RadCases Plus Q&A Neuro Imaging E-Book

• Herausgeber: Thieme Medical Publishers
• Kategorie: Fachliteratur
• Sprache: Englisch

Veröffentlichungsjahr: 2019

Beschreibung

Essential neuroradiology cases and board-type Q&A review to help you pass your exam!

Neuro Imaging Second Edition from Roy Riascos, Eliana Bonfante, and Susana Calle features 100 new cases along with two board-type multiple choice questions for each. This latest edition features state-of-the-art imaging technologies including perfusion techniques, spectroscopy, nuclear medicine, and 3D reconstructions. Updated and new classification systems have been integrated into brain tumor, traumatic spine injury, and intracranial aneurysm cases. For maximum ease of self-assessment, each case begins with the clinical presentation on the right-hand page; study that and then turn the page for imaging findings, differential diagnoses with the definitive diagnosis, essential facts, pearls and pitfalls, and more.

Key Features

• New to this edition, a question-and-answer section for each case reinforces key concepts
• Easy-to-read bulleted formatting and concise, point-by-point presentation of the Essential Facts enables learning and retention of high-yield facts and skill-building in neuroradiologic diagnosis
• Online access to additional cases enables residents to arrange study sessions, quickly extract and master information, and prepare for specialized neuroradiology conferences

Thieme's RadCases means cases selected to simulate what you will see on your exams, rounds, and rotations. RadCases helps you to identify the correct differential diagnosis for each case, including the most critical.

The series comprehensively covers the following specialties:

• Breast Imaging · Cardiac Imaging · Emergency Imaging · Gastrointestinal Imaging · Genitourinary Imaging · Head and Neck Imaging · Interventional Radiology · Musculoskeletal Radiology · Neuro Imaging · Nuclear Medicine · Pediatric Imaging · Thoracic Imaging · Ultrasound Imaging

This RadCases book comes with a code providing access to additional online cases: 100 in this book plus 250+ more cases and interactive Q&A.

Master your cases, pass your exams, and diagnose with confidence: RadCases!

This print book includes complimentary access to a digital copy on https://medone.thieme.com.

Publisher's Note: Products purchased from Third Party sellers are not guaranteed by the publisher for quality, authenticity, or access to any online entitlements included with the product.

Leseprobe

To access the additional media content available with this e-book via Thieme MedOne, please use the code and follow the instructions provided at the back of the e-book.

RadCases Plus Q&A Neuro Imaging

Second Edition

Edited by

Roy F. Riascos, MD

Professor of Radiology

Chief of Neuroradiology

Department of Diagnostic and Interventional Imaging

The University of Texas Health Science Center at Houston

Houston, Texas

Eliana Bonfante, MD

Associate Professor of Radiology

Department of Diagnostic and Interventional Imaging

The University of Texas Health Science Center at Houston

Houston, Texas

Susana Calle, MD

Staff Neuroradiologist

Department of Diagnostic and Interventional Imaging

The University of Texas Health Science Center at Houston

Houston, Texas

Series Editors

Jonathan M. Lorenz, MD, FSIR

Professor of Radiology

Section of Interventional Radiology

The University of Chicago

Chicago, Illinois

Hector Ferral, MD

Senior Medical Educator

NorthShore University HealthSystem

Evanston, Illinois

776 illustrations

ThiemeNew York • Stuttgart • Delhi • Rio de Janeiro

Executive Editor: William Lamsback

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Library of Congress Cataloging-in-Publication Data

Names: Riascos, Roy, editor. | Bonfante, Eliana, editor. | Calle, Susana, editor.

Title: RadCases plus Q&A neuro imaging / edited by Roy F. Riascos, Eliana Bonfante, Susana Calle.

Other titles: Neuro imaging (Riascos) | Q&A neuro imaging | RadCases.

Description: Second edition. | New York : Thieme, 2018. | Series: RadCases | Preceded by Neuro imaging / edited by Roy Riascos, Eliana Bonfante. 2011. | Includes bibliographical references.

Identifiers: LCCN 2018035072| ISBN 9781626232372 | ISBN 9781626232433 (e-book)

Subjects: | MESH: Central Nervous System Diseases--diagnostic imaging | Radiography | Central Nervous System--diagnostic imaging | Diagnostic Techniques, Neurological | Case Reports

Classification: LCC RC349.R3 | NLM WL 141.5.N47 | DDC 616.8/047572–dc23

LC record available at https://lccn.loc.gov/2018035072

Copyright © 2019 by Thieme Medical Publishers, Inc.Thieme Publishers New York333 Seventh Avenue, New York, NY 10001 USA+1 800 782 3488, [email protected]

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ISBN 978-1-62623-237-2

Also available as an e-book:eISBN 978-1-62623-243-3

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Dedicated to the woman for whom my heart surrenders, Maria Claudia, and to our three sons, Camilo, Felipe, and Pablo, for making my life this wonderful experience.

—RFR

This book is dedicated to my loving and supporting soulmate, Darren, and to our two wonderful and inspiring children, Matthew and Zachary.

—EB

This book is dedicated to my incredible husband, Jaime, and to my beautiful baby daughter, Elena: you mean the world to me.

