Richard S.Snell,M.R.C.S., L.R.C.P., MB, BS, MD, PhD. Emeritus ... Professor of
Anatomy, Harvard Medical School. ... Nervous System—anatomy & histology.
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CLINICAL NEUROANATOMY S E V E N T H
E D I T I O N
Richard S.Snell, M.R.C.S., L.R.C.P., MB, BS, MD, PhD Emeritus Professor of Anatomy George Washington University School of Medicine and Health Sciences Washington, DC Formerly Associate Professor of Anatomy and Medicine,Yale University Medical School; Lecturer in Anatomy King’s College University of London; and Visiting Professor of Anatomy, Harvard Medical School.
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Acquisitions Editor: Crystal Taylor Managing Editor: Kelly Horvath Marketing Manager: Emilie Linkins Managing Editor, Production: Eve Malakoff-Klein Designer: Stephen Druding Compositor: Aptara Seventh Edition Copyright © 2010, 2006, 2001, 1997, 1992, 1987, 1980 Lippincott Williams & Wilkins, a Wolters Kluwer business. 351 West Camden Street Baltimore, MD 21201
530 Walnut Street Philadelphia, PA 19106
Printed in China All rights reserved.This book is protected by copyright. No part of this book may be reproduced or transmitted in any form or by any means,including as photocopies or scanned-in or other electronic copies, or utilized by any information storage and retrieval system without written permission from the copyright owner, except for brief quotations embodied in critical articles and reviews. Materials appearing in this book prepared by individuals as part of their official duties as U.S. government employees are not covered by the above-mentioned copyright.To request permission,please contact Lippincott Williams & Wilkins at 530 Walnut Street, Philadelphia, PA 19106, via email at
[email protected], or via website at lww.com (products and services). 9 8 7 6 5 4 3 2 1 Library of Congress Cataloging-in-Publication Data Snell, Richard S. Clinical neuroanatomy / Richard S. Snell. — 7th ed. p. ; cm. Includes bibliographical references and index. ISBN 978-0-7817-9427-5 1. Neuroanatomy. I.Title. [DNLM: 1. Nervous System—anatomy & histology. WL 101 S671c 2010] QM451.S64 2010 616.8—dc22 2008040897
DISCLAIMER Care has been taken to confirm the accuracy of the information present and to describe generally accepted practices. However, the authors, editors, and publisher are not responsible for errors or omissions or for any consequences from application of the information in this book and make no warranty, expressed or implied, with respect to the currency, completeness, or accuracy of the contents of the publication. Application of this information in a particular situation remains the professional responsibility of the practitioner; the clinical treatments described and recommended may not be considered absolute and universal recommendations. The authors, editors, and publisher have exerted every effort to ensure that drug selection and dosage set forth in this text are in accordance with the current recommendations and practice at the time of publication. However, in view of ongoing research, changes in government regulations, and the constant flow of information relating to drug therapy and drug reactions, the reader is urged to check the package insert for each drug for any change in indications and dosage and for added warnings and precautions.This is particularly important when the recommended agent is a new or infrequently employed drug. Some drugs and medical devices presented in this publication have Food and Drug Administration (FDA) clearance for limited use in restricted research settings. It is the responsibility of the health care provider to ascertain the FDA status of each drug or device planned for use in their clinical practice. To purchase additional copies of this book, call our customer service department at (800) 638-3030 or fax orders to (301) 223-2320. International customers should call (301) 223-2300. Visit Lippincott Williams & Wilkins on the Internet: http://www.lww.com. Lippincott Williams & Wilkins customer service representatives are available from 8:30 am to 6:00 pm, EST.
