text:
Clinical Neuropathology. Text And Color Atlas [PDF]
Authors: Catherine Haberland
This full-color text and atlas, provides a complete overview of the structural alterations of important nervous system diseases, along with their clinical manifestations. Readers will understand the goals of the neuropathologic exam, the histologic reaction of neural tissue to diseases, and the pathologic conditions particular to the nervous system. All topics are highlighted by gross and histologic images of the brain and spinal cord, and all integrate the most recent scientific studies.
TEXT AND COLOR ATLAS
This full-color text and atlas is organized simply and logically with a core focus on major disease categories. The first of 14 chapters discusses the goals of the neuropathologic exam with representative pictures of the brain and spinal cord, and tables of histologic methods. The second chapter presents characteristic histologic reactions of neural tissue to diseases and pathologic conditions endemic to the nervous system. Additional chapters address major disease categories: • Pathologic and clinical characteristics • Gross, histologic, and clinical features of individual diseases • Pathogenic mechanisms • Case studies • End-of-chapter review questions with answers This complete and current review of the field is an invaluable reference for neurologists, pathologists, and residents. About the Author Catherine Haberland, MD, is a Clinical Professor of Neurology, Pathology, and Psychiatry at the Chicago Medical School at Rosalind Franklin University, and Attending Neurologist and Neuropathologist at the Veterans Administration Medical Center, North Chicago, Illinois.
Demos Medical Publishing 386 Park Avenue South, Suite 301 New York, NY 10016 www.demosmedpub.com
CLINICAL NEUROPATHOLOGY
Clinical Neuropathology: Text and Color Atlas provides a complete overview of the structural alterations of important nervous system diseases, along with their clinical manifestations. You will get a full understanding of the goals of the neuropathologic exam, the histologic reaction of neural tissue to diseases, and the pathologic conditions particular to the nervous system. All topics are highlighted by gross and histologic images of the brain and spinal cord, and all integrate the most recent scientific studies.
CLINICAL NEUROPATHOLOGY TEXT AND C OLOR ATLAS
CATHERINE HABERLAND
Clinical Neuropathology TEXT AND COLOR ATLAS
CATHERINE HABERLAND, MD The Chicago Medical School at Rosalind Franklin University Departments of Neurology and Pathology and Section of Neurology and Neuropathology Laboratory at the Veterans Administration Medical Center at North Chicago, Illinois
8 DEMOS MEDICAL PUBLISHING, LLC 386 Park Avenue South New York, New York 10016 Visit our website at www.demosmedpub.com © 2007 by Demos Medical Publishing, LLC. All rights reserved. This book is protected by copyright. No part of it may be reproduced, stored in a retrieval system, or transmitted in any form or by any means, electronic, mechanical, photocopying, recording, or otherwise, without the prior written permission of the publisher. Senior Editor: Craig Percy LIBRARY OF CONGRESS CATALOGING-IN-PUBLICATION DATA
Haberland, Catherine. Clinical neuropathology : text and color atlas / Catherine Haberland. p. ; cm. Includes bibliographical references and index. ISBN-13: 978-1-888799-97-2 (softcover) ISBN-10: 1-888799-97-8 (softcover) 1. Nervous system—Diseases—Atlases. I. Title. [DNLM: 1. Nervous System Diseases—pathology—Atlases. WL 17 H114c 2007] RC347.H33 2007 616.8—dc22 2006020445 Text designed by Steven Pisano Cover designed by Cathleen Elliott MANUFACTURED IN THE UNITED STATES OF AMERICA
06 07 08 09 10 5 4 3 2 1
Preface ix Acknowledements xi
Artificial Cerebral Changes 29
Introduction to Clinical Neuropathology
Cerebral Hypoxia Etiology 33
Basics of Neuropathology
Pathology 34
Reactions of Neural Tissue to Diseases
Permanent Global Ischemia: Brain Death
Types of Degenerations in the Central Nervous System 19 Cerebral Edema 21
Clinical Features 36 37
Cerebral Pathology in Chronic Epilepsy 37 Bibliography 41 Review Questions
Cerebral Changes Associated With Intracranial Expanding Mass Lesions 22 Clinical Manifestations of Intracranial Expanding Mass Lesions and Rising Intracranial Pressure 25 Hydrocephalus 26 Cerebral Changes in Physiologic Aging 27
Cerebrovascular Diseases Etiology, Pathology, and Clinical Aspects of Stroke 43 Various Stroke Etiologies: Stroke in the Young
CONT ENTS
Cerebral Pathology in Arteriolosclerosis:
Demyelinating Diseases
Vascular Dementia 77 Bibliography 80 Review Questions
Diseases with Autoimmune Pathogenesis
Diseases with Probable Autoimmune Pathogenesis 166 Bibliography 167 CHAPTER 5
Dementias 84 Motor Neuron Diseases 97
Extrapyramidal Diseases 100 Cerebellar and Spinocerebellar Degenerations
Multiple System Atrophy 112 Bibliography 116 Review Questions
Hereditary Neurometabolic Diseases Lysosomal Diseases 170
Peroxisomal Diseases 179 Leukodystrophies 182 Mitochondrial Diseases
Amino Acid Metabolic Diseases 189
Carbohydrate Metabolic Diseases
Bacterial Infections 120
Neuroaxonal Dystrophies 193
Viral Infections 124
Miscellaneous Neurometabolic Diseases 194
Mycotic Infections 136
Bibliography 196
Syphilitic Infections 138
Copper Metabolic Diseases
Parasitic Infections 142 Miscellaneous Infections 147 Bibliography 148 Review Questions
C H A P T E R 10
Acquired Neurometabolic Diseases
Prion Diseases: Transmissible Spongiform Encephalopathies
Metabolic Encephalopathies 202
Animal Prion Diseases
Calcium Metabolic Disorders 205 Neurologic Complications of Chronic Alcoholism
Human Prion Diseases 152
Toxic Diseases of the Nervous System 210
Tumors of the Central Nervous System
Congenital Malformations of the Central Nervous System
General Aspects 213
Neural Tube Defects: Dysraphic Disorders 274
