Atlas of Normal Imaging Variations of the Brain, Skull, and Craniocervical Vasculature PDF
Preview Atlas of Normal Imaging Variations of the Brain, Skull, and Craniocervical Vasculature
Alexander M. McKinney Atlas of Normal Imaging Variations of the Brain, Skull, and Craniocervical Vasculature 123 Atlas of Normal Imaging Variations of the Brain, Skull, and Craniocervical Vasculature Alexander M. McKinney Atlas of Normal Imaging Variations of the Brain, Skull, and Craniocervical Vasculature Alexander M. McKinney, MD, CIIP Professor, Peterson Chair of Neuroradiology Neuroradiology Division Department of Radiology University of Minnesota Minneapolis, MN USA ISBN 978-3-319-39789-4 ISBN 978-3-319-39790-0 (eBook) DOI 10.1007/978-3-319-39790-0 Library of Congress Control Number: 2016961315 © Springer International Publishing Switzerland 2017 This work is subject to copyright. All rights are reserved by the Publisher, whether the whole or part of the material is concerned, specifically the rights of translation, reprinting, reuse of illustrations, recitation, broadcasting, reproduction on microfilms or in any other physical way, and transmission or information storage and retrieval, electronic adaptation, computer software, or by similar or dissimilar methodology now known or hereafter developed. The use of general descriptive names, registered names, trademarks, service marks, etc. in this publication does not imply, even in the absence of a specific statement, that such names are exempt from the relevant protective laws and regulations and therefore free for general use. The publisher, the authors and the editors are safe to assume that the advice and information in this book are believed to be true and accurate at the date of publication. Neither the publisher nor the authors or the editors give a warranty, express or implied, with respect to the material contained herein or for any errors or omissions that may have been made. Printed on acid-free paper This Springer imprint is published by Springer Nature The registered company is Springer International Publishing AG The registered company address is Gewerbestrasse 11, 6330 Cham, Switzerland This is primarily dedicated to my family, who have been exceedingly patient and have attempted to keep me balanced, including Jennelle, Amina, Aliya, Zaki, and Nura. Also, to my parents Alex and Roni, and my brother Zeke, who have also helped me to stay focused on what is most important (i.e., family). My family has really supported me along the way in more ways than I could imagine. Additionally, I would like to thank my radiology mentors: Drs. Chip Truwit, Stephen Kieffer, and Charles Dietz from whom I have not just learned about neuroradiology, but also about the importance of being an academician regardless of ever-changing environments. I also would like to acknowledge and express my appreciation for three colleagues (neuroradiologists) for contributing cases: Drs. Chris Palmer, Barbara Knoll, and David Nascene, who really did take the time out to save cases just for this book. Finally, I dedicate this to my past, current, and future residents, fellows, medical students, and research assistants who I have learned from as much as they have learned from me. Without an academic environment and those individuals who are eager to learn, we would lose the initiative to improve. Foreword The distinction between normal variant, anomaly, and abnormality in the human nervous sys- tem is often subtle but carries profound clinical consequence. Imaging has become indispens- able in diagnosis and patient management in modern clinical neuroscience. The clinician is barraged frequently with new imaging sequences labeled with clever acronyms and abbrevia- tions. The result is an evolution in our understanding of what constitutes a normal variation and what is considered a pathological entity. The failure to distinguish what is normal and abnor- mal can lead to inappropriate decision making, ranging from unnecessary serial imaging to ill-fated surgical intervention. A repository of these normal variations is long overdue, and I congratulate Dr. McKinney on assuming such an arduous task. Many neuroradiology texts are actually applied works that focus on pathological conditions with clinical correlates. These integrative works tend to appeal to a broad clinical audience including neuroradiologists, neurologists, psychiatrists, and neurosurgeons. Dr. McKinney’s atlas could be classified as a work of pure neuroradiology, but its impact will be much broader. In many ways, this book carries the same significance as Krayenbṻhl and Yaşargil’s Cerebral Angiography or Osborn’s Diagnostic Neuroradiology. Like these classic texts, Dr. McKinney’s current volume will have wide appeal and importance to the same audience of clinicians. The length of this work should not intimidate the reader. However, its length requires us to contemplate the extensiveness of this subject. Our clinical focus often is directed towards pathology, and we often overlook the normal and its variants. We are passing this habit to our trainees, leading to the possibility of them not knowing the difference between normal and abnormal. This