—SC

Contents

Series Preface

Preface

Acknowledgments

Case 1

Case 2

Case 3

Case 4

Case 5

Case 6

Case 7

Case 8

Case 9

Case 10

Case 11

Case 12

Case 13

Case 14

Case 15

Case 16

Case 17

Case 18

Case 19

Case 20

Case 21

Case 22

Case 23

Case 24

Case 25

Case 26

Case 27

Case 28

Case 29

Case 30

Case 31

Case 32

Case 33

Case 34

Case 35

Case 36

Case 37

Case 38

Case 39

Case 40

Case 41

Case 42

Case 43

Case 44

Case 45

Case 46

Case 47

Case 48

Case 49

Case 50

Case 51

Case 52

Case 53

Case 54

Case 55

Case 56

Case 57

Case 58

Case 59

Case 60

Case 61

Case 62

Case 63

Case 64

Case 65

Case 66

Case 67

Case 68

Case 69

Case 70

Case 71

Case 72

Case 73

Case 74

Case 75

Case 76

Case 77

Case 78

Case 79

Case 80

Case 81

Case 82

Case 83

Case 84

Case 85

Case 86

Case 87

Case 88

Case 89

Case 90

Case 91

Case 92

Case 93

Case 94

Case 95

Case 96

Case 97

Case 98

Case 99

Case 100

Case Questions and Answers

Further Readings

Index

Series Preface

As enthusiastic partners in radiology education, we continue our mission to ease the exhaustion and frustration shared by residents and the families of residents engaged in radiology training! In launching the second edition of the RadCases series, our intent is to expand rather than replace this already rich study experience that has been tried, tested, and popularized by residents around the world. In each subspecialty edition, we serve up 100 carefully chosen new cases to raise the bar in our effort to assist residents in tackling the daunting task of assimilating massive amounts of information. RadCases second edition primes and expands on concepts found in the first edition with important variations on prior cases, updated diagnostic and management strategies, and new pathological entities. Our continuing goal is to combine the popularity and portability of printed books with the adaptability, exceptional quality, and interactive features of an electronic case–based format. The new cases will be added to the existing electronic database to enrich the interactive environment of high-quality images that allows residents to arrange study sessions, quickly extract and master information, and prepare for theme-based radiology conferences.

We owe a debt of gratitude to our own residents and to the many radiology trainees who have helped us create, adapt, and improve the format and content of RadCases by weighing in with suggestions for new cases, functions, and formatting. Back by popular demand is the concise point-by-point presentation of the Essential Facts of each case in an easy-to-read bulleted format, and a short critical differential starting with the actual diagnosis. This approach is easy on exhausted eyes and encourages repeated priming of important information during quick reviews, a process we believe is critical to radiology education. New since the previous edition is the addition of a question-and-answer section for each case to reinforce key concepts.

The intent of the printed books is to encourage repeated priming in the use of critical information by providing a portable group of exceptional core cases to master. Unlike the authors of other case-based radiology review books, we removed the guesswork by providing clear annotations and descriptions for all images. In our opinion, there is nothing worse than being unable to locate a subtle finding on a poorly reproduced image even after one knows the final diagnosis.

The electronic cases expand on the printed book and provide a comprehensive review of the entire specialty. Thousands of cases are strategically designed to increase the resident’s knowledge by providing exposure to a spectrum of case examples—from basic to advanced—and by exploring “Aunt Minnies,” unusual diagnoses, and variability within a single diagnosis. The search engine allows the resident to create individualized daily study lists that are not limited by factors such as radiology subsection. For example, tailor today’s study list to cases involving tuberculosis and include cases in every subspecialty and every system of the body. Or study only thoracic cases, including those with links to cardiology, nuclear medicine, and pediatrics. Or study only musculoskeletal cases. The choice is yours.

As enthusiastic partners in this project, we started small and, with the encouragement, talent, and guidance of Timothy Hiscock and William Lamsback at Thieme Publishers, we have further raised the bar in our effort to assist residents in tackling the daunting task of assimilating massive amounts of information. We are passionate about continuing this journey and will continue to expand the series, adapt cases based on direct feedback from residents, and increase the features intended for board review and self-assessment. First and foremost, we thank our medical students, residents, and fellows for allowing us the privilege to participate in their educational journey.

Jonathan M. Lorenz, MD, FSIRHector Ferral, MD

Preface

It is a thrill for us to come together again and create this second edition. We have designed this book with great care to maximize the amount of retained material. Our advice is to truly analyze each case as if it were presented to you at your institution of practice. As always, our patients are our best teachers. Try to extract the greatest amount of information from each image, and resist the urge to quickly turn the page and read the provided material. The flow of the cases intends to mimic what is encountered at the reading station with the added benefit of a third party signaling which images are relevant to the diagnosis. A short and concise clinical presentation is provided. Readers are invited to test their knowledge by establishing differential diagnoses and determining which is the main consideration and why the other diagnoses are less probable. The exercise of developing a working diagnosis based on a presented case is the essence of learning in radiology and will truly enhance the review process.