Tumors of the Neuroepithelium 216
Malformation of the Prosencephalon:
Tumors of the Meninges 231
Tumors of the Pituitary Gland and Sellar Region 235
Malformations of the Cerebral Hemispheres 279
Germ Cell Tumors 237
Malformations of the Midline Structures
Tumors of the Cranial and Spinal Nerves Maldevelopmental Tumors and Cysts
and Ventricles 284
Malformations of the Cerebellum 285
Hemangiomas 244
Malformations of the Brainstem 287
Lymphomas and Hematopoietic Tumors 245
Disorders of Brain Weight
Primary Central Nervous System Lymphomas Metastatic Tumors 246
Meningeal and Vascular Anomalies 288 Phakomatoses: Ectomesodermal
Tumors of the Spinal Cord, Nerve Roots, and Meninges
Dysgenetic Syndromes 288 Congenital and Neonatal Hydrocephalus 291
Tumors of the Cranium and the Spine
Chromosomal Disorders
Primary Intracranial Tumors in Children 251
Hereditary Tumor Syndromes 253
Nervous System Complications of Radiation and Chemotherapy
Paraneoplastic Diseases 256 Bibliography 257 Review Questions
Fetal and Perinatal Cerebral Pathology Pathology of Vascular Insults
CH A P T ER 12
Late Sequelae of Vascular Injuries 301
Traumatic Injuries of the Central Nervous System
Metabolic and Toxic Diseases 304 Congenital and Neonatal Infections
Sudden Infant Death Syndrome 307
Blunt Head Injuries 261
Missile Head Injuries 267
Secondary Injuries 267 Clinical Presentation of Cerebral Injuries 268 Spinal Cord Injuries 269 Other Injuries 269 Bibliography 270 Review Questions
Appendix: Answers to Review Questions Index 313
his book, Clinical Neuropathology, is particularly aimed at neurologists, pathologists-intraining, and medical students involved in clinical neurosciences and pathology. It also addresses psychiatrists and those practitioners interested in diseases of the nervous system. Over the last decade, a wealth of information has accumulated, impacting practically all disciplines of neurology. Numerous studies have enriched our knowledge of the molecular and genetic basis of neurodegenerative diseases, the genetics of neoplasms, and the molecular biology of inherited neurometabolic diseases, to mention a few. Some studies prompted new classifications, some opened new therapeutic strategies, and some still await elucidation. The intent of this book is twofold: • To provide a solid background in the structural alterations of common and less common but important nervous system diseases, along with their clinical manifestations. • To incorporate into this background new information selected from the vast number of studies on molecular
pathology and the pathogenesis of major nervous system diseases. The reader thus fi nds easy access to recent developments in basic and clinical neurology. For psychiatrists, this book presents material on the neuropathologic aspects of psychiatric disorders and on the molecular pathology of several dementing diseases. Pathologists-in-training who, due to a regrettable decline in autopsies, lack personal experience of postmortem examination of neurologic diseases, will fi nd useful material here. Medical students can easily access the essential elements of neuropathology, and those with special interests can fi nd sufficient material for their particular needs. The material is divided into 14 chapters. The fi rst chapter deals with the goals of neuropathologic examination. It includes representative pictures of the brain and spinal cord and tables of histologic methods. The second chapter presents characteristic histologic reactions of neural tissue to diseases and pathologic conditions particular to the nervous system. The following chapters deal with major disease categories. Each
P R E FAC E
category contains an overview of general pathologic and clinical characteristics; descriptions of the gross and histologic features of individual diseases, along with their clinical features; and data on the pathogenetic mechanism in particular diseases. Brief case histories and neuroimaging accompany many pathologic illustrations. Tables summarize the characteristic clinical and pathologic features of particular diseases and point out
distinctive features of other related diseases. A number of review questions follow each chapter. The answers are presented in an addendum following the last chapter. The bibliography is limited to the latest and most pertinent references. It is hoped that Clinical Neuropathology will meet the educational needs of the reader.
y thanks to the histologic technicians, photographers, and secretaries for their valuable contribution to this work. I am indebted to Tariq I. Hassan, M.D., Associate Professor of Neurology at the Chicago Medical School at Rosalind Franklin University and Chief of Staff at the Veterans Administration Medical Center at North Chicago for his continuous support for the Neuropathology Laboratory. My special thanks to Frederick Sierles, Professor of Psychiatry at the Chicago Medical School at Rosalind Franklin University for his invaluable comments and advice. I gratefully acknowledge the patience and the tireless assistance of Mrs. Janice Weber-Rasmussen, B.S., at the Neuropathology Laboratory of the Veterans Administration Medical Center at North Chicago in the
technical preparation of the manuscript. And I thank Mr. Craig Percy, Senior Editor of Demos Medical Publishing, and his staff. Gratitude is also due to the late Percival Bailey, M.D., who initiated and supported the Neuropathology Laboratory at the Illinois State Psychiatric Institute and the Illinois State Pediatric Institute. M. Perou, M.D., performed the autopsies at Dixon State School and A. Pedroso, M.D., at Chicago State Hospital. And last, my special thanks to the late Kálmán Sántha, M.D., Chairman of the Department of Neurology and Neurosurgery at the Medical School in Debrecen, Hungary for introducing me to the captivating and rewarding field of Neuropatholgy.