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P R E FA C E
T
his book contains the basic neuroanatomical facts necessary for the practice of medicine. It is suitable for medical students, dental students, nurses, and allied health students. Residents fnd this book useful during their rotations. The functional organization of the nervous system has been emphasized and indicates how injury and disease can result in neurologic deficits. The amount of factual information has been strictly limited to that which is clinically important. In this edition, the content of each chapter has been reviewed, obsolete material has been discarded, and new material added. Each chapter is divided into the following categories:
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Clinical Example. A short case report that serves to dramatize the relevance of neuroanatomy introduces each chapter. Chapter Objectives. This section details the material that is most important to learn and understand in each chapter. Basic Neuroanatomy. This section provides basic information on neuroanatomical structures that are of clinical importance. Numerous examples of normal radiographs, CT scans, MRIs, and PET scans are also provided. Many cross-sectional diagrams have been included to stimulate students to think in terms of three-dimensional anatomy, which is so important in the interpretation of CT scans and MRI images. Clinical Notes. This section provides the practical application of neuroanatomical facts that are essential in clinical practice. It emphasizes the structures that the physician
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will encounter when making a diagnosis and treating a patient. It also provides the information necessary to understand many procedures and techniques and notes the anatomical “pitfalls” commonly encountered. Clinical Problem Solving. This section provides the student with many examples of clinical situations in which a knowledge of neuroanatomy is necessary to solve clinical problems and to institute treatment; solutions to the problems are provided at the end of the chapter. Review Questions. The purpose of the questions is threefold: to focus attention on areas of importance, to enable students to assess their areas of weakness, and to provide a form of self-evaluation when questions are answered under examination conditions. Some of the questions are centered around a clinical problem that requires a neuroanatomical answer. Solutions to the problem are provided at the end of each chapter.
In addition to the full text from the book, an interactive Review Test, including over 450 questions, is provided online. The book is extensively illustrated. The majority of the figures have been kept simple and are in color. As in the previous edition, a concise Color Atlas of the dissected brain is included prior to the text. This small but important group of colored plates enables the reader to quickly relate a particular part of the brain to the whole organ. References to neuroanatomical literature are included should readers wish to acquire a deeper knowledge of an area of interest. R.S.S.
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A C K N O W L E D G M E N T S
I
am greatly indebted to the following colleagues who provided me with photographic examples of neuroanatomical material: Dr. N. Cauna, Emeritus Professor of Anatomy, University of Pittsburgh School of Medicine; Dr. F. M. J. Fitzgerald, Professor of Anatomy, University College, Galway, Ireland; and Dr. A. Peters, Professor of Anatomy, Boston University School of Medicine. My special thanks are owed to Larry Clerk, who, as a senior technician in the Department of Anatomy at the George Washington University School of Medicine and Health Sciences, greatly assisted me in the preparation of neuroanatomical specimens for photography. I am also grateful to members of the Department of Radiology for the loan of radiographs and CT scans that have been reproduced in different sections of this book. I am most
grateful to Dr. G. Size of the Department of Radiology at Yale University Medical Center for examples of CT scans and MRI images of the brain. I also thank Dr. H. Dey, Director of the PET Scan Unit of the Department of Radiology, Veterans Affairs Medical Center, West Haven, Connecticut, for several examples of PET scans of the brain. I thank the medical photographers of the Department of Radiology at Yale for their excellent work in reproducing the radiographs. As in the past, I express my sincere thanks to Myra Feldman and Ira Grunther, AMI, for the preparation of the very fine artwork. Finally, to the staff of Lippincott Williams & Wilkins, I again express my great appreciation for their continued enthusiasm and support throughout the preparation of this book.
To My Students—Past, Present, and Future This book is designed so that the information is presented without masses of confusing detail involving complicated neural connections.The arrangement permits the students and future health providers to quickly recall the essential features necessary for the diagnosis and treatment of patients.
