p><p>shows ovoid subependymal</p><p>nodules (arrows) along the</p><p>lateral ventricular walls.</p><p>Several cortical/subcortical</p><p>hyperintense lesions are also</p><p>present.</p><p>DIFFERENTIAL DIAGNOSIS:</p><p>• Tuberous sclerosis</p><p>• CNS lymphoma</p><p>• Metastases</p><p>• Gray matter heterotopia</p><p>DISCUSSION:</p><p>Tuberous sclerosis complex</p><p>(TSC) is a phakomatosis or</p><p>neuroectodermal syndrome</p><p>characterized by dysplasias and hamartomas of the brain, retinae, skin, heart, lungs,</p><p>kidneys, and bones. Histologically, there is abnormal neuronal/glial formation and</p><p>migration, with disorganized myelination and gliosis. Neuroimaging manifestations</p><p>include cortical/subcortical hamartomas, white matter abnormalities, and</p><p>subependymal nodules or giant cell astrocytomas (SEGAs). Subependymal</p><p>nodules of TSC are elongated and irregular (“candle guttering” appearance),</p><p>frequently with calcifi cation. In infants younger than 3 months, MR signal is</p><p>T1-hyperintense and T2-hypointense. As myelination progresses with age, nodules</p><p>become T2-hyperintense with variable T1 signal. There should not be associated</p><p>diffusion abnormalities or contrast enhancement. Large enhancing nodules near</p><p>the foramen of Monro suggest SEGAs—benign tumors that are typically resected</p><p>because of their propensity for hemorrhage and ventricular obstruction. Other</p><p>causes of ependymal nodularity include primary CNS lymphoma and ependymal</p><p>metastases. These are typically larger and more enhancing, with reduced diffusion.</p><p>The imaging differential also includes subependymal gray matter heterotopia, in</p><p>which nodules have a smoother and more regular appearance. Signal is isointense</p><p>to gray matter on all sequences, and there is no contrast enhancement.</p><p>References:</p><p>Baron Y, Barkovich AJ. MR imaging of tuberous sclerosis in neonates and young infants. AJNR Am</p><p>J Neuroradiol. 1999;20(5):907-916.</p><p>Pinto Gama HP, da Rocha AJ, Braga FT, et al. Comparative analysis of MR sequences to detect</p><p>structural brain lesions in tuberous sclerosis. Pediatr Radiol. 2006;36(2):119-125.</p><p>Modalities:</p><p>US, CT, MR</p><p>CANDLE GUTTERING/WAX</p><p>110 Chapter 2: Pediatric Brain</p><p>FINDINGS:</p><p>Axial contrast-enhanced T1-weighted MR shows a lobulated hyperenhancing mass</p><p>in the left trigone (arrow), with associated hydrocephalus.</p><p>DIAGNOSIS:</p><p>Choroid plexus tumor</p><p>DISCUSSION:</p><p>The choroid plexus is the most vascular structure within the ventricular system</p><p>and continuously produces cerebrospinal fl uid. As a result, choroid plexus tumors</p><p>are markedly hypervascular and associated with hydrocephalus. Benign choroid</p><p>plexus papilloma (CPP) classically has a well-circumscribed, frondlike “caulifl ower”</p><p>appearance and is contained within the ventricle. Malignant choroid plexus carcinoma</p><p>(CPC) tends to be larger and more irregular, with local invasion and metastasis.</p><p>However, there is a great deal of overlap in imaging appearances. Choroid plexus</p><p>tumors most commonly occur in the trigones in children and the fourth ventricle in</p><p>adults. There is an association with von Hippel-Lindau disease.</p><p>References:</p><p>Anderson DR, Falcone S, Bruce JH, et al. Radiologic-pathologic correlation. Congenital choroid</p><p>plexus papillomas. AJNR Am J Neuroradiol. 1995;16(10):2072-2076.</p><p>Koeller KK, Sandberg GD. From the archives of the AFIP. Cerebral intraventricular neoplasms:</p><p>radiologic-pathologic correlation. Radiographics. 2002;22(6):1473-1505.</p><p>Modalities:</p><p>US, CT, MR</p><p>CAULIFLOWER</p><p>(Cervico)Medullary Buckle/Kink/Spur, Trumpet 111</p><p>FINDINGS:</p><p>Sagittal T2-weighted MR shows acute angulation at the cervicomedullary junction</p><p>(arrow), with edema in the medulla and atrophy of the cervical cord. The cerebellar</p><p>tonsils are peglike and displaced far below the foramen magnum.</p><p>DIAGNOSIS:</p><p>Chiari malformation</p><p>DISCUSSION:</p><p>Chiari malformations involve a spectrum of complex congenital anomalies, all</p><p>with inferior displacement of the cerebellum and brainstem through the foramen</p><p>magnum. In Chiari I, tonsillar displacement may cause syringohydromyelia due</p><p>to obstruction of cerebrospinal fl uid (CSF) fl ow. With Chiari II, a lumbosacral</p><p>myelomeningocele produces additional traction on the spinal cord, resulting in</p><p>a hypoplastic posterior fossa. Inferior migration of the cerebellar tonsils causes</p><p>crowding of the foramen magnum, with brainstem elongation and kinking at the</p><p>level of the cervicomedullary junction. Edema of the medulla and atrophy of the</p><p>cervical cord yields a fl ared (“trumpet”) appearance. In Chiari III, there is also an</p><p>occipital or high cervical encephalocele.</p><p>References:</p><p>Geerdink N, van der Vliet T, Rotteveel JJ, et al. Essential features of Chiari II malformation in MR</p><p>imaging: an interobserver reliability study—part 1. Childs Nerv Syst. 2012;28(7):977-985.</p><p>Naidich TP, McLone DG, Fulling KH. The Chiari II malformation: Part IV. The hindbrain deformity.</p><p>Neuroradiology. 1983;25(4):179-197.</p><p>Modalities:</p><p>CT, MR</p><p>(CERVICO)MEDULLARY BUCKLE/KINK/SPUR, TRUMPET</p><p>112 Chapter 2: Pediatric Brain</p><p>Modalities:</p><p>CT, MR</p><p>CLEFT-DIMPLE</p><p>FINDINGS:</p><p>Axial T2-weighted MR shows focal cortical thickening and gyral enlargement in</p><p>the left frontal lobe, with dilated overlying CSF space (arrow) and subcortical white</p><p>matter hyperintensity.</p><p>DIAGNOSIS:</p><p>Cortical dysgenesis</p><p>DISCUSSION:</p><p>Cortical dysgenesis represents a spectrum of congenital cortical malformations</p><p>resulting from abnormal cellular proliferation, migration, or postmigrational</p><p>development. Abnormalities of neuronal and glial proliferation include focal</p><p>cortical dysplasia type II (Taylor dysplasia), microcephaly, and megalencephaly.</p><p>Abnormalities of neuronal migration include lissencephaly and gray matter</p><p>heterotopia. Abnormalities of postmigrational development include polymicrogyria,</p><p>schizencephaly, and non-Taylor cortical dysplasias. Imaging features of cortical</p><p>dysgenesis include cortical thickening, undersulcation, macrogyria, loss of gray-</p><p>white distinction, and abnormal white matter signal. The “cleft-dimple” complex</p><p>refers to inward buckling of the cortex (cortical “dimple”) with a prominent</p><p>CSF space (“cleft”) overlying the area of dysgenesis. This feature is particularly</p><p>helpful in detecting subtle cortical malformations and distinguishing them from</p><p>true atrophy (with volume loss and cortical thinning) or mass lesions (expanding</p><p>into and effacing the overlying CSF space).</p><p>References:</p><p>Barkovich AJ, Guerrini R, Kuzniecky RI, et al. A developmental and genetic classifi cation for</p><p>malformations of cortical development: update 2012. Brain. 2012;135(Pt 5):1348-1369.</p><p>Bronen RA, Spencer DD, Fulbright RK. Cerebrospinal fl uid cleft with cortical dimple: MR imaging</p><p>marker for focal cortical dysgenesis. Radiology. 2000;214(3):657-663.</p><p>Closed Lip 113</p><p>FINDINGS:</p><p>Coronal T2-weighted MR shows a right frontal transcortical defect (arrows) lined</p><p>by gray matter, without intervening CSF.</p><p>DIAGNOSIS:</p><p>Closed-lip schizencephaly</p><p>DISCUSSION:</p><p>Schizencephaly is caused by a full- thickness insult to the cerebral cortex during</p><p>cortical organization, which produces a gray matter-lined cleft extending from</p><p>the ventricular system to the subarachnoid space. Clefts may be small or large,</p><p>unilateral or bilateral, and classifi ed as type I (closed-lip) or type II (open-lip).</p><p>In closed-lip schizencephaly, the lips are in contact with each other; in open-lip</p><p>schizencephaly, the lips are separated by intervening CSF. The gray matter lining</p><p>the cleft is frequently polymicrogyric (multiple tiny gyri) and can extend into the</p><p>ventricle, forming subependymal gray matter heterotopia. Schizencephaly should</p><p>not be confused with porencephaly, in which an acquired insult results in a white</p><p>matter-lined cavity adjacent to the ventricular system and/or subarachnoid space.</p><p>References:</p><p>Abdel Razek AA, Kandell AY, Elsorogy LG, et al. Disorders of cortical formation: MR imaging</p><p>features. AJNR Am J Neuroradiol. 2009;30(1):4-11.</p><p>Barkovich AJ, Norman D. MR imaging of schizencephaly. AJR Am J Roentgenol. 1988;150(6):</p><p>1391-1396.</p><p>Modalities:</p><p>US, CT, MR</p><p>CLOSED LIP</p><p>114 Chapter 2: Pediatric Brain</p><p>Modalities:</p><p>CT, MR</p><p>CONVOLUTED, CURVILINEAR, GYRIFORM, SERPENTINE, TRAM LINE/TRACK</p><p>FINDINGS:</p><p>• Axial CT shows cortical calcifi cations in both parietal lobes (arrows).</p><p>• Axial contrast-enhanced T1-weighted MR shows leptomeningeal (arrows) and</p><p>choroid</p><p>plexus hyperenhancement, right greater than left.</p><p>DIFFERENTIAL DIAGNOSIS:</p><p>• Sturge-Weber syndrome</p><p>• Cortical laminar necrosis</p><p>• Meningitis</p><p>• Radiation</p><p>DISCUSSION:</p><p>Sturge-Weber syndrome (encephalotrigeminal angiomatosis) is a neurocutaneous</p><p>syndrome consisting of facial port-wine stain and leptomeningeal angiomatosis.</p><p>During development, subarachnoid vascular malformations between the arachnoid</p><p>and pia mater prevent development of cortical bridging veins that normally</p><p>connect the superfi cial and deep venous systems. Cerebral venous outfl ow is</p><p>impaired and causes enlargement of cortical, medullary, and subependymal veins</p><p>and choroid plexus (“choroidal angiomatosis”). Chronic venous hypertension</p><p>causes white matter damage and cortical calcifi cations, particularly in the parietal</p><p>and occipital lobes. Calcifi cations in apposing gyri form the classic “tram track”</p><p>appearance. An associated condition is Dyke-Davidoff-Masson syndrome, or</p><p>cerebral hemiatrophy with ipsilateral enlargement of the sinuses, mastoid air cells,</p><p>and diploic space. Other causes of gyriform calcifi cation include infarcts with</p><p>cortical laminar necrosis, meningitis, radiation, anticonvulsant therapy, folic acid</p><p>defi ciency, leukemia treated with intrathecal methotrexate, gliomas, and calcifying</p><p>hamartomas in tuberous sclerosis. Correlation with other radiologic and clinical</p><p>fi ndings is crucial for diagnosis.</p><p>References:</p><p>Akpinar E. The tram-track sign: cortical calcifi cations. Radiology. 2004;231(2):515-516.</p><p>Juhász C, Haacke EM, Hu J, et al. Multimodality imaging of cortical and white matter abnormalities</p><p>in Sturge-Weber syndrome. AJNR Am J Neuroradiol. 2007;28(5):900-906.</p><p>Cortical/Subcortical Islands, Tubers 115</p><p>FINDINGS:</p><p>Axial T2-weighted MR shows multiple hyperintense lesions (arrows) in the cortex</p><p>and subcortical white matter.</p><p>DIAGNOSIS:</p><p>Tuberous sclerosis</p><p>DISCUSSION:</p><p>Tuberous sclerosis complex (TSC) is a phakomatosis or neuroectodermal syndrome</p><p>characterized by dysplasias and hamartomas of the brain, retinae, skin, heart, lungs,</p><p>kidneys, and bones. Histologically, there is abnormal neuronal/glial formation and</p><p>migration, with disorganized myelination and gliosis. Neuroimaging manifestations</p><p>include cortical/subcortical hamartomas (“islands”), white matter abnormalities,</p><p>and subependymal nodules or giant cell astrocytomas (SEGAs). Tubers are focal</p><p>protrusions of gyri in the cerebrum and/or cerebellum, which expand the cortex</p><p>and obscure the gray-white junction. In infants younger than 3 months, MR signal</p><p>is T1-hyperintense and T2-hypointense. As myelination progresses with age, tubers</p><p>become T2-hyperintense with variable T1 signal and central cystic changes.</p><p>References:</p><p>Inoue Y, Nemoto Y, Murata R, et al. CT and MR imaging of cerebral tuberous sclerosis. Brain Dev.</p><p>1998;20(4):209-221.</p><p>Pinto Gama HP, da Rocha AJ, Braga FT, et al. Comparative analysis of MR sequences to detect</p><p>structural brain lesions in tuberous sclerosis. Pediatr Radiol. 2006;36(2):119-125.</p><p>Modalities:</p><p>CT, MR</p><p>CORTICAL/SUBCORTICAL ISLANDS, TUBERS</p><p>116 Chapter 2: Pediatric Brain</p><p>FINDINGS:</p><p>Axial contrast-enhanced T1-weighted MR shows a left cerebellar cystic lesion with</p><p>enhancing mural nodule (arrow).</p><p>DIFFERENTIAL DIAGNOSIS:</p><p>• Juvenile pilocytic astrocytoma</p><p>• Pleomorphic xanthoastrocytoma</p><p>• Ganglioglioma</p><p>• Dysembryoplastic neuroepithelial tumor</p><p>DISCUSSION:</p><p>Pediatric mixed solid/cystic tumors include juvenile pilocystic astrocytoma (JPA),</p><p>ganglioglioma (GGL), pleomorphic xanthoastrocytoma (PXA), and dysem bryoplastic</p><p>neuroepithelial tumor (DNET). The enhancing “mural nodule” corresponds to</p><p>tumor, while the cystic component represents secreted fl uid. JPAs are typically</p><p>infratentorial in the posterior fossa, but when supratentorial are usually adjacent</p><p>to the third ventricle. GGL, PXA, and DNET favor the superfi cial temporal lobes.</p><p>GGLs are typically well circumscribed with a small mural nodule. Classic DNETs</p><p>are multilobulated nonenhancing masses with calvarial scalloping. PXAs tend to be</p><p>larger and produce dural tails without skull erosion.</p><p>Reference:</p><p>Koeller KK, Henry JM. From the archives of the AFIP: superfi cial gliomas: radiologic-pathologic</p><p>correlation. Armed Forces Institute of Pathology. Radiographics. 2001;21(6):1533-1556.</p><p>Modalities:</p><p>CT, MR</p><p>CYST WITH NODULE, MURAL NODULE</p><p>Dangling Choroid 117</p><p>FINDINGS:</p><p>Fetal US, axial plane, shows enlarged lateral ventricles with dependent choroid</p><p>plexi. The choroid plexus farther from the transducer is abnormally angulated and</p><p>“dangles” from its attachment at the foramen of Monro (arrow).</p><p>DIFFERENTIAL DIAGNOSIS:</p><p>• Fetal ventriculomegaly</p><p>• Fetal hydrocephalus</p><p>DISCUSSION:</p><p>Fetal ventriculomegaly is defi ned as enlargement of the lateral ventricles, with</p><p>atrial diameter greater than 10 mm or choroid plexus-ventricular wall separation</p><p>greater than 3 to 4 mm. Normally, the choroid plexi course parallel to the ventricles</p><p>and contact both ventricular walls. In severe ventriculomegaly or hydrocephalus</p><p>(>15 mm), the choroid angles increase and the free-hanging choroid “dangles” from</p><p>its attachment at the foramen of Monro.</p><p>References:</p><p>Cardoza JD, Filly RA, Podrasky AE. The dangling choroid plexus: a sonographic observation of value</p><p>in excluding ventriculomegaly. AJR Am J Roentgenol. 1988;151(4):767-770.</p><p>Nyberg DA, McGahan JP, Pretorius DH, et al. Diagnostic Imaging of Fetal Anomalies. 2nd ed.</p><p>Philadelphia: Lippincott Williams & Wilkins; 2002.</p><p>Modalities:</p><p>US, MR</p><p>DANGLING CHOROID</p><p>118 Chapter 2: Pediatric Brain</p><p>FINDINGS:</p><p>Axial CT shows prominent hypo densities in the cerebellar hemispheres, left greater</p><p>than right. Involvement of both gray and white matter indicates cytotoxic edema.</p><p>DIAGNOSIS:</p><p>Cerebellar infarcts</p><p>DISCUSSION:</p><p>Diffuse hypodensity of the cerebellum on CT (“dark cerebellum”) is a rare fi nding</p><p>that raises concern for ischemia, particularly when both gray and white matter are</p><p>involved. Isolated cerebellar infarction is occasionally seen in premature neonates, or</p><p>in children and adolescents following an overdose of tricyclic antidepressants (TCA).</p><p>In the acute setting, MR can be ordered to confi rm the presence of reduced diffusion.</p><p>Reference:</p><p>Huisman TA, Kubat SH, Eckhardt BP. The “dark cerebellar sign.” Neuropediatrics. 2007;38(3):160-163.</p><p>Modality:</p><p>CT</p><p>DARK CEREBELLUM</p><p>Diamond, Keyhole, Trapezoid 119</p><p>Modalities:</p><p>US, CT, MR</p><p>DIAMOND, KEYHOLE, TRAPEZOID</p><p>FINDINGS:</p><p>• Axial CT shows a gaping posterior fossa with diamond-shaped CSF space</p><p>(asterisk).</p><p>• Axial T2-weighted MR shows a dilated fourth ventricle communicating (arrows)</p><p>with an enlarged cisterna magna.</p><p>DIFFERENTIAL DIAGNOSIS:</p><p>• Dandy-Walker complex</p><p>• Rhombencephalosynapsis</p><p>• Communicating hydrocephalus</p><p>• Arachnoid cyst</p><p>DISCUSSION:</p><p>Dandy-Walker complex represents a continuum of posterior fossa anomalies, which</p><p>from most to least severe are Dandy-Walker malformation, Dandy-Walker variant,</p><p>and mega cisterna magna. The posterior fossa is small with varying degrees of</p><p>vermian hypoplasia, torcular-lambdoid inversion (torcular herophili elevated above</p><p>the lambdoid suture), and cisterna magna enlargement. There is dilation of the</p><p>fourth ventricle, which communicates with the cisterna magna through a CSF space</p><p>between the cerebellar hemispheres, creating a “keyhole” or “diamond” appearance.</p><p>Rhombencephalosynapsis is a severe malformation that involves vermian hypo-</p><p>plasia, dorsal fusion of the cerebellar hemispheres, and apposition or fusion of</p><p>the dentate nuclei and cerebellar peduncles. Other mimics include communicating</p><p>hydrocephalus, posterior fossa arachnoid cyst, and the normal rhombencephalic</p><p>cavity before 18 weeks of gestational age.</p><p>Reference:</p><p>Wolfson BJ, Faerber EN, Truex RC Jr. The “keyhole”: a sign of herniation of a trapped fourth ventricle</p><p>and other posterior fossa cysts. AJNR Am J Neuroradiol. 1987;8(3):473-477.</p><p>120 Chapter 2: Pediatric Brain</p><p>Modalities:</p><p>CT, MR</p><p>DIAMOND, STAR</p><p>FINDINGS:</p><p>Axial T2-weighted MR of different</p><p>patients show diamond- (thick arrows) and</p><p>star-shaped (thin arrows) basilar cisterns. Also seen are wide incisurae, superior</p><p>herniation of the cerebellum, and interdigitation of occipital gyri.</p><p>DIAGNOSIS:</p><p>Chiari II malformation</p><p>DISCUSSION:</p><p>The Chiari II malformation is a complex congenital anomaly consisting of small</p><p>posterior fossa and lumbosacral myelomeningocele. The basilar cisterns assume</p><p>a “diamond”- or “star”-shaped morphology formed by the cistern of velum</p><p>interpositum, superior vermian cistern, and ambient cisterns. Other characteristic</p><p>imaging signs of Chiari II malformation include beaked tectum, cervicomedullary</p><p>kink, wide incisura with towering cerebellum, and fenestrated falx with</p><p>interdigitating gyri. In the Chiari III malformation, there is also an occipital or</p><p>high cervical encephalocele.</p><p>Reference:</p><p>Naidich TP, Pudlowski RM, Naidich JB. Computed tomographic signs of the Chiari II malformation,</p><p>III: ventricles and cisterns. Radiology. 1980;134(3):657-663.</p><p>Dimple, Nipple 121</p><p>FINDINGS:</p><p>Axial T2-weighted MR shows a</p><p>right perirolandic transcortical</p><p>defect lined by dysmorphic gray</p><p>matter, with a thin intervening</p><p>CSF cleft. There is associated</p><p>contour irregularity of the lateral</p><p>ventricle (arrow).</p><p>DIAGNOSIS:</p><p>Schizencephaly</p><p>DISCUSSION:</p><p>Schizencephaly is caused by</p><p>a full-thickness insult to the</p><p>cerebral cortex during cortical</p><p>organization, producing a gray</p><p>matter-lined cleft that extends</p><p>from the ventricular system to</p><p>the subarachnoid space. Clefts</p><p>may be small or large, unilateral or bilateral, and classifi ed as type I (closed-lip)</p><p>or type II (open-lip). In closed-lip schizencephaly, the lips are in contact with</p><p>each other; in open-lip schizencephaly, the lips are separated by intervening CSF.</p><p>The pia mater and ependyma meet within the cleft to form the pial-ependymal</p><p>seam, which is visible as a “dimple” along the superfi cial wall of the ventricle.</p><p>The gray matter lining the cleft is frequently polymicrogyric (multiple tiny gyri)</p><p>and can extend into the ventricle, forming subependymal gray matter heterotopia.</p><p>Schizencephaly should not be confused with porencephaly, in which an acquired</p><p>insult results in a white matter-lined cavity adjacent to the ventricular system and/</p><p>or subarachnoid space.</p><p>References:</p><p>Abdel Razek AA, Kandell AY, Elsorogy LG, et al. Disorders of cortical formation: MR imaging</p><p>features. AJNR Am J Neuroradiol. 2009;30(1):4-11.</p><p>Barkovich AJ, Norman D. MR imaging of schizencephaly. AJR Am J Roentgenol. 1988;150(6):</p><p>1391-1396.</p><p>Modalities:</p><p>US, CT, MR</p><p>DIMPLE, NIPPLE</p><p>122 Chapter 2: Pediatric Brain</p><p>FINDINGS:</p><p>Axial FLAIR MR shows cortical undersulcation and a continuous band of heterotopic</p><p>gray matter (arrows) that is separated from the cortex by intervening white matter.</p><p>DIAGNOSIS:</p><p>Band heterotopia</p><p>DISCUSSION:</p><p>Gray matter heterotopia is caused by abnormal neuronal migration, and can occur</p><p>anywhere between the subependymal region and cerebral cortex. The major types</p><p>are band, subcortical, and periventricular (sub ependymal). Band heterotopia is</p><p>associated with type I lissencephaly. Females are predominantly affected, with an</p><p>X-linked dominant pattern of inheritance. At imaging, symmetric bands of gray</p><p>matter are seen coursing parallel to the cortex (“double cortex”), with an intervening</p><p>layer of white matter (“three layer cake”). Bands may be partial, complete, or even</p><p>duplicated. The overlying cortex can be normal or pachygyric.</p><p>References:</p><p>Abdel Razek AA, Kandell AY, Elsorogy LG, et al. Disorders of cortical formation: MR imaging</p><p>features. AJNR Am J Neuroradiol. 2009;30(1):4-11.</p><p>Franzoni E, Bernardi B, Marchiani V, et al. Band brain heterotopia. Case report and literature review.</p><p>Neuropediatrics. 1995;26(1):37-40.</p><p>Modalities:</p><p>CT, MR</p><p>DOUBLE CORTEX, THREE LAYER CAKE</p><p>Enlarged Massa Intermedia 123</p><p>Modalities:</p><p>CT, MR</p><p>ENLARGED MASSA INTERMEDIA</p><p>FINDINGS:</p><p>• Sagittal T1-weighted MR shows an enlarged massa intermedia (asterisk),</p><p>hypoplastic posterior fossa with tonsillar descent, and callosal dysgenesis.</p><p>• Axial T2-weighted MR again shows the prominent massa intermedia (arrows).</p><p>DIAGNOSIS:</p><p>Chiari II malformation</p><p>DISCUSSION:</p><p>The Chiari II malformation is a complex congenital anomaly consisting of small</p><p>posterior fossa, inferior displacement of the cerebellum and brainstem, and</p><p>lumbosacral myelomeningocele. Thickening of the massa intermedia (interthalamic</p><p>adhesion) is a classic fi nding. Other characteristic imaging signs of Chiari II</p><p>malformation include beaked tectum, cervicomedullary kink, wide incisura with</p><p>towering cerebellum, and fenestrated falx with interdigitating gyri. In the Chiari III</p><p>malformation, there is also an occipital or high cervical encephalocele.</p><p>References:</p><p>Geerdink N, van der Vliet T, Rotteveel JJ, et al. Essential features of Chiari II malformation in</p><p>MR imaging: an interobserver reliability study—part 1. Childs Nerv Syst. 2012;28(7):977-985.</p><p>Naidich TP, Pudlowski RM, Naidich JB. Computed tomographic signs of Chiari II malformation,</p><p>II: midbrain and cerebellum. Radiology. 1980;134(2):391-398.</p><p>124 Chapter 2: Pediatric Brain</p><p>FINDINGS:</p><p>Axial T2-weighted MR shows absent falx cerebri, with gyri interdigitating across</p><p>the midline (arrows).</p><p>DIAGNOSIS:</p><p>Chiari II malformation</p><p>DISCUSSION:</p><p>The Chiari II malformation is a complex congenital anomaly consisting of small</p><p>posterior fossa, inferior displacement of the cerebellum and brainstem, and</p><p>lumbosacral myelomeningocele. Midline anomalies are common, including partial</p><p>absence of the falx cerebri (“fenestrated falx”) with the cerebral gyri extending across</p><p>the midline (“interdigitating gyri”). There may be associated stenogyria (packed</p><p>shallow gyri and sulci with normal cortical organization). Other characteristic</p><p>imaging signs of Chiari II malformation include beaked tectum, cervicomedullary</p><p>kink, and wide incisura with towering cerebellum. In the Chiari III malformation,</p><p>there is also an occipital or high cervical encephalocele.</p><p>References:</p><p>Geerdink N, van der Vliet T, Rotteveel JJ, et al. Essential features of Chiari II malformation in</p><p>MR imaging: an interobserver reliability study—part 1. Childs Nerv Syst. 2012;28(7):977-985.</p><p>Naidich TP, Pudlowski RM, Naidich JB, et al. Computed tomographic signs of the Chiari II</p><p>malformation. Part I: skull and dural partitions. Radiology. 1980;134(1):65-71.</p><p>Modalities:</p><p>US, CT, MR</p><p>FENESTRATED FALX, INTERDIGITATING/INTERLOCKING GYRI</p><p>Figure Eight, Hourglass, Oval 125</p><p>Modalities:</p><p>US, CT, MR</p><p>FIGURE EIGHT, HOURGLASS, OVAL</p><p>FINDINGS:</p><p>Axial CT and T2-weighted MR show poorly developed gyri with shallow sylvian</p><p>fi ssures (arrows). The cerebral cortex is diffusely smooth and thickened.</p><p>DIAGNOSIS:</p><p>Lissencephaly, type I</p><p>DISCUSSION:</p><p>Congenital brain malformations with incomplete cortical sulcation include agyria (no</p><p>gyri), pachygyria (broad gyri), and lissencephaly (underdeveloped gyri). Lissencephaly</p><p>can be divided into type I (classic) and type II (cobblestone) types. Type I lissencephaly</p><p>results from neuronal undermigration during development, with formation of four</p><p>cortical layers rather than the normal six. At imaging, there is a diffusely thickened cortex</p><p>(>3 mm) with poorly formed gyri, shallow sylvian fi ssures, and a smooth outer surface</p><p>(“fi gure 8” or “hourglass” appearance). Subcortical band heterotopia is frequently</p><p>associated. The anomaly can be isolated or seen as part of the Miller-Dieker syndrome</p><p>with associated cardiac, pulmonary, gastrointestinal, genitourinary, and musculoskeletal</p><p>anomalies. Type I lissencephaly should not be confused with polymicrogyria, in which</p><p>multiple tiny gyri are present; or with the normal fetal brain between 18 and 22 weeks,</p><p>when the primary fi ssures begin to develop.</p><p>References:</p><p>Abdel Razek AA, Kandell AY, Elsorogy LG, et al. Disorders of cortical formation: MR imaging</p><p>features. AJNR Am J Neuroradiol. 2009;30(1):4-11.</p><p>Ghai S, Fong KW, Toi A, et al. Prenatal US and MR imaging fi ndings of lissencephaly:</p><p>review of fetal</p><p>cerebral sulcal development. Radiographics. 2006;26(2):389-405.</p><p>126 Chapter 2: Pediatric Brain</p><p>Modalities:</p><p>CT, MR</p><p>FIGURE EIGHT, MENISCUS</p><p>FINDINGS:</p><p>• Axial T2-weighted MR shows crowding of the foramen magnum with the inferior</p><p>vermis (thin arrows) immediately dorsal to the medulla.</p><p>• Axial T2-weighted MR at a lower level shows a thin rim of CSF (thick arrow)</p><p>surrounding the cervical cord.</p><p>DIFFERENTIAL DIAGNOSIS:</p><p>• Tonsillar ectopia</p><p>• Tonsillar herniation</p><p>• Chiari malformation</p><p>DISCUSSION:</p><p>Inferior displacement of the cerebellar tonsils through the foramen magnum can be</p><p>seen as a normal variant, secondary to increased intracranial pressure, or as part</p><p>of a Chiari malformation. Crowding of the spinal cord and cerebellum within the</p><p>foramen magnum partially obliterates the CSF space, and in severe cases can lead</p><p>to CSF fl ow obstruction with syringohydromyelia. The “fi gure 8” appearance is</p><p>created by the abnormal juxtaposition of the medulla and inferior vermis, as well as</p><p>the cervical cord and cerebellar tonsils. The “meniscus” sign refers to the thin rim of</p><p>CSF surrounding the brainstem and cervical cord.</p><p>Reference:</p><p>Naidich TP, McLone DG, Fulling KH. The Chiari II malformation: Part IV. The hindbrain deformity.</p><p>Neuroradiology. 1983;25(4):179-197.</p><p>Flat Floor of Fourth Ventricle 127</p><p>FINDINGS:</p><p>Axial T2-weighted MR shows a hyperintense pontine mass with effacement of the</p><p>fl oor of the fourth ventricle (arrows). There is a left ventral exophytic component</p><p>that partially encases the basilar artery.</p><p>DIFFERENTIAL DIAGNOSIS:</p><p>• Brainstem glioma</p><p>• Rhombencephalitis</p><p>DISCUSSION:</p><p>The fl oor (ventral surface) of the fourth ventricle normally slopes up toward</p><p>midline, with indentations from the facial colliculi on each side. A fl attened fl oor</p><p>indicates pontine edema and/or mass effect, which can be seen in primary/metastatic</p><p>tumors or infection (rhombencephalitis); and rarely in central pontine myelinolysis,</p><p>demyelinating disease, and infarction. Brainstem gliomas are infi ltrative, expansile</p><p>primary tumors that can be focal or diffuse, and are most commonly centered in</p><p>the pons. There is an association with neurofi bromatosis type I (NF1). Lesions</p><p>have hypodense CT attenuation and hyperintense signal on T2-weighted MR.</p><p>Enhancement and reduced diffusion are rare, but indicate higher-grade tumor with a</p><p>worse prognosis. Encasement of the basilar artery and compression of surrounding</p><p>structures are highly specifi c imaging fi ndings for neoplasia. Rhombencephalitis</p><p>demonstrates signal abnormality with enhancement and/or reduced diffusion, and</p><p>may extend to involve noncontiguous structures.</p><p>References:</p><p>Donaldson SS, Laningham F, Fisher PG. Advances toward an understanding of brainstem gliomas.</p><p>J Clin Oncol. 2006;24(8):1266-1272.</p><p>Ueoka DI, Nogueira J, Campos JC, et al. Brainstem gliomas—retrospective analysis of 86 patients.</p><p>J Neurol Sci. 2009;281(1-2):20-23.</p><p>Modalities:</p><p>CT, MR</p><p>FLAT FLOOR OF FOURTH VENTRICLE</p><p>128 Chapter 2: Pediatric Brain</p><p>FINDINGS:</p><p>Fetal US, coronal plane, reveals bulging orbits and absence of supraorbital tissues.</p><p>DIAGNOSIS:</p><p>Anencephaly</p><p>DISCUSSION:</p><p>Anencephaly is the most severe neural tube defect, with absence of normal cortical</p><p>tissue and calvarium above the level of the orbits. There may be a small amount</p><p>of supraorbital angiomatous stroma or residual vascularized tissue. The orbits</p><p>are prominent, and the facial features are preserved (“frog face”). The skull base,</p><p>brainstem, and cerebellum are variably formed. Anencephaly is thought to represent</p><p>the fi nal stage of the acrania-exencephaly-anencephaly sequence. In acrania, there is</p><p>absence of the calvarium but normally formed cerebral hemispheres and meninges.</p><p>Without overlying bone, the brain and meninges are continually exposed to amniotic</p><p>fl uid and progressively disintegrate. Exencephaly refers to the stage in which some</p><p>residual brain is present and the cerebral hemispheres can still be identifi ed. Once</p><p>the brain has completely degraded, the defect is termed anencephaly. This diagnosis</p><p>should be made only after 14 weeks of gestation, once the skull has ossifi ed.</p><p>Anencephaly must be distinguished from amniotic band syndrome, in which the</p><p>head and other structures are entrapped and lacerated by crossing fi brous bands.</p><p>References:</p><p>Goldstein RB, Filly RA. Prenatal diagnosis of anencephaly: spectrum of sonographic appearances and</p><p>distinction from the amniotic band syndrome. AJR Am J Roentgenol. 1988;151(3):547-550.</p><p>Hidalgo H, Bowie J, Rosenberg ER, et al. Review. In utero sonographic diagnosis of fetal cerebral</p><p>anomalies. AJR Am J Roentgenol. 1982;139(1):143-148.</p><p>Modalities:</p><p>US, MR</p><p>FROG</p><p>Fused Thalami 129</p><p>FINDINGS:</p><p>Axial CT shows partial fusion of midline structures including thalami (arrows), with</p><p>dilated lateral ventricles.</p><p>DIAGNOSIS:</p><p>Holoprosencephaly</p><p>DISCUSSION:</p><p>Holoprosencephaly refers to a spectrum of congenital malformations in which</p><p>the embryonic forebrain (prosencephalon) fails to separate completely. Based on</p><p>the degree of midline fusion, these are classifi ed as alobar, semilobar, lobar, and</p><p>middle interhemispheric variant (syntelencephaly). The alobar variant is the most</p><p>severe with holospheric cortical fusion; absent corpus callosum, septum pellucidum,</p><p>and falx cerebri; single monoventricle; and fusion of the basal ganglia and thalami.</p><p>Semilobar and middle interhemispheric variants are less severe and exhibit variable</p><p>degrees of thalamic fusion. Lobar holoprosencephaly is the mildest form, in which</p><p>the anterior corpus callosum and falx are hypoplastic, and the thalami are usually</p><p>fully separate. Holoprosencephaly should be distinguished from hydranencephaly</p><p>caused by bilateral ICA occlusion in utero. In this condition, diffuse cortical</p><p>destruction is present, but the posterior fossa and thalami are normal.</p><p>Reference:</p><p>Hahn JS, Barnes PD. Neuroimaging advances in holoprosencephaly: Refi ning the spectrum of the</p><p>midline malformation. Am J Med Genet C Semin Med Genet. 2010;154C(1):120-132.</p><p>Modalities:</p><p>US, CT, MR</p><p>FUSED THALAMI</p><p>130 Chapter 2: Pediatric Brain</p><p>Modalities:</p><p>CT, MR</p><p>GAPING/HEART/WIDE INCISURA</p><p>FINDINGS:</p><p>Axial and coronal T2-weighted MR show a hypoplastic tentorium with wide incisura</p><p>(arrows), through which the cerebellum herniates superiorly.</p><p>DIAGNOSIS:</p><p>Chiari II malformation</p><p>DISCUSSION:</p><p>The Chiari II malformation is a complex congenital anomaly consisting of small</p><p>posterior fossa and lumbosacral myelomeningocele. Hypoplasia of the tentorium</p><p>results in a wide “heart”-shaped incisura, through which the cerebellum can</p><p>herniate superiorly and laterally around the brainstem. Other characteristic imaging</p><p>signs of Chiari II malformation include beaked tectum, cervicomedullary kink, and</p><p>fenestrated falx with interdigitating gyri. In the Chiari III malformation, there is also</p><p>an occipital or high cervical encephalocele.</p><p>References:</p><p>Geerdink N, van der Vliet T, Rotteveel JJ, et al. Essential features of Chiari II malformation in MR</p><p>imaging: an interobserver reliability study—part 1. Childs Nerv Syst. 2012;28(7):977-985.</p><p>Naidich TP, Pudlowski RM, Naidich JB, et al. Computed tomographic signs of the Chiari II</p><p>malformation, part I: skull and dural partitions. Radiology. 1980;134(1):65-71.</p><p>Hourglass, Shark Tooth 131</p><p>Modalities:</p><p>CT, MR</p><p>HOURGLASS, SHARK TOOTH</p><p>FINDINGS:</p><p>• Axial T2-weighted MR shows mild ventriculomegaly with an enlarged massa</p><p>intermedia (thick arrows) that causes waisting of the third ventricle. There is also</p><p>a wide incisura and superior herniation of the cerebellum (thin arrows).</p><p>• Axial T2-weighted MR in a different patient shows a triangular third ventricle</p><p>(arrow) with pointed dorsal tip. There is also a wide incisura, superior herniation</p><p>of the cerebellum, and interdigitating occipital gyri.</p><p>DIAGNOSIS:</p><p>Chiari II malformation</p><p>DISCUSSION:</p><p>The Chiari II malformation is a complex congenital anomaly consisting of small</p><p>posterior fossa and lumbosacral myelomeningocele.</p><p>Because of mass effect from an</p><p>enlarged massa intermedia (interthalamic adhesion), the third ventricle can assume</p><p>an “hourglass” or “shark tooth” appearance. Other characteristic imaging signs</p><p>of Chiari II malformation include beaked tectum, cervicomedullary kink, wide</p><p>incisura with towering cerebellum, and fenestrated falx with interdigitating gyri. In</p><p>the Chiari III malformation, there is also an occipital or high cervical encephalocele.</p><p>Reference:</p><p>Naidich TP, Pudlowski RM, Naidich JB. Computed tomographic signs of the Chiari II malformation,</p><p>III: ventricles and cisterns. Radiology. 1980;134(3):657-663.</p><p>132 Chapter 2: Pediatric Brain</p><p>FINDINGS:</p><p>Axial T2-weighted MR shows an encapsulated midline cyst (asterisk) between the</p><p>cerebral hemispheres and spanning the septum pellucidum.