he objectives of the neuropathologic examination are twofold: First, to identify and localize any lesion(s), interpret histologic changes and ultimately, formulate a diagnosis. Second, to correlate the location and histopathologic features of the lesion(s) with the clinical presentation. Fulfi lling these goals requires familiarity with the anatomy and histology of the nervous system. For this purpose, photographs of representative brain and spinal cord slices and myelinstained sections are provided (Figs. 1.1 through 1.5). Knowledge of the normal structure of neural tissue enables the student to recognize pathologic alterations. Thus, Chapter 2 gives a brief description of the histology of neural tissue components, along with their pathologic reactions. The histologic examination requires, in addition to conventional stains, the application of specific stains
for each constituent of the neural tissue: neuron, axon, myelin, glial cells, blood vessels, and meninges. Familiarity with staining methods is necessary to select the appropriate stains for the study of a particular disease. Histochemical stains are valuable for the study of neurometabolic diseases, and immunohistologic stains are essential for diagnosing tumors and defi ning neurodegenerative diseases (Tables 1.1 through 1.3). Electron microscopic examination is performed to defi ne tumors and delineate inherited metabolic diseases. The examination of the histologic sections begins fi rst by identifying the pathologic alterations of each tissue component involved, then combining them into an orderly whole—that is, formulating a diagnosis. The fi nal correlation of the pathologic features with the clinical features becomes a learning experience.
C L I N I C A L N E U RO PAT H O L O G Y: Te x t a n d C o l o r A t l a s
F I G U R E 1.1
Transverse slices of the brain.
F I G U R E 1. 2
Horizontal slices of the brain.
TA B L E 1.1.
Common Neurohistologic Stains Tissue Components
Neurons/glial nuclei
Nissl: thionin, toluidine blue Klüver-Barrerra: cresyl violet Bielschowsky: silver nitrate Bodian: protargol Gallyas: silver nitrate Glees and Marsland: silver nitrate Woelcke: iron hematoxylin Loyez: iron aluminum Klüver-Barrera: Luxol fast blue Klüver-Barrera: Luxol fast blue-cresyl violet Holmes Cajal: gold chloride Hortega: lithium carbonate Holzer: crystal violet Phosphotungstic acid/ hematoxylin (PTAH) Penfield: silver nitrate Hortega: silver carbonate van Gieson Masson: trichrome Gömöri: silver nitrate Verhoeff: hematoxylin Hematoxylin-eosin
Nerve fibers Neurofibrillary tangles Neuritic plaques
Neuron/myelin
Transverse slice of the cerebellum. Nerve fiber/myelin Astrocytes
Oligodendrocytes Microglia Meninges/blood vessels Reticulin fibers Elastic fibers General stain
Myelin-stained section of the A. Pons and. B. Medulla.
Lateral Corticospinal Tract
Fasciculus Cuneatus
Fasciculus Gracilis
Clarke's Column
Posterior Commissure
Posterior Horn
Spinothalamic Tract Ventral Corticospinal Tract
Cervical Cord
Ventral Spinocerebellar Tract Anterior Horn
Myelin-stained sections of the spinal cord.
Anterior B Commissure
Thoracic Cord
Intermediolateral Colum
Sacral Cord
TA B L E 1. 2 .
Common Histochemical Stains
Basic Immunohistologic Stains
Lipid*
Oil-red O Sudan III, IV Sudan B-Black Periodic acid Schiff (PAS) with and without diastase Best carmine Congo-red Congo-red in polarized light Thioflavine S in fluorescent light
Red Orange-red, orange Blue-black Bright rose red
NFP NeuN Synaptophysin S-100 protein NSE GFAP APP CD3 CD20 CD68 Cytokeratin Desmin Vimentin Aβ peptide MBP α-Synuclein TAU Ubiquitin
Glycogen Amyloid
Calcium Ferrous iron Ferric iron
Von Kossa Turnbull blue Prussian blue
Bright red Deep pink red Green refringence Yellow-yellow green Black Blue Blue
*Frozen section
BIBLIOGRAPHY Arslan, O. (2001). Neuroanatomical basis of clinical neurology. New York: The Parthenon Publishing Group.
Cell/Tissue
Astrocyte Axonal degeneration T cells B cells Macrophages Epithelial fi lament Fibroblast Endothelial cell Amyloid Myelin Neuronal/glial inclusions
NFP: neurofi lament protein, Neu N: neuronal nucleus, NSE: neuron-specific enolase, GFAP: glial fibrillary acidic protein, APP: amyloid precursor protein, MBP: myelin basic protein. *For tumor-related immunohistologic stains, see Chapter 11.
Esiri, M. M., and Perl, D. (2006). Oppenheimer's diagnostic neuropathology: a practical manual, 3rd ed. London: Hodder-Arnold.
1. You are examining an atrophic brain. The patient's clinical diagnosis is dementia, probably Alzheimer's disease. Which of the following stains is most appropriate to confirm the diagnosis? A. B. C. D. E.