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C O N T E N T S
Preface . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . iii Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . iv Color Atlas of Brain . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . xi CHAPTER 1
Introduction and Organization of the Nervous System Chapter Objectives 2 Central and Peripheral Nervous Systems 2 Major Divisions of the Central Nervous System 2 Major Divisions of the Peripheral Nervous System 10 Early Development of the Nervous System 14 Clinical Notes 17 Clinical Problem Solving 28 Answers and Explanations to Clinical Problem Solving Review Questions 30 Answers and Explanations to Review Questions 31 Additional Reading 32
CHAPTER 2
CHAPTER 3
29
The Neurobiology of the Neuron and the Neuroglia Chapter Objectives 34 Definition of a Neuron 34 Varieties of Neurons 34 Structure of the Neuron 34 Definition of Neuroglia 53 Astrocytes 53 Oligodendrocytes 54 Microglia 57 Ependyma 58 Extracellular Space 59 Clinical Notes 61 Clinical Problem Solving 63 Answers and Explanations to Clinical Problem Solving Review Questions 65 Answers and Explanations to Review Questions 67 Additional Reading 69
33
64
Nerve Fibers, Peripheral Nerves, Receptor and Effector Endings, Dermatomes, and Muscle Activity Chapter Objectives 71 Nerve Fibers 71 Peripheral Nerves 80 Conduction in Peripheral Nerves Receptor Endings 86
1
70
84 v
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Effector Endings 95 Segmental Innervation of Skin 100 Segmental Innervation of Muscles 100 Muscle Tone and Muscle Action 101 Summation of Motor Units 103 Muscle Fatigue 104 Posture 104 Clinical Notes 107 Clinical Problem Solving 120 Answers and Explanations to Clinical Problem Solving Review Questions 126 Answers and Explanations to Review Questions 129 Additional Reading 131
CHAPTER 4
123
The Spinal Cord and the Ascending and Descending Tracts Chapter Objectives 133 A Brief Review of the Vertebral Column 133 Gross Appearance of the Spinal Cord 137 Structure of the Spinal Cord 138 The Ascending Tracts of the Spinal Cord 143 Anatomical Organization 143 Functions of the Ascending Tracts 144 The Descending Tracts of the Spinal Cord 153 Anatomical Organization 153 Functions of the Descending Tracts 154 Corticospinal Tracts 155 Reticulospinal Tracts 157 Tectospinal Tract 158 Rubrospinal Tract 159 Vestibulospinal Tract 159 Olivospinal Tract 160 Descending Autonomic Fibers 160 Intersegmental Tracts 161 Reflex Arc 162 Influence of Higher Neuronal Centers on the Activities of Spinal Reflexes Renshaw Cells and Lower Motor Neuron Inhibition 164 Clinical Notes 165 Clinical Problem Solving 177 Answers and Explanations to Clinical Problem Solving 178 Review Questions 181 Answers and Explanations to Review Questions 183 Additional Reading 185
CHAPTER 5
The Brainstem Chapter Objectives 187 A Brief Review of the Skull 187 The Cranial Cavity 192 Introduction to the Brainstem 196 Gross Appearance of the Medulla Oblongata 197 Internal Structure 198 Gross Appearance of the Pons 206 Internal Structure of the Pons 208 Gross Appearance of the Midbrain 210 Internal Structure of the Midbrain 210 Clinical Notes 217 Clinical Problem Solving 221 Answers and Explanations to Clinical Problem Solving Review Questions 224 Answers and Explanations to Review Questions 227 Additional Reading 229
132
164
186
222
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CHAPTER 6
The Cerebellum and Its Connections Chapter Objective 231 Gross Appearance of the Cerebellum 231 Structure of the Cerebellum 231 Cerebellar Cortical Mechanisms 236 Cerebellar Afferent Fibers 237 Cerebellar Efferent Fibers 240 Functions of the Cerebellum 242 Clinical Notes 243 Clinical Problem Solving 245 Answers and Explanations to Clinical Problem Solving Review Questions 247 Answers and Explanations to Review Questions 249 Additional Reading 250
CHAPTER 7
230
246
The Cerebrum
251