New technologies including perfusion techniques, spectroscopy, nuclear medicine, and 3D reconstructions, among others, are included in this current edition. The purpose of this is to guide the reader to incorporate this additional information into the thought process as these modalities become more common in the workplace.

In contrast to the previous edition, questions and answers have now been added to each case in an attempt to better simulate how neuroradiology is currently taught. Our hope is that the interactive and dynamic nature of the book will serve to further strengthen the concepts presented.

Acknowledgments

There are not enough words of gratitude to thank everybody who allowed this second edition of our book to become a reality. I would like to acknowledge first of all the readers who have supported the material and have helped make this new edition. I must sincerely thank my amazing coauthors and friends, Eliana and Susana, for working with me on this project. A special thank you to all the medical students, residents, research assistants, and fellows at University of Texas Health Science Center and University of Texas Medical Branch for inspiring me to come to work every day. Appreciation to my team, to my colleagues, and to Susan John for the support. Special thanks to my beautiful wife Maria Claudia and my three wonderful kids, the true loves of my life, for being there for me and for sacrificing so much of their time to make a project like this come true. Gratitude to Lucy, Roy Sr., and Roberto for helping become who I am.Thank you.

—RFR

With each one of my academic projects, the list of people I am grateful to keeps growing and growing. It has been an honor to be invited to collaborate on a second edition of this book. It has been a blessing to receive feedback from residents and colleagues to improve and update our cases. Roy and Susana are the best partners to have. They made this project seem like we were not working, we were just having fun. Thanks to my colleagues in the Neuroradiology section, to our amazing fellows, and to our inquisitive residents for enriching my world every day. The love and support of my husband Darren and our fantastic sons, Matthew and Zachary, are the fuel that keeps me here every day. And as always, I owe who I am to my beloved parents, Juan and Ester, who taught me what perseverance gives you at the end of the day.

—EB

First and foremost, I would like to thank my coauthors for inviting me to participate in this project. It has been an honor to collaborate with you both on this second edition, and I have learned so much throughout the process. To the groups of outstanding neuroradiologists at University of Texas at Houston and MD Anderson Cancer Center, I appreciate your role in transforming me into a neuroradiologist. I have learned so much from each of you. I am forever indebted to my teachers and coresidents at Pontificia Universidad Javeriana. You were the foundation of my training and I still hear your words of advice in my daily practice. Last but definitely not least, I would like to thank my parents and my brother and sister. You are behind everything I am and all that I do.

—SC

Case 1

■ Clinical Presentation

A 6-year-old boy presents with headaches.

■ Imaging Findings

(A) Sagittal T1 image shows peg-shaped cerebellar tonsils lying > 5 mm below the level of the foramen magnum, at the level of the posterior arch of C1 (black arrow). There is associated dilatation of the central canal of the cervical cord (white arrow). (B) Axial T2-weighted image demonstrates crowding of the foramen magnum with effacement of the subarachnoid space at the craniocervical junction (white arrow). (C) Transverse gated phase-contrast MR images (cerebrospinal fluid flow study) during the systolic phase (I) and diastolic phase (II) demonstrate lack of flow-related signal at the foramen magnum during systole (black arrows). During the diastolic phase, there is patent flow ventrally at the foramen magnum (black arrowhead) with obstruction to flow dorsally due to the herniated tonsils (white arrowhead).

■ Differential Diagnosis

•Chiari I malformation: A malformation of the posterior fossa and cerebellum characterized by peg-shaped cerebellar tonsils positioned > 5 mm below the level of the foramen magnum. This condition is commonly associated with altered cerebrospinal fluid (CSF) flow dynamics at the craniocervical junction, which leads to syringohydromyelia.

•Intracranial hypotension: Acquired or spontaneous condition leading to decreased pressure typically resulting from CSF leaks secondary to trauma, surgery, or interventional spine procedures. Apart from the inferiorly displaced tonsils, intracranial hypotension also demonstrates chronic subdural collections, dilated dural sinuses, enlargement of the pituitary gland, and a “sagging” midbrain below the level of the dorsum sellae. There is no associated syringohydromyelia.

•Tonsillar ectopia: Position of the cerebellar tonsils below the level of the foramen magnum measuring < 5 mm. Generally, the morphology of the tonsils is preserved, no CSF flow alterations occur, and the posterior fossa has normal size.

■ Essential Facts

• Unclear pathogenesis, generally believed to be secondary to para-axial mesodermal insufficiency.

• The basion-opisthion line (BOL) marks the inferior margin of the foramen magnum. A perpendicular measurement of the inferior tip of the cerebellar tonsils to the BOL > 5 mm is generally considered diagnostic for Chiari I malformation.

• Tonsils typically herniate through the foramen magnum to the level of C1 or C2.

• The location of the brainstem is usually normal.

• The tonsils adopt a pointed or peg-shaped morphology.

• Cerebellar folia exhibit a vertical or oblique orientation sometimes referred to as “sergeant’s stripes.”

■ Other Imaging Findings

• Altered CSF dynamics ensue because of abnormal flow between spinal and intracranial CSF spaces, leading to syringohydromyelia in 40 to 80% of patients with symptomatic Chiari I.