Klüver-Berrera stain Hematoxylin-eosin Cajal stain Bielschowsky stain Oil-red O
2. Gross section of the pons shows a large infarct destroying parts of the basis and tegmentum. To identify the fiber tracts and neurons involved, which is the most appropriate stain? A. B. C. D. E.
Periodic acid Schiff (PAS) Klüver-Berrera stain Holzer stain Nissl stain Gallyas stain
3. You are examining a tumor in a hematoxylineosin–stained section and would like to identify the cells of astrocytic origin. Which stain would you choose? A. B. C. D. E.
PAS stain Vimentin S-100 protein GFAP Bodian stain
4. You are examining a large brain. The patient's clinical diagnosis is psychomotor regression, probably lipid storage disease. Which is the most appropriate stain to confirm the diagnosis? A. B. C. D. E.
Best carmine Congo red Phosphotungstic acid hematoxylin (PTAH) Oil-red O Von Kossa stain
I N T RO D U C T I O N T O C L I N I C A L N E U RO PAT H O L O G Y
5. All of the following stains are useful to demonstrate pathology of axons except: A. B. C. D. E.
Bielschowsky stain Klüver-Berrera stain Amyloid precursor protein (APP) Gallyas stain Bodian stain (Answers are provided in the Appendix.)
Reactions of Neural Tissue to Diseases Types of Degenerations in the Central Nervous System Cerebral Edema Cerebral Changes Associated with Intracranial Expanding Mass Lesions Clinical Manifestations of Intracranial Expanding Mass Lesions and Rising Intracranial Pressure Hydrocephalus Cerebral Changes in Physiologic Aging Artificial Cerebral Changes
he human nervous system performs greatly varied and highly complex functions: It oversees the functions of all bodily organs; it receives and integrates information from all senses; it initiates and coordinates motor activities; and notably, it processes our thoughts, generates our emotions, and stores our memories. Billions of cells are organized, categorized, and specialized to carry out these functions. The neurons are the executives, the glial cells provide adequate environment, the blood vessels furnish nutrients,
and the meninges protect from injuries. The neurons, glial cells, blood vessels, and meninges each has a distinct morphology and displays characteristic changes in diseases. This chapter presents the characteristic reactions of neural tissue to diseases, along with a brief description of their normal histology, and the pathologic conditions particular to the nervous system.
R E AC T I O N S O F N E U R A L T I S S U E TO DISEASES Neurons The neurons, derivatives of the epithelium of the embryonic neural tube, greatly vary in appearance. In the cerebral cortex, most neurons are pyramidalshaped, whereas those in the spinal ganglia are round. The largest pyramidal cells in the motor cortex (Betz cells) measure up to 100 microns, whereas the granular cells of the cerebellar cortex measure only 5 microns. A neuron consists of (a) the cell body, or soma; (b) the dendrites, and (c) the axon (nerve fiber) (Fig. 2.1).
F I G U R E 2 .1
Cortical pyramidal neuron as seen in section stained with (A) cresyl violet and (B) silver.
Cell Body The cell body contains the nucleus and the perikaryon (cytoplasm). The nucleus has a prominent nucleolus and a variable amount of chromatin. The perikaryon comprises the Nissl bodies and the argyrophilic fibrils (see Fig 2.1). The neurons in the compact zone of the substantia nigra, locus ceruleus, and dorsal nucleus of vagus contain melanin pigments. The perikaryon, at ultrastructural level, contains a variety of subcellular organelles: a rough endoplasmic reticulum with ribosomes (Nissl bodies in light microscopy), a smooth endoplasmic reticulum, Golgi apparatus, mitochondria, peroxisomes, lysosomes, and cytoskeletal organelles. Three major classes of cytoskeletal organelles are the microtubules, the intermediate filaments, and the microfilaments, all associated with proteins. The microtubules are associated with tau proteins, the neurofi laments (argyrophilic fibrils in light microscopy) with neuronspecific peptides, and the microfilaments with actin. Dendrites The dendrites, or cytoplasmic processes, are structurally similar to the perikaryon. They gradually divide into thinner processes, eventually terminating in small spines. Axons The axon, conductor of nervous impulses, arises from the axon hillock of the perikaryon, an area lacking Nissl bodies. Mitochondria and cytoskeletal organelles are the major axonal components. Two types of axons are Golgi type 1, which are long myelinated axons carrying
TA B L E 2 .1.
Major Neurotransmitters Acetylcholine Catecholamines Dopamine Norepinephrine Epinephrine Serotonin
Amino acids γ–Aminobutyric acid (GABA) Glutamate Aspartate Glycine
Neuropeptides Opioids Neurohypophyseal peptides Substance P Enkephalin
nervous impulses to distant neurons, and Golgi type 2, which are short unmyelinated axons connecting local neurons. Synapses The neurons communicate with each other at the synapses through chemical substances collectively referred to as neurotransmitters (Table 2.1). The contact between two neurons occurs at the axon of one neuron and the axon, dendrites, or soma of the other neuron. A neurotransmitter, released at the axonal terminal of a presynaptic neuron, exerts an excitatory or an inhibitory effect on a postsynaptic neuron or on an end organ (muscle, gland). Pathology of the Neurons The reactions of neurons to disease manifest in alterations in the size, shape, and staining properties of the
BA S I C S O F N E U RO PAT H O L O G Y
Neuronal alterations. A. Vacuolated swollen motor neuron in medulla. B. Chronic atrophy of pyramidal neuron: The perikaryon is shrunken, the dendrites are corkscrew-like, and the nucleus is densely basophilic. C. Axonal or retrograde changes in hypoglossal neuron caused by tumorous infi ltration of the nerve roots. The swollen perikaryon is rounded, the dendrites are retracted, the Nissl bodies are partially dissolved, and remaining ones are clustered around the peripherally displaced nucleus (hematoxylin-eosin [HE] stain). D. Ischemic Purkinje cells in the cerebellar cortex showing eosinophilic shrunken perikaryons and homogenous basophilic nuclei (HE). E. Spinal motor storage neuron in Tay-Sachs disease; the cytoplasm is markedly distended and the nucleus displaced to the periphery (LFB-CV).