Chapter Objectives 252 Subdivisions of the Cerebrum 252 Diencephalon 252 General Appearance of the Cerebral Hemispheres 257 Main Sulci 258 Lobes of the Cerebral Hemisphere 260 Internal Structure of the Cerebral Hemispheres 262 Clinical Notes 271 Clinical Problem Solving 277 Answers and Explanations to Clinical Problem Solving 278 Review Questions 279 Answers and Explanations to Review Questions 281 Additional Reading 283
CHAPTER 8
The Structure and Functional Localization of the Cerebral Cortex Chapter Objective 285 Structure of the Cerebral Cortex 285 Mechanisms of the Cerebral Cortex 287 Cortical Areas 288 Cerebral Dominance 295 Clinical Notes 296 Clinical Problem Solving 298 Answers and Explanations to Clinical Problem Solving Review Questions 300 Answers and Explanations to Review Questions 302 Additional Reading 303
CHAPTER 9
CHAPTER 10
299
The Reticular Formation and the Limbic System Chapter Objective 305 Reticular Formation 305 Limbic System 307 Clinical Notes 312 Clinical Problem Solving 312 Answers and Explanations to Clinical Problem Solving Review Questions 313 Answers and Explanations to Review Questions 314 Additional Reading 315
317
304
313
The Basal Nuclei (Basal Ganglia) and Their Connections Chapter Objective Terminology 317
284
316
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Corpus Striatum 317 Amygdaloid Nucleus 319 Substantia Nigra and Subthalamic Nuclei 319 Claustrum 319 Connections of the Corpus Striatum and Globus Pallidus 319 Connections of the Corpus Striatum 319 Connections of the Globus Pallidus 319 Functions of the Basal Nuclei 320 Clinical Notes 322 Clinical Problem Solving 327 Answers and Explanations to Clinical Problem Solving 327 Review Questions 327 Answers and Explanations to Review Questions 329 Additional Reading 329
CHAPTER 11
The Cranial Nerve Nuclei and Their Central Connections and Distribution Chapter Objective 332 The 12 Cranial Nerves 332 Organization of the Cranial Nerves 332 Olfactory Nerves (Cranial Nerve I) 335 Optic Nerve (Cranial Nerve II) 336 Oculomotor Nerve (Cranial Nerve III) 340 Trochlear Nerve (Cranial Nerve IV) 340 Trigeminal Nerve (Cranial Nerve V) 341 Abducent Nerve (Cranial Nerve VI) 344 Facial Nerve (Cranial Nerve VII) 346 Vestibulocochlear Nerve (Cranial Nerve VIII) 348 Glossopharyngeal Nerve (Cranial Nerve IX) 350 Vagus Nerve (Cranial Nerve X) 352 Accessory Nerve (Cranial Nerve XI) 354 Hypoglossal Nerve (Cranial Nerve XII) 356 Clinical Notes 358 Clinical Problem Solving 363 Answers and Explanations to Clinical Problem Solving Review Questions 365 Answers and Explanations to Review Questions 368 Additional Reading 369
CHAPTER 12
364
The Thalamus and Its Connections
371
Chapter Objective 372 General Appearances of the Thalamus 372 Subdivisions of the Thalamus 372 Connections of the Thalamus 375 Function of the Thalamus 375 Clinical Notes 378 Clinical Problem Solving 378 Answers and Explanations to Clinical Problem Solving Review Questions 379 Answers and Explanations to Review Questions 380 Additional Reading 381
CHAPTER 13
378
The Hypothalamus and Its Connections Chapter Objectives 383 The Hypothalamus 383 Hypothalamic Nuclei 383 Afferent Nervous Connections of the Hypothalamus
331
382
385
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Efferent Nervous Connections of the Hypothalamus 387 Connections of the Hypothalamus With the Hypophysis Cerebri Functions of the Hypothalamus 389 Clinical Notes 392 Clinical Problem Solving 392 Answers and Explanations to Clinical Problem Solving 393 Review Questions 393 Answers and Explanations to Review Questions 394 Additional Reading 395
CHAPTER 14
388
The Autonomic Nervous System
396