• There is effacement of the subarachnoid spaces at the craniocervical junction with the appearance of “crowding” at the foramen magnum, which is better seen on axial T2 images.

• Hydrocephalus can be seen as a complication of Chiari I malformation in ~10% of cases.

• Other rare associations include callosal dysgenesis and absence of the septum pellucidum.

✓ Pearls and ✗ Pitfalls

✓ No association with spinal dysraphism.

✓ Cervical anomalies associated with Chiari I include Klippel–Feil syndrome.

✓ In axial images, visualization of the cerebellar tonsils at the level of the dens is indicative of ectopia.

✗ Borderline inferiorly displaced and normally shaped cerebellar tonsils are consistent with tonsillar ectopia and do not fit the criteria for Chiari I malformation.

Case 2

■ Clinical Presentation

A 7-year-old male patient with developmental delay.

■ Imaging Findings

(A) Sagittal T1-weighted image (WI) demonstrates beaking of the tectum (arrow), effacement of the fourth ventricle (asterisk), small posterior fossa secondary to a low-riding torcula, and descent of the cerebellar tonsils down to the level of C2–C3 (arrowhead). (B) Axial T2WI demonstrates wrapping of the cerebellar tonsils around the medulla oblongata (arrowheads). (C) Axial T2WI at the level of the midbrain shows beaking of the tectum (arrow). (D) Coronal T2WI demonstrates descent of the cerebellar tonsils (arrow) below the level of the foramen magnum and towering of the cerebellum (arrowhead).

■ Differential Diagnosis

•Chiari II malformation: Hindbrain anomaly characterized by a small posterior fossa with crowding, deformity, and herniation of the cerebellum and brainstem. This condition is associated with lumbar myelomeningocele.

•Chiari I malformation:

◦ Low-lying cerebellar tonsils

◦ Cervical cord syrinx

◦ Hydrocephalus in up to 30% of cases

◦ Associated with skeletal anomalies including: platybasia, basilar invagination, atlanto-occipital assimilation, Sprengel deformity, Klippel–Feil syndrome

•Spinal hypotension:

◦ Most commonly results from cerebrospinal fluid (CSF) leaks in the cervical and thoracic spine.

◦ Sagging brainstem

◦ Subdural effusions

◦ Increased fluid around the optic nerves

◦ Venous sinus engorgement

◦ Pachymeningeal enhancement

■ Essential Facts

• In Chiari II malformation, the posterior fossa is small with a low insertion of the tentorium. The cerebellum herniates superiorly (towering cerebellum) and the resultant mass effect on the tectum causes a characteristic beaking effect (tectal beaking). Furthermore, the inferior displacement of the brainstem leads to medullary kinking and herniation of the tonsils and/or vermis into the cervical spinal canal.

• Other anomalies are frequent in the cerebrum (obstructive hydrocephalus, dysgenesis of the corpus callosum, prominent masa intermedia, absent septum pellucidum), dura (fenestration of the falx with interdigitated gyri, heart-shaped incisura, hypoplastic tentorium), and cranial vault (enlarged foramen magnum, scalloping of petrous temporal bone, lacunar skull).

■ Other Imaging Findings

• CSF flow studies demonstrate abnormal CSF dynamics at the foramen magnum and may be used for decisions regarding therapy.

• Associated spinal malformations include syringohydromyelia, scoliosis, segmentation anomalies, and diastematomyelia.

✓ Pearls and ✗ Pitfalls

✓ If only axial images are available, search for wrapping of the cerebellar tonsils around the medulla oblongata, beaking of the tectum, and colpocephaly as clues for this diagnosis.

✓ If there is no basilar invagination, observing the cerebellar tonsils at the same level on axial imaging as the tip of the dens indicates tonsillar ectopia.

✗ The herniated cerebellar tonsils may undergo atrophy and can be difficult to detect in the cervical spinal canal.

Case 3

■ Clinical Presentation

A neonate presents with an abnormal obstetric ultrasound.

■ Imaging Findings

(A) Sagittal ultrasound shows a small cerebellar vermis that is tilted superiorly (arrow), with the presence of a large cyst in the posterior fossa (asterisk). (B) Sagittal T1-weighted image (WI) shows the hypoplastic vermis (arrow) with a superiorly inserted torcula (arrowhead) and a large posterior fossa cyst (asterisk). (C) Axial T2WI shows a large posterior fossa cyst (asterisk) with an abnormal connection with the fourth ventricle (arrow). (D) Coronal T2WI shows the hypoplastic cerebellar vermis (arrow) and the large posterior fossa cyst (asterisk).

■ Differential Diagnosis

•Dandy–Walker malformation:

◦ Hypoplasia and elevation of the cerebellar vermis.

◦ Large cyst in the posterior fossa that is a continuation of the fourth ventricle.

◦ Enlargement of the posterior fossa with a high tentorium.

•Blake pouch cyst:

◦ Not associated with vermian hypoplasia.

◦ Cyst that extends through the foramen of Magendie and communicates with the fourth ventricle. In contrasted images, the choroid plexus will be seen extending through the cyst.

◦ Typically will not have superior displacement of the tentorium.

◦ No communication of the cyst with the subarachnoid space.