perikaryon and nucleus, and in reduction or loss of the Nissl bodies and dendrites. Some alterations are nonspecific, whereas others characterize particular diseases (Figs. 2.2 and 2.3; Table 2.2). Acute Changes Swelling, vacuolation of the perikaryon, dissolution of the Nissl bodies (chromatolysis), and shrinkage of the nucleus appear in a variety of acute infectious, toxic, vascular, and metabolic diseases. Chronic Changes Atrophic neurons with shrunken cell bodies, corkscrewlike dendrites, and shrunken and intensely basophilic nuclei are common in degenerative diseases. Lipofuscin accumulation consists of small golden brown pigments that are deposited in the perikaryon of the neurons during normal aging.
Specific Neuronal Changes Axonal or Retrograde Neuronal Changes Axonal changes develop in response to a transection of their axon. The cytoplasm swells and becomes rounded with retracted dendrites. The Nissl bodies partially dissolve and some of the remaining Nissl bodies surround the eccentrically displaced nucleus. Hypoxic-Ischemic Changes (Red Neurons) The shrunken perikaryon, partially or totally devoid of Nissl bodies, stains brightly red with eosin, and the pyknotic triangular- shaped nucleus stains uniformly blue with hematoxylin. Ferrugination of the Neurons Ferrugination in chronic ischemic-hypoxic lesions results from the deposition (incrustation) of basophilic calcium and iron granules on the dendrites and cytoplasm of dead neurons.
Neuronal inclusions. A. Neurofibrillary tangles in Alzheimer's disease (Gallyas silver stain), showing (B) positive immunostaining for tau protein, (C) Pick bodies in pyramidal neurons of hippocampus (Bodian silver stain), (D) Lewy body in substantia nigra in Parkinson's disease (HE), and (E) Hirano body in pyramidal neuron of hippocampus (HE).
TA B L E 2 . 2 .
Pathology of Neurons Acute swelling, chromatolysis Chronic atrophy Axonal/retrograde reaction Hypoxic-ischemic changes Ferrugination Distension in storage diseases Ballooned achromasia Granulovacuolar degeneration Inclusion bodies Degenerative Viral Neoplastic transformation
Ballooned Achromatic Neurons Ballooned neurons seen in corticobasal dementia display enlarged palely stained perikaryon, a lack of Nissl bodies, and argyrophilic fibrillary structures. Granulo-Vacuolar Degeneration This degenerative change manifests small basophilic granules within vacuoles in the pyramidal neurons of the hippocampus. It is found both in Alzheimer's disease and normal aging. Neuronal Inclusion Bodies in Degenerative Diseases
Distended Storage Neurons Distended storage neurons in neurometabolic diseases are markedly swollen and pear-shaped, with the nucleus and the Nissl bodies displaced toward the apical dendrite. Histochemical stains reveal the composition of the substances stored within the perikaryon.
Neuronal cytoplasmic inclusion bodies are the distinguishing features of several important neurodegenerative diseases. Some are identified in hematoxylin-eosin (HE)–stained sections, others only in silver-stained sections, and still others with immunohistologic stains (see Fig. 2.3). The molecular components of these inclusions are identified using immunohistochemical stains. Some
Neuronal Cytoplasmic Inclusions in Degenerative Diseases Inclusions
Neurofibrillary tangle Pick body Lewy body Hirano body Bunina body Skein-like inclusions
Tau protein Tau protein α-Synuclein Actin Cystatin C Ubiquitin
Diseases with Neurofibrillary Tangles Alzheimer's disease Down's syndrome Parkinson-Dementia-ALS complex of Guam Progressive supranuclear palsy Postencephalitic parkinsonism Dementia pugilistica Subacute sclerosing panencephalitis Tuberous sclerosis Niemann-Pick disease, type C Gerstmann-Sträussler-Scheinker disease
inclusions immunoreact for tau, a microtubuleassociated protein, others for α-synuclein, a synaptic protein, and still others for ubiquitin, a stress protein (Table 2.3). Intranuclear inclusions derived from the proteins of polyglutamate tracts characterize trinucleotide repeat diseases. Neurofibrillary tangles, a histologic hallmark of Alzheimer's disease, are argyrophilic torch- and basketshaped or globose filamentous cytoplasmic structures that immunoreact for tau protein. They also are found in normal aging and in a variety of diseases (Table 2.4). Pick bodies, histologic hallmarks of Pick's disease, are argyrophilic, round, homogenous structures in the swollen perikaryons of cortical and subcortical neurons. They immunoreact for tau protein. Lewy bodies are eosinophilic, round inclusions in the melanin-containing neurons of the substantia nigra and locus ceruleus in idiopathic Parkinson's disease and