</p><p>DIFFERENTIAL DIAGNOSIS:</p><p>• Callosal dysgenesis</p><p>• Arachnoid cyst</p><p>• Normal variants</p><p>DISCUSSION:</p><p>Interhemispheric cysts are focal fl uid collections that are located in the</p><p>interhemispheric fi ssure and may communicate with the ventricular system. There</p><p>is a strong association with callosal dysgenesis, in which the third ventricle is high-</p><p>riding and forms a cyst at the level of the absent corpus callosum. Other congenital</p><p>brain malformations, including Chiari II, Dandy-Walker, holoprosencephaly,</p><p>and heterotopias, may also develop midline cysts. If there are no accompanying</p><p>anatomic abnormalities, differential considerations include isolated arachnoid</p><p>cyst and normal variants of midline structures (cavum septum pellucidum, cavum</p><p>vergae, cavum velum interpositum).</p><p>References:</p><p>Epelman M, Daneman A, Blaser SI, et al. Differential diagnosis of intracranial cystic lesions at head</p><p>US: correlation with CT and MR imaging. Radiographics. 2006;26(1):173-196.</p><p>Spennato P, Ruggiero C, Aliberti F, et al. Interhemispheric and quadrigeminal cysts. World Neurosurg.</p><p>2012;79(2 Suppl):S20.e1-e7.</p><p>Modalities:</p><p>US, CT, MR</p><p>INTERHEMISPHERIC CYST</p><p>Keyhole 133</p><p>Modalities:</p><p>US, CT, MR</p><p>KEYHOLE</p><p>FINDINGS:</p><p>Axial and coronal T2-weighted MR show enlarged and curved temporal horns</p><p>(arrows), with hypoplastic and vertically oriented hippocampi.</p><p>DIAGNOSIS:</p><p>Hippocampal hypoplasia</p><p>DISCUSSION:</p><p>The hippocampal neocortex is located along the lateral temporal lobe and grows more</p><p>rapidly than the allocortex during development, resulting in medial displacement</p><p>and inversion into the temporal horns. Hippocampal hypoplasia can occur with a</p><p>variety of congenital brain malformations including callosal agenesis, lissencephaly,</p><p>schizencephaly, polymicrogyria, holoprosencephaly, and heterotopia. Failure of</p><p>hippocampal infolding produces vertically oriented and “globular” perihippocampal</p><p>fi ssures, as well as a dilated “keyhole” appearance of the temporal horns.</p><p>Reference:</p><p>Sato N, Hatakeyama S, Shimizu N, et al. MR evaluation of the hippocampus in patients with congenital</p><p>malformations of the brain. AJNR Am J Neuroradiol. 2001;22(2):389-393.</p><p>134 Chapter 2: Pediatric Brain</p><p>Modality:</p><p>MR</p><p>LACK OF CENTRAL RED DOT</p><p>FINDINGS:</p><p>Axial DTI MR of Joubert syndrome versus normal patient. In Joubert syndrome,</p><p>there is no central red dot at the level of the superior cerebellar peduncles (thick</p><p>arrow) or transverse pontine fi bers (thin arrow) in the middle cerebellar peduncles.</p><p>DIAGNOSIS:</p><p>Joubert syndrome-related disorders</p><p>DISCUSSION:</p><p>Joubert syndrome–related disorders (JSRD), or cerebello-oculo-renal disorders, are</p><p>autosomal recessive disruptions of midbrain-hindbrain development with associated</p><p>ocular, facial, hepatic, renal, and digital anomalies. Diffusion tensor imaging is an</p><p>MR technique that measures the directional diffusion of water molecules in three</p><p>dimensions. This can be used to map white matter fi ber tracts using a variety of</p><p>algorithms. DTI maps are color-coded according to the principal eigenvector</p><p>(red, left to right; blue, cranial to caudal; green, anterior to posterior). In Joubert</p><p>syndrome, there is lack of decussation of the pyramidal tracts within the superior</p><p>cerebellar peduncles. Instead, the superior cerebellar peduncles become elongated</p><p>and thickened, with a parallel orientation forming the roots of the “molar tooth.”</p><p>The transverse pontine fi bers in the middle cerebellar peduncles also fail to decussate.</p><p>This leads to “absence of the focal red dot” in the midbrain and pons, as compared</p><p>to normal patients.</p><p>References:</p><p>Brancati F, Dallapiccola B, Valente EM. Joubert syndrome and related disorders. Orphanet J Rare Dis.</p><p>2010;5:20.</p><p>Poretti A, Boltshauser E, Loenneker T, et al. Diffusion tensor imaging in Joubert syndrome. AJNR Am</p><p>J Neuroradiol. 2007;28(10):1929-1933.</p><p>Leopard Skin, Stripe, Tigroid 135</p><p>Modality:</p><p>MR</p><p>LEOPARD SKIN, STRIPE, TIGROID</p><p>FINDINGS:</p><p>Axial T2-weighted MR shows widespread periventricular white matter hyperintensity,</p><p>with internal linear radiating hypointensities.</p><p>DIFFERENTIAL DIAGNOSIS:</p><p>• Metachromatic leukodystrophy</p><p>• Pelizaeus-Merzbacher disease</p><p>DISCUSSION:</p><p>Metachromatic leukodystrophy (MLD), the most common hereditary</p><p>leukodystrophy, is an autosomal recessive disorder caused by arylsulfatase A</p><p>defi ciency. Accumulation of sulfatides in multiple organ systems impairs myelination.</p><p>This initially involves the periventricular white matter, with sparing of the</p><p>subcortical U (arcuate) fi bers and perivascular spaces. On T2-weighted MR, multiple</p><p>hypointense lines within diffusely hyperintense white matter produces a “leopard</p><p>skin” appearance. Other dysmyelinating diseases with a similar appearance include</p><p>Pelizaeus-Merzbacher disease, Alexander disease, and other lysosomal storage</p><p>disorders. Pelizaeus-Merzbacher disease (PMD) is a rare X-linked leukodystrophy</p><p>caused by proteolipidprotein (PLP1) mutations, with arrested myelin development</p><p>that involves the subcortical U fi bers. Disease distribution may be diffuse or patchy</p><p>with perivascular sparing.</p><p>References:</p><p>Cheon JE, Kim IO, Hwang YS, et al. Leukodystrophy in children: a pictorial review of MR imaging</p><p>features. Radiographics. 2002;22(3):461-476.</p><p>Kim TS, Kim IO, Kim WS, et al. MR of childhood metachromatic leukodystrophy. AJNR Am J</p><p>Neuroradiol. 1997;18(4):733-738.</p><p>136 Chapter 2: Pediatric Brain</p><p>FINDINGS:</p><p>Axial T2-weighted MR shows</p><p>linear hyperintensity radiating</p><p>from the right atrium to</p><p>parietal cortex (arrows).</p><p>Multiple subcortical tubers</p><p>and subependymal nodules</p><p>are also present.</p><p>DIFFERENTIAL DIAGNOSIS:</p><p>• Tuberous sclerosis</p><p>• Other migrational</p><p>abnormalities</p><p>DISCUSSION:</p><p>Tuberous sclerosis complex</p><p>(TSC) is a phakomatosis or</p><p>neuroectodermal syndrome</p><p>characterized by dysplasias</p><p>and hamartomas of the brain,</p><p>retinae, skin, heart, lungs, kidneys, and bones. Neuroimaging manifestations include</p><p>cortical/subcortical hamartomas, white matter abnormalities, and subependymal</p><p>nodules or giant cell astrocytomas (SEGAs). Radial bands are straight or curvilinear</p><p>areas of abnormal white matter signal. These are usually seen supratentorially,</p><p>radiating from the periventricular to subcortical regions; but can occasionally be</p><p>present in the cerebellum. Histologically, these correspond to heterotopic clusters of</p><p>cells along the glial-neuronal migration unit. In infants younger than 3 months, MR</p><p>signal is T1-hyperintense and T2-hypointense. As myelination progresses with age,</p><p>bands become T2-hyperintense with variable T1 signal. Radial bands can be seen</p><p>in association with cortical tubers and other migrational abnormalities, including</p><p>cortical dysplasia.</p><p>References:</p><p>Abdel Razek AA, Kandell AY, Elsorogy LG, et al. Disorders of cortical formation: MR imaging</p><p>features. AJNR Am J Neuroradiol. 2009;30(1):4-11.</p><p>Bernauer TA. The radial bands sign. Radiology. 1999;212(3):761-762.</p><p>Modalities:</p><p>CT, MR</p><p>LINEAR, MIGRATION TRACTS, RADIAL BANDS</p><p>Mickey Mouse 137</p><p>FINDINGS:</p><p>Fetal US, coronal plane, reveals absent cranium above the level of the orbits. The</p><p>cerebral hemispheres (arrows) fl oat freely in the amniotic fl uid.</p><p>DIAGNOSIS:</p><p>Exencephaly</p><p>DISCUSSION:</p><p>Exencephaly is a lethal neural</p><p>tube defect characterized by a poorly formed cranial</p><p>vault. Some brain tissue is present, but it is not covered by meninges or bone. The</p><p>cerebral hemispheres project from the head (“Mickey Mouse” sign), fl oat freely in the</p><p>amniotic fl uid, and may attach to the amniotic membrane. Exencephaly is thought</p><p>to represent the middle stage of the acrania-exencephaly-anencephaly sequence. In</p><p>acrania, there is absence of the calvarium, but normally formed cerebral hemispheres</p><p>and meninges. Without overlying bone, the brain and meninges are continually</p><p>exposed to amniotic fl uid and progressively disintegrate. Exencephaly refers to the</p><p>stage in which some residual brain is present, and the cerebral hemispheres can still be</p><p>identifi ed. Once the brain has completely degraded, the defect is termed anencephaly.</p><p>This diagnosis should be made only after 14 weeks of gestation, once the skull has</p><p>ossifi ed. Anencephaly must be distinguished from amniotic band syndrome, in which</p><p>the head and other structures are entrapped and lacerated by crossing fi brous bands.</p><p>References:</p><p>Goldstein RB, Filly RA. Prenatal diagnosis of anencephaly: spectrum of sonographic appearances and</p><p>distinction from the amniotic band syndrome. AJR Am J Roentgenol. 1988;151(3):547-550.</p><p>Hidalgo H, Bowie J, Rosenberg ER, et al. Review. In utero sonographic diagnosis of fetal cerebral</p><p>anomalies. AJR Am J Roentgenol. 1982;139(1):143-148.</p><p>Modalities:</p><p>US, MR</p><p>MICKEY MOUSE</p><p>138 Chapter 2: Pediatric Brain</p><p>FINDINGS:</p><p>Axial T2-weighted MR shows a deep interpeduncular fossa (thick arrow), thin</p><p>midbrain isthmus, and parallel enlarged superior cerebellar peduncles (thin arrows).</p><p>There is also vermian hypoplasia and enlarged cisterna magna.</p><p>DIAGNOSIS:</p><p>Joubert syndrome–related disorders</p><p>DISCUSSION:</p><p>Joubert syndrome–related disorders (JSRD), or cerebello-oculo-renal disor ders, are</p><p>autosomal recessive disruptions of midbrain-hindbrain development with associated</p><p>ocular, facial, hepatic, renal, and digital anomalies. Lack of decussation of the</p><p>superior cerebellar peduncles across the midline results in thinning of the midbrain</p><p>isthmus and deepening of the interpeduncular fossa (“crown” of the molar tooth).</p><p>The nondecussating pyramidal tracts run parallel to each other within the superior</p><p>cerebellar peduncles, which have a thickened and horizontal orientation (“root”</p><p>of the molar tooth). Other imaging signs of JSRD include “bullet” third ventricle,</p><p>“bat-wing” fourth ventricle, and vermian hypoplasia.</p><p>References:</p><p>Brancati F, Dallapiccola B, Valente EM. Joubert syndrome and related disorders. Orphanet J Rare Dis.</p><p>2010;5:20.</p><p>McGraw P. The molar tooth sign. Radiology. 2003;229(3):671-672.</p><p>MOLAR TOOTH</p><p>Modalities:</p><p>US, CT, MR</p><p>Mushroom 139</p><p>FINDINGS:</p><p>Coronal T2-weighted MR shows enlargement of deep sulci with sparing of surface</p><p>gyri, particularly in the parasagittal cortex. There is abnormal hyperintense signal</p><p>throughout the subcortical white matter.</p><p>DIAGNOSIS:</p><p>Ulegyria</p><p>DISCUSSION:</p><p>Ulegyria refers to cortical injury with preferential atrophy of the deep cortical layers</p><p>(cortical laminar necrosis). The usual etiology is mild hypoxic-ischemic injury in full-</p><p>term infants, preferentially affecting the parasagittal watershed areas. This results</p><p>in atrophy of the deep sulci with sparing of surface gyri, creating a “mushroom”</p><p>appearance. Associated subcortical white matter signal abnormalities are common.</p><p>Clinical presentation includes mental retardation, cerebral palsy, and epilepsy.</p><p>References:</p><p>Nikas I, Dermentzoglou V, Theofanopoulou M, et al. Parasagittal lesions and ulegyria in hypoxic-</p><p>ischemic encephalopathy: neuroimaging fi ndings and review of the pathogenesis. J Child Neurol.</p><p>2008;23(1):51-58.</p><p>Villani F, D’Incerti L, Granata T, et al. Epileptic and imaging fi ndings in perinatal hypoxic-ischemic</p><p>encephalopathy with ulegyria. Epilepsy Res. 2003;55(3):235-243.</p><p>Modalities:</p><p>US, CT, MR</p><p>MUSHROOM</p><p>140 Chapter 2: Pediatric Brain</p><p>Modalities:</p><p>US, CT, MR</p><p>NODULAR, PEARLS ON A STRING</p><p>FINDINGS:</p><p>Axial T2-weighted MR in two different patients show multiple heterotopic</p><p>nodules of gray matter in the deep periventricular white matter (thick arrows) and</p><p>subependymal lateral ventricles (thin arrows).</p><p>DIFFERENTIAL DIAGNOSIS:</p><p>• Gray matter heterotopia</p><p>• Tuberous sclerosis</p><p>DISCUSSION:</p><p>Gray matter heterotopia is caused by abnormal neuronal migration and can occur</p><p>anywhere between the subependymal region and cerebral cortex. The major types</p><p>are band, subcortical, and periventricular (subependymal). Subcortical heterotopias</p><p>are located within the subcortical or deep white matter, contiguous with the cortex or</p><p>ventricular system. Morphology tends to be curvilinear when superfi cial, and nodular</p><p>when deep. Periventricular heterotopias are located close to ventricular walls and project</p><p>into the ventricular lumen or periventricular white matter. Location is frequently along</p><p>the atria or occipital horns, and more common on the right due to later migration of</p><p>right-sided neuroblasts. Lesions appear smooth and ovoid, with signal isointense to gray</p><p>matter and absence of contrast enhancement. In tuberous sclerosis, the subependymal</p><p>nodules have a more irregular morphology (“candle guttering”), signal distinct from</p><p>gray matter, and often calcify. Primary CNS lymphoma and metastases are also</p><p>enhancing and more irregular.</p><p>Reference:</p><p>Abdel Razek AA, Kandell AY, Elsorogy LG, et al. Disorders of cortical formation: MR imaging</p><p>features. AJNR Am J Neuroradiol. 2009;30(1):4-11.</p><p>Open Lip 141</p><p>FINDINGS:</p><p>Axial T2-weighted MR shows a gaping right frontoparietal transcortical defect lined</p><p>by gray matter, with intervening CSF (asterisk).</p><p>DIAGNOSIS:</p><p>Open-lip schizencephaly</p><p>DISCUSSION:</p><p>Schizencephaly is caused by a full-thickness insult to the cerebral cortex during</p><p>cortical organization, which produces a gray matter-lined cleft that extends from the</p><p>ventricular system to the subarachnoid space. Clefts may be small or large, unilateral</p><p>or bilateral, and classifi ed as type I (closed-lip) or type II (open-lip). In closed-lip</p><p>schizencephaly, the lips are in contact with each other; in open-lip schizencephaly, the</p><p>lips are separated by intervening CSF. The gray matter lining the cleft is frequently</p><p>polymicrogyric (multiple tiny gyri) and can extend into the ventricle, forming</p><p>subependymal gray matter heterotopia. Schizencephaly should not be confused</p><p>with porencephaly, in which an acquired insult results in a white matter-lined cavity</p><p>adjacent to the ventricular system and/or subarachnoid space.</p><p>References:</p><p>Abdel Razek AA, Kandell AY, Elsorogy LG, et al. Disorders of cortical formation: MR imaging</p><p>features. AJNR Am J Neuroradiol. 2009;30(1):4-11.</p><p>Barkovich AJ, Norman D. MR imaging of schizencephaly. AJR Am J Roentgenol. 1988;150(6):</p><p>1391-1396.</p><p>Modalities:</p><p>US, CT, MR</p><p>OPEN LIP</p><p>142 Chapter 2: Pediatric Brain</p><p>FINDINGS:</p><p>Axial T2-weighted MR shows widely spaced and parallel lateral ventricles (arrows),</p><p>with pointed frontal horns and dilated occipital horns.</p><p>DIAGNOSIS:</p><p>Callosal agenesis</p><p>DISCUSSION:</p><p>Dysgenesis of the corpus callosum is caused by abnormalities in neural development</p><p>between 12 and 18 weeks of gestation. The sequence of formation is largely ventral to</p><p>dorsal, beginning with the genu and progressing through the anterior body, posterior</p><p>body, splenium, and rostrum. In callosal agenesis, there is complete absence of the</p><p>normal crossing white matter tracts. Instead, nondecussating white matter fi bers</p><p>known as Probst bundles course anteroposteriorly along the medial edges of the</p><p>lateral ventricles. The lateral ventricles assume a parallel orientation, with narrow</p><p>elongated frontal horns and dilated occipital horns (colpocephaly, “racing car”</p><p>appearance). Without crossing fi bers to displace and invert them, the cingulate gyri</p><p>remain everted and the cingulate sulcus is unformed. Other imaging signs of callosal</p><p>agenesis include high-riding third ventricle, radiating gyri, and “keyhole”</p><p>Beth Israel Deaconess Medical Center</p><p>Harvard Medical School</p><p>Boston, Massachusetts</p><p>Ajith J. Thomas, MD</p><p>Chief of Cerebrovascular Surgery</p><p>Beth Israel Deaconess Medical Center</p><p>Harvard Medical School</p><p>Boston, Massachusetts</p><p>Jesse L. Wei, MD</p><p>Director of Radiology Informatics</p><p>Instructor in Abdominal Radiology</p><p>Beth Israel Deaconess Medical Center</p><p>Harvard Medical School</p><p>Boston, Massachusetts</p><p>Carol Wilcox, RT(R), (CT)</p><p>Senior Imaging Technologist</p><p>Beth Israel Deaconess Medical Center</p><p>Harvard Medical School</p><p>Boston, Massachusetts</p><p>Donna Wolfe, MFA</p><p>Medical Editor in Radiology</p><p>Beth Israel Deaconess Medical Center</p><p>Harvard Medical School</p><p>Boston, Massachusetts</p><p>This page intentionally left blank</p><p>Abbreviations</p><p>3D = three-dimensional</p><p>ACA = anterior cerebral artery</p><p>ACOM = anterior communicating artery</p><p>ADC = apparent diffusion coeffi cient</p><p>ADH = antidiuretic hormone</p><p>AICA = anterior inferior cerebellar artery</p><p>AIDS = acquired immune defi ciency disorder</p><p>AP = anteroposterior</p><p>ASL = arterial spin labeling</p><p>AVF = arteriovenous fi stula</p><p>AVM = arteriovenous malformation</p><p>CCA = common carotid artery</p><p>CN = cranial nerve</p><p>CNS = central nervous system</p><p>CSF = cerebrospinal fl uid</p><p>CT = computed tomography</p><p>CTA = computed tomography arteriography</p><p>CTP = computed tomography perfusion</p><p>CTV = computed tomography venography</p><p>dAVF = dural arteriovenous fi stula</p><p>DTI = diffusion tensor imaging</p><p>DTPA = diethylene triamine pentaacetic acid</p><p>DVA = developmental venous anomaly</p><p>DWI = diffusion-weighted imaging</p><p>ECA = external carotid artery</p><p>ECD = ethyl cysteinate dimer</p><p>EDH = epidural hematoma</p><p>FDG = fl uorodeoxyglucose</p><p>FLAIR = fl uid-attenuated inversion recovery</p><p>Ga-67, 67Ga = gallium-67</p><p>GBM = glioblastoma multiforme</p><p>HAART = highly active antiretroviral therapy</p><p>HMPAO = hexamethyl propylene amine oxime</p><p>I-123, 123I = iodine-123</p><p>IAC = internal auditory canal</p><p>ICA = internal carotid artery</p><p>In-111, 111In = indium-111</p><p>MCA = middle cerebral artery</p><p>MIP = maximum intensity projection</p><p>MMA = middle meningeal artery</p><p>MPR = multiplanar reformat</p><p>MR = magnetic resonance</p><p>MRA = magnetic resonance arteriography</p><p>MRP = magnetic resonance perfusion</p><p>MRS = magnetic resonance spectroscopy</p><p>MRV = magnetic resonance venography</p><p>MS = multiple sclerosis</p><p>NAA = N-acetyl aspartate</p><p>NF1 = neurofi bromatosis type I</p><p>NF2 = neurofi bromatosis type II</p><p>NM = nuclear medicine</p><p>PA = posteroanterior</p><p>PCA = posterior cerebral artery</p><p>PCNSL = primary central nervous system lymphoma</p><p>PCOM = posterior communicating artery</p><p>PD = proton density</p><p>PET = positron emission tomography</p><p>PICA = posterior inferior cerebellar artery</p><p>PNET = primitive neuroectodermal tumor</p><p>SAH = subarachnoid hemorrhage</p><p>SCA = superior cerebellar artery</p><p>SDH = subdural hematoma</p><p>SPECT = single photon emission computed tomography</p><p>STA = superfi cial temporal artery</p><p>STIR = short-tau inversion recovery</p><p>SWI = susceptibility-weighted imaging</p><p>TB = tuberculosis</p><p>Tc-99m, 99mTc = metastable technetium-99</p><p>TOF = time-of-fl ight</p><p>US = ultrasonography</p><p>WHO = World Health Organization</p><p>XA = angiography</p><p>XR = radiography</p><p>xxi</p><p>Contents</p><p>1. ADULT AND GENERAL BRAIN ...........................................1</p><p>2. PEDIATRIC BRAIN ............................................................89</p><p>3. HEAD, NECK, AND ORBITS ...........................................155</p><p>4. VASCULAR .....................................................................223</p><p>5. SKULL AND FACIAL BONES ...........................................273</p><p>6. VERTEBRAE ....................................................................329</p><p>7. SPINAL CORD AND NERVES ..........................................415</p><p>Index ........................................................................................................................................451</p><p>This page intentionally left blank</p><p>1</p><p>1</p><p>FINDINGS:</p><p>Axial T2-weighted MR shows a mass in the anterior interhemispheric fi ssure, with</p><p>surrounding T2-hyperintense rim. There is lateral displacement of the frontal lobe</p><p>gyri (arrows) and mild vasogenic edema.</p><p>DIAGNOSIS:</p><p>Extraaxial mass (meningioma)</p><p>DISCUSSION:</p><p>Correct localization of an intracranial mass is crucial for accurate diagnosis and</p><p>surgical planning. Intraaxial masses expand the brain parenchyma, with surrounding</p><p>vasogenic edema. Extraaxial masses displace and compress the adjacent brain,</p><p>with inward bowing of gyri (“accordion” or “buckling” sign) and less edema than</p><p>intraaxial lesions. Other useful fi ndings of an extraaxial mass include the “CSF</p><p>cleft” and “dural tail” signs. Meningioma is the most common extraaxial mass, and</p><p>comprises 15% of all brain tumors.</p><p>References:</p><p>Drevelegas A. Extra-axial brain tumors. Eur Radiol. 2005;15(3):453-467.</p><p>George AE, Russell EJ, Kricheff II. White matter buckling: CT sign of extraaxial intracranial mass.</p><p>AJR Am J Roentgenol. 1980;135(5):1031-1036.</p><p>ACCORDION, BUCKLING</p><p>CHAPTER ONE</p><p>ADULT AND GENERAL BRAIN</p><p>Modalities:</p><p>CT, MR</p><p>2 Chapter 1: Adult and General Brain</p><p>FINDINGS:</p><p>Sagittal T2-weighted MR shows signal voids within the aqueduct of Sylvius (thick</p><p>arrow), fourth ventricle, and cisterna magna (thin arrow). There is mild dilation of</p><p>the cerebral aqueduct.</p><p>DIFFERENTIAL DIAGNOSIS:</p><p>• Communicating hydrocephalus</p><p>• Intracranial volume loss</p><p>DISCUSSION:</p><p>Cerebrospinal fl uid (CSF) is produced in the choroid plexus of the ventricles,</p><p>circulates continuously through the brain and spinal cord, and is reabsorbed by</p><p>arachnoid granulations and/or lymphatic channels. CSF circulation is propagated</p><p>by the heart in a pulsatile fashion. High-velocity and turbulent fl ow can produce</p><p>signal voids within the ventricular system on T2-weighted MR images. Findings</p><p>are most apparent in and can distend the aqueduct of Sylvius, creating a “trumpet”</p><p>appearance in conjunction with the fourth ventricle. This is characteristic of normal</p><p>pressure hydrocephalus (NPH), but may occur with any cause of increased CSF</p><p>volume, including other forms of communi cating (nonobstructive) hydrocephalus</p><p>and intracranial volume loss. Other imaging signs of NPH include rounding of</p><p>the frontal and temporal horns, enlarged sylvian fi ssures, crowding of gyri at the</p><p>vertex, and upward bowing of the corpus callosum. Quantitative CSF fl ow imaging</p><p>using phase-contrast techniques is helpful in assessing the severity of disease and</p><p>predicting response to CSF shunting.</p><p>References:</p><p>Bradley WG Jr, Kortman KE, Burgoyne B. Flowing cerebrospinal fl uid in normal and hydrocephalic</p><p>states: appearance on MR images. Radiology. 1986;159(3):611-616.</p><p>McCoy MR, Klausner F, Weymayr F, et al. Aqueductal fl ow of cerebrospinal fl uid (CSF) and anatomical</p><p>confi guration of the cerebral aqueduct (AC) in patients with communicating hydrocephalus—the</p><p>trumpet sign. Eur J Radiol. 2013;82(4):664-670.</p><p>AQUEDUCTAL/CSF FLOW VOID, TRUMPET</p><p>Modality:</p><p>MR</p><p>Arc, Broken/Incomplete/Open Ring, Crescent, Horseshoe, Leading Edge 3</p><p>FINDINGS:</p><p>Axial contrast-enhanced T1-</p><p>weighted MR shows multiple</p><p>enhancing lesions, including</p><p>the right frontal operculum</p><p>and left inferior parietal lobule</p><p>(arrows). These demonstrate</p><p>curvilinear enhancement, with</p><p>discontinuity along the</p><p>superfi cial margins.</p><p>DIFFERENTIAL DIAGNOSIS:</p><p>• Demyelinating disease</p><p>• Primary tumor</p><p>• Lymphoma</p><p>DISCUSSION:</p><p>Approximately half of tumefactive demyelinating lesions demonstrate pathologic</p><p>enhancement. “Incomplete ring” enhancement is a relatively specifi c sign, helping</p><p>to distinguish active demyelination (particularly multiple sclerosis) from infectious</p><p>and neoplastic etiologies. The enhancing component represents the active (leading)</p><p>edge of demyelination and extends toward the white matter. The nonenhancing</p><p>component represents the inactive (trailing) edge of demyelination and can point</p><p>toward the gray matter or basal ganglia. A central nonenhancing core may also</p><p>be present, corresponding to chronic infl ammation with gliosis. Vasogenic edema</p><p>may be present, especially in regions of active disease. The general mnemonic</p><p>for cerebral ring-enhancing lesions is “MAGIC DR L”: metastasis, abscess,</p><p>glioblastoma</p><p>temporal</p><p>horns.</p><p>References:</p><p>Atlas SW. Magnetic Resonance Imaging of the Brain and Spine. 4th ed, vol. 1. Philadelphia: Wolters</p><p>Kluwer; 2008.</p><p>Barkovich AJ, Raybaud C. Pediatric Neuroimaging. 5th ed. Philadelphia: Wolters Kluwer; 2011.</p><p>Modalities:</p><p>US, CT, MR</p><p>PARALLEL VENTRICLES, RACING CAR</p><p>Peg, Sergeant Stripes, Tail, Tongue 143</p><p>FINDINGS:</p><p>Sagittal T2-weighted MR shows inferior descent of the cerebellar tonsils below the</p><p>foramen magnum, with a pointed appearance (arrow).</p><p>DIAGNOSIS:</p><p>Chiari malformation</p><p>DISCUSSION:</p><p>Chiari malformations involve a spectrum of complex congenital anomalies,</p><p>characterized by posterior fossa hypoplasia and descent of the cerebellar tonsils</p><p>over 3 to 5 mm below the foramen magnum. In Chiari I, isolated tonsillar</p><p>displacement may cause syringohydromyelia secondary to obstruction of CSF fl ow.</p><p>With Chiari II, a lumbosacral myelomeningocele produces additional traction on</p><p>the spinal cord, resulting in a hypoplastic posterior fossa. In Chiari III, there is</p><p>also an occipital or high cervical encephalocele. Characteristic pointing (“peg” or</p><p>“sergeant stripes” appearance) of the cerebellar tonsils refl ects dysplasia of the</p><p>cerebellar pyramis, uvula, and nodulus. This is a specifi c sign that can distinguish</p><p>Chiari malformations from other causes of low-lying tonsils, such as tonsillar</p><p>ectopia or tonsillar herniation.</p><p>Reference:</p><p>Naidich TP, McLone DG, Fulling KH. The Chiari II malformation, part IV: the hindbrain deformity.</p><p>Neuroradiology. 1983;25(4):179-197.</p><p>Modalities:</p><p>CT, MR</p><p>PEG, SERGEANT STRIPES, TAIL, TONGUE</p><p>144 Chapter 2: Pediatric Brain</p><p>Modalities:</p><p>CT, MR</p><p>PLASTIC, TONGUE, TOOTHPASTE</p><p>FINDINGS:</p><p>Axial and sagittal contrast-enhanced T1-weighted MR show a heterogeneously</p><p>enhancing, lobulated mass fi lling the fourth ventricle and extending through the</p><p>foramen of Magendie (thick arrow) into the cisterna magna and posterior cervical</p><p>canal (thin arrow).</p><p>DIAGNOSIS:</p><p>Ependymoma</p><p>DISCUSSION:</p><p>Ependymomas are benign tumors that arise from ependymal cells lining the ventricles</p><p>and central canal of the spinal cord. These have a heterogeneous appearance with</p><p>variable degrees of enhancement, cystic changes, hemorrhage, and calcifi cation.</p><p>The fl oor of the fourth ventricle is the most common location, with tumor fi lling</p><p>the ventricle and insinuating into foramina—the so-called “plastic” appearance.</p><p>Classically, extension occurs through the foramen of Magendie into the cisterna</p><p>magna, and through the foramina of Luschka into the cerebellopontine angles.</p><p>Ventricular obstruction can result in hydrocephalus and/or syringomyelia. There</p><p>is an association with neurofi bromatosis type II (MISME: multiple inherited</p><p>schwannomas, meningiomas, and ependymomas). Denser intraventricular neoplasms</p><p>such as medulloblastoma, choroid plexus tumor, and metastases grow by direct</p><p>extension, rather than conforming to the shape of the ventricles.</p><p>Reference:</p><p>Koeller KK, Sandberg GD. From the archives of the AFIP. Cerebral intraventricular neoplasms:</p><p>radiologic-pathologic correlation. Radiographics. 2002;22(6):1473-1505.</p><p>Point, Wedge 145</p><p>FINDINGS:</p><p>Axial T2-weighted MR shows a hyperintense wedge-shaped mass in the left middle</p><p>frontal gyrus, extending from frontal horn (thin arrow) to cortex (thick arrow).</p><p>DIAGNOSIS:</p><p>Dysembryoplastic neuroepithelial tumor</p><p>DISCUSSION:</p><p>Dysembryoplastic neuroepithelial tumors (DNETs) are benign, slow-growing</p><p>neuroepithelial tumors arising from cortical or deep gray matter. Patients are typically</p><p>male and under age 20. The temporal lobe is the most common location, followed</p><p>by the frontal lobe. Simple DNETs are T2-hyperintense multiseptated “bubbly”</p><p>masses with little vasogenic edema, enhancement, or mass effect. On FLAIR MR,</p><p>there is nulling of the cystic components of tumor with a characteristic “bright</p><p>rim,” which may be complete or incomplete. Pathologically, this corresponds to</p><p>peripheral loose neuroglial elements, and suggests residual or recurrent tumor in</p><p>the postoperative setting. Complex DNETs have varying amounts of solid tissue</p><p>and low-level enhancement. Lesions typically have a wedge-shaped morphology, in</p><p>which the apex points toward the ventricle, and the outer surface extends to cortex</p><p>with remodeling of the inner table. Associated cortical dysplasia is common.</p><p>Reference:</p><p>Koeller KK, Henry JM. From the archives of the AFIP: superfi cial gliomas: radiologic-pathologic</p><p>correlation. Armed Forces Institute of Pathology. Radiographics. 2001;21(6):1533-1556.</p><p>Modality:</p><p>MR</p><p>POINT, WEDGE</p><p>146 Chapter 2: Pediatric Brain</p><p>FINDINGS:</p><p>Sagittal T1-weighted MR shows a high-riding third ventricle (arrow), with gyri</p><p>radiating outward to the cortical surface.</p><p>DIAGNOSIS:</p><p>Callosal agenesis</p><p>DISCUSSION:</p><p>Dysgenesis of the corpus callosum is caused by abnormalities in neural development</p><p>between 12 and 18 weeks of gestation. The sequence of formation is largely ventral</p><p>to dorsal, beginning with the genu and progressing through anterior body, posterior</p><p>body, splenium, and rostrum. In callosal agenesis, there is nonconvergence of the</p><p>major fi ssures. As a result, gyri radiate outward from the third ventricle and extend to</p><p>the cortical surface in a “sunburst” pattern. Other imaging signs of callosal agenesis</p><p>include parallel lateral ventricles, colpocephaly, and “keyhole” temporal horns.</p><p>References:</p><p>Atlas SW. Magnetic Resonance Imaging of the Brain and Spine. 4th ed, vol. 1. Philadelphia: Wolters</p><p>Kluwer; 2008.</p><p>Barkovich AJ, Raybaud C. Pediatric Neuroimaging. 5th ed. Philadelphia: Wolters Kluwer; 2011.</p><p>Modalities:</p><p>US, CT, MR</p><p>POINTING, RADIAL, SPOKE, SUNBURST</p><p>Pseudohydrocephalus 147</p><p>FINDINGS:</p><p>Fetal US, axial plane, shows diffusely hypoechoic cerebral tissue. The choroid plexi</p><p>remain parallel to the interhemispheric fi ssure.</p><p>DIAGNOSIS:</p><p>Normal fetal brain</p><p>DISCUSSION:</p><p>In the second trimester of pregnancy, the cerebral hemispheres appear hypoechoic</p><p>and can mimic hydrocephalus. In true ventriculomegaly, the choroid angles increase</p><p>and the free-hanging choroid “dangles” from the foramen of Monro. Absence of</p><p>these imaging signs, with choroid plexi remaining parallel to the interhemispheric</p><p>fi ssure, confi rms this normal variant.</p><p>References:</p><p>Cardoza JD, Filly RA, Podrasky AE. The dangling choroid plexus: a sonographic observation of value</p><p>in excluding ventriculomegaly. AJR Am J Roentgenol. 1988;151(4):767-770.</p><p>Nyberg DA, McGahan JP, Pretorius DH, et al. Diagnostic Imaging of Fetal Anomalies. 2nd ed.</p><p>Philadelphia: Lippincott Williams & Wilkins; 2002.</p><p>Modality:</p><p>US</p><p>PSEUDOHYDROCEPHALUS</p><p>148 Chapter 2: Pediatric Brain</p><p>Modalities:</p><p>US, CT, MR</p><p>SPOKE WHEEL</p><p>FINDINGS:</p><p>Fetal US, axial and coronal planes, show a multiloculated cystic structure arising</p><p>from the posterior neck (arrows).</p><p>DIAGNOSIS:</p><p>Cystic hygroma</p><p>DISCUSSION:</p><p>Cystic hygroma (lymphangioma) is a congenital lymphatic malformation</p><p>that usually involves the head and neck. The classic imaging appearance</p><p>is a multiloculated, septated cystic structure that can extend into multiple</p><p>compartments. Internal contents include serous fl uid with varying amounts of</p><p>protein and hemorrhage, producing fl uid-fl uid levels. The most common location</p><p>is the posterior triangle of the neck, with multiple septa radiating out in a “spoke-</p><p>wheel” pattern. There is an association with hydrops fetalis, Turner and Noonan</p><p>syndromes, and trisomies.</p><p>Reference:</p><p>Ibrahim M, Hammoud K, Maheshwari M, et al. Congenital cystic lesions of the head and neck.</p><p>Neuroimaging Clin N Am. 2011;21(3):621-639.</p><p>Swiss Cheese 149</p><p>FINDINGS:</p><p>Axial FLAIR MR shows advanced encephalomalacia with multiple periventricular</p><p>cystic spaces (arrows), white matter volume loss, and ventriculomegaly.</p><p>DIAGNOSIS:</p><p>Periventricular leukomalacia, end-stage</p><p>DISCUSSION:</p><p>In premature infants, the periventricular white matter is most susceptible to</p><p>hypoxic injury because it is supplied by ventriculopetal penetrating arteries from</p><p>the cortical surface. Periventricular leukomalacia</p><p>(PVL) is the most common</p><p>preterm brain injury, manifesting with periventricular white matter changes that</p><p>appear echogenic on US, hypodense on CT, and hyperintense on T2-weighted MR.</p><p>Localized venous infarctions produce “fan” or “triangle”-shaped abnormalities,</p><p>refl ecting the vascular borderzones in this age group. After 2-6 weeks, the white</p><p>matter begins to involute, with ex vacuo dilation of the ventricles creating an</p><p>“angular” or “scalloped” morphology. End-stage PVL is characterized by cystic</p><p>encephalomalacia (“Swiss cheese” brain) with severe white matter loss and</p><p>ventriculomegaly.</p><p>References:</p><p>Chao CP, Zaleski CG, Patton AC. Neonatal hypoxic-ischemic encephalopathy: multimodality imaging</p><p>fi ndings. Radiographics. 2006;26(Suppl 1):S159-S172.</p><p>Nakamura Y, Okudera T, Hashimoto T. Vascular architecture in white matter of neonates: its</p><p>relationship to periventricular leukomalacia. J Neuropathol Exp Neurol. 1994;53(6):582-589.</p><p>Modalities:</p><p>US, CT, MR</p><p>SWISS CHEESE</p><p>150 Chapter 2: Pediatric Brain</p><p>FINDINGS:</p><p>Axial T2-weighted MR shows parallel lateral ventricles with pointed frontal horns</p><p>and massively dilated, rounded atria and occipital horns.</p><p>DIAGNOSIS:</p><p>Callosal agenesis</p><p>DISCUSSION:</p><p>Dysgenesis of the corpus callosum is caused by abnormalities in neural development</p><p>between 12 and 18 weeks of gestation. The sequence of formation is largely ventral to</p><p>dorsal, beginning with the genu and progressing through the anterior body, posterior</p><p>body, splenium, and rostrum. In callosal agenesis, there is complete absence of the</p><p>normal crossing white matter tracts. Instead, nondecussating white matter fi bers</p><p>known as Probst bundles course anteroposteriorly along the medial edges of the lateral</p><p>ventricles. The lateral ventricles assume a parallel orientation, with narrow elongated</p><p>frontal horns and dilated occipital horns (colpocephaly, “teardrop” appearance).