•Posterior fossa arachnoid cyst:

◦ Variable locations within the posterior fossa.

◦ The cerebellar vermis can either exhibit a normal configuration or can be deformed by mass effect from the cyst.

◦ Large cysts may cause hydrocephalus.

◦ The cerebellar falx may be displaced off the midline.

◦ No communication of the cyst with the fourth ventricle.

■ Essential Facts

• Hydrocephalus is present in 90% of cases and is the most common manifestation in the first months of life.

• Thirty to 50% of cases can have additional malformations such as callosal dysgenesis, occipital encephalocele, polymicrogyria, and heterotopia.

■ Other Imaging Findings

• Dandy–Walker malformation can be identified in prenatal ultrasound.

• MRI is the best diagnostic tool.

• Contrast helps differentiate between a Blake pouch cyst and Dandy–Walker malformation by identifying enhancing choroid plexus extending through the cyst in Blake pouch cysts.

✓ Pearls and ✗ Pitfalls

✓ Fifty percent of cases are associated with chromosomal anomalies or Mendelian disorders.

✓ Most patients present with symptoms of increased intracranial pressure in the first year of life.

✗ Look for associated anomalies to identify different syndromes:

• Meckel–Gruber syndrome: encephalocele, polydactyly

• Walker–Warburg syndrome: encephalocele, lissencephaly, microphthalmia

✗ If axial scans are acquired with a steep angle, an abnormal communication between the fourth ventricle and the cisterna magna can be erroneously suggested.

Case 4

■ Clinical Presentation

A child presents with developmental delay.

■ Imaging Findings

(A) Axial T2-weighted image (WI) demonstrates a parallel orientation of the lateral ventricles (black arrows), also termed the “race car sign.” Between the widely spaced lateral ventricles there is a midline cyst (asterisk), with a vessel running through it, extending from the third ventricle (white arrowhead) to the subarachnoid space (black arrowhead). (B) Coronal T2WI shows a high-riding third ventricle due to absence of the corpus callosum (white arrowhead), with bundles of Probst indenting the superomedial bodies of the lateral ventricles (black arrowheads). The configuration of the ventricles mimics a “moose head” with the third ventricle representing the moose’s head (black arrow) and the lateral ventricles being the antlers (white arrows). (C) Coronal T2WI shows the cystic structure (asterisk) at the midline between the posterior bodies of the lateral ventricles (black arrows). (D) Sagittal T2WI of the brain demonstrates agenesis of the corpus callosum with eversion of the cingulate gyrus. The vertically oriented paramedic gyri radiate toward the expected location of the corpus collosum and conform the so-called “sun ray appearance” (black arrowheads). The interhemispheric cyst (asterisk) communicates the ventricular system (black arrow) with the subarachnoid space (white arrow).

■ Differential Diagnosis

•Callosal agenesis with interhemispheric cyst (CAwith IHC): CA with IHC is a distinct condition that is believed to vary in cause when compared to other forms of agenesis of the corpus callosum. This condition is characterized by a deficient formation of the corpus callosum associated with a midline cyst that can present with or without communication to the ventricular system.

•Porencephaly: Congenital or acquired condition secondary to a wide range of traumatic, ischemic, and/or infectious causes. The insult ultimately leads to a cerebrospinal fluid (CSF)–filled cyst or cleft, lined by white matter, that communicates with the subarachnoid space and/or the ventricular system.

•Cystic encephalomalacia: Irregular cystic cavity at the anatomic site of remote insult with surrounding gliosis and no communication with the adjacent ventricle. Cystic encephalomalacia has no specific association with dysgenesis of the corpus callosum.

■ Essential Facts

• Type 1:

◦ Single cyst

◦ Signal intensity follows CSF.

◦ Thought to represent a diverticulum of the ventricle. Therefore, the cyst and the ventricle communicate.

◦ More common in males.

◦ Associated with macrocephaly and cranial malformations.

• Type 2:

◦ Multiple cysts/multiloculated cyst

◦ Does not communicate with the ventricle.

◦ Signal intensity does not exactly follow CSF.

◦ Associated with subcortical heterotopia and polymicrogyria.

■ Other Imaging Findings

• CA with IHC can also be associated with Dandy–Walker malformation.

• The cyst tends to grow proportionally to increasing ventricular size, which may indicate that cysts may develop as a consequence of elevated ventricular pressure.

✓ Pearls and ✗ Pitfalls

✓ The conditions associated with agenesis of the corpus callosum include anomalies of cortical development, lipomas, Dandy–Walker complex, Chiari II malformation, holoprosencephaly, and encephalocele.

✓ The communication of the IHC to the ventricle, the number of cysts, and their internal signal intensity allow for an accurate classification.

✗ Although the cyst is located at the midline, its morphology may be asymmetric and involve one side preferentially.

✗ In patients with an enlarged third ventricle secondary to hydrocephalus, the evaluation of the corpus callosum is limited because of the thinning and superior displacement of the fibers. Evaluation after decompression facilitates the diagnosis.

Case 5

■ Clinical Presentation

Clinical history was withheld.

