Dating Neurological Injury
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Jeff L. Creasy Dating Neurological Injury A Forensic Guide for Radiologists, Other Expert Medical Witnesses, and Attorneys
Jeff L. Creasy Associate Professor of Neuroradiology Vanderbilt University Medical Center Nashville, TN USA jeff.creasy@vanderbilt.edu ISBN 978-1-60761-249-0 e-isbn 978-1-60761-250-6 DOI 10.1007/978-1-60761-250-6 Springer New York Dordrecht Heidelberg London Springer Science+Business Media, LLC 2011 All rights reserved. This work may not be translated or copied in whole or in part without the written permission of the publisher (Springer Science+Business Media, LLC, 233 Spring Street, New York, NY 10013, USA), except for brief excerpts in connection with reviews or scholarly analysis. Use in connection with any form of information storage and retrieval, electronic adaptation, computer software, or by similar or dissimilar methodology now known or hereafter developed is forbidden. The use in this publication of trade names, trademarks, service marks, and similar terms, even if they are not identified as such, is not to be taken as an expression of opinion as to whether or not they are subject to proprietary rights. While the advice and information in this book are believed to be true and accurate at the date of going to press, neither the authors nor the editors nor the publisher can accept any legal responsibil-ity for any errors or omissions that may be made. The publisher makes no warranty, express or im-plied, with respect to the material contained herein. Printed on acid-free paper Springer is part of Springer Science+Business Media (www.springer.com)
Preface Why do we need a book on the dating of neurological injury? Over the last decade, I have personally reviewed more than 80 medical legal cases related to neurological disease in which some aspect of the case involved imaging technology. Many cases in clinical situations, such as alleged birthrelated hypoxia or ischemia, surgically-related injuries, or trauma-induced spinal cord or brain substance abnormalities, for example shared the need both to detect the presence of an injury and to date the time it occurred. While a minority of cases involved the misdiagnosis of an aneurysm, a delayed diagnosis of spinal fracture, or orbital injury during a surgical procedure, the large majority of cases used modern imaging, first to detect if an injury had occurred to the brain substance or the spinal cord (collectively referred to as the central nervous system) and second to determine, if an injury did occur, at what time it occurred. In a medical legal setting, the interplay between the radiographic findings and the clinical findings has several possible scenarios. On one extreme, the imaging findings may be so unequivocal that no doubt exists as to what occurred and even little doubt about when it occurred. On the opposite extreme, the radiologic findings may be either completely noncontributory or may show that an event occurred but offer no insight into when it occurred (and hence its proximate cause). In between is a gray area in which the clinical history can often be very helpful in delineating the imaging findings to more accuracy and specificity; and the reverse may also be true, i.e., that the radiology may help clarify the clinical picture. My hope is that this text will be helpful in all situations from those in which radiology is clear, to those in which the findings are less certain though still present by providing guidelines and principles for the application of imaging findings. The realm of this book is not to discuss specific clinical and radiographic findings at the level of the medical expert radiologist, nor is it intended to be an exhaustive treatise on recognizing the imaging signs of brain abnormality, as that is more appropriately covered in a textbook on medical imaging. Rather, I intend to represent in a systematic fashion the principles involved in the interpretation of images of the central nervous system specifically in a medical legal setting where concern exists about the occurrence and timing of an injury. What this book uniquely presents is a new way to approach the dating of neurological injury as imaged by modern computed tomography (CT), magnetic resonance (MR), and ultrasound (US). Throughout the text, I describe dating by two distinct but complementary methods. In the first, I explain how knowledge of the dynamic and rapidly changing imaging findings that occur in the first few weeks after an injury permit dating in this acute period. In the second, I illustrate how patterns of injury with specific features can date with some accuracy the time an injury occurs, which may be much earlier than the time when the image was obtained. This tends to be dating that occurs in the chronic period. Chapters are presented in a logical progression beginning with the general appearance of normal brain and progressing to the way abnormalities manifest themselves on CT, MR, and US images. The emphasis in these discussions is on the appearance of edema and of hemorrhage, as these two findings are the brain s most common response to injury. I discuss the role of contrast in central v
vi Preface nervous system (CNS) imaging, which will lead to a discussion of how infarction (death of tissue), ischemia (decreased blood flow to tissue that is still potentially alive and recoverable), and hemorrhage change with time as seen on CT, MR, and US images, and a dialog of what different patterns of injury tells us about the mechanism, severity, and duration of injury. This then permits a statement of what I consider the overriding principles of image interpretation as they relate to legal matters and a frank discussion, based on everything mentioned up to this point, of what can and what cannot be said in a medical legal setting based on the imaging findings. The last chapter is on the root causes for uncertainty in dating neurologic events from imaging studies.