</p><p>Without crossing fi bers to displace and invert them, the cingulate gyri remain everted</p><p>and the cingulate sulcus is unformed. Other imaging signs of callosal agenesis include</p><p>high-riding third ventricle, radiating gyri, and “keyhole” temporal horns.</p><p>References:</p><p>Atlas SW. Magnetic Resonance Imaging of the Brain and Spine. 4th ed, vol. 1. Philadelphia: Wolters</p><p>Kluwer; 2008.</p><p>Barkovich AJ, Raybaud C. Pediatric Neuroimaging. 5th ed. Philadelphia: Wolters Kluwer; 2011.</p><p>Modalities:</p><p>US, CT, MR</p><p>TEARDROP</p><p>Tectal Beak/Point/Spur 151</p><p>Modalities:</p><p>US, CT, MR</p><p>TECTAL BEAK/POINT/SPUR</p><p>FINDINGS:</p><p>Sagittal T1-weighted MR shows posterior beaking of the tectal plate (arrow). There</p><p>is also a low-lying tentorium cerebelli, hypoplastic posterior fossa with tonsillar</p><p>descent, cervicomedullary kink, and callosal dysgenesis.</p><p>DIAGNOSIS:</p><p>Chiari II malformation</p><p>DISCUSSION:</p><p>The Chiari II malformation is a complex congenital anomaly consisting of small</p><p>posterior fossa, inferior displacement of the cerebellum and brainstem, and</p><p>lumbosacral myelomeningocele. The characteristic tectal “beak” refl ects fusion of</p><p>the superior and/or inferior colliculi, with formation of an elongated conical mass</p><p>that extends up between the cerebellar hemispheres. Other characteristic imaging</p><p>signs of Chiari II malformation include cervicomedullary kink, wide incisura with</p><p>towering cerebellum, and fenestrated falx with interdigitating gyri. In the Chiari III</p><p>malformation, there is also an occipital or high cervical encephalocele.</p><p>References:</p><p>Geerdink N, van der Vliet T, Rotteveel JJ, et al. Essential features of Chiari II malformation in MR</p><p>imaging: an interobserver reliability study—part 1. Childs Nerv Syst. 2012;28(7):977-985.</p><p>Naidich TP, Pudlowski RM, Naidich JB. Computed tomographic signs of Chiari II malformation,</p><p>II: midbrain and cerebellum. Radiology. 1980;134(2):391-398.</p><p>152 Chapter 2: Pediatric Brain</p><p>FINDINGS:</p><p>Fetal US, axial plane, shows dilated lateral ventricles with decreased ventricle-to-</p><p>occiput distance (arrows).</p><p>DIFFERENTIAL DIAGNOSIS:</p><p>• Fetal Chiari II</p><p>• Spinal dysraphism</p><p>DISCUSSION:</p><p>Accurate diagnosis of fetal neural tube defects is crucial for guiding further imaging</p><p>evaluation, genetic workup, and prenatal counseling. The Chiari II malformation is</p><p>a complex congenital deformity involving a small posterior fossa and lumbosacral</p><p>myelomeningocele. Infratentorial abnormalities can be diffi cult to detect in early</p><p>pregnancy. Before 24 weeks of gestational age, there is ventriculomegaly with</p><p>characteristic posterior displacement (“too-far-back” ventricle) and pointing of the</p><p>occipital horns (“angular” appearance). Fetal MR may help to further characterize</p><p>the spectrum of anatomic abnormalities.</p><p>Reference:</p><p>Filly MR, Filly RA, Barkovich AJ, et al. Supratentorial abnormalities in the Chiari II malformation,</p><p>IV: the too-far-back ventricle. J Ultrasound Med. 2010;29(2):243-248.</p><p>Modalities:</p><p>US, MR</p><p>TOO-FAR-BACK VENTRICLE</p><p>Transmantle 153</p><p>Modality:</p><p>MR</p><p>TRANSMANTLE</p><p>FINDINGS:</p><p>Axial T2-weighted and coronal FLAIR MR show left frontal cortical thickening and</p><p>loss of gray-white distinction (thick arrows). A band of hyperintense signal extends</p><p>from the cortex to the frontal horn (thin arrows).</p><p>DIAGNOSIS:</p><p>Focal cortical dysplasia, type II (transmantle dysplasia)</p><p>DISCUSSION:</p><p>Focal cortical dysplasia (FCD), fi rst described by Taylor et al. in 1971, is a common</p><p>cause of intractable childhood epilepsy. FCD represents a spectrum of developmental</p><p>migrational anomalies with varying embryologic, genetic, histopathologic, and</p><p>imaging features. In 2011, the International League Against Epilepsy (ILAE)</p><p>reclassifi ed the disease into three tiers: FCD type I refers to isolated cortical</p><p>dyslamination in the radial (type Ia), tangential (type Ib), or both (type Ic) directions.</p><p>FCD type II involves dysmorphic neurons, either without (type IIa) or with (type IIb)</p><p>balloon cells. FCD type III occurs adjacent to a principal lesion such as hippocampal</p><p>sclerosis (type IIIa), tumor (type IIIb), vascular malformation (type IIIc), or other</p><p>acquired conditions such as trauma/ischemia/infection (type IIId). On MR, imaging</p><p>features include cortical thickening and expansion, loss of gray-white distinction,</p><p>and T2-hyperintense signal. The “transmantle” sign refers to T2 signal abnormality</p><p>extending across the cerebral mantle, from cortical surface to ventricle. Morphology</p><p>may be linear, curvilinear, radial, or funnel-shaped. This fi nding is most often</p><p>associated with FCD type II, and characteristically seen in the frontal lobes. The</p><p>imaging differential includes dysembryoplastic neuroepithelial tumor (“wedge”</p><p>appearance), radial bands of tuberous sclerosis, and other migrational anomalies.</p><p>References:</p><p>Barkovich AJ, Kuzniecky RI, Bollen AW, et al. Focal transmantle dysplasia: a specifi c malformation of</p><p>cortical development. Neurology. 1997;49(4):1148-1152.</p><p>Blümcke I, Thom M, Aronica E, et al. The clinicopathologic spectrum of focal cortical dysplasias:</p><p>a consensus classifi cation proposed by an ad hoc Task Force of the ILAE Diagnostic Methods</p><p>Commission. Epilepsia. 2011;52(1):158-174.</p><p>This page intentionally left blank</p><p>155</p><p>FINDINGS:</p><p>Axial contrast-enhanced CT shows an avidly enhancing mass centered in the right</p><p>sphenopalatine foramen. This extends laterally into the pterygopalatine fossa with</p><p>anterior bowing of the posterior maxillary sinus wall (arrow), anteriorly into the</p><p>nasal cavity, and posteriorly into the sphenoid sinus.</p><p>DIAGNOSIS:</p><p>Juvenile nasopharyngeal angiofi broma</p><p>DISCUSSION:</p><p>Juvenile nasopharyngeal angiofi broma (JNA) is a benign, locally aggressive tumor</p><p>seen in adolescent males presenting with unilateral nasal obstruction, rhinorrhea,</p><p>and epistaxis. It originates in the region of the sphenopalatine foramen and extends</p><p>anteriorly into the nasal cavity, laterally toward the pterygopalatine fossa, posteriorly</p><p>into the sphenoid sinus, and inferiorly into the infratemporal fossa. Pterygopalatine</p><p>fossa involvement produces the antral or Holman-Miller sign, represented by anterior</p><p>bowing of the</p><p>posterior wall of the maxillary sinus (antrum of Highmore). Infratemporal</p><p>fossa involvement produces the Hondousa sign, which refers to widening of the gap</p><p>between the mandibular ramus and maxillary body. Tumors are highly vascular, with</p><p>avid enhancement and fl ow voids on MR. Treatment is total surgical resection, often</p><p>preceded by angiographic embolization of the feeding vessel (internal maxillary branch</p><p>of the ECA) to reduce bleeding, followed by adjuvant radiation. Other nasal cavity</p><p>tumors in this age group include rhabdomyosarcoma, lymphoma, and hemangioma,</p><p>which are typically less vascular and have different growth patterns.</p><p>Reference:</p><p>Ludwig BJ, Foster BR, Saito N, et al. Diagnostic imaging in nontraumatic pediatric head and neck</p><p>emergencies. Radiographics. 2010;30(3):781-799.</p><p>Modalities:</p><p>XR, CT, MR</p><p>CHAPTER THREE</p><p>HEAD, NECK, AND ORBITS3</p><p>ANTRAL, HOLMAN-MILLER, HONDOUSA</p><p>156 Chapter 3: Head, Neck, and Orbits</p><p>FINDINGS:</p><p>• Sialogram in mild sialadenitis shows smooth parotid ducts with peripheral pruning</p><p>and innumerable tiny contrast collections throughout the gland.</p><p>• Moderate sialadenitis shows segmental ductal stricturing and dilation, with several</p><p>globular contrast collections.</p><p>• End-stage sialadenitis shows severe distortion of the parotid ductal system, with</p><p>large bizarre extraductal collections.</p><p>DIAGNOSIS:</p><p>Chronic sialadenitis</p><p>DISCUSSION:</p><p>Sialography is a radiographic technique used to visualize salivary gland ducts</p><p>(parotid: Stensen duct, submandibular: Wharton duct, sublingual: Gartner duct).</p><p>The procedure involves evoked salivation, direct cannulation with a microcatheter,</p><p>and injection of contrast under fl uoroscopy. Noninvasive imaging techniques include</p><p>US or MR sialography using high-resolution, heavily T2-weighted sequences.</p><p>Normal salivary ducts are smooth and branch to the gland periphery. With recurrent</p><p>sialadenitis, ductal irregularity progresses through four stages. In the punctate</p><p>stage, tiny (</p><p>seeds the surgical bed. If untreated, there is a 10%-25% risk</p><p>of malignant transformation, known as carcinoma ex pleomorphic adenoma</p><p>(malignant mixed tumor). Imaging features suggestive of malignant transformation</p><p>include T2-hypointense or heterogeneous signal, irregular margins, infi ltrative</p><p>growth, rapidly increasing size, and lymphadenopathy.</p><p>References:</p><p>Kakimoto N, Gamoh S, Tamaki J, et al. CT and MR images of pleomorphic adenoma in major and</p><p>minor salivary glands. Eur J Radiol. 2009;69(3):464-472.</p><p>Kashiwagi N, Murakami T, Chikugo T, et al. Carcinoma ex pleomorphic adenoma of the parotid</p><p>gland. Acta Radiol. 2012;53(3):303-306.</p><p>Bow Tie, Oval, Rectangle 161</p><p>Modalities:</p><p>CT, MR</p><p>BOW TIE, OVAL, RECTANGLE</p><p>FINDINGS:</p><p>• Axial contrast-enhanced CT shows mild symmetric retropharyngeal edema</p><p>(arrows).</p><p>• Axial contrast-enhanced CT in a different patient shows a multiloculated fl uid</p><p>collection distending the retropharyngeal (thick arrows) and pharyngeal mucosal</p><p>spaces (thin arrows).</p><p>DIFFERENTIAL DIAGNOSIS:</p><p>• Retropharyngeal edema</p><p>• Retropharyngeal abscess</p><p>DISCUSSION:</p><p>The retropharyngeal space (RPS) extends from the clivus to the upper thoracic</p><p>spine (T1-T6), posterior to the pharynx/esophagus and anterior to the prevertebral</p><p>muscles. Its boundaries include the visceral fascia anteriorly, alar/prevertebral fascia</p><p>posteriorly, and carotid sheaths laterally. Retropharyngeal edema is nonsuppurative</p><p>infl ammation caused by venolymphatic obstruction, longus colli calcifi c tendinitis,</p><p>radiation therapy, or adjacent infection. At imaging, there is smooth symmetric</p><p>expansion of the RPS with a “bow tie,” “ovoid,” or “rectangular” confi guration. No</p><p>wall thickening or enhancement is present, and the condition resolves with correction</p><p>of the underlying cause. Retropharyngeal abscess is a purulent fl uid collection</p><p>originating from direct or hematogenous spread of infection. At imaging, a large</p><p>rim-enhancing fl uid collection distends the RPS, causing mass effect on adjacent</p><p>structures. Prompt surgical drainage is indicated to prevent airway compromise and</p><p>spread of infection into the perivertebral, carotid, and mediastinal spaces.</p><p>Reference:</p><p>Hoang JK, Branstetter BF 4th, Eastwood JD, et al. Multiplanar CT and MRI of collections in the</p><p>retropharyngeal space: is it an abscess? AJR Am J Roentgenol. 2011;196(4):W426-W432.</p><p>162 Chapter 3: Head, Neck, and Orbits</p><p>FINDINGS:</p><p>Axial T2-weighted MR shows bilateral elongation and kinking of the optic nerves</p><p>(arrows).</p><p>DIAGNOSIS:</p><p>Optic nerve gliomas</p><p>DISCUSSION:</p><p>Optic glioma is the most common optic nerve tumor. There are three subtypes:</p><p>childhood syndromic (neuro fi bromatosis type I), childhood sporadic, and adult.</p><p>Gliomas in children are low grade (WHO I-II), whereas in adults they are higher</p><p>grade (WHO grade III-IV). These manifest with enlargement and elongation of</p><p>the optic nerves (“buckled” appearance), chiasm, and/or radiations. MR signal</p><p>is generally T2-hyperintense (“pseudo-CSF” appearance). Syndromic gliomas are</p><p>smooth, focally tortuous, and minimally enhancing. Sporadic gliomas are larger,</p><p>nodular/cystic, and moderately enhancing. Adult gliomas are diffuse, invasive, and</p><p>heterogeneously enhancing. Other conditions affecting the optic nerve include optic</p><p>neuritis (nerve edema and enhancement), optic nerve meningioma (tumor of the nerve</p><p>sheath), orbital pseudotumor (localized infl ammation of periorbital structures), and</p><p>sarcoidosis (multifocal orbital and intracranial manifestations).</p><p>References:</p><p>Millar WS, Tartaglino LM, Sergott RC, et al. MR of malignant optic glioma of adulthood. AJNR Am</p><p>J Neuroradiol. 1995;16(8):1673-1676.</p><p>Taylor T, Jaspan T, Milano G, et al. Radiological classifi cation of optic pathway gliomas: experience</p><p>of a modifi ed functional classifi cation system. Br J Radiol. 2008;81(970):761-766.</p><p>Modalities:</p><p>US, CT, MR</p><p>BUCKLED, KINKED, TWISTED</p><p>Bull Neck 163</p><p>Modalities:</p><p>CT, MR</p><p>BULL NECK</p><p>FINDINGS:</p><p>Coronal contrast-enhanced CT shows a lobulated, rim-enhancing fl uid collection</p><p>(thick arrow) in the fl oor of mouth. Surrounding fat stranding extends into the</p><p>subcutaneous tissues of the face and neck (thin arrows).</p><p>DIAGNOSIS:</p><p>Ludwig angina</p><p>DISCUSSION:</p><p>Ludwig angina is an aggressive cellulitis of the fl oor of mouth, usually secondary to</p><p>untreated dental infection. Progression of disease leads to extensive facial/cervical</p><p>cellulitis, fasciitis, and/or abscess formation (“bull neck” appearance). Elevation and</p><p>posterior displacement of the tongue can cause critical airway compromise. Other</p><p>potential complications include jugular thrombophlebitis (Lemierre syndrome),</p><p>mandibular osteomyelitis, mediastinitis, and pleuritis.</p><p>References:</p><p>Bosemani T, Izbudak I. Head and neck emergencies. Semin Roentgenol. 2013;48(1):4-13.</p><p>Branstetter BF 4th, Weissman JL. Infection of the facial area, oral cavity, oropharynx, and retropharynx.</p><p>Neuroimaging Clin N Am. 2003;13(3):393-410, ix.</p><p>164 Chapter 3: Head, Neck, and Orbits</p><p>Modality:</p><p>MR</p><p>BULLSEYE, CLAW, INTRACYSTIC NODULE, POSTERIOR LEDGE</p><p>FINDINGS:</p><p>Coronal T2-weighted and contrast-enhanced T1-weighted MR with fat saturation</p><p>show a left pituitary cystic lesion with T2-hypointense, T1-hyperintense central</p><p>nodule (arrows).</p><p>DIAGNOSIS:</p><p>Rathke cleft cyst</p><p>DISCUSSION:</p><p>The Rathke pouch is an ectodermal outpouching of the primitive oral cavity that</p><p>separates to form the anterior pituitary gland. The anterior wall of the pouch</p><p>proliferates to form the pars distalis, which comprises the majority of the anterior</p><p>gland; and the pars tuberalis, which wraps around the pituitary stalk. The posterior</p><p>wall of the pouch does not proliferate and forms the pars intermedia. The lumen of</p><p>the pouch normally involutes, but may persist as the Rathke cleft. Rathke cleft cyst</p><p>(RCC) is a benign expansion of this residual cavity, and is usually asymptomatic. At</p><p>imaging, it appears as a nonenhancing, noncalcifi ed cystic lesion with a surrounding</p><p>rim of enhancing pituitary gland (“claw” sign). MR signal varies depending on</p><p>whether cyst contents are serous (T1-hypointense, T2-hyperintense) or mucoid</p><p>(T1-hyperintense, T2-hypointense). Rathke cleft cyst usually measures less than</p><p>1.5 cm in size and may be diffi cult to distinguish from a small craniopharyngioma</p><p>with cystic components. Characteristic imaging features include the “intracystic</p><p>nodule” and “posterior ledge” signs. Within the cyst, there may be a mucin-containing</p><p>nodule with variably T1-hyperintense and T2-hypointense signal. Occasionally,</p><p>the cyst can extend superiorly through the diaphragma sellae and drape over the</p><p>posterior pituitary, forming the “posterior ledge” sign.</p><p>Reference:</p><p>Byun WM, Kim OL, Kim D. MR imaging fi ndings of Rathke’s cleft cysts: signifi cance of intracystic</p><p>nodules. AJNR Am J Neuroradiol. 2000;21(3):485-488.</p><p>Candle Dripping, Fuzzy, Shaggy 165</p><p>FINDINGS:</p><p>Lateral neck radiograph shows tracheal wall thickening and irregularity, with</p><p>sloughing of membranes (arrow).</p><p>DIAGNOSIS:</p><p>Bacterial tracheitis</p><p>DISCUSSION:</p><p>Bacterial tracheitis (exudative trache itis, membranous croup, membranous</p><p>laryngotracheobronchitis) is a purulent infection that can be caused by</p><p>Staphylococcus aureus, Streptococcus pneumoniae, Haemophilus infl uenzae, and</p><p>Moraxella catarrhalis. It usually affects children between 6 and 10 years of age.</p><p>Severe infl ammation results in exudative plaques and sloughing of membranes</p><p>in the larynx, trachea, and/or bronchi with a “shaggy” appearance. On frontal</p><p>radiographs, there is subglottic airway narrowing, which is typically more asymmetric</p><p>and irregular than in croup. On lateral radiographs, tracheal wall irregularity and</p><p>intraluminal fi lling defects are diagnostic. Because of the risk of airway obstruction</p><p>and respiratory failure, there is need for prompt airway management, antibiotics,</p><p>and endoscopic membrane stripping. In comparison, croup affects younger patients</p><p>(6 months to 3 years), is a self-limited infection, and shows smooth symmetric</p><p>subglottic narrowing.</p><p>Reference:</p><p>Sammer M, Pruthi S. Membranous croup (exudative tracheitis or membranous laryngotracheo-</p><p>bronchitis). Pediatr Radiol. 2010;40(5):781.</p><p>Modalities:</p><p>XR, CT</p><p>CANDLE DRIPPING, FUZZY, SHAGGY</p><p>166 Chapter 3: Head, Neck, and Orbits</p><p>FINDINGS:</p><p>Coronal T2-weighted</p><p>MR shows a right nasal</p><p>cavity mass (arrows)</p><p>extending into the right</p><p>maxillary sinus with a</p><p>convoluted and double-</p><p>layered appearance.</p><p>DIFFERENTIAL</p><p>DIAGNOSIS:</p><p>• Inverted papilloma</p><p>• Oncocytic papilloma</p><p>• Sinonasal carcinoma</p><p>DISCUSSION:</p><p>The Schneiderian membrane is ciliated mucosa of ectodermal origin that lines the</p><p>sinonasal tract, and is distinct from the endodermally derived mucosa of the upper</p><p>respiratory tract. Benign neoplasms of the Schneiderian membrane are known as</p><p>Schneiderian papillomas and classifi ed into three types: fungiform, inverted, and</p><p>oncocytic. Fungiform (exophytic, septal) papillomas grow out from the nasal septum</p><p>and do not involve the paranasal sinuses. Inverted (endophytic) papillomas arise</p><p>from the lateral nasal wall (classically at the hiatus semilunaris) and extend into the</p><p>sinuses (typically maxillary or ethmoid). Focal hyperostosis and entrapped bone can</p><p>be seen at the point of tumor attachment. On T2-weighted MR, contrast-enhanced</p><p>T1-weighted MR, and contrast-enhanced CT, tumors may demonstrate a convoluted</p><p>and layered “cerebriform” appearance. Oncocytic (cylindrical cell) papillomas are</p><p>the rarest subtype, occurring in the lateral nasal wall or sinuses. They appear similar</p><p>to inverted papillomas on imaging, but show both exo- and endophytic growth</p><p>patterns at histology. Treatment of papillomas involves complete resection because</p><p>associated synchronous and/or metachronous carcinomas (particularly squamous</p><p>cell carcinoma) are seen in 10% of cases. At imaging, the presence of carcinoma is</p><p>suggested by loss of the “cerebriform” pattern, central necrosis, irregular margins,</p><p>and bone destruction.</p><p>References:</p><p>Barnes L. Schneiderian papillomas and nonsalivary glandular neoplasms of the head and neck. Mod</p><p>Pathol. 2002;15(3):279-297.</p><p>Jeona TY, Kima HJ, Chungb SK, et al. Sinonasal inverted papilloma: value of convoluted cerebriform</p><p>pattern on MR imaging. Am J Neuroradiol. 2008;29:1556-1560.</p><p>Modalities:</p><p>CT, MR</p><p>CEREBRIFORM, CONVOLUTED, STRIATED</p><p>Claw 167</p><p>Modalities:</p><p>US, CT, MR</p><p>CLAW</p><p>FINDINGS:</p><p>Axial contrast-enhanced CT shows a midline cystic lesion deep to and partially</p><p>embedded in the strap muscles (arrows).</p><p>DIAGNOSIS:</p><p>Thyroglossal duct cyst</p><p>DISCUSSION:</p><p>Thyroglossal duct cyst (TGDC) is the most common congenital neck lesion. It</p><p>represents remnant thyroglossal duct tissue along the path of migration between the</p><p>foramen cecum at the base of tongue and the thyroid bed in the infrahyoid neck.</p><p>TGDCs are typically located close to midline (within 2 cm) and may occur in the</p><p>infrahyoid, hyoid, or suprahyoid regions. Infrahyoid TGDCs that extend anteriorly</p><p>become embedded in the strap muscles (sternohyoid, sternothyroid, thyrohyoid, and</p><p>omohyoid), creating the pathognomonic “claw” sign. At imaging, TGDCs appear</p><p>as thin-walled cystic lesions, though thicker enhancing walls may develop with</p><p>superinfection. Nodularity and coarse calcifi cations are concerning for malignant</p><p>transformation into thyroid carcinoma. The treatment of choice is resection of the</p><p>entire cyst, remnant tract, and central hyoid bone (Sistrunk procedure).</p><p>References:</p><p>Glastonbury CM, Davidson HC, Haller JR, et al. The CT and MR imaging features of carcinoma</p><p>arising in thyroglossal duct remnants. AJNR Am J Neuroradiol. 2000;21(4):770-774.</p><p>Koeller KK, Alamo L, Adair CF, et al. Congenital cystic masses of the neck: radiologic-pathologic</p><p>correlation. Radiographics. 1999;19(1):121-146; quiz 152-153.</p><p>168 Chapter 3: Head, Neck, and Orbits</p><p>Modalities:</p><p>US, CT, MR</p><p>FINDINGS:</p><p>Axial contrast-enhanced T1-weighted MR with fat saturation shows fusiform</p><p>enlargement and hyperenhancement of the extraocular muscles (arrows), with sparing</p><p>of the tendinous insertions. There is bilateral proptosis and increased periorbital fat.</p><p>DIAGNOSIS:</p><p>Thyroid ophthalmopathy</p><p>DISCUSSION:</p><p>Thyroid ophthalmopathy is the most common cause of proptosis in adults and</p><p>is usually seen in patients with thyroid disease, particularly Graves disease. It is</p><p>postulated that antibodies to thyroid-stimulating hormone cross-react with orbital</p><p>antigens, resulting in infl ammation and fi brosis with mucopolysaccharide/collagen</p><p>deposition in the extraocular muscles and orbital fat. There is fusiform enlargement</p><p>of the extraocular muscle bellies with sparing of the tendinous insertions, resembling</p><p>the contour of a Coca-Cola bottle. The mnemonic “I’M SLO” describes the typical</p><p>order of involvement: inferior rectus, medial rectus, superior rectus, lateral rectus, and</p><p>superior/inferior obliques. Severe muscle enlargement can compress the optic nerve</p><p>and superior ophthalmic vein at the orbital apex, leading to optic nerve dysfunction</p><p>and venous congestion of the periorbital fat. Treatment options include radioactive</p><p>iodine ablation, antithyroid medications, and orbital decompression.</p><p>Reference:</p><p>Parmar H, Ibrahim M. Extrathyroidal manifestations of thyroid disease: thyroid ophthalmopathy.</p><p>Neuroimaging Clin N Am. 2008;18(3):527-536, viii-ix.</p><p>COCA-COLA BOTTLE</p><p>Cochlear Cleft 169</p><p>FINDINGS:</p><p>Axial temporal bone CT shows an ill-defi ned lucency posterior to the tensor tympani</p><p>and anterior to the vestibule, in the region of the fi ssula ante fenestram (arrow).</p><p>DIFFERENTIAL DIAGNOSIS:</p><p>• Bone dyscrasia</p><p>• Fracture</p><p>• Normal variant</p><p>DISCUSSION:</p><p>Lucencies of the otic capsule are commonly seen in children, and refl ect incomplete</p><p>endochondral ossifi cation with cartilaginous remnants. A normal variant is the</p><p>cochlear cleft, which is C-shaped and courses parallel to the basal turn of the cochlea.</p><p>This occurs in close association with the fi ssula ante fenestram, a fi brocartilaginous</p><p>region just anterior to the oval window. Otic capsule-violating temporal bone</p><p>fractures can also occur here. In the adult, the mature bony labyrinth is avascular</p><p>and undergoes virtually no remodeling. Ill-defi ned lucencies suggest a bone dyscrasia</p><p>such as otospongiosis, osteogenesis imperfecta, or Paget disease. Otospongiosis, which</p><p>exclusively affects the otic capsule and auditory ossicles, is a leading cause of adult-onset</p><p>hearing loss. The normally dense avascular endochondral bone is replaced by spongy</p><p>vascular haversian bone. This manifests as hypodensity on CT, most commonly at the</p><p>fi ssula ante fenestram (fenestral otospongiosis), and in advanced cases surrounding</p><p>the cochlea (retrofenestral otospongiosis). Sclerosis occurring in the chronic (healing)</p><p>phase is known as otosclerosis. Osteogenesis imperfecta and Paget disease show more</p><p>diffuse involvement of the temporal bone, as well as evidence of systemic disease.</p><p>References:</p><p>Chadwell JB, Halsted MJ, Choo DI, et al. The cochlear cleft. AJNR Am J Neuroradiol. 2004;25(1):</p><p>21-24.</p><p>Mafee MF, Valvassori GE, Deitch RL, et al. Use of CT in the evaluation of cochlear otosclerosis.</p><p>Radiology. 1985;156(3):703-708.</p><p>Modality:</p><p>CT</p><p>COCHLEAR CLEFT</p><p>170 Chapter 3: Head, Neck, and Orbits</p><p>FINDINGS:</p><p>Axial contrast-enhanced CT shows an elongated cystic structure originating from</p><p>the right sublingual space (thin arrow) and tracking posteriorly into the right</p><p>submandibular space (thick arrow).</p><p>DIAGNOSIS:</p><p>Diving ranula</p><p>DISCUSSION:</p><p>Ranulas are mucus retention cysts of the minor salivary glands, most commonly the</p><p>sublingual gland. They may be congenital, infl ammatory, or traumatic. Simple ranulas</p><p>are lined by epithelium and confi ned to the sublingual space, above the mylohyoid</p><p>muscle. Diving (plunging, deep) ranulas are pseudocysts with contained rupture into</p><p>the submandibular space. The “tail” sign represents the collapsed portion of the</p><p>cyst within the sublingual space. Ruptures usually track posteriorly over the back</p><p>of the mylohyoid muscle to terminate in the posteromedial</p><p>submandibular space.</p><p>Less commonly, they can extend laterally through a mylohyoid defect (boutonnière)</p><p>into the anterior submandibular space. Rarely, large ranulas may ascend into the</p><p>parapharyngeal space.</p><p>Reference:</p><p>La’porte SJ, Juttla JK, Lingam RK. Imaging the fl oor of the mouth and the sublingual space.</p><p>Radiographics. 2011;31(5):1215-1230.</p><p>COMET, PEAR, TAIL</p><p>Modalities:</p><p>US, CT, MR</p><p>Cone, Funnel, Martini/Wine Glass, Triangle, Tubular 171</p><p>Modalities:</p><p>US, CT, MR FINDINGS:</p><p>Axial fat-saturated T2-weighted MR shows a conical soft-tissue mass extending from</p><p>the lens to the optic nerve head (thick arrow). There is a linear area of low signal</p><p>intensity within the mass (thin arrow), representing remnant hyaloid vasculature.</p><p>DIAGNOSIS:</p><p>Persistent hyperplastic primary vitreous</p><p>DISCUSSION:</p><p>The fetal intraocular vascular system consists of anterior and posterior divisions. The</p><p>anterior system supplies the iris anterior to the lens, whereas the posterior system</p><p>has three components: hyaloid artery supplying the central primary vitreous, vasa</p><p>hyaloidea propria supplying the peripheral primary vitreous, and tunica vasculosa</p><p>lentis supplying the iris and lens. The primary vitreous forms between the lens</p><p>and the retina around 7 weeks of gestation, and begins involuting by 20 weeks as</p><p>it is replaced by the secondary vitreous. Persistent hyperplastic primary vitreous</p><p>(PHPV) refers to persistence of this system, which can affect the anterior and/or</p><p>posterior compartments. In anterior PHPV, there is a shallow anterior chamber and</p><p>retrolental fi brovascular membrane. In posterior PHPV, there is a retrolental mass,</p><p>funnel-shaped retinal detachment, and a stalk extending from the optic nerve to the</p><p>posterior lens (remnant of hyaloid canal carrying the hyaloid artery) creating the</p><p>“martini glass” appearance. Bilateral PHPV is associated with trisomy 13 (Patau</p><p>syndrome), Norrie disease, and Walker-Warburg syndrome.</p><p>References:</p><p>Castillo M, Wallace DK, Mukherji SK. Persistent hyperplastic primary vitreous involving the anterior</p><p>eye. AJNR Am J Neuroradiol. 1997;18(8):1526-1528.</p><p>Kaste SC, Jenkins JJ 3rd, Meyer D, et al. Persistent hyperplastic primary vitreous of the eye: imaging</p><p>fi ndings with pathologic correlation. AJR Am J Roentgenol. 1994;162(2):437-440.</p><p>CONE, FUNNEL, MARTINI/WINE GLASS, TRIANGLE, TUBULAR</p><p>172 Chapter 3: Head, Neck, and Orbits</p><p>FINDINGS:</p><p>Axial T2-weighted MR shows an asym metrically enlarged right globe (arrow).</p><p>DIAGNOSIS:</p><p>Macrophthalmos</p><p>DISCUSSION:</p><p>Macrophthalmos refers to enlargement of the globe, which usually presents in the</p><p>fi rst 3 months of life. Buphthalmos (Greek for “ox or cow eye”) is enlargement</p><p>due to increased intraocular pressure in the fi rst 3-4 years of life, when the sclera</p><p>is still malleable. This occurs in congenital glaucoma and acquired glaucoma</p><p>secondary to aniridia, neurofi bromatosis type I, Sturge-Weber syndrome, Proteus</p><p>syndrome, Peter anomaly, retinoblastoma, and melanoma. Patients with connective</p><p>tissue disorders have fl oppy sclerae and can present with ocular enlargement at any</p><p>age. Megalophthalmos has been used to denote globe enlargement with normal</p><p>intraocular pressures. Nonglaucomatous causes of globe enlargement include axial</p><p>myopia, staphyloma, coloboma, and anophthalmos with cyst (congenital cystic eye).</p><p>Reference:</p><p>Som PM, Curtin HD. Head and Neck Imaging. 5th ed. St Louis, MO: Mosby; 2011.</p><p>Modalities:</p><p>US, CT, MR</p><p>COW/OX EYE</p><p>Crescent, Dodd 173</p><p>Modalities:</p><p>XR, CT</p><p>FINDINGS:</p><p>Axial and sagittal CT show a soft-tissue mass arising in the left maxillary sinus and</p><p>expanding the antrum (asterisk). This extends posteriorly through the nasal cavity</p><p>and choana into the nasopharynx, where it is outlined by a crescent of air (arrow).</p><p>DIAGNOSIS:</p><p>Choanal polyp</p><p>DISCUSSION:</p><p>Choanal (Killian) polyps are infl ammatory polyps that produce unilateral nasal</p><p>obstruction in teenagers and young adults. They arise from the sinonasal mucosa</p><p>and herniate through the sinus ostium into the nasal cavity, causing smooth bone</p><p>remodeling. Polyps that are suffi ciently large can prolapse through the choana</p><p>into the nasopharynx. Antrochoanal polyps are the most common, appearing as</p><p>dumbbell-shaped mucoid masses at the maxillary sinus antrum that extend through</p><p>an accessory or major ostium into the ipsilateral nasal cavity. Continued growth</p><p>through the choana yields a bulbous nasopharyngeal component, which rests on the</p><p>soft palate and is surrounded by a crescent of air (Dodd sign). In contrast, sinonasal</p><p>inverted papillomas arise from the lateral nasal wall near the hiatus semilunaris and</p><p>demonstrate peripheral growth into the sinuses, with a “cerebriform” pattern at</p><p>imaging. Less common types of choanal polyps are nasochoanal, sphenochoanal,</p><p>frontochoanal, and ethmochoanal.</p><p>References:</p><p>Aydin O, Keskin G, Ustünda E, et al. Choanal polyps: an evaluation of 53 cases. Am J Rhinol.</p><p>2007;21(2):164-168.</p><p>Chung SK, Chang BC, Dhong HJ. Surgical, radiologic, and histologic fi ndings of the antrochoanal</p><p>polyp. Am J Rhinol. 2002;16(2):71-76.</p><p>CRESCENT, DODD</p><p>174 Chapter 3: Head, Neck, and Orbits</p><p>Modalities:</p><p>US, CT, MR</p><p>FINDINGS:</p><p>• Axial T2-weighted MR shows partial retinal detachment, with the detached leaves</p><p>of the retina (thin arrows) converging toward the optic disc.</p><p>• Axial T2-weighted MR in a different patient shows complete retinal detachment,</p><p>in which the outer retinal membrane (thick arrow) has completely separated from</p><p>the inner sensory layer.</p><p>DIAGNOSIS:</p><p>Retinal detachment</p><p>DISCUSSION:</p><p>The globes are lined by three concentric coverings: the internal nervous, middle</p><p>vascular, and external fi brous tunics. The retina contains photoreceptors (rods,</p><p>cones, and photosensitive ganglion cells) that process light stimuli and send impulses</p><p>through the optic nerve to the brain. The choroid consists of vascular pigmented</p><p>connective tissue, which is responsible for nutrition and gas exchange, and forms</p><p>the uveal tract along with the ciliary body and iris. The sclera, which is composed</p><p>of protective fi brous tissue, is continuous anteriorly with the cornea. Retinal</p><p>detachment (RD) refers to separation of the retina from the choroid, which can</p><p>occur following infl ammation (tractional), fl uid accumulation (exudative), or trauma</p><p>(rhegmatogenous). In partial RD, the leaves of the retina converge toward the optic</p><p>disc (“V” appearance). In complete RD, the optic attachment is also disrupted</p><p>(“crescent” appearance). Therapeutic options include pneumatic, silicone, laser, or</p><p>cryoretinopexy and scleral buckle.</p><p>Reference:</p><p>Mafee MF, Peyman GA. Retinal and choroidal detachments: role of magnetic resonance imaging and</p><p>computed tomography. Radiol Clin North Am. 1987;25(3):487-507.</p><p>CRESCENT, FUNNEL, V</p><p>Danger Space 175</p><p>FINDINGS:</p><p>Sagittal contrast-enhanced CT shows a</p><p>rim-enhancing prever tebral fl uid collection</p><p>that extends inferiorly into the upper</p><p>thorax (arrows).</p><p>DIFFERENTIAL DIAGNOSIS:</p><p>• Danger space abscess</p><p>• Retropharyngeal abscess</p><p>DISCUSSION:</p><p>The danger space is a potential space</p><p>between the alar and prevertebral fasciae,</p><p>extending from the level of the skull base</p><p>to the posterior diaphragm. This is a</p><p>conduit for spread of infection and tumor</p><p>between the neck and the mediastinum.</p><p>Danger space infections can be diffi cult</p><p>to distinguish from infections of the</p><p>retropharyngeal space, which are located</p><p>more anteriorly between the visceral</p><p>(buccopharyngeal) and alar fasciae.</p><p>Collections are often unilateral because</p><p>of the presence of a midline raphe,</p><p>and do not extend beyond the upper</p><p>mediastinum.</p><p>Reference:</p><p>Bosemani T, Izbudak I. Head and neck emergencies. Semin Roentgenol. 2013;48(1):4-13.</p><p>Modalities:</p><p>CT, MR</p><p>DANGER SPACE</p><p>176 Chapter 3: Head, Neck, and Orbits</p><p>Modality:</p><p>MR</p><p>FINDINGS:</p><p>• Axial T1-weighted MR shows a well-circumscribed hypointense mass in the left</p><p>parotid (arrows), which extends through the stylomandibular foramen and is</p><p>deformed by surrounding structures.</p><p>• Axial</p><p>T2-weighted MR and contrast-enhanced T1-weighted MR with fat</p><p>saturation show the mass (arrows) becoming isointense to parotid parenchyma.</p><p>DIAGNOSIS:</p><p>Parotid oncocytoma</p><p>DISCUSSION:</p><p>Parotid oncocytoma (oncocytic adenoma, oxyphilic granular cell adenoma,</p><p>oxyphilic adenoma) is a rare benign epithelial tumor consisting of mitochondria-</p><p>rich oncocytes. Imaging features are nonspecifi c and overlap with other benign</p><p>parotid tumors. The majority of lesions are well-defi ned, enhancing, and can be</p><p>bilateral. There may be internal nonenhancing curvilinear clefts and cystic areas,</p><p>corresponding histologically to a central scar. On MR, oncocytomas are classically</p><p>T1-hypointense, becoming isointense on T2-weighted images with fat saturation</p><p>and contrast-enhanced T1-weighted images (“vanishing” lesions). Nuclear medicine</p><p>features include high uptake on Tc-99m pertechnetate scans and 18F-FDG PET.</p><p>Large tumors can be distorted by surrounding structures, creating a “deformable”</p><p>appearance. Because oncocytes are radioresistant, complete surgical resection is the</p><p>treatment of choice. There is a low risk of transformation to oncocytic carcinoma.</p><p>References:</p><p>Patel ND, van Zante A, Eisele DW, et al. Oncocytoma: the vanishing parotid mass. AJNR Am J</p><p>Neuroradiol. 2011;32(9):1703-1706.