book, which is comprised mostly of images, represents an endeavor to halt this tendency. The accompanying text is purposefully brief but informative and reads easily. The reader will not need nearly as many years to review this work as was required to compose it. Like many atlases, it will serve as a valuable reference on our shelves. Even on a limited sched- ule, the determined student of clinical neuroscience can review all the material presented in this book in a short period. As contemporaries in clinical neuroscience, Dr. McKinney and I have overlapped in our training and now in our respective practices. While a resident and fellow, he routinely collected cases for future reference and didactic material. I doubt he knew at the time that those cases would be the seed for this book. The absence of a single source about anatomic variations combined with Dr. McKinney’s curiosity and indefatigability laid the foundations for this impressive atlas. I am confident that the reader will affirm the author’s and my own notion that this atlas is a work of art. Despite the exhaustive approach taken by Dr. McKinney, we must recognize that this vol- ume is incomplete. As noted in the author’s preface, there are neurological variations outside of the brain, skull, and vasculature that must be cataloged. Dr. McKinney may be reluctant to produce another volume to address these issues because of the time and energy necessary for such an endeavor. Based on the quality of the current work, let us all persuade him to reconsider. Minneapolis, MN, USA Ramachandra P. Tummala, MD vii Preface I would opine that “art can be work” and “work can be art,” depending on how much someone enjoys their profession. I certainly feel this way about the field of neuroradiology. I must con- fess that this book has undergone evolution for several reasons since I agreed to undertake this topic during my third year as a staff neuroradiologist (and now in my 15th!). Most notable is that the book was originally intended to include three parts: brain, spine, and head and neck, but I found that I am so meticulous that it was impossible to ignore the topics of craniocervical vasculature and skull, as these structures are immediately adjacent to the brain. This work was also driven by my quest to be practical. For example, I feel strongly that in order to properly interpret a routine brain MRI, a working knowledge of vascular variants is necessary even if an MR angiogram was not performed. Similarly, variants of the skull may also simulate disease when interpreting a routine brain MRI. Thus, given size constraints, normal variations of the spine and head and neck were not included here, and are left for a possible, future book. For the abovementioned reason that this might be akin to composing “art,” this book is hands-down the hardest work I have completed, and took the longest; finding rare cases of variants compounded that difficulty. I find that composing journal articles, reviews, and chap- ters in a book is quicker and more straightforward, since there is a limited range of possibili- ties. In fact, what makes the subject of normal variations so difficult to address is that one may not realize the importance of a finding because either: (1) it is not seen or mentioned as it is of no consequence anyway; (2) it is seen but constantly called abnormal and never proven to be so, as it is not a surgical entity; (3) in the reverse of #1, it is thought to be abnormal, but dedi- cated imaging and attention to detail is sometimes necessary, which may require “putting one’s shoulder against the ocean liner” of physicians ready to perform surgery or other unnecessary therapy. Certainly, #3 is the most clinically important scenario for normal variations, particu- larly with regards to the brain, where operating on a suspected finding that is actually a normal variant can have catastrophic consequences. To prevent situation #3 and to prevent expectation bias, I routinely urge the residents and fellows that, prior to looking at the clinical history, to first simply “say what they see” about an image (to borrow the words of our famous neurora- diology predecessor in Minnesota, Harold O. Peterson). Often times, what is suspected to be a normal variant by a radiologist is often just that; however, proof may be lacking. Thus, the goal of this book is to compile the most common and identifiable (or the most interesting) variants, and to provide the most facile methods or sequences to identify them expediently, as well as provide a range of appearances. And yet another reason that this book evolved over several years to the point of being delayed is that I not only wanted to include the common, standard variants that most radiolo- gists and neuroradiologists are already aware of (e.g., cavum septum pellucidum, hyperostosis frontalis, etc.) but I also sought to cover newly identified variants that can be proven or described further by newer techniques (e.g., brain capillary telangiectasias on susceptibility weighted imaging [SWI]). Regarding those techniques, such as SWI, diffusion-weighted imaging (DWI), and multidetector/multislice CT, I also sought to cover artifacts