in the cortical neurons of the diffuse Lewy body dementia. They immunoreact for α-synuclein and ubiquitin. Hirano bodies are rod-shaped or ovoid eosinophilic structures within or adjacent to the pyramidal neurons of the hippocampus in Alzheimer's disease, and they are also found in normal aging. They immunoreact for actin. Bunina bodies are small, eosinophilic granules in the cytoplasm of motor neurons in amyotrophic lateral sclerosis (ALS). They immunoreact for cystatin C. Skein-like inclusions in ALS immunoreact for ubiquitin. Lafora bodies in Lafora disease with myoclonus epilepsy are round, basophilic cytoplasmic inclusions containing polyglucosans that stain strongly with PAS reagent. Neuronal Inclusions in Viral Infections In viral diseases, the inclusions are commonly intranuclear, except that in rabies they occur in the cytoplasm of the Purkinje cells and the pyramidal neurons of the Ammon's horn. Neoplastic Transformation Transformation of the neurons into neurocytomas, neuroblastomas, and gangliogliomas are relatively rare but may occur from infancy to old age. Pathology of the Dendrites The reduction and loss of dendritic processes in cortical neurons occur in neurodegenerative diseases, chiefly in Alzheimer's disease, prion diseases, and HIV encephalitis. Cactus formation refers to a focal enlargement of the dendrites of the Purkinje cells in Menkes kinky hair disease, storage diseases, and granular cell aplasia of the cerebellum. Pathology of the Axons Degeneration of the axons occurs in a number of diseases: traumatic, demyelinating, infectious, metabolic,
Death of the Neurons
and ischemic. The injured axons swell, become fusiform, and disintegrate into small argyrophilic fragments that are gradually removed by macrophages. Early degeneration of axons is readily detected with immunohistologic stain using antibodies against β-amyloid precursor protein (β-APP) (Fig. 2.4).The β-APP- immunoreactivity of damaged axons precedes changes observed in conventional histologic stain. Axonal spheroids are round, homogenous, or slightly granular eosinophilic and argyrophilic structures commonly found in traumatic shearing injuries and at the edge of infarcts. They consist of axoplasm extruded from the disrupted ends of the axons (see Fig. 2.4). Axonal torpedo, a fusiform enlargement of the proximal portion of the Purkinje cell axon, frequently occurs in cerebellar cortical degenerations (see Fig. 2.4). Dystrophic axonal spheroids are distinctive histologic features of infantile neuroaxonal dystrophy. They also may occur in congenital biliary atresia, mucoviscidosis of children, and in nucleus gracilis of elderly subjects.
Neurons die in one of two ways: through apoptosis or necrosis. Apoptosis, or programmed cell death, is genetically regulated and commonly occurs in degenerative diseases. During brain development, the apoptosis of excess neurons is physiologic. In apoptotic cell death, the nuclear chromatin condenses into masses of various sizes and shapes, the nuclear membrane buds and fragments. These nuclear buds, along with cytoplasmic buds, form the apoptotic bodies, which then are phagocytosed by macrophages or neighboring cells. An apoptotic cell in HE-stained section appears as a round, dense, strongly eosinophilic mass. Apoptosis occurs rapidly, usually affects individual neurons, and elicits no inflammatory response. Necrosis is initiated by a variety of exogenous factors: toxins, infectious pathogens, metabolic disorders and, chiefly, by hypoxia and ischemia. The nucleus undergoes pyknosis, fragmentation, and lysis. The cytoplasm loses its organelles, becomes strongly eosinophilic and, ultimately, by enzymatic digestion, dissolves.
Axonal degeneration. (A) Fusiform swelling and (B) disintegration of axon into small argyrophilic fragments (Holmes stain). C. Beta-amyloid precursor protein (β-APP) immunoreaction of injured axons (immunostain). D. Axonal spheroids in traumatic injury (Holmes stain) E. Fusiform enlargement of the axon (torpedo) of a degenerated Purkinje cell (Bodian stain).
Necrosis usually affects a group of neurons and is accompanied by an inflammatory response.
Glial Cells Astrocytes, oligodendrocytes, and ependymal cells originate, as do neurons, from the primitive neuroepithelium of the neural tube, whereas microglial cells originate from bone marrow–derived monocytes. Glial cells play important roles in both physiologic and pathologic conditions: • They maintain an environment appropriate for the efficient functioning of the neurons. • They respond to diseases by removing tissue debris, repairing damaged tissue, and taking the place of lost tissue. • They are specifically implicated in a number of degenerative, infectious, and metabolic diseases. By displaying cytoplasmic inclusions, glial cells are important in defi ning several neurodegenerative diseases. Infected glial cells are pathologic markers for certain viral diseases. Furthermore, glial changes are the diagnostic features of several metabolic diseases. • Glial cells are capable of proliferating into a variety of gliomas, which constitute the largest group of primary intracranial tumors.