</p><p>Tan TJ, Tan TY. CT features of parotid gland oncocytomas: a study of 10 cases and literature review.</p><p>AJNR Am J Neuroradiol. 2010;31(8):1413-1417.</p><p>DEFORMABLE, VANISHING</p><p>Dome, Mound, Mushroom 177</p><p>Modalities:</p><p>US, CT, MR</p><p>FINDINGS:</p><p>Axial noncontrast and contrast-enhanced CT show a partially calcifi ed,</p><p>heterogeneously enhancing mass that replaces the right globe and invades the optic</p><p>nerve (arrows).</p><p>DIFFERENTIAL DIAGNOSIS:</p><p>• Ocular melanoma</p><p>• Metastasis</p><p>DISCUSSION:</p><p>Melanoma is the most common primary intraocular malignancy in adults. It arises</p><p>from melanocytes within the pigmented uveal tract (choroid, ciliary body, and iris).</p><p>The typical imaging appearance is a solid, diffusely enhancing mass with intrinsic</p><p>T1 hyperintensity and T2 hypointensity on MR. The choroid is the most common</p><p>location, with a “dome” or “mushroom” morphology. The latter appearance implies</p><p>penetration through the Bruch membrane, a structure that normally separates the</p><p>choroid and retina. Associated retinal detachment and subretinal effusions may be</p><p>seen. Further tumor spread can occur posteriorly along the optic nerve and anteriorly</p><p>into the globe, ciliary body, and iris. Other invasive ocular masses include metastases</p><p>from breast, lung, thyroid, renal, and gastrointestinal primaries. Retinoblastoma,</p><p>the most common ocular tumor in children, tends to be more densely calcifi ed.</p><p>References:</p><p>Peyster RG, Augsburger JJ, Shields JA, et al. Intraocular tumors: evaluation with MR imaging.</p><p>Radiology. 1988;168(3):773-779.</p><p>Tong KA, Osborn AG, Mamalis N, et al. Ocular melanoma. AJNR Am J Neuroradiol. 1993;14(6):</p><p>1359-1366.</p><p>DOME, MOUND, MUSHROOM</p><p>178 Chapter 3: Head, Neck, and Orbits</p><p>Modalities:</p><p>US, CT, MR</p><p>FINDINGS:</p><p>Coronal contrast-enhanced T1-weighted MR shows an enhancing mass (arrow) that</p><p>circumferentially encases and compresses the left optic nerve.</p><p>DIAGNOSIS:</p><p>Perioptic meningioma</p><p>DISCUSSION:</p><p>Perioptic meningiomas are benign tumors arising from the arachnoid cap cells</p><p>in the optic nerve sheath. They may arise within the orbit (optic nerve sheath</p><p>meningioma), optic nerve canal (intracanalicular meningioma), or optic foramen</p><p>(foraminal meningioma). Three distinct morphologies have been described: tubular,</p><p>exophytic, and fusiform. The tubular form symmetrically surrounds and compresses</p><p>the optic nerve, with associated enhancement and/or calcifi cation. This gives rise</p><p>to the “doughnut” sign en face and the “tram-track” sign in long axis. In contrast,</p><p>optic gliomas are infi ltrative tumors that are intimately associated with the optic</p><p>nerve. Other causes of perioptic enhancement include orbital pseudotumor, infection,</p><p>sarcoidosis, leukemia/lymphoma, and metastases.</p><p>Reference:</p><p>Kanamalla US. The optic nerve tram-track sign. Radiology. 2003;227(3):718-719.</p><p>DONUT/DOUGHNUT</p><p>Dotted I, Sausage 179</p><p>FINDINGS:</p><p>Axial T2-weighted MR</p><p>shows enlargement and</p><p>kinking of the left optic</p><p>nerve (arrows).</p><p>DIAGNOSIS:</p><p>Optic nerve glioma</p><p>DISCUSSION:</p><p>Optic glioma is the most</p><p>common optic nerve tumor.</p><p>There are three subtypes:</p><p>childhood syndromic (neu-</p><p>rofi bromatosis type I),</p><p>childhood sporadic, and</p><p>adult. Gliomas in children</p><p>are low-grade (WHO I-II),</p><p>whereas in adults they</p><p>are higher grade (WHO grade</p><p>III-IV). These manifest with</p><p>fusiform enlargement and</p><p>elongation of the optic nerve</p><p>(“dotted i” appearance),</p><p>chiasm, and/or radiations.</p><p>MR signal is generally</p><p>T2-hyperintense (“pseudo-</p><p>CSF” appearance). Syn dromic gliomas are smooth, focally tortuous, and minimally</p><p>enhancing. Sporadic gliomas are larger, nodular/cystic, and moderately enhancing.</p><p>Adult gliomas are diffuse, invasive, and heterogeneously enhancing. Other conditions</p><p>affecting the optic nerve include optic neuritis (nerve edema and enhancement),</p><p>optic nerve meningioma (tumor of the nerve sheath), orbital pseudotumor (localized</p><p>infl ammation of various periorbital structures), and sarcoidosis (multifocal orbital and</p><p>intracranial manifestations).</p><p>References:</p><p>Millar WS, Tartaglino LM, Sergott RC, et al. MR of malignant optic glioma of adulthood. AJNR Am</p><p>J Neuroradiol. 1995;16(8):1673-1676.</p><p>Taylor T, Jaspan T, Milano G, et al. Radiological classifi cation of optic pathway gliomas: experience</p><p>of a modifi ed functional classifi cation system. Br J Radiol. 2008;81(970):761-766.</p><p>Modalities:</p><p>US, CT, MR</p><p>DOTTED I, SAUSAGE</p><p>180 Chapter 3: Head, Neck, and Orbits</p><p>FINDINGS:</p><p>Axial temporal bone CT shows a ringlike lucency (arrows) encircling the cochlea.</p><p>There is also involvement of the fi ssula ante fenestram.</p><p>DIFFERENTIAL DIAGNOSIS:</p><p>• Retrofenestral otospongiosis</p><p>• Osteogenesis imperfecta</p><p>DISCUSSION:</p><p>The otic capsule is composed of dense avascular endochondral bone, which ossi fi es</p><p>and undergoes virtually no remodeling after development. However, disorganization</p><p>of bone can be induced by such conditions as otospongiosis, infl ammation/infection,</p><p>radiation, trauma, Paget disease, osteopetrosis, and fi brous dysplasia. Otospongiosis,</p><p>which exclusively affects the otic capsule and auditory ossicles, is a leading cause of</p><p>adult-onset hearing loss. The normally dense avascular endochondral bone is replaced</p><p>by spongy vascular haversian bone. This typically begins at the fi ssula ante fenestram</p><p>(fenestral otospongiosis), a fi brocartilaginous region just anterior to the oval window. In</p><p>the late stages, the disease spreads peripherally to surround the cochlea (retrofenestral</p><p>or cochlear otospongiosis). This appearance has been termed the “fourth turn” of the</p><p>cochlea. Sclerosis in the chronic (healing) phase is known as otosclerosis. Osteogenesis</p><p>imperfecta mimics severe cochlear otospongiosis, but with systemic manifestations.</p><p>Paget disease diffusely involves the temporal bone and skull base, progressing from</p><p>peripheral to central. Fibrous dysplasia has an expansile, ground-glass appearance with</p><p>relative sparing of the otic capsule. Chronic otitis media and cholesteatoma demonstrate</p><p>middle ear opacifi cation with bone erosion and remodeling. Osteoradionecrosis results</p><p>in diffuse “moth-eaten” demineralization of the temporal bone.</p><p>Reference:</p><p>Mafee MF, Valvassori GE, Deitch RL, et al. Use of CT in the evaluation of cochlear otosclerosis.</p><p>Radiology. 1985;156(3):703-708.</p><p>Modality:</p><p>CT</p><p>DOUBLE RING/HALO/LUCENT, FOURTH TURN</p><p>Dumbbell 181</p><p>FINDINGS:</p><p>Coronal CT shows a soft-tissue mass involving the right maxillary sinus and nasal</p><p>cavity, with enlargement of the intervening maxillary antrum (arrows).</p><p>DIAGNOSIS:</p><p>Choanal polyp</p><p>DISCUSSION:</p><p>Choanal (Killian) polyps are infl a mmatory polyps that produce unilateral nasal</p><p>obstruction in teenagers and young adults. They arise from the sinonasal mucosa</p><p>and herniate through the sinus ostium</p><p>into the nasal cavity, causing smooth bone</p><p>remodeling. Polyps that are suffi ciently large can prolapse through the choana</p><p>into the nasopharynx. Antrochoanal polyps are the most common, appearing as</p><p>“dumbbell”-shaped mucoid masses that extend from the maxillary sinus through</p><p>an accessory or major ostium into the ipsilateral nasal cavity. In contrast, sinonasal</p><p>inverted papillomas arise from the lateral nasal wall near the hiatus semilunaris and</p><p>demonstrate peripheral growth into the sinuses, with a “cerebriform” pattern at</p><p>imaging. Less common types of choanal polyps are nasochoanal, sphenochoanal,</p><p>frontochoanal, and ethmochoanal.</p><p>References:</p><p>Aydin O, Keskin G, Ustünda E, et al. Choanal polyps: an evaluation of 53 cases. Am J Rhinol.</p><p>2007;21(2):164-168.</p><p>Chung SK, Chang BC, Dhong HJ. Surgical, radiologic, and histologic fi ndings of the antrochoanal</p><p>polyp. Am J Rhinol. 2002;16(2):71-76.</p><p>Modalities:</p><p>CT, MR</p><p>DUMBBELL</p><p>182 Chapter 3: Head, Neck, and Orbits</p><p>FINDINGS:</p><p>Axial T2-weighted MR shows a lobulated hyperintense mass in the left parotid</p><p>gland, deep to the retromandibular vein (thin arrow). There is extension through the</p><p>stylomandibular foramen (thick arrows) into the parapharyngeal space.</p><p>DIAGNOSIS:</p><p>Parotid tumor, deep lobe</p><p>DISCUSSION:</p><p>The parotid gland is anatomically divided into superfi cial and deep lobes by the</p><p>extracranial facial nerve. The superfi cial lobe represents the palpable, dominant</p><p>portion of the gland. It constitutes approximately two-thirds of total gland volume</p><p>and extends from the external auditory canal and mastoid tip to below the angle</p><p>of the mandible (parotid tail). The deep lobe, which projects into the lateral</p><p>parapharyngeal space, comprises the remaining one-third of gland volume. Because</p><p>the intraparotid facial nerve is too small to visualize on conventional imaging, the</p><p>retromandibular vein (which lies directly medial to CN VII) is used as a marker for its</p><p>course. Deep lobe tumors can occasionally grow through the stylomandibular tunnel</p><p>into the parapharyngeal space, creating a “dumbbell” appearance. This behavior is</p><p>concerning for malignancy, though benign lesions (including pleomorphic adenomas</p><p>and schwannomas) can have a similar appearance. Symptoms are nonspecifi c due to</p><p>containment within an anatomically limited space. This means that metastasis may</p><p>occur before the primary tumor is diagnosed. If the tumor has not metastasized,</p><p>defi nitive therapy involves total parotidectomy with facial nerve preservation. This</p><p>may require external, transoral, or combined surgical approaches. Resection of the</p><p>styloid process of the temporal bone is necessary to enlarge the stylomandibular</p><p>foramen and ensure complete tumor removal.</p><p>References:</p><p>Christe A, Waldherr C, Hallett R, et al. MR imaging of parotid tumors: typical lesion characteristics in</p><p>MR imaging improve discrimination between benign and malignant disease. AJNR Am J Neuroradiol.</p><p>2011;32(7):1202-1207.</p><p>Patey DH, Thackray AC. The pathological anatomy and treatment of parotid tumours with</p><p>retropharyngeal extension (dumb-bell tumours); with a report of 4 personal cases. Br J Surg. 1957;</p><p>44(186):352-358.</p><p>DUMBBELL</p><p>Modalities:</p><p>CT, MR</p><p>Dumbbell 183</p><p>FINDINGS:</p><p>Axial T2-weighted and contrast-enhanced T1-weighted MR show a bilobed solid</p><p>and cystic mass extending from the left cerebellopontine angle (thick arrows) into</p><p>the Meckel cave and cavernous sinus. There is signifi cant left pontine and cerebellar</p><p>compression, effacement of the fourth ventricle, and medial deviation of the left</p><p>cavernous ICA (thin arrows).</p><p>DIAGNOSIS:</p><p>Trigeminal nerve schwannoma</p><p>DISCUSSION:</p><p>Schwannomas (neurilemmomas) are benign nerve sheath tumors composed of</p><p>myelinating Schwann cells. These frequently involve the cranial nerves, with a</p><p>characteristic fusiform appearance and smooth bony expansion. Large tumors can</p><p>extend through osseous foramina to create a bilobed or “dumbbell” morphology.</p><p>Common locations include CN V (trigeminal), VII (facial), VIII (vestibulocochlear), and</p><p>X (vagal). Multiple schwannomas are seen in schwannomatosis and neurofi bromatosis</p><p>type II (MISME: multiple inherited schwannomas, meningiomas, and ependymomas).</p><p>References:</p><p>Al-Mefty O, Ayoubi S, Gaber E. Trigeminal schwannomas: removal of dumbbell-shaped tumors</p><p>through the expanded Meckel cave and outcomes of cranial nerve function. J Neurosurg.</p><p>2002;96(3):453-463.</p><p>Kadri PA, Al-Mefty O. Surgical treatment of dumbbell-shaped jugular foramen schwannomas.</p><p>Neurosurg Focus. 2004;17(2):E9.</p><p>Salzman KL, Davidson HC, Harnsberger HR, et al. Dumbbell schwannomas of the internal auditory</p><p>canal. AJNR Am J Neuroradiol. 2001;22(7):1368-1376.</p><p>DUMBBELL</p><p>Modalities:</p><p>CT, MR</p><p>184 Chapter 3: Head, Neck, and Orbits</p><p>Modalities:</p><p>CT, MR</p><p>FINDINGS:</p><p>Coronal contrast-enhanced T1-weighted MR shows an enhancing sellar/suprasellar</p><p>mass with focal constriction at the diaphragma sellae (arrows).</p><p>DIAGNOSIS:</p><p>Pituitary macroadenoma</p><p>DISCUSSION:</p><p>Pituitary macroadenomas are benign, usually nonfunctioning tumors greater than</p><p>1 cm in size. Over time, these gradually replace the pituitary gland, grow up through</p><p>the diaphragma sellae into the suprasellar region with a “snowman” appearance,</p><p>and elevate the optic chiasm. Often, there is heterogeneous enhancement with areas</p><p>of cystic change, necrosis, and hemorrhage. Aggressive adenomas can invade and</p><p>remodel the sella, sphenoid, clivus, and cavernous sinuses. Other sellar/suprasellar</p><p>masses include craniopharyngioma, Rathke cleft cyst, and meningioma, which</p><p>do not typically show focal constriction at the diaphragma sellae. The general</p><p>mnemonic for suprasellar masses is “SATCHMOE”: sellar/parasellar neoplasm,</p><p>aneurysm, teratoma/germ cell tumor, craniopharyngioma, hypothalamic hamartoma</p><p>or Langerhans cell histiocytosis, meningioma or metastasis, optic or hypothalamic</p><p>glioma, and epidermoid or dermoid cyst.</p><p>Reference:</p><p>Hess CP, Dillon WP. Imaging the pituitary and parasellar region. Neurosurg Clin N Am. 2012;23(4):</p><p>529-542.</p><p>DUMBBELL, FIGURE EIGHT, SNOWMAN</p><p>Dumbbell, Waist 185</p><p>Modalities:</p><p>CT, MR</p><p>FINDINGS:</p><p>Coronal contrast-enhanced T1-weighted MR shows an enhancing mass centered at</p><p>the cribriform plate (arrows), with intracranial and intranasal extension. Peritumoral</p><p>cysts are present along the superior margin of the mass.</p><p>DIFFERENTIAL DIAGNOSIS:</p><p>• Esthesioneuroblastoma</p><p>• Sinonasal carcinoma</p><p>DISCUSSION:</p><p>Esthesioneuroblastoma (olfactory neuroblastoma) is a rare malignant primitive</p><p>neuroectodermal tumor (PNET) that arises from the olfactory epithelium in the</p><p>superior nasal cavity. Typically, signal is T2 iso- to hyperintense and T1-hypointense</p><p>on MR, with avid enhancement. Progressive tumor expansion can cause destruction</p><p>of surrounding bone with extension into the paranasal sinuses, contralateral nasal</p><p>cavity, orbits, and/or cranial cavity. Invasion through the cribriform plate produces</p><p>a “dumbbell” shape, and cystic degeneration may be identifi ed at the tumor-brain</p><p>junction. The differential includes other sinonasal malignancies (squamous cell</p><p>carcinoma, adenocarcinoma, non-Hodgkin lymphoma, undifferentiated carcinoma),</p><p>which usually occur in older patients. On imaging, these tend to demonstrate more</p><p>irregular morphology, lower-level heterogeneous enhancement, and absence of</p><p>peritumoral cysts.</p><p>References:</p><p>Pickuth D, Heywang-Köbrunner SH, Spielmann RP. Computed tomography and magnetic resonance</p><p>imaging features of olfactory neuroblastoma: an analysis of 22 cases. Clin Otolaryngol Allied Sci.</p><p>1999;24(5):457-461.</p><p>Yu T, Xu YK, Li L, et al. Esthesioneuroblastoma methods of intracranial extension: CT and MR</p><p>imaging fi ndings. Neuroradiology. 2009;51(12):841-850.</p><p>DUMBBELL, WAIST</p><p>186 Chapter 3: Head, Neck, and Orbits</p><p>Modalities:</p><p>CT, MR</p><p>FINDINGS:</p><p>Coronal CT shows normal bilateral jugular foramina (thick arrows) and jugular</p><p>tubercles (thin arrows) curving superiorly over the hypoglossal canals.</p><p>DIAGNOSIS:</p><p>Normal jugular tubercles</p><p>DISCUSSION:</p><p>The jugular tubercles</p><p>are lateral protuberances of the occipital bone that curve</p><p>posterosuperiorly over the hypoglossal canals. The pointed “eagle beak” appearance</p><p>was fi rst described on anteroposterior tomographic images, but can now be seen on</p><p>coronal CT or MR. This appearance may be disrupted by tumors or bone dyscrasias.</p><p>Reference:</p><p>Osborn AG, Brinton WR, Smith WH. Radiology of the jugular tubercles. AJR Am J Roentgenol.</p><p>1978;131(6):1037-1040.</p><p>EAGLE BEAK/HEAD</p><p>Earring 187</p><p>Modalities:</p><p>US, CT, MR</p><p>FINDINGS:</p><p>Coronal contrast-enhanced CT shows heterogeneously enhancing rounded masses</p><p>in the bilateral parotid tails (arrows).</p><p>DIFFERENTIAL DIAGNOSIS:</p><p>• Warthin tumor</p><p>• Pleomorphic adenoma</p><p>• Lymphoma</p><p>DISCUSSION:</p><p>The parotid gland is anatomically divided into superfi cial and deep lobes by the</p><p>extracranial facial nerve. The superfi cial lobe represents the palpable, dominant</p><p>portion of the gland. It constitutes approximately two-thirds of total gland volume</p><p>and extends from the external auditory canal and mastoid tip to below the angle of the</p><p>mandible. The parotid tail is the most inferior aspect of the superfi cial lobe, and lies</p><p>close to the posterior submandibular space. On axial images, a parotid tail mass can</p><p>easily be mistaken for a submandibular or jugulodigastric lymph node, particularly</p><p>if the lesion is pedunculated and/or the parotid gland is atrophic. Review of coronal</p><p>images is essential to demonstrate a connection to the parotid gland (“earring”</p><p>appearance). The most common parotid tail lesion is Warthin tumor (papillary</p><p>cystadenoma lymphomatosum, adenolymphoma, lymphomatous adenoma), which</p><p>arises from salivary lymphoid tissue in intraparotid and periparotid nodes. This</p><p>is the second most common benign tumor of the parotid gland, and is typically</p><p>seen in older male smokers. Lesions have a heterogeneous solid/cystic appearance</p><p>and can be bilateral. Various other lesions can occur in the parotid tail, including</p><p>pleomorphic adenoma, lymphoma, metastases, mucoepidermoid carcinoma, lipoma,</p><p>oncocytoma, infection, venolymphatic malformation, lymphoepithelial cyst, and</p><p>fi rst branchial cleft cyst. Surgical resection is typically required for tissue diagnosis.</p><p>Reference:</p><p>Hamilton BE, Salzman KL, Wiggins RH 3rd, et al. Earring lesions of the parotid tail. AJNR Am J</p><p>Neuroradiol. 2003;24(9):1757-1764.</p><p>EARRING</p><p>188 Chapter 3: Head, Neck, and Orbits</p><p>FINDINGS:</p><p>Coronal CT shows bilateral maxillary antrostomy, middle turbinectomy, and internal</p><p>ethmoidectomy.</p><p>DIAGNOSIS:</p><p>Sinus surgery</p><p>DISCUSSION:</p><p>The paired nasal turbinates are responsible for controlling, heating, humidifying,</p><p>and fi ltering airfl ow through the nose. Normal nasal cycling occurs every 3-6 hours,</p><p>in which one side of the nose congests with blood and regenerates, while the other</p><p>side remains decongested and performs the workload of breathing. In patients with</p><p>chronic sinusitis, turbinectomy may be performed to alleviate obstruction. In cases</p><p>of excessive turbinectomy, the remaining mucosa loses the ability to regenerate,</p><p>becomes infl amed, and eventually atrophies (“empty nose” appearance). Symptoms</p><p>include chronic dryness and a paradoxical sense of obstruction.</p><p>Reference:</p><p>Coste A, Dessi P, Serrano E. Empty nose syndrome. Eur Ann Otorhinolaryngol Head Neck Dis.</p><p>2012;129(2):93-97.</p><p>Modalities:</p><p>CT, MR</p><p>EMPTY NOSE</p><p>Empty Pituitary Fossa, Empty Sella 189</p><p>FINDINGS:</p><p>Sagittal T1-weighted MR</p><p>shows increased CSF within</p><p>the sella, with fl attening of</p><p>the pituitary gland (arrow)</p><p>against the sellar fl oor.</p><p>DIFFERENTIAL DIAGNOSIS:</p><p>• Normal variant</p><p>• Idiopathic intracranial</p><p>hypertension</p><p>• Secondary empty sella</p><p>DISCUSSION:</p><p>The sella turcica is a</p><p>depression in the sphenoid</p><p>bone that encloses the</p><p>pituitary gland. Empty sella</p><p>refers to a pituitary fossa</p><p>that is largely devoid of tissue</p><p>and fi lled with cerebrospinal</p><p>fl uid. This is thought to</p><p>represent extension of the</p><p>subarachnoid space through a defect in the diaphragma sellae. Primary empty sella</p><p>is a common incidental fi nding, though there is an association with pseudotumor</p><p>cerebri (idiopathic intracranial hypertension). Secondary empty sella can occur due</p><p>to surgery, trauma, radiation, medications, infection, infarction, or hemorrhage.</p><p>In the days of radiography, “empty sella” denoted the fi nding of a symmetrically</p><p>enlarged pituitary fossa with thinned bony margins, for which no mass was identifi ed</p><p>at pneumoencephalography or surgery. With cross-sectional imaging, enlargement of</p><p>the CSF space can be seen, with a traversing midline infundibulum and compression</p><p>of the pituitary gland against the sellar fl oor.</p><p>References:</p><p>Haughton VM, Rosenbaum AE, Williams AL, et al. Recognizing the empty sella by CT: the</p><p>infundibulum sign. AJR Am J Roentgenol. 1981;136(2):293-295.</p><p>Yuh WT, Zhu M, Taoka T, et al. MR imaging of pituitary morphology in idiopathic intracranial</p><p>hypertension. J Magn Reson Imaging. 2000;12(6):808-813.</p><p>Modalities:</p><p>XR, CT, MR</p><p>EMPTY PITUITARY FOSSA, EMPTY SELLA</p><p>190 Chapter 3: Head, Neck, and Orbits</p><p>FINDINGS:</p><p>Sagittal T1-weighted MR</p><p>shows an enlarged pituitary</p><p>gland (arrow) that fi lls the</p><p>sella turcica and bulges into</p><p>the suprasellar region.</p><p>DIFFERENTIAL DIAGNOSIS:</p><p>• Venous congestion</p><p>• Pituitary hyperplasia</p><p>• Pituitary tumor</p><p>• Pituitary infl ammation</p><p>• Normal variant</p><p>DISCUSSION:</p><p>Pituitary size and height</p><p>vary widely with age,</p><p>gender, and hormonal status.</p><p>Pseudoenlargement of the</p><p>gland can occur with a shallow</p><p>sella or medialization of the</p><p>cavernous ICAs. Pituitary</p><p>hyperplasia is common in</p><p>patients with elevated hormonal activity. At imaging, there is convex bulging of the</p><p>gland with homogeneous enhancement. Pituitary cysts and nonfunctioning adenomas</p><p>(“incidentalomas”) can enlarge the gland without symptoms. On dynamic contrast-</p><p>enhanced MR, these appear as focal nonenhancing or hypoenhancing masses. Pituitary</p><p>apoplexy, or Sheehan syndrome, refers to acute infarction and/or hemorrhage, usually</p><p>in association with an underlying adenoma. Other infl ammatory and infi ltrative</p><p>processes that enlarge the pituitary gland and/or infundibulum include sarcoidosis,</p><p>Langerhans cell histiocytosis, lymphocytic hypophysitis, leukemia, lymphoma,</p><p>and metastases. Rarely, venous congestion from intracranial hypotension (CSF</p><p>hypovolemia) or a dural arteriovenous fi stula can cause pituitary edema.</p><p>References:</p><p>Argyropoulou MI, Kiortsis DN. MRI of the hypothalamic-pituitary axis in children. Pediatr Radiol.</p><p>2005;35(11):1045-1055.</p><p>Tsunoda A, Okuda O, Sato K. MR height of the pituitary gland as a function of age and sex:</p><p>especially physiological hypertrophy in adolescence and in climacterium. AJNR Am J Neuroradiol.</p><p>1997;18(3):551-554.</p><p>Modalities:</p><p>CT, MR</p><p>ENLARGED/SWOLLEN PITUITARY</p><p>Figure Eight, Snowman 191</p><p>FINDINGS:</p><p>Axial CT cisternogram and high-resolution T2-weighted MR of the temporal bone</p><p>show a bulbous appearance of the cochlea (thick arrows), which consists of a single</p><p>turn with connection to a dilated vestibule (thin arrows). There is enlargement of</p><p>the semicircular canals and internal auditory canal. Contrast is seen leaking from the</p><p>inner ear into the middle ear cavity.</p><p>DIAGNOSIS:</p><p>Incomplete partition type I (cystic cochleovestibular anomaly)</p><p>DISCUSSION:</p><p>Cochleovestibular malformations are thought to result from interruptions in inner</p><p>ear development between the third and seventh weeks of embryogenesis, with earlier</p><p>insults producing more severe anomalies. Associated fi ndings include enlarged</p><p>vestibular aqueduct, semicircular canal dysplasia, and cranial nerve defi ciency. The</p><p>spectrum of cochleovestibular abnormalities has been classifi ed by Sennaroglu into</p><p>six categories. From most to least severe, these are labyrinthine aplasia (Michel</p><p>deformity), cochlear aplasia, common cavity, incomplete partition type I (cystic</p><p>cochleovestibular anomaly), cochleovestibular hypoplasia, and incomplete partition</p><p>type II (Mondini deformity, large endolymphatic sac anomaly). In labyrinthine aplasia,</p><p>there is complete absence of cochlea and vestibule. In cochlear aplasia, the cochlea</p><p>is absent and a rudimentary vestibule is present. In common cavity, the cochlea and</p><p>vestibule are fused into a single large cystic cavity. In IP-I, the cochlea and vestibule</p><p>are cystic and partially separated, forming a “fi gure 8” pattern. In cochleovestibular</p><p>hypoplasia, the cochlea and vestibule are separate and smaller than normal. In IP-II,</p><p>the cochlea is hypoplastic with a decreased number of turns (classically 1.5), cystic</p><p>apex (fused middle and apical turns), and defi cient modiolus.</p><p>References:</p><p>Harnsberger HR, Glastonbury CM, Michel MA, et al. Diagnostic Imaging: Head and Neck. 2nd ed.</p><p>Lippincott Williams & Wilkins; 2010.</p><p>Sennaroglu L, Saatci I. A new classifi cation for cochleovestibular malformations. Laryngoscope.</p><p>2002;112(12):2230-2241.</p><p>Modalities:</p><p>CT, MR</p><p>FIGURE EIGHT, SNOWMAN</p><p>192 Chapter 3: Head, Neck, and Orbits</p><p>FINDINGS:</p><p>Axial CT shows a collapsed and post eriorly fl attened right globe (arrow), with</p><p>intraocular hemorrhage and severe preseptal edema.</p><p>DIAGNOSIS:</p><p>Scleral rupture</p><p>DISCUSSION:</p><p>The globes are lined by three concentric coverings: the internal nervous, middle</p><p>vascular, and external fi brous tunics. The retina contains photoreceptors (rods, cones,</p><p>and photosensitive gan glion cells) that process light stimuli and send impulses through</p><p>the optic nerve to the brain. The choroid consists of vascular pigmented connective</p><p>tissue responsible for nutrition and gas exchange, and forms the uveal tract along</p><p>with the ciliary body and iris. The sclera is composed of protective fi brous tissue, and</p><p>is continuous anteriorly with the cornea. Scleral rupture is the most severe form of</p><p>ocular trauma, and is usually clinically obvious. However, posterior ruptures may be</p><p>occult and identifi ed on CT as fl attening and posterior thickening of the globe (“fl at</p><p>tire” or “umbrella”). Vitreous hemorrhage, intraocular gas, and foreign bodies may</p><p>also be present. Therapy involves prompt wound closure and ocular reconstruction.</p><p>Reference:</p><p>Sevel D, Krausz H, Ponder T, et al. Value of computed tomography for the diagnosis of a ruptured eye.</p><p>J Comput Assist Tomogr. 1983;7(5):870-875.</p><p>Modalities:</p><p>US, CT, MR</p><p>FLAT TIRE, UMBRELLA</p><p>High Heel Footprint 193</p><p>Modality:</p><p>CT</p><p>FINDINGS:</p><p>Axial CT of the skull base shows the elongated foramina ovale anteromedially</p><p>(arrows) and the punctate foramina spinosum posterolaterally.</p><p>DIAGNOSIS:</p><p>Normal foramen ovale and foramen spinosum</p><p>DISCUSSION:</p><p>The skull base transmits several important neurovascular foramina. Within the</p><p>greater wing of the sphenoid, the foramen rotundum, ovale, and spinosum are seen</p><p>from anteromedial to posterolateral. The foramen rotundum has a small rounded</p><p>shape, courses anteroposteriorly, and contains the maxillary nerve (CN V2). The</p><p>foramen ovale is large and ovoid, transmitting several structures per the mnemonic</p><p>“OVALE”: otic ganglion, CN V3 (mandibular nerve), accessory meningeal artery,</p><p>lesser petrosal nerve (of CN IX), and emissary veins. The punctate foramen spinosum,</p><p>which is adjacent to the foramen ovale, contains the recurrent meningeal nerve,</p><p>middle meningeal artery, and middle meningeal vein. On axial images, the foramina</p><p>ovale and spinosum resemble a “high heel footprint.”</p><p>References:</p><p>Barra FR, Gonçalves FG, Matos VL, et al. Signs in neuroradiology—part 2. Radiol Bras. 2011;44(2):</p><p>129-133.</p><p>Ginsberg LE, Pruett SW, Chen MY, et al. Skull-base foramina of the middle cranial fossa: reassessment</p><p>of normal variation with high-resolution CT. AJNR Am J Neuroradiol. 1994;15(2):283-291.</p><p>HIGH HEEL FOOTPRINT</p><p>194 Chapter 3: Head, Neck, and Orbits</p><p>Modalities:</p><p>CT, MR</p><p>FINDINGS:</p><p>Axial contrast-enhanced CT shows heterogeneous enhancement of both parotid</p><p>glands (arrows), with multiple specks of fat and calcifi cation.</p><p>DIAGNOSIS:</p><p>Sjögren syndrome</p><p>DISCUSSION:</p><p>Sjögren (sicca) syndrome is a systemic autoimmune disorder affecting the salivary</p><p>and lacrimal glands. The primary form occurs in isolation, while the secondary form</p><p>is seen in conjunction with other autoimmune disorders such as lupus, rheumatoid</p><p>arthritis, or scleroderma. In the acute phase, the parotid glands appear swollen</p><p>and edematous. In early subacute disease, numerous lymphoepithelial cysts can be</p><p>seen in a miliary distribution. In late subacute disease, there is a mixed cystic and</p><p>solid appearance with calcifi cations. Discrete nodules in the gland may represent</p><p>infl ammatory pseudomasses (Kuttner tumor, or chronic sclerosing sialadenitis),</p><p>lymphoid hyperplasia, or lymphoma. In the chronic phase, there is diffuse gland</p><p>atrophy with fatty replacement and fi brosis. The combination of parotid parenchyma,</p><p>cysts, calcifi cation, and fat produces a “salt and pepper” appearance on both CT</p><p>and MR.</p><p>References:</p><p>Takashima S, Takeuchi N, Morimoto S, et al. MR imaging of Sjögren syndrome: correlation with</p><p>sialography and pathology. J Comput Assist Tomogr. 1991;15(3):393-400.</p><p>Yousem DM, Kraut MA, Chalian AA. Major salivary gland imaging. Radiology. 2000;216(1):19-29.</p><p>HONEYCOMB, SALT AND PEPPER, STIPPLED</p><p>Honeycomb, Speckled, Stippled 195</p><p>Modality:</p><p>CT</p><p>FINDINGS:</p><p>• Axial temporal bone CT shows an expansile lytic lesion with punctate sclerotic</p><p>foci in the perigeniculate region (arrow).</p><p>• Axial contrast-enhanced T1-weighted MR shows speckled enhancement with</p><p>central low-signal foci in the geniculate ganglion (arrow).</p><p>DIFFERENTIAL DIAGNOSIS:</p><p>• Facial nerve venous malformation</p><p>• Geniculate ganglion meningioma</p><p>DISCUSSION:</p><p>Facial nerve venous malformation (previously known as ossifying hemangioma)</p><p>is a benign developmental vascular lesion of CN VII that frequently occurs in</p><p>the region of the geniculate ganglion, and rarely in the internal auditory canal.</p><p>These are avidly enhancing, irregular masses that induce reactive changes in the</p><p>surrounding bone, with amorphous “honeycomb” matrix and high-density fl ecks or</p><p>spicules. Geniculate ganglion meningiomas are rare tumors that arise from ectopic</p><p>arachnoid cell rests. As they grow, they tend to infi ltrate the temporal bone with a</p><p>permeative and sclerotic appearance. Facial nerve schwannomas are tubular masses</p><p>that smoothly enlarge the facial nerve canal. Perineural spread of malignancy shows</p><p>contiguous enlargement and enhancement of CN VII, extending proximally through</p><p>the stylomastoid foramen.</p><p>References:</p><p>Curtin HD, Jensen JE, Barnes L Jr, et al. “Ossifying” hemangiomas of the temporal bone: evaluation</p><p>with CT. Radiology. 1987;164(3):831-835.</p><p>Mijangos SV, Meltzer DE. Case 171: facial nerve hemangioma. Radiology. 2011;260(1):296-301.</p><p>HONEYCOMB, SPECKLED, STIPPLED</p><p>196 Chapter 3: Head, Neck, and Orbits</p><p>FINDINGS:</p><p>Axial temporal bone CT shows a normal incudomalleal joint (arrow), with the head</p><p>of the malleus articulating with the body of the incus.</p><p>DIAGNOSIS:</p><p>Normal incus-malleus confi guration</p><p>DISCUSSION:</p><p>The auditory ossicles are a chain of movable bones in the middle ear, which transmit</p><p>vibrations from the external auditory canal to the inner ear. The malleus (Latin</p><p>for “hammer”) consists of a head, neck, lateral process, anterior process, and</p><p>manubrium. The manubrium (Latin for “handle”) contacts the tympanic membrane</p><p>at its lateral margin. The oval head of the malleus (“ice cream”) articulates posteriorly</p><p>with the body of the incus (“cone”). The incus (Latin for “anvil”) consists of a body,</p><p>short process, long process, and lenticular process. The stapes (Latin for “stirrup”)</p><p>consists of a head, neck, anterior and posterior crura, and a base (footplate) that</p><p>articulates directly with the oval window.</p><p>Reference:</p><p>Gray H. Anatomy of the Human Body. Bartleby; 1918.</p><p>Modality:</p><p>CT</p><p>ICE CREAM CONE</p><p>Ice Cream Cone, Mushroom, Trumpet, Tail 197</p><p>FINDINGS:</p><p>Axial contrast-enhanced T1-</p><p>weighted MR shows an</p><p>enhancing mass extending</p><p>from the left cerebellopontine</p><p>angle through the porus</p><p>acousticus (arrow) into the</p><p>internal auditory canal.</p><p>DIAGNOSIS:</p><p>Vestibular</p><p>multiforme, infarct (subacute), contusion, demyelinating disease,</p><p>radiation necrosis, and lymphoma. Other than demyelinating disease, incomplete</p><p>ring enhancement is occasionally seen in low-grade primary tumors and lymphoma</p><p>affecting immunocompromised patients.</p><p>References:</p><p>Given CA 2nd, Stevens BS, Lee C. The MRI appearance of tumefactive demyelinating lesions. AJR Am</p><p>J Roentgenol. 2004;182(1):195-199.</p><p>Masdeu JC, Quinto C, Olivera C, et al. Open-ring imaging sign: highly specifi c for atypical brain</p><p>demyelination. Neurology. 2000;54(7):1427-1433.</p><p>Smirniotopoulos JG, Murphy FM, Rushing EJ, et al. Patterns of contrast enhancement in the brain</p><p>and meninges. Radiographics. 2007;27(2):525-551.</p><p>ARC, BROKEN/INCOMPLETE/OPEN RING, CRESCENT, HORSESHOE, LEADING EDGE</p><p>Modalities:</p><p>CT, MR</p><p>4 Chapter 1: Adult and General Brain</p><p>FINDINGS:</p><p>Axial contrast-enhanced T1-</p><p>weighted MR shows a left</p><p>basal ganglia rim-enhancing</p><p>lesion with large eccentric</p><p>nodule (arrow).</p><p>DIFFERENTIAL DIAGNOSIS:</p><p>• Toxoplasmosis</p><p>• Other infection</p><p>• Malignancy</p><p>DISCUSSION:</p><p>Toxoplasmosis refers to</p><p>infection by the protozoan</p><p>Toxoplasma gondii and</p><p>occurs from exposure to</p><p>feces from infected cats, who</p><p>are the primary hosts; or by</p><p>ingestion of infected raw meat</p><p>such as pork. Ingested oocysts</p><p>from cat feces and tissue cysts</p><p>from contaminated meat transform into tachyzoites within the bloodstream. These</p><p>preferentially localize in CNS and muscle tissue, where they develop into cystic</p><p>bradyzoites. In pregnant women, tachyzoites can also cross the placental barrier</p><p>and cause neonatal infection. Toxoplasmosis brain lesions are usually multifocal,</p><p>with rim enhancement and large irregular nodules representing a combination of</p><p>infl ammation, hemorrhage, and necrosis. In the cortex and deep gray matter, the</p><p>nodules tend to be eccentrically located (“asymmetric target” sign), corresponding</p><p>pathologically to necrotizing abscesses with penetrating vessels. Deep parenchymal</p><p>lesions may demonstrate a more concentric appearance (“concentric target” sign),</p><p>which is more specifi c for toxoplasmosis and corresponds pathologically to central</p><p>hemorrhage. In contrast, bacterial abscesses are typically smooth and ring-enhancing</p><p>without associated nodularity. Neurocysticercosis demonstrates small calcifi ed</p><p>“dotlike” lesions, corresponding pathologically to parasitic scolices. Primary cystic</p><p>neoplasms and metastases are usually more heterogeneous in appearance.