■ Imaging Findings

(A) Sagittal T1-weighted image (WI) without contrast shows cerebellar atrophy most prominent at the superior aspect (arrow). (B) Axial fluid-attenuated inversion recovery (FLAIR) image shows thickened superior cerebellar peduncles (arrows), which give the midbrain the characteristic “molar tooth appearance.” (C) Axial T2WI shows thickened superior cerebellar peduncles (arrows) and the “molar tooth” configuration of the midbrain.

■ Differential Diagnosis

•Joubert syndrome: Agenesis or dysgenesis of the vermis, a deep interpeduncular fossa, and long thickened superior cerebellar peduncles give the midbrain the characteristic “molar tooth” appearance on axial MR images. There is absence of normal fiber tract decussation at the superior cerebellar peduncles. Axial MR images in the posterior fossa classically show the “bat wing” configuration of the fourth ventricle, reminiscent of a bat with outstretched wings.

•Progressive supranuclear palsy:

◦ Neurodegenerative disorder

◦ Decreased cognition, abnormal eye movements (supranuclear vertical gaze palsy), postural instability and falls, as well as parkinsonian features and speech disturbances

◦ MRI: midbrain atrophy (Mickey Mouse appearance, morning glory sign, hummingbird sign). T2 hyperintense lesions involve the pontine tegmentum, the tectum, and the inferior olivary nuclei.

•Walker–Warburg syndrome:

◦ A genetically heterogeneous disease presenting with congenital muscular dystrophy, type II lissencephaly, hydrocephalus, cerebellar malformations, and eye abnormalities.

◦ Cerebellar/brainstem malformations include cerebellar hypoplasia, primitive Z-shaped configuration of the brainstem, and bifid pons/medulla oblongata.

■ Essential Facts

• Joubert syndrome represents a group of disorders that present clinically with ataxia, hypotonia, abnormal breathing, and mental retardation.

• Autosomal recessive inheritance.

• Several causal genes have been identified, all involved in the function of the primary cilia and basal body organelle, which are believed to play a role in signaling pathways during cerebellar development.

■ Other Imaging Findings

• Other associated central nervous system abnormalities include hydrocephalus, cystic enlargement of the posterior fossa, corpus callosum anomalies, white matter cysts, hypothalamic hamartomas, absence of the pituitary gland, migration anomalies, and occipital encephalocele.

• Associated multiorgan involvement such as retinal dystrophy, nephrolithiasis, hepatic fibrosis, and polydactyly may be present.

✓ Pearls and ✗ Pitfalls

✓ In Joubert syndrome, diffusion tensor imaging and fiber tractography reveal absence of decussation of both the superior cerebellar peduncles and corticospinal tracts.

✗ Vermian hypoplasia is best assessed on sagittal views. Thin slices help prevent volume averaging with the hemispheres.

✗ The size of the vermis must also be assessed on axial and coronal views, paying particular attention to whether cerebrospinal fluid is present at the midline between the hemispheres.

Case 6

■ Clinical Presentation

A 7-year-old boy presents with seizures.

■ Imaging Findings

(A) Diffusion-weighted image (WI) shows a well-defined line of increased signal that affects mostly the deep white matter of the parietal lobes (arrow). (B) Axial T2WI shows confluent symmetric areas of hyperintensity that affect mostly the periventricular and deep white matter in the parietal lobes (arrow). The signal abnormality extends anteriorly in the medial aspect of the frontal lobes (asterisk). The subcortical “U” fibers are spared in some areas (arrowhead). (C) Axial fluid-attenuated inversion recovery (FLAIR) T2 sequence shows increased signal in the corticospinal tracts (arrowhead) and in the middle cerebellar peduncles (arrow). (D) There are three concentric layers of signal abnormality in the periatrial region: central low signal (asterisk), surrounded by linear enhancement (arrow), and a peripheral nonenhancing area of low T1 signal (arrowhead). The areas of linear enhancement correspond to the areas of restricted diffusion.

■ Differential Diagnosis

•X-linked adrenoleukodystrophy (ALD):

◦ Peroxisomal disorder affecting males.

◦ Approximately 35% of the cases present in childhood.

◦ The radiologic presentation precedes the clinical symptoms.

◦ Symmetric periventricular and deep white matter hyperintensities with parietal and occipital predominance, sparing the subcortical “U” fibers in the initial stages.

◦ Not associated with macrocephaly.

•Alexander disease (fibrinoid leukodystrophy):

◦ This leukodystrophy typically presents with symmetric bifrontal subcortical U-fiber involvement early in the disease.

◦ The brainstem involvement of the long fibers is frequent. Contrast enhancement is not characteristic.

◦ The patients are typically macrocephalic.

•Canavan disease (spongiform degeneration of the white matter):

◦ Presents with macrocephaly, extensive white matter changes with frontal predominance, and abnormalities of the thalamus and globus pallidus, sparing the striatum.

◦ This disease typically begins in the subcortical white matter and progresses to the deep white matter.

◦ The cerebellum is a common site of involvement.

◦ No enhancement is seen.

◦ Increased N-acetylaspartate (NAA) and NAA:creatinine ratio on MR spectroscopy.