Astrocytes The role of astrocytes begins during brain development, when the radial astrocytes guide the migrating neurons. After birth, the astrocytes are important in a number of physiologic processes: They provide support and nutrients to the neurons, protect them from excitotoxic neurotransmitters, contribute to the blood–brain barrier, and maintain homeostasis in the extracellular compartment. Astrocytes are star-shaped. In HE-stained section, only the nucleus is visible; it is medium-sized, round or oval, with a moderate amount of chromatin and one or two nucleoli. Astrocytic processes and fibrils are visualized with specific stains. A longer process is attached to the capillary walls or the pial surface by a foot-plate. The fibrils contain glial fibrillary acidic protein (GFAP), an important astrocytic marker (Fig. 2.5). The two types of astrocytes are protoplasmic and fibrillary. Protoplasmic astrocytes, predominantly in the cortex and subcortical gray structures, display shorter processes and less fibrils. Fibrillary astrocytes, predominantly in the white matter, contain abundant fibrils. In diseases, protoplasmic astrocytes may convert to fibrillary. Pathology The pathology of astrocytes is summarized in Table 2.5. Swelling is an early reaction to a variety of injuries,
Astrocytes. A. Protoplasmic astrocytes. Cerebral cortex shows oval and round astrocytic nuclei with moderate amount of chromatin and prominent nucleoli (Cresyl violet). B. Fibrillary astrocytes display numerous short, fi ne processes and one long process attached to the capillary wall with a foot plate (Cajal gold stain). C. Positive immunostaining for glial fibrillary acidic protein (GFAP).
Pathology of Glial Cells Astrocytes
Oligodendrocytes
Swelling Hypertrophy/hyperplasia Gemistocytic astrocytes Fibrillary gliosis Alzheimer type 1 and 2 glia Rosenthal fibers Corpora amylacea Inclusions Argyrophilic Viral Neoplastic transformation
Swelling Satellitosis Inclusions Argyrophilic Viral Neoplastic transformation
Ependymal glia
Atrophy–tearing Granular ependymitis Viral inclusions Neoplastic transformation
Rod-shaped activated microglia Multinucleated giant cell Macrophage
chiefly hypoxia, and results from an influx of fluid and electrolytes into the cytoplasm (cellular edema). In histologic preparations, the swollen cytoplasm appears clear, and the nucleus is prominent. Hypertrophy and hyperplasia. In acute and chronic diseases, astrocytes commonly increase in size and number. A gemistocytic or hypertrophied astrocyte displays a large, round cytoplasm with short fibrillated processes and a vesicular, eccentrically displaced nucleus. The cytoplasm stains intensely with eosin and immunoreacts strongly with GFAP (Fig. 2.6). Fibrillary gliosis. Astrocytes are capable of replacing destroyed tissue by producing more and more fibrils and ultimately forming a dense fibrillary gliosis or glial scar. A glial scar is isomorphic when the astrocytic fibers conform to the pattern of the original structures, or is anisomorphic when the pattern is haphazard (see Fig. 2.6). Alzheimer's type 1 and type 2 astrocytes. Alzheimer's type 2 astrocytes have large, round or lobulated vesicu-
lar nuclei with scanty chromatin condensed at the margin of well-defi ned nuclear membranes (see Fig. 2.6). They are characteristic fi ndings in hepatic and other metabolic encephalopathies and Wilson disease, and are commonly found in the cerebral cortex, pallidum, and dentate nucleus. Alzheimer's type 1 astrocytes, also found in metabolic encephalopathies, have large lobulated nuclei and large slightly granular cytoplasms. Rosenthal fibers. These alterations in astrocytic processes appear as homogenous oval, round, elongated, or carrot-shaped eosinophilic structures. They are found in the walls of cystic cavities, fibrillary gliosis, and astrocytic tumors, and are the diagnostic hallmark of Alexander's leukodystrophy (see Fig. 2.6). Corpora amylacea. Corpora amylacea are the degenerative products of astrocytic processes. They are round, basophilic and argyrophilic structures, 20 to 50 microns in diameter. They commonly occur beneath the pia mater and around the ventricles and blood vessels. They contain polyglucosans, are PAS positive, and immunoreact for ubiquitin. Corpora amylacea are found in variable amounts in brains after the age of 40 to 45 years, and are particularly abundant in chronic degenerative diseases (see Fig. 2.6). Cytoplasmic argyrophilic and tau positive inclusions. These features are characteristic of several neurodegenerative diseases collectively referred to as tauopathies (see Fig. 2.6). Viral nuclear inclusions. These inclusions are found in herpes simplex encephalitis, subacute sclerosing panencephalitis, and in progressive multifocal leukoencephalopathy, in which the astrocytes are transformed into large atypical cells. Neoplastic transformation. Astrocytes have the capacity to proliferate into a variety of relatively benign or malignant astrocytomas constituting the most common glial tumors.
Pathology of astrocytes. A. Gemistocytic (reactive) astrocytes display a large eosinophilic glassy cytoplasm with short processes and a peripherally displaced nucleus (HE). B. Fibrillary astrogliosis beneath the pia mater. Fibrous astrocytes showing numerous fi ne fibrillated processes (Holzer stain). C. Alzheimer's type 2 astrocytes display a large vesicular nucleus with scanty chromatin and a prominent nucleolus (HE). D. Rosenthal fibers in an astrocytoma appear as eosinophilic rod-shaped, homogenous structures (HE). E. Corpora amylacea around blood vessels (HE). F. Argyrophilic astrocytic plaque in cortical basal degeneration (Gallyas). G. Bergmann astrocytes replace degenerated Purkinje cells in cerebellar cortex (HE).