</p><p>References:</p><p>Kumar GG, Mahadevan A, Guruprasad AS, et al. Eccentric target sign in cerebral toxoplasmosis:</p><p>neuropathological correlate to the imaging feature. J Magn Reson Imaging. 2010;31(6):1469-1472.</p><p>Mahadevan A, Ramalingaiah AH, Parthasarathy S, et al. Neuropathological correlate of the</p><p>“concentric target sign” in MRI of HIV-associated cerebral toxoplasmosis. J Magn Reson Imaging.</p><p>2013;38(2):488-495.</p><p>ASYMMETRIC/ECCENTRIC TARGET</p><p>Modalities:</p><p>CT, MR</p><p>Bat, Bearded Skull, Dragon Claw 5</p><p>FINDINGS:</p><p>• Axial T2-weighted MR reveals edema in the ventral midbrain (arrows) with</p><p>sparing of the red nuclei.</p><p>• Axial CT shows edema in the posterior limbs of the internal capsules (arrows),</p><p>optic radiations, and splenium.</p><p>DIAGNOSIS:</p><p>Toxic leukoencephalopathy</p><p>DISCUSSION:</p><p>Toxic leukoencephalopathy can be caused by drug abuse, environmental toxins,</p><p>immunosuppressive medications, and cranial irradiation. Classically, there is diffuse</p><p>supratentorial white matter T2 hyperintensity and reduced diffusion. Selective</p><p>involvement of the internal capsules and optic radiations produces a “dragon claw”</p><p>appearance. Infratentorial abnormalities may also occur, particularly in cases of</p><p>heroin inhalation (“chasing the dragon”). The “bat” sign of the midbrain refers to</p><p>edema in the medial lemnisci and spinothalamic tracts (“face”) with sparing of the</p><p>substantia nigra and red nuclei (“eyes”). The pontocerebellar “bearded skull” sign</p><p>represents edema of the corticospinal tracts (“eyes”), medial lemnisci and central</p><p>tegmental tracts (“mouth”), and cerebellar white matter, sparing the dentate nuclei</p><p>(“beard”). Findings can be diffi cult to distinguish from other leukoencephalopathies,</p><p>and clinical correlation is essential for diagnosis.</p><p>Reference:</p><p>Keogh CF, Andrews GT, Spacey SD, et al. Neuroimaging features of heroin inhalation toxicity:</p><p>“chasing the dragon.” AJR Am J Roentgenol. 2003;180(3):847-850.</p><p>BAT, BEARDED SKULL, DRAGON CLAW</p><p>Modalities:</p><p>CT, MR</p><p>6 Chapter 1: Adult and General Brain</p><p>Modality:</p><p>MR</p><p>BAT WING, BUTTERFLY, TRIDENT</p><p>FINDINGS:</p><p>Axial T2-weighted MR in two different patients shows central pontine</p><p>hyperintensities, sparing the tegmentum ventrally and corticospinal tracts laterally.</p><p>DIAGNOSIS:</p><p>Osmotic demyelination syndrome</p><p>DISCUSSION:</p><p>Osmotic demyelination syndrome (ODMS), formerly classifi ed into central</p><p>pontine myelinolysis (CPM) and extrapontine myelinolysis (EPM), refers to acute</p><p>demyelination caused by rapid changes in serum osmolality. The classic presentation</p><p>is an alcoholic, hyponatremic patient who undergoes rapid correction of serum</p><p>sodium levels, resulting in massive fl uid effl ux from the brain into the serum.</p><p>Symmetric T2-hyperintense signal and reduced diffusion are seen in the central pons,</p><p>basal ganglia, and/or cerebral white matter. Mild injury produces signal abnormality</p><p>in the median raphe and basis pontis, with a bilobed (“bat wing”) or triangular</p><p>(“trident”) morphology. More profound injury affects the entire pons with relative</p><p>sparing of the tegmentum, corticobulbar, and corticospinal tracts (“snake eyes”</p><p>appearance). In the subacute period, signal changes improve or resolve completely.</p><p>The differential for central pontine T2 hyperintensity includes infarction, neoplasm,</p><p>demyelination, infection, metabolic disorders, and radiation. However, combined</p><p>fi ndings of CPM and EPM are essentially pathognomonic for ODMS.</p><p>References:</p><p>Ho VB, Fitz CR, Yoder CC, et al. Resolving MR features in osmotic myelinolysis (central pontine and</p><p>extrapontine myelinolysis). AJNR Am J Neuroradiol. 1993;14(1):163-167.</p><p>Miller GM, Baker HL Jr, Okazaki H, et al. Central pontine myelinolysis and its imitators: MR fi ndings.</p><p>Radiology. 1988;168(3):795-802.</p><p>Black/Dark Cerebellum 7</p><p>FINDINGS:</p><p>• Axial T2-weighted MR of the cerebrum shows diffuse edema with abnormally</p><p>hyperintense cortex and gyral swelling.</p><p>• Axial T2-weighted MR of the cerebellum shows normal signal (arrows), which</p><p>appears artifactually hypointense relative to the cerebrum.</p><p>DIAGNOSIS:</p><p>Diffuse cerebral edema</p><p>DISCUSSION:</p><p>Diffuse cerebral edema occurs in various settings including trauma, hypoxia,</p><p>ischemia, and infection. There is relative sparing of the basal ganglia, brainstem,</p><p>and cerebellum. The mechanism is unknown but may represent preferential arterial</p><p>circulation, delayed venous drainage, or decompression by transtentorial herniation.</p><p>The preserved cerebellum appears brighter than the edematous cerebrum on CT</p><p>(“white cerebellum”) and darker on T2-weighted MR (“black cerebellum”), which</p><p>is the reverse of the normal appearance.</p><p>References:</p><p>Bird CR, Drayer BP, Gilles FH. Pathophysiology of “reverse” edema in global cerebral ischemia.</p><p>AJNR Am J Neuroradiol. 1989;10(1):95-98.</p><p>Brant WE, Helms C. Fundamentals of Diagnostic Radiology, 3rd ed. Baltimore: Lippincott Williams</p><p>and Wilkins, 2012.</p><p>BLACK/DARK CEREBELLUM</p><p>Modality:</p><p>MR</p><p>8 Chapter 1: Adult and General Brain</p><p>FINDINGS:</p><p>Axial contrast-enhanced T1-weighted MR shows multiple T1-hypointense,</p><p>nonenhancing periventricular foci (arrows).</p><p>DIFFERENTIAL DIAGNOSIS:</p><p>• Chronic demyelination</p><p>• Focal encephalomalacia</p><p>DISCUSSION:</p><p>Multiple sclerosis (MS) is a chronic demyelinating disorder characterized by spatial</p><p>and temporal heterogeneity. Acute demyelinating lesions are associated with</p><p>edema, enhancement, and/or reduced diffusion. In the chronic stage, permanent</p><p>axonal damage yields gliotic “black holes” that are hypodense on CT, hypointense</p><p>on T1-weighted MR, and nonenhancing. There is a moderate correlation</p><p>schwannoma</p><p>DISCUSSION:</p><p>Vestibular schwannomas (acoustic neuromas) are benign Schwann cell tumors</p><p>arising from the vestibular portion of CN VIII at the glial-Schwann cell junction.</p><p>Small intracanalicular schwannomas may appear as ovoid or cylindrical masses</p><p>with punctate enhancement in the internal auditory canal. Larger lesions can fi ll the</p><p>cerebellopontine angle and IAC, bulging through the porus acousticus (“ice cream</p><p>cone” sign). Cystic change is common, while hemorrhage and calcifi cation are rare</p><p>in untreated tumors. Patients present with unilateral sensorineural hearing loss, for</p><p>which stereotactic radiosurgery is the recommended therapy. If surgery is planned,</p><p>a middle cranial fossa approach can be used for small intracanalicular masses to</p><p>preserve CN VII and VIII. A suboccipital (retrosigmoid) or translabyrinthine</p><p>approach is required to access CPA and deep IAC locations. Bilateral vestibular</p><p>schwannomas should suggest the diagnosis of neurofi bromatosis type II (MISME:</p><p>multiple inherited schwannomas, meningiomas, and ependymomas). The differential</p><p>for cerebellopontine angle masses is wide and includes schwannoma, meningioma,</p><p>epidermoid cyst, arachnoid cyst, metastasis, aneurysm, and lipoma. Facial nerve</p><p>schwannomas have a similar appearance within the IAC, but can extend peripherally</p><p>into the labyrinthine segment and geniculate ganglion of CN VII (“dumbbell” lesion).</p><p>Meningiomas are usually dural-based, eccentric to the porus acousticus, and may</p><p>be calcifi ed. Epidermoid cysts have an insinuating “caulifl ower” morphology with</p><p>reduced diffusion. Arachnoid cysts are well marginated and follow the intensity of</p><p>CSF. Metastases are enhancing and multifocal. Aneurysms occur along the course</p><p>of the vertebrobasilar circulation and follow blood pool signal. Lipomas follow fat</p><p>signal on all sequences.</p><p>References:</p><p>Silk PS, Lane JI, Driscoll CL. Surgical approaches to vestibular schwannomas: what the radiologist</p><p>needs to know. Radiographics. 2009;29(7):1955-1970.</p><p>Smirniotopoulos JG, Yue NC, Rushing EJ. Cerebellopontine angle masses: radiologic-pathologic</p><p>correlation. Radiographics. 1993;13(5):1131-1147.</p><p>Modality:</p><p>MR</p><p>ICE CREAM CONE, MUSHROOM, TRUMPET, TAIL</p><p>198 Chapter 3: Head, Neck, and Orbits</p><p>FINDINGS:</p><p>Coronal contrast-enhanced T1-weighted MR shows a hypoenhancing mass in the</p><p>left pituitary gland (asterisk), with contralateral infundibular deviation (arrow).</p><p>DIFFERENTIAL DIAGNOSIS:</p><p>• Sellar mass</p><p>• Normal variant</p><p>DISCUSSION:</p><p>The pituitary stalk (infundibulum) connects the hypothalamus to the posterior pituitary</p><p>gland (neurohypophysis). It carries neurosecretory axons down to the posterior</p><p>pituitary, where the hormones oxytocin and vasopressin (antidiuretic hormone)</p><p>are released into the blood. In the presence of sellar enlargement, visualization of a</p><p>midline infundibulum extending to the sellar fl oor is compatible with the diagnosis of</p><p>an empty sella. Deviation of the infundibulum to one side suggests displacement by a</p><p>pituitary cyst or mass, though normal patients can have a small degree of tilt.</p><p>References:</p><p>Ahmadi H, Larsson EM, Jinkins JR. Normal pituitary gland: coronal MR imaging of infundibular tilt.</p><p>Radiology. 1990;177(2):389-392.</p><p>Haughton VM, Rosenbaum AE, Williams AL et al. Recognizing the empty sella by CT: the infundibulum</p><p>sign. AJR Am J Roentgenol. 1981;136(2):293-295.</p><p>Modalities:</p><p>CT, MR</p><p>INFUNDIBULUM, PITUITARY STALK DEVIATION/TILT</p><p>Inverted V, Pencil Tip, Steeple 199</p><p>FINDINGS:</p><p>Frontal radiograph shows tracheal wall edema with loss of the lateral convexities</p><p>and smooth symmetric subglottic narrowing (arrows).</p><p>DIFFERENTIAL DIAGNOSIS:</p><p>• Croup</p><p>• Bacterial tracheitis</p><p>DISCUSSION:</p><p>Croup (acute laryngotracheobronchitis) refers to viral airway infl ammation, usually</p><p>caused by parainfl uenza or respiratory syncytial virus, and seen in children between</p><p>6 months and 3 years of age. There is diffuse tracheal wall edema, with loss of the</p><p>normal lateral convexities (“shoulders”) of the true vocal cords. Below the vocal</p><p>cords, smooth symmetric luminal narrowing produces the characteristic “steeple”</p><p>shape. This can cause proximal obstruction with dilation of the hypopharynx and</p><p>laryngeal ventricles. Treatment is supportive and the condition is self-limiting. In</p><p>contrast, bacterial tracheitis is an aggressive infection that occurs in older children</p><p>(6-10 years) who present with toxic symptoms. Subglottic airway narrowing is also</p><p>present, but tends to be more irregular and asymmetric. Additional causes of the</p><p>steeple sign are epiglottitis, thermal injury, and angioedema. Therefore, clinical</p><p>evaluation is key for diagnosis.</p><p>Reference:</p><p>Salour M. The steeple sign. Radiology. 2000;216(2):428-429.</p><p>Modalities:</p><p>XR, CT</p><p>INVERTED V, PENCIL TIP, STEEPLE</p><p>200 Chapter 3: Head, Neck, and Orbits</p><p>FINDINGS:</p><p>Axial CT shows hemorrhagic</p><p>choroidal detachment along</p><p>the medial and lateral walls</p><p>of the globe, with contact in</p><p>the midline (arrow).</p><p>DIAGNOSIS:</p><p>Choroidal detachment</p><p>DISCUSSION:</p><p>The globes are lined by</p><p>three concentric coverings:</p><p>the internal nervous, middle</p><p>vascular, and external fi brous</p><p>tunics. The retina contains</p><p>photoreceptors (rods, cones,</p><p>and photosensitive ganglion</p><p>cells) that process light</p><p>stimuli and send impulses</p><p>through the optic nerve to the brain. The choroid consists of vascular pigmented</p><p>connective tissue, which is responsible for nutrition and gas exchange and forms the</p><p>uveal tract along with the ciliary body and iris. The sclera is composed of protective</p><p>fi brous tissue and is continuous anteriorly with the cornea. Choroidal detachment</p><p>refers to separation of the choroid from the sclera, due to either fl uid transudation</p><p>(serous) or trauma with rupture of choroidal vessels (hemorrhagic). The uveal tract</p><p>is anchored anteriorly at the scleral spur and posteriorly by the posterior ciliary</p><p>vessels. Therefore, fl uid fi lls zones of loose attachment along the medial and lateral</p><p>walls of the globe, known as the suprachoroidal space. In severe cases, the detached</p><p>leaves can contact each other in the midline (“kissing” appearance). Therapy</p><p>includes topical corticosteroids, cycloplegics, mydriatics, and intraocular pressure-</p><p>lowering drugs. Suprachoroidal paracentesis is performed in medically refractory</p><p>cases.</p><p>References:</p><p>Berrocal T, de Orbe A, Prieto C, et al. US and color Doppler imaging of ocular and orbital disease in</p><p>the pediatric age group. Radiographics. 1996;16(2):251-272.</p><p>Mafee MF, Peyman GA. Retinal and choroidal detachments: role of magnetic resonance imaging and</p><p>computed tomography. Radiol Clin North Am. 1987;25(3):487-507.</p><p>Modalities:</p><p>US, CT, MR</p><p>KISSING CHOROID, LENTIFORM</p><p>Kissing Tonsils, Striated, Tigroid 201</p><p>Modalities:</p><p>CT, MR</p><p>FINDINGS:</p><p>Axial contrast-enhanced CT shows enlarged kissing palatine tonsils (arrows) with</p><p>striated enhancement.</p><p>DIAGNOSIS:</p><p>Tonsillitis</p><p>DISCUSSION:</p><p>Tonsillitis and peritonsillar abscesses are the most common deep neck infections</p><p>in adolescents and young adults. Causative organisms include β-hemolytic</p><p>Streptococcus, Staphylococcus aureus, Pneumococcus, Haemophilus infl uenzae,</p><p>and Epstein-Barr virus. On CT, the tonsils appear enlarged with linear striated</p><p>enhancement (“tigroid” appearance). Intervening areas of hypodensity suggest</p><p>edema and suppurative changes; true intratonsillar abscesses are rare. However,</p><p>infection that penetrates the tonsillar capsule can produce a peritonsillar abscess and</p><p>require drainage.</p><p>Reference:</p><p>Capps EF, Kinsella JJ, Gupta M, et al. Emergency imaging assessment of acute, nontraumatic conditions</p><p>of the head and neck. Radiographics. 2010;30(5):1335-1352.</p><p>KISSING TONSILS, STRIATED, TIGROID</p><p>202 Chapter 3: Head, Neck, and Orbits</p><p>Modality:</p><p>MR</p><p>FINDINGS:</p><p>Axial high-resolution T2-weighted MR in a patient with left hemifacial spasm shows</p><p>bilateral tortuous AICAs, contacting the CN VII root entry zone on the left (arrow).</p><p>DIAGNOSIS:</p><p>Neurovascular compression syndrome</p><p>DISCUSSION:</p><p>Neurovascular compression</p><p>syndrome refers to abnormal contact between an</p><p>intracranial vessel and cranial nerve at the root entry/exit zone or CNS segment. At</p><p>imaging, a tortuous vascular “loop” or aneurysm may be identifi ed. Involvement</p><p>of cranial nerves V, VII, VIII, and IX has been associated with trigeminal neuralgia,</p><p>hemifacial spasm, vestibular paroxysmia, and glossopharyngeal neuralgia,</p><p>respectively. Treatment options include neuropathic medications, microvascular</p><p>decompression with placement of a spacer between the nerve and blood vessel,</p><p>and direct neurectomy or rhizotomy. For hemifacial spasm, superfi cial injections of</p><p>botulinum toxin can provide temporary relief.</p><p>References:</p><p>De Ridder D, Møller A, Verlooy J, et al. Is the root entry/exit zone important in microvascular</p><p>compression syndromes? Neurosurgery. 2002;51(2):427-433.</p><p>Langner S, Schroeder HW, Hosten N, et al. Diagnosing neurovascular compression syndromes. Rofo.</p><p>2012;184(3):220-228.</p><p>LOOP</p><p>Lyre, Omega, Splayed 203</p><p>FINDINGS:</p><p>Sagittal contrast-enhanced CT shows an avidly</p><p>enhancing carotid bifurcation mass, splaying the</p><p>ICA and ECA (arrows).</p><p>DIAGNOSIS:</p><p>Carotid body tumor</p><p>DISCUSSION:</p><p>Glomus tumors (paragangliomas, chemodectomas,</p><p>glomangiomas) are neuro endocrine neoplasms</p><p>in the head and neck region originating from</p><p>paraganglia. Lesions are frequently multiple</p><p>and occur in characteristic locations: carotid</p><p>body (glomus caroticum or carotid body tumor),</p><p>middle ear (glomus tympanicum), jugular</p><p>foramen (glomus jugulare), vagus nerve (glomus</p><p>vagale), and facial nerve canal (glomus faciale).</p><p>The carotid body is located at the carotid</p><p>bifurcation and detects variations in oxygen,</p><p>carbon dioxide, pH, and temperature levels.</p><p>Carotid body tumors (CBTs) characteristically</p><p>splay the carotid bifurcation (“lyre” sign). As</p><p>they grow, they encase but do not narrow the</p><p>ICA and ECA. Due to their hypervascularity,</p><p>CBTs show avid contrast enhancement. On CT,</p><p>large tumors (> 1-2 cm) demonstrate hyperdense</p><p>areas signifying enhancement or calcifi cation</p><p>(“salt”), and hypodense areas suggesting necrosis</p><p>(“pepper”). On MR, there are T1-hyperintense</p><p>foci representing hemorrhage or slow fl ow (“salt”), and T2-hypointense foci due</p><p>to high-velocity arterial fl ow voids and calcifi cation (“pepper”). Because glomus</p><p>tumors are frequently multiple, somatostatin receptor scintigraphy with indium-111</p><p>octreotide can help confi rm the diagnosis and detect additional lesions.</p><p>References:</p><p>Olsen WL, Dillon WP, Kelly WM, et al. MR imaging of paragangliomas. AJR Am J Roentgenol.</p><p>1987;148(1):201-204.</p><p>Rao AB, Koeller KK, Adair CF. From the archives of the AFIP. Paragangliomas of the head and</p><p>neck: radiologic-pathologic correlation. Armed Forces Institute of Pathology. Radiographics.</p><p>1999;19(6):1605-1632.</p><p>Modalities:</p><p>CT, MR</p><p>LYRE, OMEGA, SPLAYED</p><p>204 Chapter 3: Head, Neck, and Orbits</p><p>Modality:</p><p>CT</p><p>FINDINGS:</p><p>Temporal bone CT double-oblique sagittal MPR shows the incudomalleal joint</p><p>(arrow), malleus manubrium anteriorly, and the long process of the incus posteriorly.</p><p>DIAGNOSIS:</p><p>Normal incus-malleus confi guration</p><p>DISCUSSION:</p><p>In the early days of polytomography, lateral projections of the temporal bone</p><p>depicted the combined outline of the incus and malleus, resembling a “molar tooth”</p><p>with the head of the malleus and the body of the incus forming the “crown,” the</p><p>incudomalleal joint forming a central “saddle,” the malleus manubrium forming the</p><p>“anterior root,” and the long process of the incus forming the “posterior root.” On</p><p>temporal bone CT, axial and coronal images do not optimally depict the long axes</p><p>of the malleus and incus, which are oriented posteromedially. The double-oblique</p><p>sagittal MPR recreates the polytomographic lateral view of the incudomalleal joint,</p><p>while the double-oblique coronal MPR visualizes the malleus and incudostapedial</p><p>joint. Loss of the normal “molar tooth” appearance can be caused by cholesteatoma</p><p>with ossicular erosions, traumatic dislocation, and congenital anomalies.</p><p>References:</p><p>Lane JI, Lindell EP, Witte RJ, et al. Middle and inner ear: improved depiction with multiplanar</p><p>reconstruction of volumetric CT data. Radiographics. 2006;26(1):115-124.</p><p>Potter GD. The lateral projection in tomography of the petrous pyramid. Am J Roentgenol Radium</p><p>Ther Nucl Med. 1968;104(1):194-200.</p><p>MOLAR TOOTH</p><p>Moustache 205</p><p>FINDINGS:</p><p>Axial and coronal T2-weighted MR show a complex sellar/suprasellar cystic mass</p><p>with adjacent edema in the posterior limbs of the internal capsules (thick arrows)</p><p>and optic tracts (thin arrows).</p><p>DIAGNOSIS:</p><p>Pituitary region mass (craniopharyngioma)</p><p>DISCUSSION:</p><p>Craniopharyngioma is a benign (WHO grade I) neoplasm, derived from the Rathke</p><p>pouch epithelium that gives rise to the anterior pituitary gland. The adamantinomatous</p><p>type usually occurs in children, and is the most common pediatric intracranial tumor</p><p>of nonglial origin. At imaging, it appears as a mixed cystic and solid mass in the sellar/</p><p>suprasellar region. Both the solid components and cyst walls enhance avidly. Cysts</p><p>are intrinsically T1-hyperintense due to “machinery oil”-like cholesterol, protein,</p><p>and blood contents. Dense calcifi cations are also common. The papillary type of</p><p>craniopharyngioma, which is less frequent, occurs in adults and has a primarily solid</p><p>composition. Craniopharyngiomas can grow to very large sizes, extending into the</p><p>suprasellar region and cranial fossae. Mass effect on the diencephalon produces a</p><p>characteristic “moustache” pattern of edema in the hypothalami, optic tracts, and</p><p>posterior limbs of the internal capsules. White matter fi bers in these structures are</p><p>densely packed and fairly resistant to edema. However, large tumors can compress</p><p>the Virchow-Robin spaces and block drainage of interstitial fl uid. This phenomenon</p><p>is most commonly described in craniopharyngioma, but can also occur with other</p><p>sellar/suprasellar lesions including pituitary macroadenoma, germ cell tumor,</p><p>meningioma, lymphoma, and metastases.</p><p>References:</p><p>Higashi S, Yamashita J, Fujisawa H, et al. “Moustache” appearance in craniopharyngiomas: unique</p><p>magnetic resonance imaging and computed tomographic fi ndings of perifocal edema. Neurosurgery.</p><p>1990;27(6):993-996.</p><p>Saeki N, Uchino Y, Murai H, et al. MR imaging study of edema-like change along the optic tract in</p><p>patients with pituitary region tumors. AJNR Am J Neuroradiol. 2003;24(3):336-342.</p><p>Modalities:</p><p>CT, MR</p><p>MOUSTACHE</p><p>206 Chapter 3: Head, Neck, and Orbits</p><p>Modalities:</p><p>CT, MR</p><p>FINDINGS:</p><p>Axial contrast-enhanced CT shows a thickened and curled epiglottis (arrows).</p><p>DIAGNOSIS:</p><p>Laryngomalacia</p><p>DISCUSSION:</p><p>Laryngomalacia refers to inward collapse of the epiglottis during inhalation,</p><p>due to cartilage defi ciency and/or neuromuscular weakness. Shortening of the</p><p>aryepiglottic folds results in tight curling of the epiglottis over the airway. Infantile</p><p>laryngomalacia usually resolves as the child matures, but severe cases can be treated</p><p>with supraglottoplasty, epiglottopexy, and/or tracheostomy.</p><p>Reference:</p><p>Prescott CA. The current status of corrective surgery for laryngomalacia. Am J Otolaryngol.</p><p>1991;12(4):230-235.</p><p>OMEGA</p><p>Panda 207</p><p>FINDINGS:</p><p>Anterior planar 67Ga-citrate</p><p>scan shows tracer uptake in</p><p>the lacrimal glands, parotid</p><p>glands, and nasopharynx.</p><p>DIFFERENTIAL DIAGNOSIS:</p><p>• Sarcoidosis</p><p>• Malignancy</p><p>• Collagen vascular disorder</p><p>• Renal disease</p><p>• AIDS</p><p>DISCUSSION:</p><p>Gallium-67 scanning is used to</p><p>identify sites of infl ammation</p><p>and infection, and was the gold</p><p>standard for cancer staging</p><p>prior to the emergence of</p><p>positron emission tomography</p><p>(PET). A common application is in sarcoidosis, a systemic infl ammatory disease</p><p>characterized histologically by noncaseating granulomas. Within the face, symmetric</p><p>uptake in the lacrimal and salivary glands is superimposed on normal nasopharyngeal</p><p>uptake, giving the appearance of a “panda.” In the chest, the “lambda” sign refers</p><p>to uptake in right paratracheal and bilateral hilar lymph nodes. Less</p><p>common causes</p><p>of the “panda” sign include malignancy (lymphoma, leukemia, carcinoma); collagen</p><p>vascular disorders (Sjögren syndrome, lupus, scleroderma, rheumatoid arthritis);</p><p>renal disease; and AIDS.</p><p>References:</p><p>Kurdziel KA. The panda sign. Radiology. 2000;215(3):884-885.</p><p>Sulavik SB, Spencer RP, Weed DA, et al. Recognition of distinctive patterns of gallium-67 distribution</p><p>in sarcoidosis. J Nucl Med. 1990;31(12):1909-1914.</p><p>Modality:</p><p>NM</p><p>PANDA</p><p>208 Chapter 3: Head, Neck, and Orbits</p><p>FINDINGS:</p><p>Axial temporal bone CT shows parallel orientation of the tensor tympani and malleus</p><p>neck anteriorly; and the lenticular process of the incus, incudostapedial joint, and</p><p>stapes superstructure posteriorly (arrows).</p><p>DIAGNOSIS:</p><p>Normal auditory ossicles</p><p>DISCUSSION:</p><p>Axial temporal bone CT normally demonstrates two parallel lines in the middle ear.</p><p>The anterior line is formed by the tensor tympani and malleus neck. The posterior</p><p>line is formed by the lenticular process of the incus, incudostapedial joint, and</p><p>stapes superstructure. Defects in the posterior line may be observed in patients with</p><p>cholesteatoma and ossicular erosions.</p><p>Reference:</p><p>Swartz JD, Loevner LA. Imaging of the Temporal Bone. 4th ed. New York: Thieme; 2008.</p><p>Modality:</p><p>CT</p><p>PARALLEL LINES, TWO DASHES</p><p>Patchy, Tuft 209</p><p>FINDINGS:</p><p>Axial contrast-enhanced T1-weighted MR shows patchy enhancement in the distal</p><p>meatal (arrow), labyrinthine, and proximal tympanic segments of the right facial nerve.</p><p>DIFFERENTIAL DIAGNOSIS:</p><p>• Bell palsy</p><p>• Infection/infl ammation</p><p>• Demyelination</p><p>• Lymphoma</p><p>DISCUSSION:</p><p>The facial nerve has seven segments, which from central to peripheral are the</p><p>intraaxial (brainstem), cisternal (cerebellopontine angle), canalicular/meatal</p><p>(internal auditory canal), labyrinthine (internal auditory canal to geniculate</p><p>ganglion), tympanic (geniculate ganglion to pyramidal eminence), mastoid</p><p>(pyramidal eminence to stylomastoid foramen), and extracranial (distal to</p><p>stylomastoid foramen). The geniculate ganglion, tympanic, and mastoid segments</p><p>can normally enhance because of their rich circumneural vascular plexus. However,</p><p>enhancement of the distal intrameatal and labyrinthine segments is pathologic and</p><p>presents clinically with facial nerve palsy. It has been theorized that the decreased</p><p>caliber of the facial canal in the premeatal and midtympanic regions predisposes</p><p>to infl ammation between these segments (“bottleneck” theory of Fisch). The</p><p>most common etiology is Bell palsy, which is idiopathic and self-limited. Imaging</p><p>is unnecessary for diagnosis, but reveals patchy “tuftlike” enhancement. Other</p><p>causes of facial nerve enhancement include infection (viral, bacterial, fungal);</p><p>infl ammation (sarcoid); demyelination; trauma; benign tumors (hemangioma,</p><p>schwannoma); and malignant tumors (lymphoma, metastases, perineural spread).</p><p>References:</p><p>Fisch U, Esslen E. Total intratemporal exposure of the facial nerve. Arch Otolaryngol. 1972;95:335-341.</p><p>Kinoshita T, Ishii K, Okitsu T, et al. Facial nerve palsy: evaluation by contrast-enhanced MR imaging.</p><p>Clin Radiol. 2001;56(11):926-932.</p><p>Modality:</p><p>MR</p><p>PATCHY, TUFT</p><p>210 Chapter 3: Head, Neck, and Orbits</p><p>FINDINGS:</p><p>Sagittal T1-weighted MR</p><p>shows normal hyper-</p><p>intensity of the posterior</p><p>pituitary (arrow).</p><p>DIAGNOSIS:</p><p>Normal posterior pituitary</p><p>DISCUSSION:</p><p>The posterior pituitary</p><p>gland (neuro hypophysis)</p><p>is connected to the hypo-</p><p>thalamus via the pituitary</p><p>stalk (infundibulum) and</p><p>produces the hormones</p><p>oxytocin and vasopressin</p><p>(antidiuretic hormone).</p><p>In the majority of normal</p><p>individuals, the posterior</p><p>pituitary demonstrates</p><p>T1-hyperintense signal</p><p>due to the presence of neurosecretory granules containing ADH, neurophysin/</p><p>copeptin proteins, and phospholipid membranes. Absence of this fi nding should</p><p>prompt a search for an ectopic posterior pituitary gland, an important cause of</p><p>infundibuloneurohypophyseal dysfunction. Displacement or absence of the “bright</p><p>spot” can also occur because of infi ltration/compression by a sellar mass or enlarged</p><p>CSF space (empty sella). Occasionally, the anterior pituitary (adenohypophysis) can</p><p>also appear T1-hyperintense because of hormonal hypersecretion. This is typically</p><p>seen in newborns and pregnant, postpartum, or lactating women.</p><p>References:</p><p>Bonneville F, Cattin F, Marsot-Dupuch K, et al. T1 signal hyperintensity in the sellar region: spectrum</p><p>of fi ndings. Radiographics. 2006;26(1):93-113.</p><p>Kurokawa H, Fujisawa I, Nakano Y, et al. Posterior lobe of the pituitary gland: correlation between signal</p><p>intensity on T1-weighted MR images and vasopressin concentration. Radiology. 1998;207(1):79-83.</p><p>Modality:</p><p>MR</p><p>POSTERIOR PITUITARY BRIGHT SPOT</p><p>Reverse Cupping 211</p><p>FINDINGS:</p><p>Axial T2-weighted MR shows bilateral tortuous and fl uid-fi lled optic nerve sheaths,</p><p>fl attened posterior sclerae, and abnormal protrusion of the optic discs (arrows) into</p><p>the globes.</p><p>DIAGNOSIS:</p><p>Papilledema</p><p>DISCUSSION:</p><p>Papilledema refers to optic disc swelling caused by increased intracranial pressure.</p><p>The optic nerve sheaths are continuous with the intracranial subarachnoid space.</p><p>When under increased pressure, they become dilated and tortuous. Severe cases</p><p>produce edema of the optic nerve heads with reduced diffusion and/or enhancement,</p><p>inversion/protrusion of the optic discs (“reverse cupping”), and fl attening of the</p><p>posterior sclerae. Unilateral papilledema suggests ipsilateral orbital pathology. In</p><p>rare cases, a frontal lobe tumor can compress the adjacent optic nerve and raise</p><p>intracranial pressure, producing ipsilateral optic nerve atrophy with contralateral</p><p>papilledema (Foster-Kennedy syndrome). Bilateral papilledema indicates increased</p><p>intracranial pressure, which may be idiopathic (pseudotumor cerebri) or secondary</p><p>hemorrhage, tumor, infection, or arterial/venous ischemia. Prompt treatment of the</p><p>underlying cause is crucial, as longstanding papilledema leads to denervation and</p><p>permanent visual impairment.</p><p>Reference:</p><p>Passi N, Degnan AJ, Levy LM. MR imaging of papilledema and visual pathways: effects of increased</p><p>intracranial pressure and pathophysiologic mechanisms. AJNR Am J Neuroradiol. 2012 Mar 15.</p><p>Modalities:</p><p>US, MR</p><p>REVERSE CUPPING</p><p>212 Chapter 3: Head, Neck, and Orbits</p><p>Modalities:</p><p>XR, CT</p><p>FINDINGS:</p><p>Coronal CT shows a calcifi ed dacryolith (arrow) impacted in the right nasolacrimal</p><p>duct, with surrounding edema.</p><p>DIAGNOSIS:</p><p>Dacryolithiasis</p><p>DISCUSSION:</p><p>Dacryolithiasis is a complication of chronic dacryocystitis, usually with fungal</p><p>colonization. Over time, mineralized proteins and debris accumulate in the</p><p>lacrimal sac and/or nasolacrimal duct. This is diffi cult to identify on conventional</p><p>radiographs, and much better seen on CT with a calcifi ed “rice kernel” appearance.</p><p>Dacryocystography identifi es round or oval fi lling defects within the nasolacrimal</p><p>duct. Treatment involves surgical removal, often with balloon dacryocystoplasty or</p><p>dacryocystorhinostomy.</p><p>Reference:</p><p>Asheim J, Spickler E. CT demonstration of dacryolithiasis complicated by dacryocystitis. AJNR Am J</p><p>Neuroradiol. 2005;26(10):2640-2641.</p><p>RICE KERNEL</p><p>Rose Thorn 213</p><p>Modalities:</p><p>CT, MR</p><p>FINDINGS:</p><p>Axial and coronal contrast-enhanced T1-weighted MR with fat saturation show an</p><p>enhancing left parasellar mass that extends along the left sulcus chiasmaticus into</p><p>the optic nerve canal (arrows).</p><p>DIAGNOSIS:</p><p>Intracanalicular optic nerve meningioma</p><p>DISCUSSION:</p><p>Perioptic (optic nerve sheath) meningiomas are benign tumors arising from the</p><p>arachnoid cap cells in the optic nerve sheath. They may arise within the orbit (optic</p><p>nerve sheath meningioma), optic nerve canal (intracanalicular meningioma), or optic</p><p>foramen (foraminal meningioma). Intracanalicular meningiomas can demonstrate a</p><p>“rose-thorn” appearance with proximal nodular component and en plaque extension</p><p>along the optic groove (sulcus chiasmaticus), orbital apex, and optic nerve canal.</p><p>Distinction from optic neuritis (infl ammation of the optic nerve) is</p><p>key, as patients</p><p>present with early visual loss due to nerve compression in the anatomically limited</p><p>orbital apex.</p><p>Reference:</p><p>Jackson A, Patankar T, Laitt RD. Intracanalicular optic nerve meningioma: a serious diagnostic pitfall.</p><p>AJNR Am J Neuroradiol. 2003;24(6):1167-1170.</p><p>ROSE THORN</p><p>214 Chapter 3: Head, Neck, and Orbits</p><p>Modalities:</p><p>CT, MR</p><p>SAIL</p><p>FINDINGS:</p><p>• Axial contrast-enhanced CT shows enlargement of the right laryngeal ventricle</p><p>(arrow).</p><p>• Axial contrast-enhanced CT in a different patient shows enlargement of the right</p><p>laryngeal ventricle and piriform sinus, with medialization of the aryepiglottic fold</p><p>(arrow).</p><p>DIAGNOSIS:</p><p>Vocal cord paralysis</p><p>DISCUSSION:</p><p>Vocal cord paralysis results from injury or compression of the vagus nerve (CN X)</p><p>anywhere between the medulla and the recurrent laryngeal branches. CN X originates</p><p>from the medulla, traverses the jugular foramen, and descends down the neck within</p><p>the carotid sheath. On the right, it extends to the clavicle and recurs around the</p><p>right subclavian artery; on the left, it extends into the mediastinum and recurs via</p><p>the aortopulmonary window. The recurrent laryngeal nerves then ascend to the larynx</p><p>within the tracheoesophageal grooves. In cases of suspected vocal cord paralysis, contrast-</p><p>enhanced CT with coverage from skull base to carina is the imaging examination of</p><p>choice. The paralyzed cord is fl accid and may be fi xed in a medial or lateral position.</p><p>Imaging signs include ballooning of the laryngeal ventricle (“sail” sign), enlargement</p><p>of the pyriform sinus, medial displacement and thickening of the aryepiglottic fold,</p><p>anteromedial rotation of the arytenoid cartilage, and atrophy of the posterior</p><p>cricoarytenoid muscle. On PET, the denervated cord shows absent uptake compared</p><p>to the normal contralateral cord. Therapeutic options include voice therapy, vocal cord</p><p>augmentation with temporary or permanent injectables, and laryngeal framework</p><p>surgery (medialization thyroplasty, arytenoid adduction, and laryngeal re-innervation).</p><p>References:</p><p>Chin SC, Edelstein S, Chen CY, et al. Using CT to localize side and level of vocal cord paralysis. AJR</p><p>Am J Roentgenol. 2003;180(4):1165-1170.</p><p>Kumar VA, Lewin JS, Ginsberg LE. CT assessment of vocal cord medialization. AJNR Am J</p><p>Neuroradiol. 2006;27(8):1643-1646.</p><p>Salt and Pepper 215</p><p>Modalities:</p><p>CT, MR</p><p>SALT AND PEPPER</p><p>FINDINGS:</p><p>Axial contrast-enhanced CT and contrast-enhanced T1-weighted MR with fat</p><p>saturation show a heterogeneous and avidly enhancing mass in the left carotid space</p><p>(arrows).</p><p>DIAGNOSIS:</p><p>Glomus vagale</p><p>DISCUSSION:</p><p>Glomus tumors (paragangliomas, chemodectomas, glomangiomas) are neuroendocrine</p><p>neoplasms in the head and neck region originating from paraganglia. Lesions are</p><p>frequently multiple and occur in characteristic locations: carotid body (glomus</p><p>caroticum or carotid body tumor), middle ear (glomus tympanicum), jugular foramen</p><p>(glomus jugulare), vagus nerve (glomus vagale), and facial nerve canal (glomus faciale).</p><p>Because of their hypervascularity, glomus tumors show avid contrast enhancement.</p><p>On CT, large tumors (>1-2 cm) demonstrate hyperdense areas signifying enhancement</p><p>or calcifi cation (“salt”), and hypodense areas suggesting necrosis (“pepper”). On</p><p>MR, there are T1-hyperintense foci representing hemorrhage or slow fl ow (“salt”),</p><p>and T2-hypointense foci due to high-velocity arterial fl ow voids and calcifi cation</p><p>(“pepper”). Permeative and destructive changes may be present in the surrounding</p><p>bone. Other vascular lesions, such as hypervascular schwannomas and metastases, can</p><p>occasionally have a similar appearance. Because glomus tumors are frequently multiple,</p><p>somatostatin receptor scintigraphy with indium-111 octreotide can help confi rm the</p><p>diagnosis and detect additional lesions.