Chapter Objective 397 Organization of the Autonomic Nervous System 397 The Large Autonomic Plexuses 400 Autonomic Ganglia 400 Preganglionic Transmitters 400 Fast, Slow, and Inhibitory Synaptic Potentials 401 Ganglion-Stimulating Agents 402 Ganglion-Blocking Agents 402 Postganglionic Nerve Endings 402 Postganglionic Transmitters 402 Other Postganglionic Transmitters 403 Blocking of Cholinergic Receptors 403 Blocking of Adrenergic Receptors 403 Higher Control of the Autonomic Nervous System 404 The “Enteric Nervous System” 404 Functions of the Autonomic Nervous System 404 Important Anatomical, Physiologic, and Pharmacologic Differences Between the Sympathetic and Parasympathetic Parts of the Autonomic Nervous System 405 Some Important Autonomic Innervations 407 Some Important Physiological Reflexes Involving the Autonomic Nervous System Clinical Notes 417 Clinical Problem Solving 420 Answers and Explanations to Clinical Problem Solving 421 Review Questions 422 Answers and Explanations to Review Questions 425 Additional Reading 426
CHAPTER 15
The Meninges of the Brain and Spinal Cord Chapter Objectives 428 Meninges of the Brain 428 Meninges of the Spinal Cord 436 Clinical Notes 438 Clinical Problem Solving 441 Answers and Explanations to Clinical Problem Solving Review Questions 443 Answers and Explanations to Review Questions 444 Additional Reading 444
CHAPTER 16
427
442
The Ventricular System, the Cerebrospinal Fluid, and the Blood-Brain and Blood–Cerebrospinal Fluid Barriers Chapter Objectives 446 Ventricular System 446 Subarachnoid Space 457 Cerebrospinal Fluid 458 Blood-Brain and Blood–Cerebrospinal Fluid Barriers Clinical Notes 466
415
462
445
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Clinical Problem Solving 467 Answers and Explanations to Clinical Problem Solving Review Questions 469 Answers and Explanations to Review Questions 472 Additional Reading 473
CHAPTER 17
The Blood Supply of the Brain and Spinal Cord Chapter Objectives 475 Blood Supply of the Brain 475 Brain Capillaries 481 Cerebral Circulation 481 Blood Supply of the Spinal Cord 481 Clinical Notes 483 Clinical Problem Solving 493 Answers and Explanations to Clinical Problem Solving Review Questions 497 Answers and Explanations to Review Questions 499 Additional Reading 500
CHAPTER 18
474
495
The Development of the Nervous System Chapter Objectives 502 Spinal Cord 502 Brain 504 Clinical Notes 512 Clinical Problem Solving 516 Answers and Explanations to Clinical Problem Solving Review Questions 516 Answers and Explanations to Review Questions 518 Additional Reading 519
APPENDIX
468
501
516
Important Neuroanatomical Data of Clinical Significance
521
Index
529
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COLOR ATLAS OF BRAIN
Frontal pole
Longitudinal fissure Precentral sulcus
Frontal lobe
Precentral gyrus
Central sulcus Left cerebral hemisphere
Postcentral gyrus Postcentral sulcus
Parietal lobe
Occipital lobe Occipital pole
Frontal lobe
Longitudinal fissure
Olfactory tract Right cerebral hemisphere
Optic chiasma
Temporal lobe Oculomotor nerve Midbrain Pons Pyramid
Cerebellum Olive Medulla oblongata
Figure CA-1
Top: Superior view of the brain. Bottom: Inferior view of the brain.
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xii
Color Atlas of Brain
Longitudinal fissure
Right cerebral hemisphere Superior frontal gyrus
Frontal pole Pons
Medulla oblongata
Temporal pole
Parieto-occipital sulcus
Left cerebral hemisphere
Occipital lobe
Occipital pole
Horizontal fissure of cerebellum Cavity of fourth ventricle
Vermis of cerebellum
Inferior cerebellar peduncle
Left cerebellar hemisphere
Gracile tubercle
Medulla oblongata
Figure CA-2
Cuneate tubercle
Top: Anterior view of the brain. Bottom: Posterior view of the brain.
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Color Atlas of Brain xiii
Postcentral sulcus
Postcentral gyrus
Central sulcus
Precentral gyrus
Precentral sulcus Superior frontal gyrus
Parieto-occipital sulcus
Middle frontal gyrus Inferior frontal gyrus
Occipital lobe
Lateral sulcus
Superior temporal gyrus Right cerebellar hemisphere
Middle temporal gyrus
Medulla oblongata
Inferior temporal gyrus
Corpus callosum
Central sulcus
Septum pellucidum Fornix Anterior commissure
Cingulate gyrus Cerebral aqueduct of midbrain Parieto-occipital sulcus Cuneus
Optic chiasma
Calcarine sulcus
Temporal lobe
Vermis of cerebellum
Pons Medulla oblongata
Cavity of fourth ventricle
Figure CA-3 Top: Right lateral view of the brain. Bottom: Medial view of the right side of the brain following median sagitttal section.