■ Essential Facts

• ALD presents with white matter changes, hypoadrenalism, and/or primary hypogonadism. It has been described in the parieto-occipital lobes (typical), the anterior frontal lobe, and the temporal lobes. The visual and auditory tracts, the corpus callosum, and the corticospinal projection fibers can also be involved. Lastly, involvement of the middle cerebellar peduncles has recently been described.

• MRI shows three zones: a central zone of irreversible gliosis, an intermediate enhancing zone that represents active inflammation and breakdown of the blood–brain barrier, and a third peripheral zone of active demyelination.

■ Other Imaging Findings

• MR is important for the diagnosis and the follow-up of therapy with hematopoietic stem cell transplantation.

• Diffusion-weighted imaging (DWI) shows a decrease in the fraction of anisotropy in the demyelinating zone and increased DWI signal on the intermediate zone.

✓ Pearls and ✗ Pitfalls

✓ Consider ALD if white matter changes involve the posterior brain.

✓ Pontomedullary junction and corticospinal tract involvement is rarely seen in any other form of leukodystrophy.

✓ ALD is not associated with macrocephaly.

✗ Not all patients with ALD present with the typical posterior cerebral pattern.

✗ Spectroscopy findings are not specific in ALD.

Case 7

■ Clinical Presentation

A 40-year-old woman presents with known agenesis of the corpus callosum with an additional abnormal finding.

■ Imaging Findings

(A–C) Axial T1 (A), T2 (B), and fluid-attenuated inversion recovery (FLAIR) (C) images of the brain demonstrate a white matter–lined cleft communicating the occipital horn of the left lateral ventricle with the subarachnoid space (white arrows). The left lateral ventricle is enlarged (asterisk) due to associated parenchymal volume loss. The adjacent skull shows subtle thinning and remodeling (black arrows).

■ Differential Diagnosis

•Porencephaly: Congenital or acquired condition secondary to a wide range of traumatic, ischemic, and/or infectious causes that ultimately lead to a cerebrospinal fluid (CSF)-filled cyst or cleft, lined by white matter, that communicates with the subarachnoid space and/or the ventricular system.

•Open lip schizencephaly: Early brain malformation characterized by a cleft lined by dysplastic gray matter extending from the ventricle to the pial cortical surface. The cleft can show intervening CSF space (open lip), or the sides of the cleft can closely appose each other (closed lip).

•Cystic encephalomalacia: Irregular cystic cavity at the anatomic site of remote insult, with surrounding gliosis and no communication with the adjacent ventricle.

■ Essential Facts

• Smooth, well-demarcated CSF-filled cavities resulting from a wide range of damaging processes including trauma, ischemia, infection, or surgery.

• The cysts vary widely in size and can be small or involve almost entire hemispheres.

• Characteristically, porencephaly or porencephalic cysts extend from the ventricle to the cortex.

• CSF pulsation caused by the communication between the ventricle and the subarachnoid space may secondarily remodel the adjacent skull.

• Parenchymal volume loss adjacent to the involved region of brain causes a focally enlarged ventricle.

• The contents of the cyst or cleft follow CSF on all sequences and completely suppress on fluid-attenuated inversion recovery (FLAIR) image.

■ Other Imaging Findings

• Can be unilateral or bilateral.

• Often follows an arterial territory distribution.

• Heterogeneous internal signal intensity can be seen in large porencephalic cysts due to CSF flow turbulence.

• White matter lining the cleft may be gliotic or spongiotic.

✓ Pearls and ✗ Pitfalls

✓ The porencephalic cyst may communicate with the subarachnoid space while schizencephaly communicates with the subpial space. This feature is not appreciable on imaging.

✓ Porencephaly is not a static process. Adhesions within the defect may create valve effects that gradually enlarge the CSF-filled space or ventricle over time.

✗ Gliotic or spongiotic white matter along the cleft surface may simulate dysplastic gray matter, making differentiation between porencephaly and schizencephaly difficult.

Case 8

■ Clinical Presentation

A newborn presents with increased head circumference and a history of abnormal fetal ultrasound.

■ Imaging Findings

(A) Sagittal T2-weighted image (WI) demonstrates a large supratentorial cystic structure communicating with the ventricular system (arrow). The aqueduct and fourth ventricle are small (arrowhead). (B) Axial T2WI shows fusion of the frontal lobes (arrowhead), a monoventricle (arrow), and absence of the falx. A large cystic structure (asterisk) replaces the posterior temporal, occipital, and parietal lobes. (C) Axial T2WI shows fusion of the frontal lobes (arrowhead), absence of the interhemispheric fissure, and a large cystic structure (asterisk) replacing the posterior temporal, occipital, and parietal lobes. (D) Coronal T2WI shows continuity of the frontal lobes at the midline (arrow) and fusion of the thalami (arrowhead).

■ Differential Diagnosis

•Alobar holoprosencephaly:

◦ The most severe form of holoprosencephaly.

◦ Prosencephalic cleavage fails, resulting in a single midline forebrain with a primitive monoventricle often associated with a large dorsal cyst.

•Hydranencephaly:

◦ In utero destruction of the cerebral hemispheres.

◦ Absent cortical tissue with preserved thalami and posterior fossa.