</p><p>References:</p><p>Eldevik OP, Gabrielsen TO, Jacobsen EA. Imaging fi ndings in schwannomas of the jugular foramen.</p><p>AJNR Am J Neuroradiol. 2000;21(6):1139-1144.</p><p>Olsen WL, Dillon WP, Kelly WM, et al. MR imaging of paragangliomas. AJR Am J Roentgenol.</p><p>1987;148(1):201-204.</p><p>Rao AB, Koeller KK, Adair CF. From the archives of the AFIP. Paragangliomas of the head and</p><p>neck: radiologic-pathologic correlation. Armed Forces Institute of Pathology. Radiographics.</p><p>1999;19(6):1605-1632.</p><p>216 Chapter 3: Head, Neck, and Orbits</p><p>FINDINGS:</p><p>• Axial contrast-enhanced T1-weighted MR with fat saturation shows an enhancing</p><p>mass (arrows) encasing the optic nerve.</p><p>• Axial noncontrast CT in a different patient shows linear calcifi cations along the</p><p>optic nerve sheath (arrows).</p><p>DIAGNOSIS:</p><p>Perioptic meningioma</p><p>DISCUSSION:</p><p>Perioptic meningiomas are benign tumors arising from the arachnoid cap cells</p><p>in the optic nerve sheath. These may arise within the orbit (optic nerve sheath</p><p>meningioma), optic nerve canal (intracanalicular meningioma), or optic foramen</p><p>(foraminal meningioma). Three distinct morphologies have been described: tubular,</p><p>exophytic, and fusiform. The tubular form symmetrically surrounds and compresses</p><p>the optic nerve, with associated enhancement and/or calcifi cation. This gives rise</p><p>to the “doughnut” sign en face and the “tram-track” sign in long axis. In contrast,</p><p>optic gliomas are infi ltrative tumors that are intimately associated with the optic</p><p>nerve. Other causes of perioptic enhancement include orbital pseudotumor, infection,</p><p>sarcoidosis, leukemia/lymphoma, and metastases.</p><p>References:</p><p>Jackson A, Patankar T, Laitt RD. Intracanalicular optic nerve meningioma: a serious diagnostic pitfall.</p><p>AJNR Am J Neuroradiol. 2003;24(6):1167-1170.</p><p>Kanamalla US. The optic nerve tram-track sign. Radiology. 2003;227(3):718-719.</p><p>Modalities:</p><p>US, CT, MR</p><p>SANDWICH, TRAM TRACK</p><p>Sitting Duck 217</p><p>FINDINGS:</p><p>Axial temporal bone CT shows the normal jugular foramen with smaller anteromedial</p><p>pars nervosa (thin arrow) and larger posterolateral pars vascularis (thick arrow).</p><p>DIAGNOSIS:</p><p>Normal jugular foramen</p><p>DISCUSSION:</p><p>The jugular foramen is located on the medial and inferior surface of the petrous</p><p>pyramid, which is formed by the temporal and occipital bones. It consists of two</p><p>divisions that are separated by a fi brous or bony septum (“sitting duck” appearance).</p><p>The smaller pars nervosa is located anteromedially, and houses the inferior petrosal</p><p>sinus and glossopharyngeal nerve (CN IX). The larger pars vascularis is located</p><p>posterolaterally and contains the jugular bulb, as well as the vagus and spinal</p><p>accessory nerves (CN X and XI). The wall of the jugular fossa is smooth and well</p><p>corticated, with small dehiscences for the tympanic branch of the glossopharyngeal</p><p>nerve (Jacobson nerve) and auricular branch of the vagus nerve (Arnold nerve).</p><p>Reference:</p><p>Caldemeyer KS, Mathews VP, Azzarelli B, et al. The jugular foramen: a review of anatomy, masses,</p><p>and imaging characteristics. Radiographics. 1997;17(5):1123-1139.</p><p>Modalities:</p><p>CT, MR</p><p>SITTING DUCK</p><p>218 Chapter 3: Head, Neck, and Orbits</p><p>FINDINGS:</p><p>Coronal temporal bone CT intersects the facial nerve at the labyrinthine segment</p><p>superomedially and the tympanic segment inferolaterally (arrows).</p><p>DIAGNOSIS:</p><p>Normal facial nerve</p><p>DISCUSSION:</p><p>The facial nerve is a mixed cranial nerve with motor, parasympathetic, and sensory</p><p>branches. It originates in the brainstem nuclei, courses through the temporal bone and</p><p>parotid gland, and innervates the face. The major segments are intraaxial, cisternal</p><p>(cerebellopontine angle), canalicular/meatal (internal auditory canal), labyrinthine</p><p>(internal auditory canal to geniculate ganglion), tympanic (geniculate ganglion to</p><p>pyramidal eminence), mastoid (pyramidal eminence to stylomastoid foramen), and</p><p>extracranial (distal to stylomastoid foramen). Coronal CT through the cochlea, just</p><p>anterior to the internal auditory canal, intersects the facial nerve in two areas. This</p><p>produces the characteristic “snake eyes” appearance, with the labyrinthine segment</p><p>superomedially and the tympanic segment inferolaterally. More anteriorly, these two</p><p>segments converge</p><p>to the geniculate ganglion.</p><p>Reference:</p><p>Swartz JD, Loevner LA. Imaging of the Temporal Bone. 4th ed. New York: Thieme; 2008.</p><p>Modality:</p><p>CT</p><p>SNAKE EYES</p><p>Teardrop 219</p><p>FINDINGS:</p><p>Coronal CT shows a left orbital blowout fracture with herniation of inferior rectus</p><p>and periorbital fat (arrow) into the maxillary sinus.</p><p>DIAGNOSIS:</p><p>Orbital blowout fracture</p><p>DISCUSSION:</p><p>Blowout fractures, the most common fractures of the orbit, are caused by direct</p><p>trauma to the globe or upper eyelid. The orbital fl oor is most commonly fractured,</p><p>followed by the medial wall. The “teardrop” sign refers to prolapse of periorbital</p><p>fat and/or orbital contents into the maxillary sinus. Complications to identify at</p><p>imaging include extraocular muscle herniation and entrapment, hemorrhage, globe</p><p>injury, and infraorbital nerve injury.</p><p>Reference:</p><p>Winegar BA, Murillo H, Tantiwongkosi B. Spectrum of critical imaging fi ndings in complex facial</p><p>skeletal trauma. Radiographics. 2013;33(1):3-19.</p><p>Modalities:</p><p>XR, CT</p><p>TEARDROP</p><p>220 Chapter 3: Head, Neck, and Orbits</p><p>FINDINGS:</p><p>Temporal bone CT MPR, Pöschl plane, shows a large defect (arrow) in the roof of</p><p>the right superior semicircular canal.</p><p>DIAGNOSIS:</p><p>Superior semicircular canal dehiscence</p><p>DISCUSSION:</p><p>Third window abnormalities are defects in the bony structure of the inner ear, forming</p><p>a superfl uous communication with the middle ear in addition to the physiologic</p><p>oval and round windows. Classic clinical fi ndings including sound/pressure-induced</p><p>vertigo (Tullio/Hennebert signs), a low-frequency air-bone gap at audiometry, and</p><p>decreased thresholds for vestibular evoked myogenic potentials (VEMPs). Superior</p><p>semicircular canal dehiscence, or loss of the bony roof of the semicircular canal,</p><p>is the prototypical example of third window pathology. This is best identifi ed on</p><p>temporal bone CT with multiplanar reconstruction in the Pöschl plane, parallel</p><p>to the superior semicircular canal. The third window phenomenon has also been</p><p>described in posterior semicircular canal dehiscence, carotid-cochlear dehiscence,</p><p>perilabyrinthine fi stula, enlarged vestibular aqueduct, and X-linked stapes gusher.</p><p>References:</p><p>Merchant SN, Rosowski JJ. Conductive hearing loss caused by third-window lesions of the inner ear.</p><p>Otol Neurotol. 2008;29(3):282-289.</p><p>Minor LB, Solomon D, Zinreich JS, et al. Sound- and/or pressure-induced vertigo due to bone</p><p>dehiscence of the superior semicircular canal. Arch Otolaryngol Head Neck Surg. 1998;124:249-258.</p><p>Modality:</p><p>CT</p><p>THIRD WINDOW</p><p>Thumb 221</p><p>FINDINGS:</p><p>Sagittal contrast-enhanced</p><p>T1-weighted MR shows an</p><p>exophytic enhancing clival</p><p>mass that indents the pons</p><p>(arrow).</p><p>DIFFERENTIAL DIAGNOSIS:</p><p>• Notochordal lesion</p><p>• Chondrosarcoma</p><p>DISCUSSION:</p><p>Notochordal remnants are</p><p>present in the midline spheno-</p><p>occipital synchondrosis and</p><p>may proliferate along the</p><p>dorsal wall of the clivus</p><p>into the prepontine cistern.</p><p>From least to most aggressive, the spectrum of notochordal retroclival lesions</p><p>includes ecchordosis physaliphora (EP), benign notochordal cell tumor (BNCT),</p><p>and malignant chordoma. EP is classically small and T2-hyperintense with a bony</p><p>pedicle, no enhancement, and no mass effect. BNCT has an intermediate appearance,</p><p>with variable enhancement and mass effect. Chordomas are large and expansile</p><p>with soft tissue components, heterogeneous “honeycomb” enhancement, and bone</p><p>destruction. Classic chordomas are T2-hyperintense with reduced diffusion due to</p><p>myxoid stroma. Poorly differentiated chordomas may be T2-hypointense and show</p><p>even more reduced diffusion. In contrast to notochordal lesions, chondrosarcoma</p><p>is a malignant mesenchymal tumor that tends to occur off midline at the petro-</p><p>occipital (petroclival) synchondrosis. This tumor also appears T2-hyperintense with</p><p>heterogeneous enhancement. However, “arc and ring” mineralization on CT and</p><p>increased (rather than reduced) diffusion on MR may be identifi ed, because of the</p><p>cartilaginous stroma.</p><p>References:</p><p>Golden LD, Small JE. Benign notochordal lesions of the posterior clivus: retrospective review of</p><p>prevalence and imaging characteristics. J Neuroimaging. 2013 Mar 6.</p><p>Mehnert F, Beschorner R, Küker W, et al. Retroclival ecchordosis physaliphora: MR imaging and</p><p>review of the literature. AJNR Am J Neuroradiol. 2004;25(10):1851-1855.</p><p>Yeom KW, Lober RM, Mobley BC, et al. Diffusion-weighted MRI: distinction of skull base chordoma</p><p>from chondrosarcoma. AJNR Am J Neuroradiol. 2012 Nov 1.</p><p>Modalities:</p><p>CT, MR</p><p>THUMB</p><p>222 Chapter 3: Head, Neck, and Orbits</p><p>Modalities:</p><p>XR, CT</p><p>FINDINGS:</p><p>Lateral radiograph and sagittal CT show epiglottic enlargement and edema (arrows),</p><p>with obscuration of the vallecula.</p><p>DIAGNOSIS:</p><p>Epiglottitis</p><p>DISCUSSION:</p><p>The epiglottis is a small fl ap of cartilage that projects over the glottis (vocal folds)</p><p>and closes over the trachea during swallowing to prevent aspiration. On lateral</p><p>radiographs, the normal epiglottis has a thin appearance likened to a “little fi nger.”</p><p>Acute epiglottitis can be caused by infection with Haemophilus infl uenzae or</p><p>Streptococci. The epiglottis becomes severely swollen and edematous, resembling</p><p>a “thumb.” In addition, there is loss of defi nition of the epiglottic vallecula behind</p><p>the root of tongue.</p><p>References:</p><p>Ducic Y, Hébert PC, MacLachlan L, et al. Description and evaluation of the vallecula sign: a new</p><p>radiologic sign in the diagnosis of adult epiglottitis. Ann Emerg Med. 1997;30(1):1-6.</p><p>Podgore JK, Bass JW. Letter: The “thumb sign” and “little fi nger sign” in acute epiglottitis. J Pediatr.</p><p>1976;88(1):154-155.</p><p>THUMB(PRINT), VALLECULA</p><p>223</p><p>4</p><p>FINDINGS:</p><p>Axial T2-weighted MR shows absent fl ow voids and abnormal hyperintense</p><p>intraluminal signal in the ICAs (thick arrows), ACAs, and MCAs (thin arrows).</p><p>DIAGNOSIS:</p><p>Brain death</p><p>DISCUSSION:</p><p>Accurate diagnosis of brain death is necessary prior to discontinuing life support in</p><p>a comatose patient, particularly when organ donation is being considered. Clinical</p><p>examination is only reliable in the absence of hypothermia, barbiturates, sedatives,</p><p>and hypnotics. If the diagnosis is unclear, imaging examinations such as nuclear</p><p>medicine, CT, MR, or angiography may be helpful. Contrast-enhanced imaging</p><p>reveals absence of intracranial perfusion above the level of the skull base. On</p><p>T2-weighted MR, intermediate-signal intraluminal thrombus replaces the normal</p><p>signal voids seen with high-velocity arterial fl ow (“absence of fl ow voids”). Care</p><p>must be taken to distinguish absent fl ow from very slow fl ow within the cerebral</p><p>arteries and/or veins. Additional imaging signs include diffuse cerebral edema with</p><p>obscuration of gray-white differentiation, as well as downward transtentorial and</p><p>tonsillar herniation. Increased collateral fl ow to the ECA may result in nasal and</p><p>scalp enhancement (“MR hot nose” sign).</p><p>Reference:</p><p>Ishii K, Onuma T, Kinoshita T, et al. Brain death: MR and MR angiography. AJNR Am J Neuroradiol.</p><p>1996;17(4):731-735.</p><p>Modality:</p><p>MR</p><p>ABSENCE OF FLOW VOIDS</p><p>CHAPTER FOUR</p><p>VASCULAR</p><p>224 Chapter 4: Vascular</p><p>Modality:</p><p>CT</p><p>FINDINGS:</p><p>• Axial CT shows diffuse subarachnoid hemorrhage concentrated in the right</p><p>sylvian fi ssure (arrow).</p><p>• Axial CTA shows a ruptured right MCA bifurcation aneurysm (arrow).</p><p>DIAGNOSIS:</p><p>Ruptured MCA bifurcation aneurysm</p><p>DISCUSSION:</p><p>The middle cerebral artery is divided into four major segments. The M1 (sphenoidal</p><p>or horizontal) segment originates from the ICA and bifurcates into superior and</p><p>inferior divisions. The M2 (insular) segment begins at the MCA bifurcation, coursing</p><p>laterally and anteriorly to the margin of the insula. The M3 (opercular) segment</p><p>begins at the circular sulcus of the insula, then loops and curves over the frontal</p><p>and temporal opercula to reach the surface of the sylvian fi ssure. The M4 (cortical</p><p>or terminal) segment consists of various branches that course over the cerebral</p><p>convexity and supply the cortex. When MCA bifurcation aneurysms rupture, the</p><p>resulting subarachnoid</p><p>hemorrhage can track along the ipsilateral sylvian fi ssure and</p><p>outline the frontotemporal operculum, producing an “arrow” sign.</p><p>References:</p><p>Fossett DT, Caputy AJ, eds. Operative Neurosurgical Anatomy. New York: Thieme; 2002.</p><p>Maramattom BV, Wijdicks EF. Arrow sign in MCA trifurcation aneurysm. Neurology. 2004;63(7):1323.</p><p>ARROW</p><p>Arterial Hyperintensity, (Central) Dot, (Hyper) Dense Artery, Hyperintense Vessel, Susceptibility 225</p><p>Modalities:</p><p>CT, MR</p><p>ARTERIAL HYPERINTENSITY, (CENTRAL) DOT, (HYPER) DENSE ARTERY, HYPERINTENSE</p><p>VESSEL, SUSCEPTIBILITY</p><p>FINDINGS:</p><p>• Axial noncontrast CT shows a hyperdense right MCA (arrow).</p><p>• Axial SWI MR shows intraluminal susceptibility (arrow), compatible with</p><p>thrombus. There is cytotoxic edema in the right temporal and occipital lobes.</p><p>DIAGNOSIS:</p><p>Arterial infarct</p><p>DISCUSSION:</p><p>Cerebral arterial slow fl ow and occlusion produce increased attenuation within the</p><p>arterial lumen, yielding a “hyperdense artery” sign in long axis or “central dot” en</p><p>face. This is the earliest CT sign of arterial ischemia and is best appreciated in the</p><p>MCA, with a lower detection rate in the vertebrobasilar arteries, ICA, ACA, and</p><p>PCA. On MR, arterial thrombus produces intraluminal hyperintensity on FLAIR</p><p>and T2-weighted sequences (“hyperintense vessel” sign), as well as hypointensity on</p><p>SWI (“susceptibility” sign). Mimics include elevated hematocrit (“diffuse hyperdense</p><p>intracranial circulation”), mural calcifi cations in atherosclerosis, and cerebral edema</p><p>or atrophy with relatively hypodense brain parenchyma.</p><p>References:</p><p>Koo CK, Teasdale E, Muir KW. What constitutes a true hyperdense middle cerebral artery sign?</p><p>Cerebrovasc Dis. 2000;10(6):419-423.</p><p>Makkat S, Vandevenne JE, Verswijvel G, et al. Signs of acute stroke seen on fl uid-attenuated inversion</p><p>recovery MR imaging. AJR Am J Roentgenol. 2002;179(1):237-243.</p><p>Shinohara Y, Kinoshita T, Kinoshita F. Changes in susceptibility signs on serial T2*-weighted single-</p><p>shot echo-planar gradient-echo images in acute embolic infarction: comparison with recanalization</p><p>status on 3D time-of-fl ight magnetic resonance angiography. Neuroradiology. 2012;54(5):427-434.</p><p>226 Chapter 4: Vascular</p><p>Modalities:</p><p>CT, MR</p><p>ATTENUATED/DENSE SINUS/VEIN, CORD, TRAM TRACK</p><p>FINDINGS:</p><p>• Axial noncontrast CT shows a curvilinear hyperdensity in the expected region of</p><p>the right transverse sinus (arrow).</p><p>• Coronal contrast-enhanced T1-weighted MR shows nonocclusive centralized</p><p>thrombus outlined by contrast in the right transverse sinus (arrow).</p><p>DIAGNOSIS:</p><p>Cerebral venous thrombosis</p><p>DISCUSSION:</p><p>Cerebral venous thrombosis is a rare and frequently misdiagnosed condition</p><p>that can affect the dural venous sinuses, deep veins, and superfi cial veins. Risk</p><p>factors include young age, dehydration, sinusitis, pregnancy, various medications</p><p>(oral contraceptives, steroids), trauma or surgery, intracranial hypotension</p><p>or hypertension, hematologic and autoimmune disorders, malignancy, and</p><p>other hypercoagulable states. Newly formed thrombus may be appreciated on</p><p>noncontrast CT as a “cordlike” hyperdensity in the expected region of the sinus</p><p>or vein. Subacute thrombus demonstrates variable hyperintensity on T1-weighted</p><p>MR and hypointensity on T2-weighted and SWI MR. Contrast-enhanced images</p><p>may demonstrate a “tram track” sign with contrast outlining a centralized fi lling</p><p>defect. Dedicated CTV or MRV should be performed to confi rm the diagnosis</p><p>and evaluate the extent of disease. In the acute setting, prompt correction of the</p><p>underlying cause is indicated with consideration for anticoagulation, as untreated</p><p>cerebral venous thrombosis can progress to venous infarction and hemorrhage. In</p><p>addition, chronic venous thrombosis can be complicated by dural arteriovenous</p><p>fi stula (dAVF) formation.</p><p>Reference:</p><p>Rizzo L, Crasto SG, Rudà R, et al. Cerebral venous thrombosis: role of CT, MRI and MRA in the</p><p>emergency setting. Radiol Med. 2010;115(2):313-325.</p><p>Modalities:</p><p>XA, CT, MR</p><p>FINDINGS:</p><p>• Axial T2-weighted MR shows multiple serpiginous fl ow voids centered in the left</p><p>temporal and occipital lobes (arrow), with associated mass effect.</p><p>• Left vertebral artery angiogram, lateral projection, identifi es the large nidus</p><p>(arrow), with early arterial enhancement and superfi cial venous drainage.</p><p>DIAGNOSIS:</p><p>Arteriovenous malformation</p><p>DISCUSSION:</p><p>Arteriovenous malformation (AVM) is a high-fl ow vascular malformation</p><p>characterized by abnormal arteriovenous shunting without an intervening capillary</p><p>bed. Communication can occur through either a nidus (tangle of abnormal vessels)</p><p>or a direct fi stulous communication (forming a pial arteriovenous fi stula). The</p><p>nidus can be glomerular (compact) or diffuse (proliferative) with interspersed brain</p><p>parenchyma. At imaging, the nidus has a tortuous “bag of worms” appearance,</p><p>with early arterial enhancement and venous drainage. Characteristics that increase</p><p>the risk of rupture include feeding artery or intranidal aneurysms, venous ectasias,</p><p>and venous stenoses. Complications include hemorrhage, infarction, seizures, and</p><p>hydrocephalus. Treatment options include radiation, transcatheter embolization, and</p><p>surgical resection. Operative outcome correlates with the Spetzler-Martin grading</p><p>system, which evaluates nidus size (1 point: 6 cm); venous drainage (0 points: superfi cial, 1 point: deep); and eloquence of</p><p>adjacent brain (0 points: non-eloquent, 1 point: eloquent). Spetzler-Martin grades</p><p>range from 1 to 5, with 6 being reserved for non-operative candidates. Multiple</p><p>AVMs can be seen in cerebrofacial arteriovenous metameric syndrome (Wyburn-</p><p>Mason syndrome, Bonnet-Dechaume-Blanc disease) and hereditary hemorrhagic</p><p>telangiectasia (Osler-Weber-Rendu syndrome).</p><p>Reference:</p><p>Geibprasert S, Pongpech S, Jiarakongmun P, et al. Radiologic assessment of brain arteriovenous</p><p>malformations: what clinicians need to know. Radiographics. 2010;30(2):483-501.</p><p>BAG OF WORMS, HONEYCOMB, SERPENTINE, SOAP BUBBLE, TANGLE</p><p>Bag of Worms, Honeycomb, Serpentine, Soap Bubble, Tangle 227</p><p>228 Chapter 4: Vascular</p><p>Modalities:</p><p>XA, CT, MR</p><p>FINDINGS:</p><p>ICA angiogram, lateral projection, shows an anteriorly directed ACOM aneurysm</p><p>(arrow).</p><p>DIAGNOSIS:</p><p>Berry aneurysm</p><p>DISCUSSION:</p><p>The majority of intracranial aneurysms are small saccular (“berry”) aneurysms that</p><p>develop at major arterial branch points, where there is thinning of the internal elastic</p><p>lamina and tunica media. Characteristic locations include the distal ICA, ACOM,</p><p>PCOM, MCA bifurcation, basilar tip, SCA, and PICA. Multiple cerebral aneurysms</p><p>are seen in association with various acquired and congenital disorders including</p><p>hypertension, hyperlipidemia, vasculitis, drug abuse, connective tissue disorders,</p><p>autosomal dominant polycystic kidney disease, neurofi bromatosis type I, tuberous</p><p>sclerosis, hereditary hemorrhagic telangiectasia (Osler-Weber Rendu syndrome),</p><p>Klippel-Trenaunay-Weber syndrome, and alpha-1-antitrypsin (AAT1) defi ciency. The</p><p>main cause of morbidity and mortality is aneurysm rupture, which depends on several</p><p>factors including aneurysm size, morphology, and location; underlying etiology;</p><p>and patient comorbidities. Ruptured aneurysms should be treated emergently. For</p><p>unruptured aneurysms, defi nitive therapy (endovascular therapy or surgical clipping)</p><p>should be considered for sizes exceeding 7 mm and location within the posterior</p><p>fossa, because of the signifi cantly increased risk of rupture.</p><p>Reference:</p><p>Hacein-Bey L, Provenzale JM. Current imaging assessment and treatment of intracranial aneurysms.</p><p>AJR Am J Roentgenol. 2011;196(1):32-44.</p><p>BERRY</p><p>Berry, Mulberry, Popcorn (Ball), Stone 229</p><p>Modalities:</p><p>CT, MR</p><p>FINDINGS:</p><p>Axial T2-weighted MR shows a multiloculated left cerebellar lesion (arrow)</p><p>with associated fl uid-blood levels, peripheral hemosiderin, and vasogenic edema.</p><p>Superfi cial siderosis is also noted along the cerebellar folia and pons.</p><p>DIAGNOSIS:</p><p>Giant cavernoma</p><p>DISCUSSION:</p><p>Cavernous malformations (angiomas, cavernomas, cavernous hemangiomas) are</p><p>slow-fl ow vascular malformations consisting of capillary/cavernous spaces and</p><p>vascular sinusoids without intervening brain parenchyma. They are angiographically</p><p>occult or “cryptic” lesions, due to their slow fl ow. Repeated episodes of hemorrhage</p><p>produce blood products of various ages, which can be associated with vasogenic</p><p>edema, fl uid-blood levels, and calcifi cation. Over time, hemosiderin is cleared from</p><p>the center of the lesion and deposited around the periphery, producing a “dark</p><p>halo” on T2-weighted and SWI MR. Large multiloculated lesions demonstrate a</p><p>“popcorn ball” appearance, also known as “hemangioma calcifi cans” or “brain</p><p>stone.” Multiple cavernomas are seen in familial multiple cavernous malformation</p><p>syndrome, and also occur following cranial irradiation.</p><p>References:</p><p>Hegde AN, Mohan S, Lim CC. CNS cavernous haemangioma: “popcorn” in the brain and spinal</p><p>cord. Clin Radiol. 2012;67(4):380-388.</p><p>Vilanova JC, Barceló J, Smirniotopoulos JG, et al. Hemangioma from head to toe: MR imaging with</p><p>pathologic correlation. Radiographics. 2004;24(2):367-385.</p><p>BERRY, MULBERRY, POPCORN (BALL), STONE</p><p>230 Chapter 4: Vascular</p><p>FINDINGS:</p><p>Axial SWI MR shows a right perirolandic lesion with peripheral rim of suscepti bility</p><p>(arrow).</p><p>DIFFERENTIAL DIAGNOSIS:</p><p>• Cavernoma</p><p>• Hematoma</p><p>• Abscess</p><p>DISCUSSION:</p><p>Cavernous malformations (angiomas, cavernomas, cavernous hemangiomas)</p><p>are developmental vascular malformations consisting of capillary/cavernous</p><p>vascular spaces and sinusoids without intervening brain parenchyma. These</p><p>are angiographically occult, because of their slow fl ow. Repeated episodes of</p><p>microhemorrhage produce blood products of various ages, which can be associated</p><p>with fl uid-blood levels and calcifi cation. Over time, hemosiderin is cleared from</p><p>the center of the lesion and deposited around the periphery, producing a “dark</p><p>halo” on T2-weighted and SWI MR. Rarely, other hemorrhagic lesions (hematoma,</p><p>primary and metastatic tumors, granulomatous disease) may demonstrate a</p><p>hemosiderin rim, but this tends to be more discontinuous and irregular. Abscesses</p><p>can also demonstrate a dark rim, which is thought to relate to free radical formation</p><p>and macrophage activity.</p><p>References:</p><p>Haimes AB, Zimmerman RD, Morgello S, et al. MR imaging of brain abscesses. AJR Am J Roentgenol.</p><p>1989;152(5):1073-1085.</p><p>Vilanova JC, Barceló J, Smirniotopoulos JG, et al. Hemangioma from head to toe: MR imaging with</p><p>pathologic correlation. Radiographics. 2004;24(2):367-385.</p><p>BLACK/DARK HALO, IRON RIM/RING</p><p>Modality:</p><p>MR</p><p>Border Zone 231</p><p>FINDINGS:</p><p>• Axial DWI MR shows wedge-shaped areas of reduced diffusion along the bilateral</p><p>MCA/PCA border zones (thick arrows).</p><p>• Axial ASL MR shows signal dropout along the bilateral MCA/PCA border zones</p><p>(thin arrows), with high signal in the surrounding cortex.</p><p>DIAGNOSIS:</p><p>External watershed infarct</p><p>DISCUSSION:</p><p>Watershed (borderland, border zone, boundary zone, end zone, terminal zone)</p><p>infarcts are caused by decreased perfusion at the boundaries between arterial</p><p>territories. External (cortical) border zones are located at the junctions of the</p><p>anterior, middle, and posterior cerebral artery territories. Strokes in these locations</p><p>are associated with atherosclerosis and microembolism, with or without global</p><p>hypoperfusion. On DWI MR, multiple ovoid or wedge-shaped areas of reduced</p><p>diffusion are seen in a watershed distribution. Arterial spin labeling (ASL), a</p><p>noncontrast MR technique for measuring cerebral perfusion, shows signal dropout</p><p>in watershed areas. Often, there is high signal in the surrounding cortex, which is</p><p>thought to represent labeled blood in feeding arteries that has not yet reached the</p><p>capillary bed (“arterial transit artifact”).</p><p>Reference:</p><p>Zaharchuk G, Bammer R, Straka M, et al. Arterial spin-label imaging in patients with normal bolus</p><p>perfusion-weighted MR imaging fi ndings: pilot identifi cation of the borderzone sign. Radiology.</p><p>2009;252(3):797-807.</p><p>BORDER ZONE</p><p>Modalities:</p><p>CT, MR</p><p>232 Chapter 4: Vascular</p><p>Modalities:</p><p>XA, CT, MR</p><p>BOWTIE</p><p>FINDINGS:</p><p>Right ICA angiogram, AP</p><p>projection, shows early</p><p>opacifi cation of the right</p><p>cavernous sinus (thick</p><p>arrow). This communicates</p><p>across midline with the</p><p>left cavernous sinus (thin</p><p>arrow). There is early</p><p>drainage into the bilateral</p><p>superior/inferior petrosal</p><p>sinuses, sigmoid sinuses,</p><p>and internal jugular veins.</p><p>DIAGNOSIS:</p><p>Carotid-cavernous fi stula</p><p>DISCUSSION:</p><p>Carotid-cavernous fi stula</p><p>(CCF) is an abnormal</p><p>communication between</p><p>the arteries and veins within the cavernous sinus. Predisposing factors include</p><p>trauma, surgery, pregnancy, aneurysm rupture, connective tissue disorders,</p><p>atherosclerosis, and infection. Direct CCF refers to a single-hole, high-fl ow direct</p><p>communication between the ICA and cavernous sinus. Indirect CCF is a low-fl ow</p><p>dural arteriovenous fi stula (dAVF) that involves multiple ECA and/or ICA branches.</p><p>The Barrow classifi cation separates CCF into four types: A = direct CCF, B = indirect</p><p>CCF with ICA supply, C = indirect CCF with ECA supply, D = indirect CCF with</p><p>ICA and ECA supply. Angiography is the most sensitive imaging examination and</p><p>shows early opacifi cation of the ipsilateral cavernous sinus in the arterial phase.</p><p>Due to communication through anterior and posterior intercavernous sinuses, the</p><p>contralateral cavernous sinus also enhances, creating a “bowtie” pattern. There is</p><p>early venous drainage, often through the ipsilateral superior ophthalmic vein. This</p><p>appears dilated and tortuous with accompanying proptosis, extraocular muscle</p><p>enlargement, and periorbital edema. Treatment options include conservative</p><p>management, carotid compression therapy, transcatheter embolization, and</p><p>surgical repair.</p><p>References:</p><p>Chen CC, Chang PC, Shy CG, et al. CT angiography and MR angiography in the evaluation of carotid</p><p>cavernous sinus fi stula prior to embolization: a comparison of techniques. AJNR Am J Neuroradiol.</p><p>2005;26(9):2349-2356.</p><p>Ducruet AF, Albuquerque FC, Crowley RW, et al. The evolution of endovascular treatment of carotid</p><p>cavernous fi stulas: a single-center experience. World Neurosurg. 2013.</p><p>Brush 233</p><p>Modalities:</p><p>XA, CT, MR</p><p>FINDINGS:</p><p>Axial SWI MR shows increased size and number of deep medullary veins (arrows).</p><p>DIAGNOSIS:</p><p>Moyamoya disease</p><p>DISCUSSION:</p><p>Moyamoya, the Japanese term for “puff of smoke,” refers to progressive stenosis/</p><p>occlusion of the distal ICAs and proximal ACAs/MCAs with relative sparing of</p><p>the posterior circulation. The etiology may be idiopathic (moyamoya disease) or</p><p>secondary (moyamoya syndrome) to various conditions including atherosclerosis,</p><p>Down syndrome, neurofi bromatosis, sickle cell anemia, and connective tissue</p><p>disorders. Collateral circulation is supplied by basal parenchymal perforators,</p><p>leptomeningeal branches from the PCA, and transdural vessels from the ECA.</p><p>Hypertrophy of the deep medullary veins produces the “brush” sign, with multiple</p><p>parallel vessels that are best seen on SWI MR. Pediatric patients tend to present</p><p>with cerebral ischemia or infarction, whereas adults can develop infarction or</p><p>hemorrhage due to rupture of small aneurysms. Surgical procedures are aimed at</p><p>revascularization and include direct (STA-MCA bypass) or indirect (encephalo-</p><p>duro-arterio-synangiosis, encephalo-myo-synangiosis, pial synangiosis, omental</p><p>transplantation) techniques.</p><p>Reference:</p><p>Horie N, Morikawa M, Nozaki A, et al. “Brush sign” on susceptibility-weighted MR imaging indicates</p><p>the severity of moyamoya disease. AJNR Am J Neuroradiol. 2011;32(9):1697-1702.</p><p>BRUSH</p><p>234 Chapter 4: Vascular</p><p>FINDINGS:</p><p>Coronal contrast-enhanced T1-weighted MR shows patchy enhance ment in the</p><p>right temporal lobe (arrow).</p><p>DIAGNOSIS:</p><p>Capillary telangiectasia</p><p>DISCUSSION:</p><p>Capillary telangiectasia is the second most common vascular anomaly of the</p><p>central nervous system, following developmental venous anomaly. This</p><p>is a</p><p>slow-fl ow malformation consisting histologically of dilated capillaries with</p><p>a thin endothelial lining, sometimes accompanied by a dilated draining vein</p><p>(“dot in the spot” appearance). The intervening brain parenchyma is normal,</p><p>without mass effect. Lesions are iso- to hypointense on T1-weighted MR, iso-</p><p>to hyperintense on T2-weighted MR, and hypointense on SWI MR due to the</p><p>presence of deoxyhemoglobin. On contrast-enhanced T1-weighted MR, there is</p><p>ill-defi ned “lattice”-like enhancement. Small capillary telangiectasias are generally</p><p>asymptomatic and occult on CT or angiography. Larger lesions (over 1 cm)</p><p>may be symptomatic and complicated by hemorrhage. The majority of capillary</p><p>telangiectasias occur in the pons, but can also be seen in the cerebrum, cerebellum,</p><p>and spinal cord. Lesions may be accompanied by other vascular anomalies including</p><p>DVA, cavernoma, and AVM. Syndromic associations include Osler-Weber-Rendu</p><p>(hereditary hemorrhagic telangiectasia), Louis-Bar (ataxia-telangiectasia), and</p><p>Sturge-Weber (encephalotrigeminal angiomatosis).</p><p>References:</p><p>Lee RR, Becher MW, Benson ML, et al. Brain capillary telangiectasia: MR imaging appearance and</p><p>clinicohistopathologic fi ndings. Radiology. 1997;205(3):797-805.</p><p>Sayama CM, Osborn AG, Chin SS, et al. Capillary telangiectasias: clinical, radiographic, and</p><p>histopathological features. J Neurosurg. 2010;113(4):709-714.</p><p>BRUSH, DOT, LACE, LATTICE, PAINT, SPECKLED, STIPPLED</p><p>Modality:</p><p>MR</p><p>Candelabra, Sylvian Point, Sylvian Triangle 235</p><p>CANDELABRA, SYLVIAN POINT, SYLVIAN TRIANGLE</p><p>Modality:</p><p>XA</p><p>FINDINGS:</p><p>Right ICA angiogram, AP and lateral projections, show the angular artery curving</p><p>to exit the sylvian fi ssure (thick arrows). The sylvian triangle (dotted lines) is formed</p><p>by prefrontal arteries (thin arrows), insular loops, and the MCA trunk.</p><p>DIAGNOSIS:</p><p>Normal MCA</p><p>DISCUSSION:</p><p>On AP angiography, the “sylvian point” represents the most medial aspect of the</p><p>highest cortical MCA branch (usually the angular artery). Here, the artery turns</p><p>anteriorly and inferiorly to exit the sylvian fi ssure, demarcating the posterior margin</p><p>of the insula. On lateral angiography, the tops of multiple insular loops form a</p><p>relatively straight line. This is known as the “superior insular line,” and terminates</p><p>posteriorly at the sylvian point. The operculofrontal (ascending frontal) complex</p><p>arises from the superior division of the MCA and consists of prefrontal and central</p><p>sulcus arteries. On lateral angiography, the prefrontal arteries fan out over the</p><p>frontal operculum, creating a “candelabra” appearance. These supply the middle and</p><p>inferior frontal gyri, including the Broca area. The inferior insular line connects the</p><p>base of the most anterior branch of the candelabra to the sylvian point, paralleling</p><p>the MCA trunk. The “sylvian triangle” is formed superiorly by the superior insular</p><p>line, anteriorly by the candelabra, and posteroinferiorly by the inferior insular line.</p><p>Displacements of the sylvian point and triangle are important signs of supratentorial</p><p>mass effect or volume loss.</p><p>References:</p><p>Lee SH, Goldberg HI. The normal angiographic sylvian point on the lateral cerebral angiogram.</p><p>Neuroradiology. 1979;17(2):101-103.</p><p>Rowbotham GF, Little E. The candelabra arteries and the circulation of the cerebral cortex. Br J Surg.</p><p>1963;50:694-697.</p><p>236 Chapter 4: Vascular</p><p>Modalities:</p><p>XA, CT, MR</p><p>FINDINGS:</p><p>Axial contrast-enhanced CT and contrast-enhanced T1-weighted MR show</p><p>anomalous cerebellar draining veins (thick arrows) that converge toward a common</p><p>pontine venous trunk (thin arrows). Several associated pontine cavernomas are</p><p>present, with fl uid-blood levels and susceptibility.</p><p>DIAGNOSIS:</p><p>Developmental venous anomaly</p><p>DISCUSSION:</p><p>Developmental venous anomaly (DVA), formerly known as venous angioma, is</p><p>the most common vascular malformation of the central nervous system. This is a</p><p>slow-fl ow malformation consisting histologically of dilated and thin-walled veins</p><p>separated by intervening brain. On venous phase imaging, dilated and radially</p><p>arranged collecting veins converge toward a common trunk (“Medusa head” or</p><p>“palm tree” appearance), which drains to either the superfi cial or deep venous</p><p>network. Deoxyhemoglobin also produces susceptibility artifact on T2-weighted</p><p>and SWI MR. The most common locations are the frontal lobe, parietal lobe, and</p><p>posterior fossa. DVA is usually asymptomatic and should not be resected, as this</p><p>represents the primary venous drainage pathway for involved brain. There is an</p><p>association with other vascular malformations including cavernoma, cervicofacial</p><p>venous malformations, and blue rubber bleb nevus syndrome.</p><p>References:</p><p>Lee C, Pennington MA, Kenney CM 3rd. MR evaluation of developmental venous anomalies:</p><p>medullary venous anatomy of venous angiomas. AJNR Am J Neuroradiol. 1996;17(1):61-70.</p><p>Saba PR. The caput medusae sign. Radiology. 1998;207(3):599-600.