Acknowledgments The following individuals were instrumental in helping me bring this book to publication. I wish to thank them all. Dr. James Scatliff and Dr. Robert Whaley - my Neuroradiology mentors at UNC in Chapel Hill The Vanderbilt radiology fellows and attending staff who assisted with case acquisitions The members of the Neuroradiology section at Vanderbilt who assisted me Dr. Jeanette Norton for her assistance in multiple revisions of the first chapter on anatomy. Janet Staley for her effort as an editorial and grammatical assistant who reviewed the entire manuscript several times prior to submission. Dominic Doyle for his preparation of the illustrations Administrative secretarial assistance from Tara Timmons, Debbie Holland and Dewain Patterson The Springer editorial staff in both New York and in India And most importantly, Lynn and our family, Erin, David, John and Carrie. They have continually supported me in my effort to write this book with their encouragement and understanding. It is to them that I dedicate this book. vii
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Contents Part I Fundamentals 1 The Structure of the Normal Brain and Its Imaging Appearance... 3 Introduction... 3 The Layers of the Scalp, Skull, and Meninges... 4 The Scalp... 4 The Skull... 4 The Epidural Space... 5 The Dura... 6 The Subdural Space... 6 The Arachnoid Membrane and Subarachnoid Space... 7 The Pia... 8 The Visible Outer Surface of the Brain... 8 The Imaging Appearance of the Normal Scalp, Skull, and Meninges... 8 Brief Overview of Brain Anatomy... 9 The Blood Supply to the Brain... 10 The Arterial Vessels... 10 The Venous Vessels... 14 Methods for Imaging the Intracerebral Arteries and Venous Structures... 16 The Cerebral Hemispheres... 20 The Lobes of the Cerebral Hemispheres... 20 The Cortical Gray Matter... 22 White Matter of the Cerebral Hemispheres... 22 Deep Gray Matter Nuclei of the Cerebral Hemispheres... 23 Imaging Appearance of the Normal Cerebral Hemispheres... 24 Cerebellum... 27 Gray Matter of the Cerebellar Hemispheres... 32 Deep Cerebellar White Matter... 32 Imaging Appearance of the Cerebellar Hemispheres... 32 Brainstem... 32 The Imaging Appearance of the Normal Brain Stem... 35 Ventricles... 35 The Ventricles Normal Shape, Size, and Position... 35 The Nonventricular CSF Spaces (Cisterns)... 37 CSF Dynamics... 38 Imaging Appearance of the Normal Ventricles, CSF Spaces,and CSF Dynamics... 40 References... 40 ix
x Contents 2 The General Appearance of Edema and Hemorrhage on CT, MR and US (Including a General Introduction to CT, MR and US Scanning)... 43 Introduction... 43 CT Scanning: The Absolute Basics... 43 MR Scanning: The Absolute Basics... 45 US Scanning: The Absolute Basics... 47 Edema... 48 Edema on CT Scanning... 51 Edema on MR Scanning... 52 Edema on US Scanning... 52 The General Appearance of Hemorrhage... 53 Hemorrhage on CT Scanning... 54 Hemorrhage on MR Scanning... 55 Hemorrhage on Ultrasound... 55 Chapter Summary... 57 References... 58 3 The Basics of Contrast and Its Role in Dating... 59 Introduction... 59 Basic Principles to Understanding the Use of Contrast in the Brain... 59 For CT Contrast... 61 For MR Contrast... 61 MR Contrast Dose and Pulse Sequence Choice... 62 MR Contrast Effects vs. Flow Void Effects... 62 Clinical Importance of Contrast Enhancement... 67 References... 67 4 How the Imaging Appearance of Edema and Hemorrhage Change Over Time on CT, MR, and US: Dynamic (Acute) Dating... 69 Introduction... 69 Changes of Edema Over Time on CT... 70 Changes of Edema Over Time on MR... 71 Locations of Possible Intracerebral Hemorrhage... 74 Changes of Hemorrhage Over Time on CT... 75 Changes of Hemorrhage Over Time on MR... 76 T1 Changes Over Time Within a Hemorrhage on MR Scanning... 81 T2 Changes Over Time Within a Hemorrhage on MR Scanning... 81 FLAIR Changes Over Time Within a Hemorrhage on MR Scanning... 84 Gradient Echo (Magnetic Susceptibility-Weighted) Changes Over Time Within a Hemorrhage on MR... 85 Changes of Edema and Hemorrhage Over Time on US... 85 References... 86 5 Patterns of Parenchymal Injury: Pattern (Chronic) Dating... 89 Introduction... 89 Beginning Principles... 89 Factors Affecting the Outcome of a Region of Ischemia... 90 Regional Variations in Perfusion... 90 Variations in Severity of Insult... 91 Variations in Duration of Injury... 91 Variations in Metabolic Activity... 92
Contents xi Patterns of Parenchymal Injury... 92 Patterns Where There Has Been Total Loss of a Focal Region of Brain Parenchyma... 92 Injuries That Affect the Brain Diffusely... 94 Common Patterns That Show Targeting, with Partial or Total Cell Loss... 95 References... 100 Part II Application to the Medical-Legal Setting 6 Principles of Dynamic Dating in the Medical Legal Setting... 103 Introduction... 103 General Comments on Dating an Event by CT and/or MR and/or US in the First 2 Weeks... 103 Dating Edema by CT Alone... 104 Dating Hemorrhage by CT Alone... 104 Dating Edema by MR Alone... 105 Dating Hemorrhage by MR Alone... 106 Dating Edema by US Alone... 107 Dating Hemorrhage by US Alone... 107 Dating Events by CT in Conjunction with MR, and with US... 107 7 Principles of Pattern Dating in the Medical Legal Setting... 111 Introduction... 111 Concerning Edema and Infarction... 111 Concerning Hemorrhage... 113 Conclusion... 115 8 Therefore, What Can Be Said Based on the Images, and What Can t Be Said Based on the Images... 117 Introduction... 117 9 The Root Causes of Uncertainty in Dating Neurologic Events Based on Imaging Findings... 119 Introduction... 119 The Interpretation of the Available Images Varies from Expert to Expert, with Disagreement as to Whether Certain Findings Are Present or Not... 120 Image Findings Are Acknowledged to be Present by All Observers; However, the Interpretation of the Findings Varies from Expert to Expert... 120 Multiple Findings are Present for Which the Neuroradiological Dating Methods We Have Discussed Produce Conflicting Time Periods as to the Probable Occurrence of the Injury... 121 Radiographic Findings Which Are at Odds with the Clinical Picture... 121 Conclusion... 121 Index... 123
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