◦ Islands of residual tissue can be seen at the occipital poles and orbitofrontal regions.

◦ The falx is usually present.

◦ Choroid can often be identified within the fluid-filled sac.

•Dandy–Walker malformation:

◦ Posterior fossa cyst that communicates with the fourth ventricle.

◦ Abnormal development of the cerebellar vermis.

◦ Cystic dilatation of the fourth ventricle extending posteriorly.

◦ Enlarged posterior fossa with torcular-lambdoid inversion.

■ Essential Facts

• Holoprosencephaly is the result of failed or incomplete separation of the forebrain early in gestation.

• Types:

◦ Alobar holoprosencephaly: Small single forebrain ventricle, no interhemispheric division, absent olfactory bulbs and tracts, absent corpus callosum, no separation of the deep gray nuclei.

◦ Semilobar: Rudimentary cerebral lobes with incomplete interhemispheric division, varying separation of the deep gray nuclei.

◦ Lobar: Fully developed cerebral lobes, except for continuous midline frontal neocortex; distinct interhemispheric division; absent, hypoplastic, or normal corpus callosum; separation of deep gray nuclei.

◦ Middle interhemispheric variant (also known as syntelencephaly): Failure of separation of the posterior frontal and parietal lobes. The body of the corpus callosum is absent, whereas the genu and splenium are normally formed. The hypothalamus and lentiform nuclei are normally separated.

■ Other Imaging Findings

• Other anomalies include cyclopia, proboscis, median or bilateral cleft lip/palate in severe forms, ocular hypotelorism, or solitary median maxillary central incisor.

• “The face predicts the brain”: If facial malformations are present, the brain must be studied.

✓ Pearls and ✗ Pitfalls

✓ Semilobar holoprosencephaly is one of the few pathologies where the rostrum and splenium of the corpus callosum are well formed in the absence of a callosal body.

✓ In the sagittal images, the large cyst is in the supratentorial compartment, unlike the infratentorial location and communication with the fourth ventricle seen in Dandy–Walker malformation.

✗ Prominence of the masa intermedia seen in Chiari II malformation should not be confused with fused thalami.

Case 9

■ Clinical Presentation

A newborn boy presents with a hairy patch on his lower back.

■ Imaging Findings

(A) Sagittal T2-weighted image (WI) of the lumbosacral region shows a superficial lipoma and a dermal sinus (arrow). The lipoma extends into the spinal canal through a sacral dysraphism (asterisk). The patient has a tethered cord, and the placode–lipoma interface is inside of the spinal canal (arrowhead). (B) Axial T1WI of the lower lumbar spine shows a lipoma in the spinal canal (asterisk) and a linear hypointensity corresponding to a dermal sinus (arrowhead). (C, D) Sagittal T1WI (C) and sagittal short tau inversion recovery (STIR) images (D) of the lumbosacral region show a superficial lipoma and a dermal sinus (arrow). The lipoma extends into the spinal canal through a sacral dysraphism (asterisk).

■ Differential Diagnosis

•Lipomyelocele and lipomyelomeningoceles: These correspond to closed spinal dysraphisms with subcutaneous lumbosacral lipomas and dural defects. The subcutaneous lipoma is located above the intergluteal crease. The lipoma tends to be excentric and extends into the spinal canal through a large sacral dorsal dysraphism. All cases are associated with tethered cord. No abnormal enhancement is seen.

•Sacrococcygeal teratoma: Unlike lipomyelocele and lipomyelomeningoceles, sacrococcygeal teratomas are located below the intergluteal crease. These are complex masses that may present with calcifications (60%), debris, and skin appendages. The solid components of the teratoma typically enhance.

•Terminal myelocystocele: Terminal hydromyelia associated with expansion of the central canal of the caudal spinal cord and surrounding distension of the dural sac. Typically associated with a dural lipoma.

■ Essential Facts

• Lipomyelocele and lipomeningocele are types of closed spinal dysraphism that feature a lipoma and a dural defect.

• They are considered abnormalities of primary neurulation, disjunction between the neuroectoderm and cutaneous ectoderm.

• If the lipoma–placode interface is inside of the canal, is it called lipomyelocele or lipomyeloschisis (75%).

• If the lipoma–placode interface is outside of the canal, the condition is termed lipomyelomeningocele (25%), and the dural defect is typically located laterally toward the lipoma.

■ Other Imaging Findings

• Prenatal ultrasound can detect the fat in the spinal canal.

• MRI shows the defect, and the lipoma–placode interface is seen as hypointense on both T1- and T2-weighted images.

• The size of the canal can increase depending on the size of the lipoma, but the subarachnoid space ventral to the spinal cord is always normal.

✓ Pearls and ✗ Pitfalls

✓ If treatment is not established before 6 months of age, irreversible neurologic sequelae will likely occur.

✓ In half of the cases, skin abnormalities such as hypertrichosis, sacral dimple, dermal sinus tract, and capillary hemangioma are present.

✗ Look closely for the location of the lipoma–placode interface to differentiate lipomyelocele from lipomyelomeningocele.

Case 10

■ Clinical Presentation

A child presents with seizures.