</p><p>CAPUT MEDUSAE, CROWN, FAN, (INVERSE) UMBRELLA, MEDUSA HEAD, PALM TREE,</p><p>SPOKE WHEEL, WEDGE</p><p>Cartwheel, Linear, Radial, Spoke Wheel, Sunburst, Tree Root 237</p><p>Modalities:</p><p>XA, CT, MR</p><p>FINDINGS:</p><p>• ECA angiography with selective MMA injection, lateral projection, shows arterial</p><p>tumor blush with radiating feeding vessels (arrows).</p><p>• ICA angiography, lateral projection, in a different patient shows tumor blush (thick</p><p>arrows) with feeding vessels radiating from a central vascular pedicle. Arterial</p><p>supply is from meningohypophyseal and inferolateral branches of the cavernous</p><p>ICA (thin arrow).</p><p>DIFFERENTIAL DIAGNOSIS:</p><p>• Meningioma</p><p>• Hemangiopericytoma</p><p>• Metastasis</p><p>DISCUSSION:</p><p>Meningioma is a usually benign extra-axial tumor arising from the arachnoid cap</p><p>cells of the meninges. Tumors are hypervascular and often derive blood supply from</p><p>branches of the ECA (particularly the MMA), which course into the center of the</p><p>lesion. As tumors gradually enlarge, a “sunburst” of hypertrophied arterial branches</p><p>is seen radiating from the central vascular pedicle. Ultimately, lesions outgrow this</p><p>blood supply and recruit ICA branches to supply the periphery. In tumors with dual</p><p>blood supply, ECA angiography classically shows “spoke-wheel” enhancement</p><p>within the tumor, whereas ICA angiography yields a “doughnut” appearance along</p><p>the periphery. This angiographic appearance is characteristic of meningioma, but</p><p>can be seen in other vascular neoplasms such as hemangiopericytoma or metastasis.</p><p>Reference:</p><p>Manelfe C, Lasjaunias P, Ruscalleda J. Preoperative embolization of intracranial meningiomas. AJNR</p><p>Am J Neuroradiol. 1986;7(5):963-972.</p><p>CARTWHEEL, LINEAR, RADIAL, SPOKE WHEEL, SUNBURST, TREE ROOT</p><p>238 Chapter 4: Vascular</p><p>Modality:</p><p>MR</p><p>FINDINGS:</p><p>Axial DWI MR shows bilateral foci of reduced diffusion, right greater than left.</p><p>Linearly arranged microinfarcts are seen in the right centrum semiovale (arrows).</p><p>DIAGNOSIS:</p><p>Internal watershed infarcts</p><p>DISCUSSION:</p><p>Watershed (borderland, border zone, boundary zone, end zone, terminal zone) infarcts</p><p>are caused by decreased perfusion at the boundaries between arterial territories.</p><p>External (cortical) border zones are located at the junctions of the anterior, middle,</p><p>and posterior cerebral artery territories. Strokes in these locations are associated</p><p>with atherosclerosis and microembolism, with or without global hypoperfusion. At</p><p>imaging, they have an ovoid or wedge-shaped appearance. Internal (subcortical)</p><p>border zones are located at the junctions of the cerebral artery territories with the</p><p>medial striate, lenticulostriate, and anterior choroidal artery territories. Infarcts in</p><p>these locations are caused by arterial stenosis/occlusion or hemodynamic compromise,</p><p>and have a poorer prognosis. At imaging, these are classifi ed as partial or confl uent.</p><p>Partial infarcts appear linearly arranged with a “cigar” or “rosary” appearance,</p><p>paralleling the lateral ventricle in the centrum semiovale or corona radiata.</p><p>References:</p><p>Mangla R, Kolar B, Almast J, et al. Border zone infarcts:</p><p>pathophysiologic and imaging characteristics.</p><p>Radiographics. 2011;31(5):1201-1214.</p><p>Moustafa RR, Momjian-Mayor I, Jones PS, et al. Microembolism versus hemodynamic impairment</p><p>in rosary-like deep watershed infarcts: a combined positron emission tomography and transcranial</p><p>Doppler study. Stroke. 2011;42(11):3138-3143.</p><p>CIGAR, ROSARY, STRING OF PEARLS</p><p>Corkscrew, Pseudophlebitic 239</p><p>Modalities:</p><p>XA, CT, MR</p><p>FINDINGS:</p><p>• ECA angiogram, arterial phase in the lateral projection, shows early opacifi cation</p><p>of tortuous collaterals with multifocal dilations (thick arrows).</p><p>• Venous phase shows direct shunting into superfi cial and deep veins, with delayed</p><p>drainage to the cerebral venous sinuses (thin arrows).</p><p>DIAGNOSIS:</p><p>Dural arteriovenous fi stula</p><p>DISCUSSION:</p><p>Dural arteriovenous fi stula (dAVF) is a pathologic, high-fl ow shunt between dural</p><p>arteries and venous sinuses, meningeal veins, and/or cortical veins. The majority</p><p>are idiopathic, but there is an association with dural venous thrombosis, venous</p><p>hypertension, prior craniotomy, trauma, and infection. At imaging, tortuous</p><p>feeding arteries and draining veins produce a “corkscrew” or “pseudophlebitic”</p><p>pattern. Flow-related aneurysms, venous stenosis, and thrombosis increase the</p><p>risk of complications, including venous infarction and hemorrhage. Treatment</p><p>options include radiation, transcatheter embolization, venous angioplasty/</p><p>stenting, and surgical resection. Prognosis correlates with the Merland-Cognard</p><p>or Borden classifi cations. The Merland-Cognard classifi cation consists of</p><p>5 categories (I: antegrade drainage into venous sinus, IIa: drainage into and refl ux</p><p>within sinus, IIb: drainage into sinus with refl ux into cortical veins, III: cortical</p><p>venous drainage, IV: cortical venous drainage with ectasia, V: spinal perimedullary</p><p>venous drainage). The Borden classifi cation includes types of venous drainage</p><p>(I: anterograde, II: anterograde and retrograde, III: retrograde) and number of</p><p>fi stulae (a: single, b: multiple).</p><p>References:</p><p>Gandhi D, Chen J, Pearl M, et al. Intracranial dural arteriovenous fi stulas: classifi cation, imaging</p><p>fi ndings, and treatment. AJNR Am J Neuroradiol. 2012;33(6):1007-1013.</p><p>Gomez J, Amin AG, Gregg L, et al. Classifi cation schemes of cranial dural arteriovenous fi stulas.</p><p>Neurosurg Clin N Am. 2012;23(1):55-62.</p><p>CORKSCREW, PSEUDOPHLEBITIC</p><p>240 Chapter 4: Vascular</p><p>FINDINGS:</p><p>Axial CT shows edema of the right insula (arrows), obscuring the adjacent putamen.</p><p>DIAGNOSIS:</p><p>MCA infarct</p><p>DISCUSSION:</p><p>The insular cortex is supplied by the insular branches of the middle cerebral artery.</p><p>When the MCA circulation is occluded, this area effectively becomes a watershed</p><p>arterial zone distal to the ACA and PCA circulations. Acute insular edema (“insular</p><p>ribbon”) obscures the adjacent basal ganglia and is an early fi nding of MCA</p><p>infarction, along with the “dense artery” sign.</p><p>Reference:</p><p>Truwit CL, Barkovich AJ, Gean-Marton A, et al. Loss of the insular ribbon: another early CT sign of</p><p>acute middle cerebral artery infarction. Radiology. 1990;176(3):801-806.</p><p>CORTICAL/INSULAR RIBBON, DISAPPEARING BASAL GANGLIA, LENTIFORM NUCLEUS</p><p>EDEMA, OBSCURATION OF LENTIFORM NUCLEUS</p><p>Modalities:</p><p>CT, MR</p><p>Crescent 241</p><p>Modalities:</p><p>CT, MR</p><p>FINDINGS:</p><p>• Axial T1-weighted MR with fat saturation shows a hyperintense crescent of</p><p>hemorrhage (arrow) surrounding the left ICA.</p><p>• Axial contrast-enhanced T1-weighted MR with fat saturation shows intermediate-</p><p>signal thrombus (arrow) surrounding and narrowing the left ICA lumen.</p><p>DIAGNOSIS:</p><p>ICA dissection</p><p>DISCUSSION:</p><p>Carotid artery dissection results from a primary intramural hematoma or intimal</p><p>tear, enabling penetration of blood into the arterial wall. The extracranial portion</p><p>of the ICA is most commonly affected, due to its greater mobility and proximity</p><p>to the cervical spine and styloid process. Predisposing conditions include trauma,</p><p>atherosclerosis, connective tissue disorders, fi bromuscular dysplasia, and vasculitis.</p><p>When thrombosed, the false lumen can compress the true lumen and serve as</p><p>a nidus for distal embolization. Subacute hemorrhage appears hyperintense on</p><p>T1-weighted MR with fat saturation, and may produce an eccentric (“crescent”)</p><p>or concentric (“target”) morphology. Bilateral ICA dissections have been described</p><p>with a “puppy eyes” appearance. Patients can present with head or neck pain,</p><p>Horner syndrome, and anterior circulation ischemia. Treatment options include</p><p>anticoagulation or antiplatelet therapy, thrombolysis, endovascular angioplasty/</p><p>stenting, and surgical reconstruction.</p><p>References:</p><p>Feddersen B, Linn J, Klopstock T. Neurological picture. “Puppy sign” indicating bilateral dissection of</p><p>internal carotid artery. J Neurol Neurosurg Psychiatry. 2007;78(10):1055.</p><p>Rodallec MH, Marteau V, Gerber S, et al. Craniocervical arterial dissection: spectrum of imaging</p><p>fi ndings and differential diagnosis. Radiographics. 2008;28(6):1711-1728.</p><p>CRESCENT</p><p>242 Chapter 4: Vascular</p><p>Modalities:</p><p>XA, CT, MR</p><p>CUTOFF, MENISCUS</p><p>FINDINGS:</p><p>Right ICA angiogram, LAO Townes projection, shows abrupt truncation of the</p><p>proximal right M1 (arrow) with absence of distal MCA opacifi cation.</p><p>DIAGNOSIS:</p><p>Acute arterial occlusion</p><p>DISCUSSION:</p><p>Stroke is a leading cause of morbidity and mortality in developed countries. Imaging</p><p>workup is performed to assess for hemorrhage, identify etiology, and determine</p><p>appropriate therapy. Ischemic stroke can be embolic or thrombotic in nature. At</p><p>imaging, arterial occlusion manifests as a sharp vessel cutoff with failure of distal</p><p>opacifi cation. Acute occlusive emboli appear as convex fi lling defects outlined by</p><p>a “meniscus” of contrast. Therapeutic options include intravenous or intraarterial</p><p>thrombolysis and mechanical thrombectomy.</p><p>References:</p><p>Hunter GJ, Hamberg LM, Ponzo JA, et al. Assessment of cerebral perfusion and arterial anatomy in</p><p>hyperacute stroke with three-dimensional functional CT: early clinical results. AJNR Am J Neuroradiol.</p><p>1998;19(1):29-37.</p><p>Srinivasan A, Goyal M, Al Azri F, et al. State-of-the-art imaging of acute stroke. Radiographics.</p><p>2006;26(Suppl 1):S75-S95.</p><p>Daughter Sac, Murphy 243</p><p>Modalities:</p><p>XA, CT, MR</p><p>FINDINGS:</p><p>Left ICA angiogram, LAO Townes projection, and 3D reconstruction show a</p><p>ruptured PCOM aneurysm with irregularity at the apex (arrows).</p><p>DIAGNOSIS:</p><p>Ruptured aneurysm</p><p>DISCUSSION:</p><p>The majority of intracranial aneurysms are small saccular (“berry”) aneurysms that</p><p>develop at major arterial branch points, where there is thinning of the internal elastic</p><p>lamina and tunica media. Weakening of an artery wall causes focal outpouching</p><p>of the vessel. According to the law of Laplace, wall tension increases with vessel</p><p>radius for a given blood pressure. The aneurysm continues to expand until wall</p><p>tension exceeds wall strength, at which point the aneurysm ruptures. Irregularly</p><p>shaped aneurysms have a higher risk of rupture, due to unbalanced mechanical</p><p>stresses. The apex of an aneurysm is located farthest from the blood supply within</p><p>the lumen, and is most prone to ischemia. The Murphy sign or “daughter sac” refers</p><p>to a focal outpouching at the apex. This represents the site of prior or impending</p><p>aneurysm rupture, and should be urgently treated.</p><p>Reference:</p><p>Hacein-Bey L, Provenzale JM. Current imaging assessment and treatment of intracranial aneurysms.</p><p>AJR Am J Roentgenol. 2011;196(1):32-44.</p><p>DAUGHTER SAC, MURPHY</p><p>244 Chapter 4: Vascular</p><p>Modalities:</p><p>CT, MR</p><p>FINDINGS:</p><p>• Axial noncontrast CT shows triangular hyperdensity in the superior sagittal sinus</p><p>(arrow).</p><p>• Axial contrast-enhanced CT shows a central fi lling defect outlined by contrast in</p><p>the superior sagittal sinus (arrow).</p><p>DIAGNOSIS:</p><p>Sagittal sinus thrombosis</p><p>DISCUSSION:</p><p>Cerebral venous thrombosis is a rare and frequently misdiagnosed condition</p><p>that can affect the dural venous sinuses, deep veins, and superfi cial veins. Risk</p><p>factors include young age, dehydration, sinusitis, pregnancy, various medications</p><p>(oral contraceptives, steroids), trauma or surgery, intracranial hypotension</p><p>or hypertension, hematologic and autoimmune disorders, malignancy, and</p><p>other hypercoagulable states. Newly formed thrombus may be appreciated on</p><p>noncontrast CT as hyperdensity in the expected region of the sinus or vein. The</p><p>“dense triangle” sign is seen on axial images when the superior sagittal sinus</p><p>is involved. Care must be taken to distinguish this from the “pseudo-delta”</p><p>sign due to adjacent cerebral edema or atrophy, hyperdense dura in children, or</p><p>interhemispheric subdural hemorrhage. Contrast-enhanced images demonstrate</p><p>an “empty delta” appearance, with central fi lling defect surrounded by contrast.</p><p>Dedicated CTV or MRV should be performed to confi rm the diagnosis and</p><p>evaluate the extent of disease. In the acute setting, prompt correction of the</p><p>underlying cause is indicated with consideration for anticoagulation, as untreated</p><p>cerebral venous thrombosis can progress to venous infarction and hemorrhage. In</p><p>addition, chronic venous thrombosis can be complicated by dural arteriovenous</p><p>fi stula (dAVF) formation.</p><p>References:</p><p>Daif A, Kolawole TM, Ogunniyi A, et al. The pseudo-delta sign is unreliable in differentiating between</p><p>aneurysmal SAH and sinus thrombosis in unenhanced brain CT. Eur J Radiol. 1998;28(1):95-97.</p><p>Renowden S. Cerebral venous sinus thrombosis. Eur Radiol. 2004;14(2):215-226.</p><p>DENSE TRIANGLE, EMPTY DELTA</p><p>Diffuse Hyperdense Intracranial Circulation 245</p><p>Modality:</p><p>CT</p><p>DIFFUSE HYPERDENSE INTRACRANIAL CIRCULATION</p><p>FINDINGS:</p><p>Axial noncontrast CT shows mildly increased density of the intracranial arteries</p><p>(arrows).</p><p>DIFFERENTIAL DIAGNOSIS:</p><p>• Elevated hematocrit</p><p>• Physiologic hyperdensity</p><p>DISCUSSION:</p><p>Elevated hematocrit can produce diffuse hyperdensity throughout the intracranial</p><p>arterial circulation. Causes include dehydration, chronic hypoxia, polycythemia</p><p>vera, malignancy, and medications. In addition, diffuse cerebral hypodensity</p><p>caused by edema or atrophy can cause normal vessels to appear relatively</p><p>hyperdense. With severe edema, crowding of the subarachnoid spaces also mimics</p><p>subarachnoid hemorrhage (“pseudo-SAH”). In newborns, the cerebral arteries</p><p>and dural venous sinuses are normally hyperdense relative to the unmyelinated</p><p>and relatively edematous brain parenchyma. Care must be taken to distinguish</p><p>diffuse hyperdense intracranial circulation from the “dense artery” sign of early</p><p>infarction, which is focal and unilateral.</p><p>References:</p><p>Morita S, Ueno E, Masukawa A, et al. Hyperattenuating signs at unenhanced CT indicating acute</p><p>vascular disease. Radiographics. 2010;30(1):111-125.</p><p>Rancier R, Woessner H, Freeman WD. The diffuse hyperdense intracranial circulation sign.</p><p>Neurohospitalist. 2011;1(3):137.</p><p>246 Chapter 4: Vascular</p><p>Modality:</p><p>CT</p><p>FINDINGS:</p><p>Axial CTA shows right insular hemorrhage with a large arterially enhancing focus</p><p>(thick arrow) and multiple small enhancing arteries (thin arrows).</p><p>DIAGNOSIS:</p><p>Actively bleeding hematoma</p><p>DISCUSSION:</p><p>In patients with acute intracranial hema tomas, CT is the imaging examination of</p><p>choice to identify the cause of bleeding. The CTA or CTP “spot” sign has been</p><p>defi ned as a focal area of enhancement greater than 1.5 mm, with attenuation</p><p>at least twice that of the background hematoma. The presence of arterial</p><p>enhancement indicates active extravasation within the hematoma. Occasionally,</p><p>the bleeding artery can be identifi ed as a linear density or “tail” extending into</p><p>the collection. More numerous, larger, and denser spots indicate a higher risk of</p><p>hematoma expansion and poorer prognosis. Aggressive blood pressure control</p><p>with emergent endovascular or surgical therapy is necessary to minimize patient</p><p>morbidity and mortality.</p><p>References:</p><p>Koculym A, Huynh TJ, Jakubovic R, et al. CT perfusion spot sign improves sensitivity for prediction</p><p>of outcome compared with CTA and postcontrast CT. AJNR Am J Neuroradiol. 2012.</p><p>Thompson AL, Kosior JC, Gladstone DJ, et al. Defi ning the CT angiography ‘spot sign’ in primary</p><p>intracerebral hemorrhage. Can J Neurol Sci. 2009;36(4):456-461.</p><p>DOT, SPOT, TAIL</p><p>Double Barrel/Lumen, Intimal Flap 247</p><p>Modalities:</p><p>US, CT, MR FINDINGS:</p><p>• Axial CTA shows left cervical ICA dissection with intimal fl ap (arrow).</p><p>• Sagittal US shows the intimal fl ap (arrow) separating the true and false lumens.</p><p>DIAGNOSIS:</p><p>ICA dissection</p><p>DISCUSSION:</p><p>Carotid artery dissection results from a primary intramural hematoma or intimal</p><p>tear, enabling penetration of blood into the arterial wall. The extracranial portion</p><p>of the ICA is most commonly affected, due to its greater mobility and proximity</p><p>to the cervical spine and styloid process. Predisposing conditions include trauma,</p><p>atherosclerosis, connective tissue disorders, fi bromuscular dysplasia, and vasculitis.</p><p>At imaging, the displaced intimal fl ap may be identifi ed as a linear intraluminal</p><p>fi lling defect. Flow through both true and false lumens creates a “double barrel”</p><p>appearance en face. The true lumen opacifi es earlier, while slower fl ow in the false</p><p>lumen predisposes to thrombosis and can serve as a nidus for distal embolization.</p><p>Treatment options include anticoagulation or antiplatelet therapy, thrombolysis,</p><p>endovascular angioplasty/stenting, and surgical reconstruction.</p><p>Reference:</p><p>Rodallec MH, Marteau V, Gerber S, et al. Craniocervical arterial dissection: spectrum of imaging</p><p>fi ndings and differential diagnosis. Radiographics. 2008;28(6):1711-1728.</p><p>DOUBLE BARREL/LUMEN, INTIMAL FLAP</p><p>248 Chapter 4: Vascular</p><p>Modality:</p><p>XA</p><p>DOUBLE DENSITY</p><p>FINDINGS:</p><p>Right ICA angiogram, LAO Townes projections, show a clinoid ICA aneurysm (thin</p><p>arrows) that is partially superimposed on the ICA lumen (thick arrow) in the initial</p><p>projection, and better delineated on the subsequent view.</p><p>DIAGNOSIS:</p><p>Aneurysm</p><p>DISCUSSION:</p><p>The majority of intracranial aneurysms are small saccular (“berry”) aneurysms that</p><p>develop at major arterial branch points, where there is thinning of the internal elastic</p><p>lamina and tunica media. Characteristic locations include the distal ICA, ACOM,</p><p>PCOM, MCA bifurcation, basilar tip, SCA, and PICA. On angiography, small</p><p>aneurysms may be overlooked if they project in front of or behind a vessel of similar</p><p>caliber. The “double density” sign refers to an area of focally increased density in a</p><p>vessel that cannot be attributed to tortuosity or branching. This raises concern for</p><p>a superimposed aneurysm, and requires oblique views for confi rmation. The main</p><p>cause of morbidity and mortality is aneurysm rupture, which depends on several</p><p>factors including aneurysm size, morphology, and location; underlying etiology;</p><p>and patient comorbidities. Ruptured aneurysms should be treated emergently. For</p><p>unruptured aneurysms, defi nitive therapy (endovascular coiling or surgical clipping)</p><p>should be considered for sizes exceeding 7 mm and location within the posterior</p><p>fossa, because of the signifi cantly increased risk of rupture.</p><p>Reference:</p><p>Hacein-Bey L, Provenzale JM. Current imaging assessment and treatment of intracranial aneurysms.</p><p>AJR Am J Roentgenol. 2011;196(1):32-44.</p><p>Flame, Radish, Rat Tail 249</p><p>Modalities:</p><p>XA, US, CT,</p><p>MR</p><p>FINDINGS:</p><p>Sagittal CTA and CCA angiogram, lateral projection, show abrupt tapering of the</p><p>ICA (arrows) just above the carotid bifurcation. The ECA branches are normally</p><p>opacifi ed.</p><p>DIAGNOSIS:</p><p>ICA dissection</p><p>DISCUSSION:</p><p>Carotid artery dissection results from a primary intramural hematoma or intimal</p><p>tear, enabling penetration of blood into the arterial wall. The extracranial portion</p><p>of the ICA is most commonly affected, due to its greater mobility and proximity</p><p>to the cervical spine and styloid process. Predisposing conditions include trauma,</p><p>atherosclerosis, connective tissue disorders, fi bromuscular dysplasia, and vasculitis.</p><p>The true lumen opacifi es earlier, while slower fl ow within the false lumen predisposes</p><p>to thrombosis. This can compress the true lumen and serve</p><p>between</p><p>the development of “black holes” and the degree of clinical disability in MS. Focal</p><p>encephalomalacia caused by ischemia, infection, or trauma can demonstrate similar</p><p>imaging characteristics, though the spatial distribution differs from that of MS.</p><p>References:</p><p>Bagnato F, Jeffries N, Richert ND, et al. Evolution of T1 black holes in patients with multiple sclerosis</p><p>imaged monthly for 4 years. Brain. 2003;126(pt 8):1782-1789.</p><p>Naismith RT, Cross AH. Multiple sclerosis and black holes: connecting the pixels. Arch Neurol.</p><p>2005;62(11):1666-1668.</p><p>BLACK HOLE</p><p>Modalities:</p><p>CT, MR</p><p>Boxcar Ventricles 9</p><p>FINDINGS:</p><p>Coronal FLAIR MR shows atrophy of the caudate nuclei (arrows) with resulting</p><p>enlargement and squaring of the frontal horns.</p><p>DIFFERENTIAL DIAGNOSIS:</p><p>• Huntington disease</p><p>• Other neurodegenerative disorders</p><p>DISCUSSION:</p><p>Huntington disease is an autosomal dominant neurodegenerative disorder with onset</p><p>in middle age. Symptoms include chorea, psychiatric problems, and progressive</p><p>cognitive decline. Imaging shows selective atrophy of the basal ganglia, particularly</p><p>the caudate nuclei. This produces characteristic squaring of the frontal horns</p><p>(“boxcar ventricles”). Findings may be diffi cult to distinguish from age-related</p><p>changes and other dementing disorders, and correlation with clinical symptoms is</p><p>crucial for diagnosis.</p><p>References:</p><p>Barra FR, Gonçalves FG, de Lima Matos V, et al. Signs in neuroradiology—part 2. Radiol Bras.</p><p>2011;44(2):129-133.</p><p>Mascalchi M, Lolli F, Della Nave R, et al. Huntington disease: volumetric, diffusion-weighted, and</p><p>magnetization transfer MR imaging of brain. Radiology. 2004;232(3):867-873.</p><p>BOXCAR VENTRICLES</p><p>Modalities:</p><p>CT, MR</p><p>10 Chapter 1: Adult and General Brain</p><p>FINDINGS:</p><p>Axial T2-weighted MR shows</p><p>abnormal hyperintense signal</p><p>in the bilateral caudates and</p><p>putamina (arrows).</p><p>DIFFERENTIAL DIAGNOSIS:</p><p>• Toxic poisoning</p><p>• Metabolic derangements</p><p>• Neurodegenerative disorders</p><p>• Vascular conditions</p><p>• Infl ammation/infection</p><p>• Malignancy</p><p>DISCUSSION:</p><p>The basal ganglia and thalami</p><p>are paired deep gray matter</p><p>structures with high metabolic</p><p>activity, and are susceptible to</p><p>injury from a number of causes.</p><p>On MR, hyperintensity on T2-</p><p>and/or T1-weighted sequences (“bright basal ganglia”) can be seen with various</p><p>etiologies including toxic, metabolic, neurodegenerative, vascular, infl ammatory/</p><p>infectious, and neoplastic. Toxic etiologies include carbon monoxide, methanol,</p><p>and cyanide poisoning. Metabolic conditions include liver disease, hyperglycemia,</p><p>hypoglycemia, hypoxic-ischemic encephalopathy, hemolytic-uremic syndrome,</p><p>mitochondrial disorders, osmotic myelinolysis, and Wernicke encephalopathy.</p><p>Neurodegenerative disorders include Huntington disease, dysmyelinating disorders,</p><p>neurodegeneration with brain iron accumulation (NBIA), Creutzfeldt-Jakob</p><p>disease, and Fahr disease. Vascular abnormalities include venous thrombosis and</p><p>arterial infarction. Infl ammatory/infectious disorders include viral encephalitides,</p><p>toxoplasmosis, systemic lupus erythematosus, and Behçet disease. Neoplasms include</p><p>CNS lymphoma and glioma. Other MR sequences should be reviewed to identify</p><p>reduced diffusion, hemorrhage, contrast enhancement, and/or mass effect. Clinical</p><p>history; time course; and additional abnormalities of the thalami, cerebral cortex,</p><p>corpus callosum, white matter, cerebellum, or brainstem can also help narrow the</p><p>differential diagnosis.</p><p>References:</p><p>Hegde AN, Mohan S, Lath N, et al. Differential diagnosis for bilateral abnormalities of the basal</p><p>ganglia and thalamus. Radiographics. 2011;31(1):5-30.</p><p>Ho VB, Fitz CR, Chuang SH, et al. Bilateral basal ganglia lesions: pediatric differential considerations.</p><p>Radiographics. 1993;13(2):269-292.</p><p>BRIGHT BASAL GANGLIA</p><p>Modality:</p><p>MR</p><p>Bright/Dense/White Cerebellum, Reversal 11</p><p>FINDINGS:</p><p>Axial CT reveals diffuse cerebral edema with hypoattenuation, sulcal effacement,</p><p>and loss of gray-white distinction. The cerebellum is preserved and appears rela-</p><p>tively hyperdense (arrows).</p><p>DIAGNOSIS:</p><p>Diffuse cerebral edema</p><p>DISCUSSION:</p><p>Diffuse cerebral edema occurs in various settings including trauma, hypoxia,</p><p>ischemia, and infection. There is relative sparing of the basal ganglia, brainstem,</p><p>and cerebellum. The mechanism is unknown but may be due to preferential arterial</p><p>circulation, delayed venous drainage, or decompression by transtentorial herniation.</p><p>The preserved cerebellum appears brighter than the edematous cerebrum on CT</p><p>(“white cerebellum”) and darker on T2-weighted MR (“black cerebellum”), which</p><p>is the reverse of the normal appearance.</p><p>References:</p><p>Bird CR, Drayer BP, Gilles FH. Pathophysiology of “reverse” edema in global cerebral ischemia.</p><p>AJNR Am J Neuroradiol. 1989;10(1):95-98.</p><p>Brant WE, Helms C. Fundamentals of Diagnostic Radiology, 3rd ed. Baltimore: Lippincott Williams</p><p>and Wilkins, 2012.</p><p>BRIGHT/DENSE/WHITE CEREBELLUM, REVERSAL</p><p>Modality:</p><p>CT</p><p>12 Chapter 1: Adult and General Brain</p><p>FINDINGS:</p><p>• Axial T2-weighted MR in fi rst patient shows a multilocular lesion (arrows) in the</p><p>left lateral ventricle attached to the septum pellucidum, with blood-fl uid level in</p><p>the left frontal horn.</p><p>• Axial T2-weighted MR in second patient shows a multilocular lesion (arrow) in</p><p>the right cingulate sulcus, with infi ltrative surrounding hyperintense signal.</p><p>DIFFERENTIAL DIAGNOSIS:</p><p>• Central neurocytoma</p><p>• Oligodendroglioma</p><p>DISCUSSION:</p><p>Central neurocytomas and oligodendrogliomas have a similar histological and</p><p>imaging appearance with T2-hyperintense multilocular “bubbly” contents, variable</p><p>enhancement, and calcifi cation. However, central neurocytomas occur in younger</p><p>adults (20-40 years) and are almost always located in the lateral ventricles, abutting</p><p>the septum pellucidum. Acute symptoms may result from ventricular obstruction</p><p>and/or hemorrhage. Oligodendrogliomas occur in an older age group (over 50 years)</p><p>and are located in the cortex and subcortical white matter, most commonly within</p><p>the frontal lobe. Growth pattern is indolent and may produce pressure erosions of</p><p>the calvarium.</p><p>References:</p><p>Koeller KK, Rushing EJ. From the archives of the AFIP: Oligodendroglioma and its variants: radiologic-</p><p>pathologic correlation. Radiographics. 2005;25(6):1669-1688.</p><p>Smith AB, Smirniotopoulos JG, Horkanyne-Szakaly I. From the radiologic pathology archives:</p><p>intraventricular neoplasms: radiologic-pathologic correlation. Radiographics. 2013;33(1):21-43.</p><p>BUBBLY, FEATHERY, SOAP BUBBLE, SWISS CHEESE</p><p>Modalities:</p><p>CT, MR</p><p>Bullseye, Concentric Target 13</p><p>FINDINGS:</p><p>Axial contrast-enhanced T1-</p><p>weighted MR shows a left</p><p>perirolandic ring-enhancing lesion</p><p>with central enhancing focus</p><p>(arrow).</p><p>DIFFERENTIAL DIAGNOSIS:</p><p>• Tuberculoma</p><p>• Toxoplasmosis</p><p>• Metastasis</p><p>DISCUSSION:</p><p>CNS tuberculosis occurs following</p><p>hematogenous dissemination from</p><p>the respiratory or gastrointestinal</p><p>systems. Superfi cial infection</p><p>results in meningitis or cerebritis,</p><p>whereas deep infection produces</p><p>tuberculoma (caseating granuloma) and liquefi ed abscess. The “target” appearance</p><p>refl ects a central nidus of granulomatous infl ammation, which enhances and may</p><p>later calcify. However, this appearance is not specifi c and can be seen with other</p><p>infections (particularly fungal), tumefactive demyelination (Balo concentric sclerosis),</p><p>partially thrombosed aneurysms, and metastases. In immunocompromised patients,</p><p>toxoplasmosis should be a major diagnostic consideration. Toxoplasmosis brain</p><p>lesions are usually multifocal, with rim enhancement and large irregular nodules</p><p>representing a combination of infl ammation, hemorrhage, and necrosis. In the cortex</p><p>and deep gray matter, the nodules tend to be eccentrically located (“asymmetric</p><p>target” sign), corresponding pathologically to necrotizing abscesses with penetrating</p><p>vessels. Deep parenchymal lesions may demonstrate a more concentric appearance</p><p>(“concentric target” sign), which is more specifi c for toxoplasmosis and corresponds</p><p>pathologically</p><p>as a nidus for distal</p><p>embolization. In severe cases, apposition of the intimal fl ap with the opposite wall</p><p>causes complete occlusion of the true lumen, with a tapered “fl ame” appearance.</p><p>Patients can present with head or neck pain, Horner syndrome, and anterior circulation</p><p>ischemia. Treatment options include anticoagulation or antiplatelet therapy,</p><p>thrombolysis, endovascular angioplasty/stenting, and surgical reconstruction.</p><p>Reference:</p><p>Rodallec MH, Marteau V, Gerber S, et al. Craniocervical arterial dissection: spectrum of imaging</p><p>fi ndings and differential diagnosis. Radiographics. 2008;28(6):1711-1728.</p><p>FLAME, RADISH, RAT TAIL</p><p>250 Chapter 4: Vascular</p><p>FINDINGS:</p><p>• Anterior planar images from a 99mTc-HMPAO scan in the arterial phase show</p><p>decreased tracer uptake in the right (thin arrow) and left (thick arrow) MCA</p><p>territories.</p><p>• Venous phase image shows persistently decreased activity on the right and slightly</p><p>increased uptake on the left.</p><p>DIAGNOSIS:</p><p>Cerebral ischemia</p><p>DISCUSSION:</p><p>Planar radionuclide brain imaging is an infrequently performed study, with the</p><p>most common application being evaluation of brain death. Nuclear medicine agents</p><p>include technetium-99m ethyl cysteinate dimer (99mTc-ECD), hexamethylpropylene</p><p>amine oxime (99mTc-HMPAO), and diethylene triamine pentaacetic acid (99mTc-</p><p>DTPA). HMPAO and ECD are preferred, being lipophilic agents that selectively cross</p><p>the blood-brain barrier and are taken up by the brain parenchyma. Initial dynamic</p><p>fl ow images are acquired in the anterior projection, followed by delayed static blood</p><p>pool images in anterior, posterior, and lateral projections. Acute arterial ischemia</p><p>(1 month) results in encephalomalacia with decreased uptake in all phases.</p><p>References:</p><p>Gado MH, Coleman RE, Merlis AL, et al. Comparison of computerized tomography and radionuclide</p><p>imaging in “stroke.” Stroke. 1976;7(2):109-113.</p><p>MacDonald A, Burrell S. Infrequently performed studies in nuclear medicine: part 2. J Nucl Med</p><p>Technol. 2009;37(1):1-13.</p><p>FLIP-FLOP</p><p>Modality:</p><p>NM</p><p>Hairpin 251</p><p>Modalities:</p><p>XA, CT, MR</p><p>FINDINGS:</p><p>Selective injection of a left intercostal</p><p>artery, AP projection, shows the artery of</p><p>Adamkiewicz (thick arrow) ascending across</p><p>midline, then taking an abrupt downward</p><p>turn to join the anterior spinal artery (thin</p><p>arrow).</p><p>DIAGNOSIS:</p><p>Artery of Adamkiewicz</p><p>DISCUSSION:</p><p>The thoracolumbar spinal cord receives</p><p>its vascular supply from intercostal and</p><p>lumbar branches of the aorta, which divide</p><p>into anterior and posterior branches.</p><p>The posterior branch subdi vides into</p><p>a radiculomedullary artery, muscular</p><p>branch, and dorsal somatic branch. The</p><p>radiculomedullary artery further divides into</p><p>anterior and posterior radiculomedullary</p><p>arteries. The artery of Adamkiewicz (great</p><p>anterior radiculomedullary artery) is the</p><p>largest anterior radiculomedullary artery and</p><p>supplies the lower third of the spinal cord.</p><p>It usually arises from a lower intercostal or</p><p>upper lumbar artery on the left. The artery</p><p>enters the spinal canal through a left-sided</p><p>neural foramen and briefl y ascends before</p><p>making an abrupt downward “hairpin”</p><p>turn to join the anterior spinal artery. This</p><p>confi guration refl ects faster growth of vertebrae relative to the spinal cord during</p><p>development, resulting in relative ascent of the cord. Angiography is the gold standard</p><p>for identifying the artery of Adamkiewicz, but CTA and MRA can also be utilized.</p><p>An important mimic is the relationship of the anterior radiculomedullary vein and</p><p>anterior spinal vein, which demonstrate a wider (“coat hook”) angle. These vessels</p><p>are also larger, opacify later, and are not continuous with the aorta. Identifi cation of</p><p>the artery of Adamkiewicz prior to endovascular and surgical procedures is essential</p><p>to minimize the risk of spinal cord ischemia and paraplegia.</p><p>References:</p><p>Murthy NS, Maus TP, Behrns CL. Intraforaminal location of the great anterior radiculomedullary</p><p>artery (artery of Adamkiewicz): a retrospective review. Pain Med. 2010;11(12):1756-1764.</p><p>Yoshioka K, Niinuma H, Ehara S, et al. MR angiography and CT angiography of the artery of</p><p>Adamkiewicz: state of the art. Radiographics. 2006;26(Suppl 1):S63-S73.</p><p>HAIRPIN</p><p>252 Chapter 4: Vascular</p><p>Modalities:</p><p>XA, CT, MR</p><p>FINDINGS:</p><p>• Axial FLAIR MR shows multifocal subarachnoid hyperintensities (arrows).</p><p>• Axial contrast-enhanced T1-weighted MR shows corresponding leptomeningeal</p><p>enhancement (arrows).</p><p>• Right ICA angiogram, AP projection, shows stenosis of the supraclinoid ICA,</p><p>ACA, and MCA, with diffuse leptomeningeal collaterals (arrows).</p><p>DIAGNOSIS:</p><p>Moyamoya disease</p><p>DISCUSSION:</p><p>Moyamoya, the Japanese term for “puff of smoke,” refers to progressive stenosis/</p><p>occlusion of the distal ICAs and proximal ACAs/MCAs with relative sparing of</p><p>the posterior circulation. The etiology may be idiopathic (moyamoya disease) or</p><p>secondary (moyamoya syndrome) to various conditions including atherosclerosis,</p><p>Down syndrome, neurofi bromatosis, sickle cell anemia, and connective tissue</p><p>disorders. Collateral circulation is supplied by basal parenchymal perforators,</p><p>leptomeningeal branches from the PCA, and transdural vessels from the ECA.</p><p>Engorgement and congestion of superfi cial pial vessels produces the “ivy” sign, with</p><p>subarachnoid hyperintensities on FLAIR MR and leptomeningeal enhancement</p><p>on contrast-enhanced images. Pediatric patients tend to present with cerebral</p><p>ischemia or infarction, whereas adults can develop infarcts or hemorrhage due to</p><p>rupture of small aneurysms. Surgical procedures are aimed at revascularization and</p><p>include direct (STA-MCA bypass) or indirect (encephalo-duro-arterio-synangiosis,</p><p>encephalo-myo-synangiosis, pial synangiosis, omental transplantation) techniques.</p><p>Reference:</p><p>Yoon HK, Shin HJ, Chang YW. “Ivy sign” in childhood moyamoya disease: depiction on fl uid-</p><p>attenuated inversion recovery (FLAIR) and contrast-enhanced T1-weighted MR images. Radiology.</p><p>2002;223(2):384-389.</p><p>IVY</p><p>Kissing Carotids 253</p><p>Modalities:</p><p>CT, MR</p><p>FINDINGS:</p><p>Axial CTA shows medial deviation of both ICAs (arrows) into the retropharyngeal</p><p>region.