or appear- ances that simulate disease using those techniques, which I felt has not been covered well in prior texts, although there may have been online descriptions or literature references. ix x Preface I also attempted to provide “Comparison Cases” for many normal variants. I opine that one way to cement the appearance of a normal variant in one’s mind is to demonstrate the actual abnormality that the radiologist is worried about it being. In this fashion, I hope such cases in this text create a “spectrum of normal” in radiologists’ minds for future and immediate com- parison to cases they are considering being potential normal variations. Further, I felt that one particular area required much experience that can be potentially quite difficult to discern normal from abnormal: the infant brain with determination of myelination and the presence or absence of hypoxic-ischemic injury/encephalopathy (HII/HIE). To me, this topic seemed vital for my experience level with, and continued exposure to, pediatric neurora- diology to grow before I compiled the segment on the Pediatric Brain. This necessitated that I followed numerous cases within the files for years, and intermittently rechecked their medical records to make sure that a patient’s development remained normal. Hopefully, this arduous task will be rewarded, as I have also attempted to add some attributes and normal appearances of neonates, infants, and young children on MRI and CT that have not been described well in prior texts or within the literature. My development and (hopefully) capability as a pediatric neuroradiologist really has paralleled the evolution of this text. Finally, regarding the length of text and references, I have chosen to reference and describe each particular subject in what I thought would be the briefest fashion possible while simulta- neously attempting to do justice to each subject. My attempt to keep such descriptions under the length of 1–2 pages would have otherwise been rendered futile, and would have disrupted the intent of the publisher and myself for there to be “more pictures than text.” I apologize ahead of time to those who would prefer a much more meticulous description of each subtopic. But I would submit that the purpose of the References, which are generally provided in the order that the topic is described, are for more detailed analyses at the reader’s behest. I admit this book is not intended for an in-depth analysis or discussion-type of reference; rather, it could be for quick reference to a particular imaging appearance. Hence, if mistakes are identified (which I am confident there will be), I am open to an email to improve the text. Please provide a reference, if possible, and if a future version is published, I plan to acknowledge that contribution. Additionally, any suggestion for future topics to include is welcome. Minneapolis, MN, USA Alexander M. McKinney, MD Acknowledgments I personally thank and acknowledge the following individuals for their contributions to this text: Bibi Husain (University of Minnesota, Minneapolis, MN): Chief Editorial Assistant and Proofreading, Copying, Saving, and Correspondence Contributions of images: David Nascene, MD (University of Minnesota, Minneapolis, MN) contributed the following cases: Right-sided Arch (non-Mirror Image), Double Aortic Arch, Arch Origin of the External Carotid Artery, Azygous ACA/Bihemispheric ACA, Dorsal Ophthalmic artery, Duplicated MCA, Accessory MCA, Fenestrated MCA. Charles (“Chip”) Truwit, MD (Hennepin County Medical Center, Minneapolis, MN) contrib- uted the following cases: Persistent Hypoglossal Artery, Persistent Proatlantal Intersegmental Artery. Dr. Francis Hui, MD (National Neuroscience Institute, Singapore) contributed: Persistent Hypoglossal Artery. Basar Sarikaya, MD (Yeditepe University Hospital, Istanbul, Turkey) contributed: Lateral Tentorial Sinus Prominence, Azygous/Bihemispheric ACA, Primitive Olfactory Artery/ Olfactory course of the ACA. Philllipe Gailloud, MD (Johns Hopkins University, Baltimore, MD) contributed the following cases: Duplicated MCA, Accessory MCA, Fenestrated MCA. Christopher Palmer, MD (Hennepin County Medical Center, Minneapolis, MN) contributed cases of: Arch origin of the External Carotid Artery and Superficial Middle Cerebral Vein Prominence. Chang-Woo Ryu, MD (Kyung Hee University Hospital at Gangdong, Seoul, Republic of Korea) contributed cases of: Persistent Falcine Sinus. Kirk M. Welker, MD (Mayo Foundation for Medical Education and Research, Rochester, Minnesota) contributed cases of: Arrested Pneumatization (Incomplete Aeration) of the Skull Base. xi xii Acknowledgments Jeffrey Brace, MD (Suburban Radiologic Consultants, Edina, MN) contributed a case of: Aberrant Arch origin of the Right Vertebral Artery. Luke Kim and John Saali (representatives for Philips Healthcare, Andover, MA): aiding in demonstrating SENSE-related artifacts in MR Angiography. Other contributions: Offering knowledge and excellent teaching: Elisa Widjaja, MD; Manohar Shroff, MD; Charles Raybaud, MD; and Susan Blaser, MD (The Hospital for Sick Children, Toronto, Ontario, CA).
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