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Color Atlas of Brain
Anterior horn of lateral ventricle Claustrum
Insula
Lateral sulcus
Lateral ventricle
Corpus callosum Septum pellucidum Caudate nucleus
Lentiform nucleus
Corpus callosum
Caudate nucleus Third ventricle Fornix Lentiform nucleus
Medial thalamic nuclei
Mammillary body
Lateral thalamic nuclei Optic nerve Corpus callosum
Choroid plexus in lateral ventricle Pons
Figure CA-4 Coronal sections of the brain passing through the anterior horn of the lateral ventricle (top), the mammillary bodies (middle), and the pons (bottom).
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Color Atlas of Brain xv
Anterior horn of lateral ventricle Internal capsule (anterior limb) Genu of internal capsule
Genu of corpus callosum Head of caudate nucleus Anterior column of fornix Claustrum Putamen
Internal capsule (posterior limb) Third ventricle
Globus pallidus Thalamus
Posterior horn of lateral ventricle
Splenium of corpus callosum
Caudate nucleus
Corpus callosum
Thalamus Lentiform nucleus
Lentiform nucleus
Lateral ventricle Fornix Third ventricle
Internal capsule Crus cerebri of midbrain
Third ventricle (inferior part)
Pons Medulla oblongata
Figure CA-5
Cerebellum
Top: Horizontal section of the cerebrum showing the lentiform nucleus, the caudate nucleus, the thalamus, and the internal capsule. Bottom: Oblique coronal section of the brain.
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Color Atlas of Brain
Olfactory bulb Olfactory tract Optic nerve Optic chiasma Optic tract Trigeminal nerve Oculomotor nerve Vestibulocochlear nerve Roots of glossopharyngeal, vagus, and cranial part of accessory nerves Roots of hypoglossal nerve
Trochlear nerve Trigeminal nerve
Spinal root of accessory nerve
Gyrus rectus Longitudinal fissure
Optic chiasma Uncus Crus cerebri Trochlear nerve Pons
Infundibulum Mamillary body Posterior perforating substance in floor of interpeduncular fossa Oculomotor nerve Groove for basilar artery
Inferior cerebellar peduncle Olive
Figure CA-6
Anterior median fissure
Pyramid
Top: Inferior view of the brain showing cranial nerves. The abducent and facial nerves cannot be seen. Bottom: Enlarged inferior view of the central part of the brain.
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Color Atlas of Brain xvii
Vestibular area in floor of fourth ventricle Striae medullares
Midbrain
Median sulcus
Medial eminence Facial colliculus
Sulcus limitans
Hypoglossal triangle
Right cerebellar hemisphere (cut)
Vagal triangle
Gracile tubercle
Anterior lobe
Superior aspect of vermis
Primary fissure
Culmen Middle lobe Declive Left cerebellar hemisphere Right cerebellar hemisphere
Middle cerebellar peduncle
Central lobule
Flocculus Tonsil
Inferior aspect of vermis Tuber
Right cerebellar hemisphere
Figure CA-7
Left cerebellar hemisphere
Top: Posterior view of the brainstem. The greater part of the cerebellum had been removed to expose the floor of the fourth ventricle. Middle: Superior view of the cerebellum showing the vermis and right and left cerebellar hemispheres. Bottom: Inferior view of the cerebellum showing the vermis and right and left cerebellar hemispheres.
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Color Atlas of Brain
Anterior column of fornix
Interventricular foramen (entrance to lateral ventricle) Fornix Thalamus
Septum pellucidum
Central sulcus
Cingulate gyrus
Corpus callosum
Site of third ventricle Splenium Pineal body
Genu of corpus callosum Rostrum Posterior commissure Superior medullary velum Choroid plexus of the fourth ventricle Vermis of cerebellum Anterior commissure
Foramen of Magendie Tuber cinereum
Lamina terminalis
Optic chiasma
Region of hypothalamus
Mamillary body
Pons
Fourth ventricle
Central canal
Medulla oblongata
Cerebral aqueduct of midbrain
Figure CA-8 Enlarged medial view of the right side of the brain following median sagittal section, showing the continuity of the central canal, fourth ventricle, cerebral aqueduct, and the third ventricle and entrance into the lateral ventricle through the interverntricular foramen.