</p><p>DIAGNOSIS:</p><p>Retropharyngeal ICAs</p><p>DISCUSSION:</p><p>The internal carotid arteries form in utero from the third branchial arches and</p><p>cranial portion of the dorsal aorta. There is wide variation in morphology and</p><p>course, which can be straight, curved, kinked, and/or coiled. Variations are more</p><p>common in patients with craniofacial syndromes, atherosclerosis, connective</p><p>tissue disorders, and fi bromuscular dysplasia. The carotid sheath is located at the</p><p>lateral boundary of the retropharyngeal space. Therefore, medial transposition of</p><p>the cervical ICA brings the vessel directly behind the posterior pharyngeal wall.</p><p>When bilateral, this yields a “kissing carotids” appearance. Patients can present</p><p>with globus sensation and a pulsatile retrotonsillar mass on examination. Biopsy or</p><p>surgical manipulation should be avoided at all costs.</p><p>References:</p><p>Paulsen F, Tillmann B, Christofi des C, et al. Curving and looping of the ICA in relation to the pharynx:</p><p>frequency, embryology and clinical implications. J Anat. 2000;197(pt 3):373-381.</p><p>Pfeiffer J, Ridder GJ. A clinical classifi cation system for aberrant internal carotid</p><p>to central hemorrhage.</p><p>References:</p><p>Bargalló J, Berenguer J, García-Barrionuevo J, et al. The “target sign”: is it a specifi c sign of CNS</p><p>tuberculoma? Neuroradiology. 1996;38(6):547-550.</p><p>Bernaerts A, Vanhoenacker FM, Parizel PM, et al. Tuberculosis of the central nervous system: overview</p><p>of neuroradiological fi ndings. Eur Radiol. 2003;13(8):1876-1890.</p><p>Mahadevan A, Ramalingaiah AH, Parthasarathy S, et al. Neuropathological correlate of the “concentric</p><p>target sign” in MRI of HIV-associated cerebral toxoplasmosis. J Magn Reson Imaging. 2013 Feb 25.</p><p>BULLSEYE, CONCENTRIC TARGET</p><p>Modalities:</p><p>CT, MR</p><p>14 Chapter 1: Adult and General Brain</p><p>FINDINGS:</p><p>Axial T2-weighted MR shows</p><p>multiple clustered cystic lesions</p><p>expanding the bilateral sylvian</p><p>fi ssures (arrows).</p><p>DIAGNOSIS:</p><p>Racemose neurocysticercosis</p><p>DISCUSSION:</p><p>Neurocysticercosis is a neuro-</p><p>logic disease caused by the pork</p><p>tapeworm Taenia solium. It is the</p><p>most common parasitic infection</p><p>of the CNS, and the leading</p><p>cause of acquired epilepsy</p><p>worldwide. Infection occurs by</p><p>ingestion of larval eggs in raw</p><p>or undercooked pork. Once the</p><p>larvae reach the small intestine,</p><p>they attach to the intestinal wall</p><p>via scolices and release additional ova. Through fecal-oral contamination, ova are</p><p>digested in the stomach and release oncospheres. These penetrate the intestinal wall</p><p>and enter the bloodstream, preferentially depositing in brain, eyes, and muscle.</p><p>Locations of disease include subarachnoid-cisternal, parenchymal, intraventricular,</p><p>and spinal. Five stages have been described: noncystic, vesicular, colloidal vesicular,</p><p>granular nodular, and calcifi ed nodular. Noncystic neurocysticercosis is asymptomatic</p><p>with no imaging fi ndings. Vesicular neurocysticercosis demonstrates parenchymal</p><p>and/or subarachnoid cysts with associated scolices (“cyst with dot” appearance) and</p><p>little or no edema. The racemose variant (Latin for “bunch of grapes”) consists of</p><p>clustered cysts, usually without scolices. These are typically located in the sylvian</p><p>fi ssures and basal cisterns. Colloidal vesicular neurocysticercosis is marked by larval</p><p>disintegration with marked enhancement, edema, and peripheral capsule formation.</p><p>Granular nodular neurocysticercosis is characterized by cyst retraction and gliosis.</p><p>Calcifi ed nodular neurocysticercosis is the nonactive stage, in which the lesion has</p><p>completely involuted and calcifi ed.</p><p>Reference:</p><p>Kimura-Hayama ET, Higuera JA, Corona-Cedillo R, et al. Neurocysticercosis: radiologic-pathologic</p><p>correlation. Radiographics. 2010;30(6):1705-1719.</p><p>BUNCH OF GRAPES, GRAPELIKE, RACEMOSE</p><p>Modalities:</p><p>CT, MR</p><p>Butterfly, Heart 15</p><p>FINDINGS:</p><p>Anterior planar In-111 DTPA</p><p>cisternogram shows slow ascent of</p><p>tracer from the intrathecal injection</p><p>site over the cerebral convexities (thin</p><p>arrows), with refl ux into the lateral</p><p>ventricles (thick arrow).</p><p>DIFFERENTIAL DIAGNOSIS:</p><p>• Normal pressure hydrocephalus</p><p>• Cerebral atrophy</p><p>DISCUSSION:</p><p>Radionuclide cisternography involves</p><p>intrathecal injection of a radiolabeled</p><p>pharmaceutical (usually indium-111</p><p>diethylene triamine pentaacetic acid)</p><p>with sequential imaging to evaluate</p><p>CSF fl ow. In a normal patient, tracer</p><p>ascends up the spinal column to the</p><p>level of the basal cisterns by 1 hour,</p><p>the frontal poles and sylvian fi ssures</p><p>by 2-6 hours, the cerebral convexities</p><p>by 12 hours, and the superior sagittal</p><p>sinus by 24 hours. In patients with</p><p>normal pressure hydrocephalus (NPH),</p><p>there is impaired absorption of CSF</p><p>by the arachnoid granulations. This</p><p>causes early refl ux of tracer into the lateral ventricles (“butterfl y/heart” appearance),</p><p>with little fl ow over the cerebral convexities at 24-48 hours. Ventricular refl ux and</p><p>delayed ascent of tracer can be seen in cerebral atrophy, but should not persist by</p><p>24-48 hours.</p><p>Reference:</p><p>Chuang TL, Hsu MC, Wang YF. Normal pressure hydrocephalus: scintigraphic fi ndings on SPECT/CT</p><p>image. Ann Nucl Med Sci. 2010;23:169-174.</p><p>BUTTERFLY, HEART</p><p>Modality:</p><p>NM</p><p>16 Chapter 1: Adult and General Brain</p><p>FINDINGS:</p><p>Coronal contrast-enhanced T1-weighted MR shows a peripherally enhancing</p><p>bifrontal mass extending through the corpus callosum (arrow).</p><p>DIFFERENTIAL DIAGNOSIS:</p><p>• Glioblastoma multiforme</p><p>• Lymphoma</p><p>• Tumefactive multiple sclerosis</p><p>DISCUSSION:</p><p>“Butterfl y” lesions involve both cerebral hemispheres and the intervening corpus</p><p>callosum. The compact structure of the corpus callosum generally serves as a barrier to</p><p>disease spread, except in aggressive lesions such as glioblastoma multiforme (GBM),</p><p>CNS lymphoma, and tumefactive multiple sclerosis. GBM demonstrates infi ltrative</p><p>margins, with shaggy rim enhancement and internal hemorrhage/necrosis. Tumor</p><p>behavior is aggressive, with frequent recurrence after surgery and chemoradiation.</p><p>CNS lymphoma generally demonstrates smoother margins, sometimes with peripheral</p><p>notching. Due to tumor hypercellularity, lesions are typically hyperdense on CT and</p><p>hypointense on T2-weighted MR, with reduced diffusion. Tumor hypovascularity</p><p>is refl ected by mild homogeneous enhancement. There is marked improvement or</p><p>complete resolution with steroid treatment. Tumefactive MS rarely has a butterfl y</p><p>appearance and may demonstrate incomplete “leading edge” enhancement,</p><p>corresponding to active areas of demyelination. Lesions tend to be disseminated in</p><p>space and time, and are variably responsive to steroids.</p><p>Reference:</p><p>Ho ML, Moonis G, Ginat DT, Eisenberg RL. Lesions of the corpus callosum. AJR Am J Roentgenol.</p><p>2013;200(1):W1-W16.</p><p>BUTTERFLY, MIRROR IMAGE</p><p>Modalities:</p><p>CT, MR</p><p>Callosal-Septal, Stack of Coins, Subcallosal Striations, Venus Necklace 17</p><p>FINDINGS:</p><p>Sagittal FLAIR MR shows multiple linear hyperintensities (arrows) at the callosal-</p><p>septal interface.</p><p>DIAGNOSIS:</p><p>Multiple sclerosis</p><p>DISCUSSION:</p><p>Multiple sclerosis (MS) is a chronic demyelinating disorder characterized</p><p>by spatial and temporal heterogeneity. On thin-section sagittal FLAIR MR,</p><p>hyperintense foci can be seen along the undersurface of the corpus callosum at its</p><p>junction with the septum pellucidum (callosal-septal interface). These are oriented</p><p>perpendicular instead of parallel to the ependyma, creating a “stack of coins”</p><p>or “Venus necklace” appearance. The mechanism is thought to be perivenular</p><p>demyelination along subependymal veins, and is highly sensitive and specifi c for</p><p>detection of early MS.</p><p>Reference:</p><p>Palmer S, Bradley WG, Chen DY, et al. Subcallosal striations: early fi ndings of multiple sclerosis on</p><p>sagittal, thin-section, fast FLAIR MR images. Radiology. 1999;210(1):149-153.</p><p>CALLOSAL-SEPTAL, STACK OF COINS, SUBCALLOSAL STRIATIONS, VENUS NECKLACE</p><p>Modality:</p><p>MR</p><p>18 Chapter 1: Adult and General Brain</p><p>FINDINGS:</p><p>Axial T2-weighted and DWI MR show a lobulated pineal region mass (arrows) with</p><p>T2-hyperintense signal and reduced diffusion.</p><p>DIAGNOSIS:</p><p>Epidermoid cyst</p><p>DISCUSSION:</p><p>Epidermoid cysts are rare congenital inclusion cysts that typically occur in extraaxial</p><p>locations, such as the pineal region and cerebellopontine angles. Lesions demonstrate</p><p>lobulated “caulifl ower” margins with insinuation into adjacent structures and</p><p>neurovascular encasement, making complete resection diffi cult. There is continual</p><p>desquamation of epithelial cells into the cyst, resulting in gradual progressive</p><p>enlargement. On MR, internal contents are mildly T2-hyperintense to CSF with</p><p>persistent signal on FLAIR images, refl ecting complex fl uid contents. Lack of FLAIR</p><p>suppression and the presence of reduced diffusion enable distinction of epidermoid</p><p>from arachnoid cysts. Occasionally internal protein, lipid, and/or hemorrhage may</p><p>produce T1-hyperintense signal, the so-called “white epidermoid.”</p><p>Reference:</p><p>Smith AB, Rushing EJ, Smirniotopoulos JG. From the archives of the AFIP: lesions of the pineal</p><p>region: radiologic-pathologic correlation. Radiographics. 2010;30(7):2001-2020.</p><p>CAULIFLOWER, LOBULATED, SCALLOPED</p><p>Modalities:</p><p>CT, MR</p><p>Choroidal/Hippocampal Fissure Dilation, Cracked</p><p>Walnut 19</p><p>FINDINGS:</p><p>Coronal high-resolution T2-weighted MR shows enlargement of the hippocampal</p><p>and choroidal fi ssures (arrows). There is diffuse cerebral volume loss with enlargement</p><p>of sulci.</p><p>DIAGNOSIS:</p><p>Alzheimer disease</p><p>DISCUSSION:</p><p>Alzheimer disease (AD) is the most common form of dementia, with abnormal folding</p><p>of beta-amyloid proteins leading to deposition of senile plaques and neurofi brillary</p><p>tangles in the brain parenchyma. There is resulting cerebral atrophy, particularly in</p><p>the temporal and parietal lobes. A reliable early imaging marker for AD is bilateral</p><p>hippocampal atrophy with resulting dilation of the perihippocampal fi ssures. The</p><p>transverse fi ssures of Bichat extend laterally from the perimesencephalic cisterns.</p><p>Superolaterally, the choroidal fi ssures course above the hippocampi. Inferolaterally,</p><p>the hippocampal fi ssures extend between the hippocampi and parahippocampal gyri.</p><p>In advanced disease, there is more widespread atrophy with symmetrically enlarged</p><p>sulci. This fi nding is best appreciated along the high cerebral convexities, creating</p><p>a “cracked walnut” appearance. Findings may be diffi cult to distinguish from age-</p><p>related volume loss and other dementing disorders, and correlation with clinical</p><p>symptoms is crucial for diagnosis.</p><p>References:</p><p>Holodny AI, George AE, Golomb J, et al. The perihippocampal fi ssures: normal anatomy and disease</p><p>states. Radiographics. 1998;18(3):653-665.</p><p>Li Y, Li J, Segal S, et al. Hippocampal cerebrospinal fl uid spaces on MR imaging: Relationship to aging</p><p>and Alzheimer disease. AJNR Am J Neuroradiol. 2006;27(4):912-918.</p><p>CHOROIDAL/HIPPOCAMPAL FISSURE DILATION, CRACKED WALNUT</p><p>Modalities:</p><p>CT, MR</p><p>20 Chapter 1: Adult and General Brain</p><p>FINDINGS:</p><p>I-123 SPECT-CT shows</p><p>absence of tracer uptake in</p><p>the putamina and decreased</p><p>uptake in the caudate nuclei</p><p>(arrows).</p><p>DIAGNOSIS:</p><p>Parkinsonian syndromes</p><p>DISCUSSION:</p><p>Movement disorders and</p><p>dementia in the elderly</p><p>population have a variety</p><p>of etiologies. When there</p><p>is diagnostic uncertainty</p><p>between parkinsonian and</p><p>other disorders, baseline</p><p>SPECT can be performed</p><p>with the dopamine trans-</p><p>porter ligand iofl upane</p><p>(iodine-123), commercially</p><p>known as DaTscan™. An</p><p>abnormal appearance is absence of putaminal uptake with normal or decreased</p><p>caudate uptake, which may be unilateral or bilateral (“period” sign). This</p><p>indicates a nigrostriatal neurodegenerative condition (Parkinson disease, atypical</p><p>parkinsonism, and Lewy body dementia), for which dopaminergic therapy may be</p><p>benefi cial. Normally there is bilateral symmetric uptake in the caudates and putamina</p><p>(“comma” sign). This indicates a non-nigrostriatal etiology (Alzheimer dementia,</p><p>essential tremor, vascular, drug-related), which will not respond to dopaminergic</p><p>therapy.</p><p>References:</p><p>Cummings JL, Henchcliffe C, Schaier S, et al. The role of dopaminergic imaging in patients with</p><p>symptoms of dopaminergic system neurodegeneration. Brain. 2011;134(pt 11):3146-3166.</p><p>Kupsch AR, Bajaj N, Weiland F, et al. Impact of DaTscan SPECT imaging on clinical management,</p><p>diagnosis, confi dence of diagnosis, quality of life, health resource use and safety in patients with</p><p>clinically uncertain parkinsonian syndromes: a prospective 1-year follow-up of an open-label</p><p>controlled study. J Neurol Neurosurg Psychiatry. 2012;83(6):620-628.</p><p>Modality:</p><p>NM</p><p>CIRCLE, OVAL, PERIOD</p><p>Cluster, Daughter, Secondary 21</p><p>FINDINGS:</p><p>Axial contrast-enhanced T1-</p><p>weighted MR shows two ring-</p><p>enhancing lesions and several</p><p>adjacent enhancing nodules</p><p>in the right precentral gyrus</p><p>(arrow). There is surrounding</p><p>vasogenic edema.</p><p>DIAGNOSIS:</p><p>Cerebral abscess</p><p>DISCUSSION:</p><p>Cerebral abscesses may result</p><p>from penetrating trauma,</p><p>surgery, direct spread of</p><p>adjacent infection, or</p><p>hematogenous dissemination.</p><p>Various bacterial, fungal, and</p><p>parasitic pathogens have been described. Four stages of evolution have been</p><p>described at imaging, representing a spectrum from soft tissue phlegmon to</p><p>liquefi ed abscess: early cerebritis (days 1-3), late cerebritis (days 4-7), early capsule</p><p>(days 10-14), and late capsule (> day 14). If untreated, the infection may progress</p><p>with formation of one or multiple secondary (“daughter”) abscesses adjacent to</p><p>and contiguous with the parent abscess. There is a tendency for evagination toward</p><p>the deep or ventricular margin (“dimple” sign). The “daughter” appearance should</p><p>be distinguished from “satellite” lesions seen with brain tumors. These can be</p><p>remote from the primary lesion, refl ecting microscopic tumor infi ltration and/or</p><p>metastatic dissemination. In addition, tumor growth is slow compared to the rapid</p><p>evolution of cerebral infection.</p><p>References:</p><p>Britt RH, Enzmann DR. Clinical stages of human brain abscesses on serial CT scans after contrast</p><p>infusion. Computerized tomographic, neuropathological, and clinical correlations. J Neurosurg.</p><p>1983;59(6):972-989.</p><p>Hsu WC, Tang LM, Chen ST, et al. Multiple brain abscesses in chain and cluster: CT appearance.</p><p>J Comput Assist Tomogr. 1995;19(6):1004-1006.</p><p>CLUSTER, DAUGHTER, SECONDARY</p><p>Modalities:</p><p>CT, MR</p><p>22 Chapter 1: Adult and General Brain</p><p>FINDINGS:</p><p>I-123 SPECT-CT shows</p><p>normal bilateral uptake in</p><p>the caudates and putamina</p><p>(arrows).</p><p>DIAGNOSIS:</p><p>Normal I-123 scan</p><p>DISCUSSION:</p><p>Movement disorders and</p><p>dementia in the elderly</p><p>population have a variety</p><p>of etiologies. When there</p><p>is diagnostic uncertainty</p><p>between parkinsonism</p><p>and other disorders,</p><p>baseline SPECT can be</p><p>performed with the dopa-</p><p>mine transporter ligand</p><p>iofl upane (iodine-123),</p><p>commercially known as</p><p>DaTscan™. An abnormal</p><p>appearance is absence of putaminal uptake with normal or decreased caudate uptake,</p><p>which may be unilateral or bilateral (“period” sign). This indicates a nigrostriatal</p><p>neurodegenerative condition (Parkinson disease, atypical parkinsonism, and Lewy</p><p>body dementia), for which dopaminergic therapy may be benefi cial. Normally there</p><p>is bilateral symmetric uptake in the caudates and putamina (“comma” sign). This</p><p>indicates a non-nigrostriatal etiology (Alzheimer dementia, essential tremor, vascular,</p><p>drug-related) that will not respond to dopaminergic therapy.</p><p>References:</p><p>Cummings JL, Henchcliffe C, Schaier S, et al. The role of dopaminergic imaging in patients with</p><p>symptoms of dopaminergic system neurodegeneration. Brain. 2011;134(pt 11):3146-3166.</p><p>Kupsch AR, Bajaj N, Weiland F, et al. Impact of DaTscan SPECT imaging on clinical management,</p><p>diagnosis, confi dence of diagnosis, quality of life, health resource use and safety in patients with</p><p>clinically uncertain parkinsonian syndromes: a prospective 1-year follow-up of an open-label</p><p>controlled study. J Neurol Neurosurg Psychiatry. 2012;83(6):620-628.</p><p>COMMA, CRESCENT</p><p>Modality:</p><p>NM</p><p>Concentric Bands/Rings, Lamellated, Onion Skin 23</p><p>FINDINGS:</p><p>Axial FLAIR and T2-weighted MR show multiple rounded areas of white matter</p><p>hyperintensity with a concentric layered appearance (arrows).</p><p>DIAGNOSIS:</p><p>Balo concentric sclerosis</p><p>DISCUSSION:</p><p>Balo concentric sclerosis is a rare and aggressive variant of multiple sclerosis, char-</p><p>acterized by concentric layers of demyelination (“onion skin” appearance). It is</p><p>hypothesized that demyelination spreads centrifugally from a central venule, with</p><p>multiple episodes of reactivation. On T2-weighted MR, alternating hyperintense and</p><p>hypointense bands correspond pathologically to demyelinated and myelinated white</p><p>matter. Although the tumefactive appearance has been confused with neoplasia, the</p><p>lamellated imaging pattern is pathognomonic for demyelination.</p><p>References:</p><p>Caracciolo JT, Murtagh RD, Rojiani AM, et al. Pathognomonic MR imaging fi ndings in Balo</p><p>concentric sclerosis. AJNR Am J Neuroradiol. 2001;22(2):292-293.</p><p>Karaarslan E, Altintas A, Senol U, et al. Baló’s concentric sclerosis: clinical and radiologic features of</p><p>fi ve cases. AJNR Am J Neuroradiol. 2001;22(7):1362-1367.</p><p>CONCENTRIC BANDS/RINGS, LAMELLATED, ONION SKIN</p><p>Modality:</p><p>MR</p><p>24 Chapter 1: Adult and General</p><p>Brain</p><p>FINDINGS:</p><p>Axial T2-weighted MR shows expanded cerebellar folia with alternating hyperin-</p><p>tense and hypointense bands in the left cerebellar hemisphere and vermis (arrow).</p><p>DIAGNOSIS:</p><p>Lhermitte-Duclos disease</p><p>DISCUSSION:</p><p>Lhermitte-Duclos disease (dysplastic cere bellar gangliocytoma) is a rare</p><p>hamartomatous lesion of the cerebellum that is characterized by hypertrophy</p><p>of the stratum granulosum. This results in characteristic disorganization and</p><p>enlargement of the cerebellar folia, which appear T2-hyperintense to isointense</p><p>and T1-hypointense to isointense (“corduroy” sign). Lhermitte-Duclos is</p><p>associated with Cowden (multiple hamartoma) syndrome, caused by loss-of-</p><p>function mutations in the tumor suppressor gene PTEN. Patients with Cowden</p><p>syndrome exhibit hamartomas of the skin and mucous membranes. There is an</p><p>increased risk of benign and malignant tumors of various organ systems (breast,</p><p>thyroid, gastrointestinal, genitourinary, gynecologic).</p><p>Reference:</p><p>Meltzer CC, Smirniotopoulos JG, Jones RV. The striated cerebellum: an MR imaging sign in Lhermitte-</p><p>Duclos disease (dysplastic gangliocytoma). Radiology. 1995;194(3):699-703.</p><p>CORDUROY, LAMINATED, STRIATED, STRIPED, TIGROID</p><p>Modalities:</p><p>CT, MR</p><p>Cortical Ribbon 25</p><p>FINDINGS:</p><p>Axial FLAIR and DWI MR show hyperintense signal throughout the cerebral cortex.</p><p>DIFFERENTIAL DIAGNOSIS:</p><p>• Hypoxic-ischemic injury</p><p>• Creutzfeldt-Jakob disease</p><p>• Meningoencephalitis</p><p>• Metabolic disorders</p><p>• Postictal state</p><p>DISCUSSION:</p><p>Cortical gray matter is eight times more metabolically active than the white</p><p>matter, and is thus highly susceptible to injury from a number of causes. On</p><p>MR, hyperintense cortical signal on T2-weighted and DWI sequences (“cortical</p><p>ribbon”) can be seen with various etiologies including vascular, toxic/metabolic,</p><p>postictal, infl ammatory/infectious, and neoplastic. Vascular causes include arterial</p><p>infarct and venous thrombosis. Metabolic conditions include hypoxic-ischemic</p><p>encephalopathy, drug exposures, hypoglycemia, and mitochondrial disorders.</p><p>Infectious etiologies include prion, viral, tuberculous, and fungal encephalitides.</p><p>Neoplastic involvement of the cortex is suggestive of primary glial tumors. Other</p><p>MR sequences should be reviewed to identify contrast enhancement, hemorrhage,</p><p>and/or mass effect. Clinical history; time course; and additional abnormalities of</p><p>the basal ganglia, thalami, corpus callosum, white matter, cerebellum, or brainstem</p><p>can also help narrow the differential diagnosis.</p><p>Reference:</p><p>Sheerin F, Pretorius PM, Briley D, et al. Differential diagnosis of restricted diffusion confi ned to the</p><p>cerebral cortex. Clin Radiol. 2008;63(11):1245-1253.</p><p>CORTICAL RIBBON</p><p>Modality:</p><p>MR</p><p>26 Chapter 1: Adult and General Brain</p><p>Modalities:</p><p>US, CT, MR</p><p>FINDINGS:</p><p>• Axial T2-weighted MR in a patient with bilateral subdural hygromas shows</p><p>inward displacement of cortical veins (arrows) away from the dura.</p><p>• Axial T2-weighted MR in a patient with cerebral volume loss shows enlarged</p><p>subarachnoid spaces with outward displacement of cortical veins (arrows) into</p><p>the CSF.</p><p>DIFFERENTIAL DIAGNOSIS:</p><p>• Subdural fl uid collections</p><p>• Cerebral atrophy</p><p>DISCUSSION:</p><p>Subdural fl uid collections may represent hygromas or hematomas from trauma</p><p>or surgery, empyemas due to infection, or effusions in intracranial hypotension.</p><p>Subdural collections can be diffi cult to distinguish from cerebral atrophy, in which</p><p>the subarachnoid space is enlarged due to decreased gyral volume. However,</p><p>identifi cation of cortical veins along the cerebral convexities can help differentiate</p><p>the subdural and subarachnoid spaces. With subdural collections, the cortical</p><p>veins are displaced inward and away from the dura. With cerebral volume loss,</p><p>the cortical veins are displaced outward into the CSF. In infants, identifi cation of</p><p>cortical veins is also useful in distinguishing external hydrocephalus from subdural</p><p>collections. External hydrocephalus refers to benign enlargement of the bifrontal</p><p>subarachnoid spaces, a condition that is self-limiting and resolves by 2-3 years of</p><p>age. Subdural fl uid collections are always abnormal and should raise concern for</p><p>nonaccidental trauma.</p><p>References:</p><p>Deltour P, Lemmerling M, Bauters W, et al. Posttraumatic subdural hygroma: CT fi ndings and</p><p>differential diagnosis. JBR-BTR. 1999;82(4):155-156.</p><p>McCluney KW, Yeakley JW, Fenstermacher MJ, et al. Subdural hygroma versus atrophy on MR brain</p><p>scans: “the cortical vein sign.” AJNR Am J Neuroradiol. 1992;13(5):1335-1339.</p><p>CORTICAL VEIN</p><p>Crescent, Fingerlike, Granular, Scalloped 27</p><p>FINDINGS:</p><p>• Coronal FLAIR MR shows multifocal hyperintensities in the left temporal/</p><p>parietal and cerebellar white matter, with involvement of the subcortical U fi bers</p><p>(arrows).</p><p>• Axial FLAIR MR shows hyperintensities in the bilateral brachia pontis and left</p><p>corpus medullare cerebelli (arrows).</p><p>DIAGNOSIS:</p><p>Progressive multifocal leukoencephalopathy</p><p>DISCUSSION:</p><p>Progressive multifocal leukoencephalopathy (PML) is caused by reactivation</p><p>of the JC virus (JCV) in immunocompromised individuals. Involvement of</p><p>oligodendrocytes leads to rapidly progressive demyelination that may be solitary,</p><p>multifocal, or confl uent. Classically, there is bilateral asymmetric involvement</p><p>of the supratentorial white matter, basal ganglia, and thalami. This tends to</p><p>involve the subcortical U (arcuate) fi bers with a “scalloped” appearance, sparing</p><p>of periventricular white matter, and no signifi cant mass effect. In contrast, HIV</p><p>encephalopathy causes symmetric periventricular signal abnormality and spares the</p><p>subcortical U fi bers, with associated volume loss. PML can occasionally affect the</p><p>cerebellum and brainstem, with contiguous involvement of the brachium pontis and</p><p>corpus medullare cerebelli producing a “crescent” morphology. Atypical imaging</p><p>manifestations include mildly reduced diffusion, faint peripheral enhancement,</p><p>hemorrhage, and gray matter involvement. If there is signifi cant contrast enhancement</p><p>or mass effect, alternative diagnoses such as infectious encephalitis, lymphoma, and</p><p>acute disseminated encephalomyelitis (ADEM) should be considered.</p><p>Reference:</p><p>Shah R, Bag AK, Chapman PR, et al. Imaging manifestations of progressive multifocal</p><p>leukoencephalopathy. Clin Radiol. 2010;65(6):431-439.</p><p>Modalities:</p><p>CT, MR</p><p>CRESCENT, FINGERLIKE, GRANULAR, SCALLOPED</p><p>28 Chapter 1: Adult and General Brain</p><p>Modalities:</p><p>CT, MR</p><p>FINDINGS:</p><p>Axial CT shows an acute left holohemispheric subdural hematoma (arrows).</p><p>DIAGNOSIS:</p><p>Subdural hematoma</p><p>DISCUSSION:</p><p>Subdural hematomas (SDHs) are bleeds between the dura mater and arachnoid mater.</p><p>These are caused by shear stress on bridging veins due to rotational and/or linear</p><p>forces, with low-pressure bleeding. In very young, elderly, and alcoholic patients, the</p><p>presence of enlarged subdural spaces predisposes to SDH with minimal head trauma.</p><p>Symptoms include gradually increasing headache and confusion. At imaging, SDH</p><p>is typically crescentic in appearance, tracking along the cerebral convexities. These</p><p>can cross beneath cranial sutures, stopping only at dural refl ections such as the falx</p><p>cerebri and tentorium cerebelli. The differential for hyperdensity in the subdural</p><p>space includes infectious (subdural empyema), infl ammatory, and neoplastic</p><p>etiologies, which can readily be distinguished on contrast-enhanced images.</p><p>Reference:</p><p>Brant WE, Helms C. Fundamentals of Diagnostic Radiology, 3rd ed. Baltimore: Lippincott Williams</p><p>and Wilkins, 2012.</p><p>CRESCENTIC</p><p>Cruciform, Hot Cross Bun, Molar Tooth 29</p><p>FINDINGS:</p><p>• Axial T2-weighted MR shows pontine and cerebellar atrophy with a cruciform</p><p>appearance (thick arrow). The brachia conjunctivum (thin arrows) are preserved.</p><p>• Axial DWI MR shows atrophy and increased signal in the pons (thick arrow) and</p><p>brachia pontis (thin arrows). The fourth ventricle is dilated.</p><p>DIAGNOSIS:</p><p>Multiple system atrophy, cerebellar subtype</p><p>DISCUSSION:</p><p>Multiple system atrophy (MSA) is an</p><p>adult-onset neurodegenerative disease</p><p>characterized by parkinsonism, autonomic failure, cerebellar ataxia, and pyramidal</p><p>signs. Classifi cation is based on the predominant clinical characteristics and includes</p><p>MSA-P (parkinsonian) or striatonigral degeneration (SND), MSA-C (cerebellar)</p><p>or olivopontocerebellar atrophy (OPCA), and MSA-A (autonomic) or Shy-Drager</p><p>syndrome (SDS). MSA-C shows selective atrophy of the pons, cerebellum, and</p><p>middle cerebellar peduncles. The “cruciform” appearance of the pons results from</p><p>neuronal degeneration in the pontine raphe and transverse pontocerebellar fi bers,</p><p>with preservation of the pontine tegmentum and corticospinal tracts. Atrophy of the</p><p>middle cerebellar peduncles and preservation of the superior cerebellar peduncles</p><p>yields a “molar tooth” appearance, with ballooning of the intervening fourth</p><p>ventricle. Cerebellar atrophy results in a “fi ne comb” appearance of the folia and a</p><p>“fi sh-mouth” deformity on sagittal images. Spinocerebellar ataxia and vasculitis are</p><p>other rare causes of spinal cord and cerebellar atrophy.</p><p>References:</p><p>Huang YP, Tuason MY, Wu T, et al. MRI and CT features of cerebellar degeneration. J Formos Med</p><p>Assoc. 1993;92(6):494-508.</p><p>Shrivastava A. The hot cross bun sign. Radiology. 2007;245(2):606-607.</p><p>Modality:</p><p>MR</p><p>CRUCIFORM, HOT CROSS BUN, MOLAR TOOTH</p><p>30 Chapter 1: Adult and General Brain</p><p>FINDINGS:</p><p>Axial T2-weighted MR shows a right cerebellopontine angle mass with surrounding</p><p>T2-hyperintense rim (arrows). The right pons and brachium conjunctivum are</p><p>compressed and displaced away from the mass.</p><p>DIAGNOSIS:</p><p>Extraaxial mass (meningioma)</p><p>DISCUSSION:</p><p>Correct localization of an intracranial mass is crucial for accurate diagnosis and</p><p>surgical planning. Extraaxial masses frequently demonstrate a rim of high T2 signal</p><p>that separates them from subjacent brain. This has been proposed to represent</p><p>intervening cerebrospinal fl uid (“CSF cleft”), dura, vessels, and/or tumor capsule.</p><p>The classic differential for lesions of the cerebellopontine angle includes meningioma,</p><p>schwannoma, ependymoma, astrocytoma, metastasis, lipoma, epidermoid cyst, and</p><p>arachnoid cyst.</p><p>References:</p><p>Brant WE, Helms C. Fundamentals of Diagnostic Radiology, 3rd ed. Baltimore: Lippincott Williams</p><p>and Wilkins, 2012.</p><p>Takeguchi T, Miki H, Shimizu T, et al. Evaluation of the tumor-brain interface of intracranial</p><p>meningiomas on MR imaging including FLAIR images. Magn Reson Med Sci. 2003;2(4):165-169.</p><p>(CSF) CLEFT, MENISCUS</p><p>Modalities:</p><p>CT, MR</p><p>Modality:</p><p>MR</p><p>FINDINGS:</p><p>Axial FLAIR MR shows diffusely</p><p>abnormal hyperintense signal</p><p>within the subarachnoid spaces</p><p>(arrows).</p><p>DIFFERENTIAL DIAGNOSIS:</p><p>• Subarachnoid hemorrhage</p><p>• Meningitis</p><p>• Leptomeningeal carcinomatosis</p><p>• Vascular disease</p><p>• Supplemental oxygen</p><p>• Propofol</p><p>• Prior contrast administration</p><p>• Artifact</p><p>DISCUSSION:</p><p>FLAIR MR imaging utilizes an inversion recovery pulse sequence to null the signal</p><p>from cerebrospinal fl uid. Various conditions affecting the leptomeninges, CSF,</p><p>and/or vasculature can lead to inadequate nulling of subarachnoid signal (“FLAIR</p><p>hyperintensity” sign). Causes include subarachnoid hemorrhage, meningitis,</p><p>leptomeningeal carcinomatosis, acute infarct, arterial occlusive disease, supplemental</p><p>oxygen administration, propofol, prior intravenous contrast administration, and</p><p>various artifacts (motion, pulsation, susceptibility). The CT correlate of this fi nding</p><p>is known as the “pseudo-subarachnoid hemorrhage” sign.</p><p>References:</p><p>Maeda M, Yagishita A, Yamamoto T, et al. Abnormal hyperintensity within the subarachnoid space</p><p>evaluated by fl uid-attenuated inversion-recovery MR imaging: a spectrum of central nervous system</p><p>diseases. Eur Radiol. 2003;13(Suppl 4):L192-L201.</p><p>Stuckey SL, Goh TD, Heffernan T, et al. Hyperintensity in the subarachnoid space on FLAIR MRI.</p><p>AJR Am J Roentgenol. 2007;189(4):913-921.</p><p>CSF/FLAIR/SUBARACHNOID/SULCAL HYPERINTENSITY</p><p>CSF/Flair/Subarachnoid/Sulcal Hyperintensity 31</p><p>32 Chapter 1: Adult and General Brain</p><p>FINDINGS:</p><p>Axial contrast-enhanced T1-</p><p>weighted MR shows a right</p><p>frontal cystic lesion with</p><p>enhancing rim and punctate</p><p>internal focus (arrow).</p><p>DIFFERENTIAL DIAGNOSIS:</p><p>• Neurocysticercosis</p><p>• Toxoplasmosis</p><p>• Cystic neoplasms</p><p>DISCUSSION:</p><p>Neurocysticercosis is a neurologic disease caused by the pork tapeworm Taenia</p><p>solium. It is the most common parasitic infection of the CNS, and the leading</p><p>cause of acquired epilepsy worldwide. Infection occurs by ingestion of larval eggs</p><p>in raw or undercooked pork. Once the larvae reach the small intestine, they attach</p><p>to the intestinal wall via scolices and release additional ova. Through fecal-oral</p><p>contamination, ova are digested in the stomach and release oncospheres. These</p><p>penetrate the intestinal wall and enter the bloodstream, preferentially depositing</p><p>in brain, eyes, and muscle. Locations of disease include subarachnoid-cisternal,</p><p>parenchymal, intraventricular, and spinal. Five stages have been described:</p><p>noncystic, vesicular, colloidal vesicular, granular nodular, and calcifi ed nodular.</p><p>Noncystic neurocysticercosis is asymptomatic with no imaging fi ndings. Vesicular</p><p>neurocysticercosis demonstrates parenchymal and/or subarachnoid cysts with</p><p>associated scolices (larval hexacanth and head, forming the “cyst with dot”</p><p>appearance) and little or no edema. Colloidal vesicular neurocysticercosis is marked</p><p>by larval disintegration with marked enhancement, edema, and peripheral capsule</p><p>formation. Granular nodular neurocysticercosis is characterized by cyst retraction</p><p>and gliosis. Calcifi ed nodular neurocysticercosis is the nonactive stage, in which</p><p>the lesion has completely involuted and calcifi ed. In contrast, toxoplasmosis lesions</p><p>typically have larger and more irregular nodules, refl ecting associated hemorrhage</p><p>and infl ammation. Cystic neoplasms are usually more heterogeneous in appearance,</p><p>and may demonstrate an enhancing mural nodule.</p><p>Reference:</p><p>Kimura-Hayama ET, Higuera JA, Corona-Cedillo R, et al. Neurocysticercosis: radiologic-pathologic</p><p>correlation. Radiographics. 2010;30(6):1705-1719.</p><p>CYST WITH DOT</p><p>Modalities:</p><p>CT, MR</p><p>Cyst with Nodule, Mural Nodule 33</p><p>FINDINGS:</p><p>Axial contrast-enhanced T1-weighted MR shows a right cerebellar cystic lesion with</p><p>enhancing mural nodule (arrow).</p><p>DIFFERENTIAL DIAGNOSIS:</p><p>• Hemangioblastoma</p><p>• Infection</p><p>• Metastasis</p><p>DISCUSSION:</p><p>Fluid-secreting tumors have a mixed solid and cystic appearance, with the “mural</p><p>nodule” representing tumor, and the large adjacent cyst representing reactive fl uid.</p><p>In adults, the most common posterior fossa masses are hemangioblastoma and</p><p>metastases. The mural nodule of hemangioblastoma is hypervascular, with intense</p><p>contrast enhancement and fl ow voids on MR. Infection can also yield solid/cystic</p><p>lesions, but these are usually multiple and supratentorial in location. Toxoplasmosis</p><p>and neurocysticercosis lesions tend to have more well-defi ned, peripherally enhancing</p><p>cysts surrounding the parasitic organisms (“eccentric/concentric target” and “cyst</p><p>with dot” signs). Metastases rarely produce the “cyst with nodule” appearance in</p><p>the setting of internal necrosis, which tends to be more heterogeneous.</p><p>References:</p><p>Garg A, Suri A, Gupta V. Cyst with a mural nodule: unusual case of brain metastasis. Neurol India.</p><p>2004;52(1):136.</p><p>Lee SR, Sanches J, Mark AS, et al. Posterior fossa hemangioblastomas: MR imaging. Radiology.</p><p>1989;171(2):463-468.</p><p>CYST WITH NODULE, MURAL NODULE</p><p>Modalities:</p><p>CT, MR</p><p>34 Chapter 1: Adult and General Brain</p><p>FINDINGS:</p><p>Sagittal FLAIR MR shows multiple ovoid hyperintensities (arrows) contacting the</p><p>corpus callosum and radiating perpendicularly from the lateral ventricles.</p><p>DIAGNOSIS:</p><p>Multiple sclerosis</p><p>DISCUSSION:</p><p>Multiple sclerosis (MS) is a chronic demyelinating disorder characterized by spatial</p><p>and temporal heterogeneity. On T2-weighted and FLAIR MR, characteristic ovoid</p><p>plaques are seen radiating perpendicularly from the lateral ventricles (“Dawson</p><p>fi</p>