Oligodendrocytes In standard preparations, oligodendrocytes are recognized by their small, round, dark nuclei, rich in chromatin. The small perikaryons, with few and short processes, are visualized using silver stains. In the gray matter, oligodendrocytes serve as satellite cells around the neurons and regulate the perineuronal environment. In the white matter, oligodendrocytes are aligned along the myelin sheaths as interfascicular glia (Fig. 2.7). The major function of interfascicular oligodendrocytes is the formation of myelin during brain development and its maintenance thereafter. The myelin–oligodendrocyte entity plays an important role in autoimmune-mediated
myelin diseases and in some viral diseases. Reactions of oligodendrocytes to injury are few. Pathology The pathology of oligodendrocytes is summarized in Table 2.5. Swelling occurs in a variety of diseases, and it appears in HE-stained section as a clear halo of cytoplasm around the nucleus. Satellitosis, an increase in number of satellite cells, indicates neuronal injury. Cytoplasmic argyrophilic inclusions are markers of several neurodegenerative diseases. Cap-, flame-, or sickle-shaped inclusions are the histologic hallmarks of
FIGURE 2 .7
Oligodendrocytes. A. Satellite oligodendrocytes around cortical neurons (HE). B. Interfascicular oligodendrocytes along myelin sheaths (LFB-CV). Oligodendrocytes showing (C) argyrophilic cytoplasmic inclusions in multiple system atrophy (Gallyas stain).
multiple system atrophy (see Fig. 2.7). These inclusions are distinguished by positive immunostaining for ubiquitin, α-synuclein and α-β crystalline. Argyrophilic coiled bodies occur in progressive supranuclear palsy, corticobasal dementia, and argyrophilic grain dementia. Viral nuclear inclusions in large, monster-like oligodendrocytes are characteristic of progressive multifocal leukoencephalopathy. They contain virions of JC virus of the papova virus group. FIGURE 2.8
Neoplastic transformation. Oligodendrocytes commonly proliferate into slowly growing neoplasms. Ependymal Glia Ependymal glia, columnar or cuboidal ciliated epithelial cells, line the surface of the ventricles and the spinal canal (Fig. 2.8). They react to a variety of pathologic insults. Pathology The pathology of ependymal glia is summarized in Table 2.5. Atrophy, tearing, and discontinuity commonly occur in chronic hydrocephalus. Ependymitis, caused by a variety of pathogens, consists of necrosis, breaking up of the ependymal lining, and subependymal inflammatory infi ltrations. Subependymal gliosis, or granular ependymitis, develops in syphilitic and various other infectious, toxic,
Ependymal glia. Cuboidal epithelial cells cover the ventricular surface and small nodules of proliferated astrocytes project into the ventricular lumen (granular ependymitis) (HE).
metabolic, and vascular diseases. Grossly, tiny nodules from the ventricular surface project into the lumen. Histologically, these nodules are proliferated subependymal fibrillary astrocytes. Some are covered with continuous or disrupted ependymal layer and others are denuded. Occasionally, these nodules may enlarge enough to obstruct the aqueduct of Sylvius and cause hydrocephalus (see Fig. 2.8). Nuclear and cytoplasmic viral inclusions in enlarged ependymal cells are characteristic of cytomegalovirus infection. Neoplastic Transformation Ependymal cells are capable of proliferating into neoplasms that may grow into the parenchyma or project into the ventricle.
Microglia. A. Resting microglia showing small elongated nucleus, scanty cytoplasm, and bipolar processes (Hortega silver stain). B. Activated rod-shaped microglia in encephalitis. C. Macrophages showing large, round, foamy cytoplasms and small eccentric nuclei (HE).
Microglia Microglial cells, derived from bone marrow monocytes, enter the nervous tissue during early brain development. They proliferate, migrate, and mature into resident or resting microglia. A major function of microglia is the surveillance of and participation in immunologic processes. Resident microglia are distributed in gray and white matter around neurons as satellite cells and around blood vessels. Their small, round, or elongated nuclei are not readily recognizable in HE preparation. Silver stain discloses a triangular perikaryon with two or more branching processes (Fig. 2.9). Pathologic states rapidly activate the microglial cells, which then are easily identifiable. Pathology The pathology of microglial cells is summarized in Table 2.5. Activated microglia. Rod cells, prominent in viral diseases and parenchymal neurosyphilis, are distinguished by conspicuously hypertrophied rod-shaped nuclei. They are diffusely distributed in gray and white matter and are almost perpendicularly oriented to the cortical surface (see Fig. 2.9). Rod-, crescent-, and kidney–shaped microglial cells occur around neuritic plaques in Alzheimer's disease. Microglial nodules. Nodules commonly are found in viral diseases, in which they cluster around infected
neurons, invade and digest them (neuronophagia), and eventually replace them with residual nodules. Loose collections of microglial cells (shrubs) are occasionally found in the molecular layer of the cerebellar cortex. Multinucleated giant cells. These giant cells, derived from microglia and macrophages, are distinctive features of HIV encephalitis. Macrophages. Macrophages with phagocytic activity are scavengers of the neural tissue. They are prominent in vascular infarcts, acute demyelinating diseases, leukodystrophies, hemorrhages, and traumatic lesions. Distinguished by large, rounded, foamy cytoplasms and small eccentric nuclei, the macrophages engulf and remove degraded myelin, necrotic tissue debris, and hemosiderin pigments (see Fig. 2.9). Myelin Myelin ensheathes the nerve fibers in a spiral lamellar fashion, promoting a faster and more effective conduction of nervous impulses along the nerve fibers. It is produced by the oligodendrocytes during development of the brain and spinal cord and maintained by them after completion of myelination (Fig. 2.10). The major chemical components of myelin are lipids, which constitute about 70% to 85%. The sphingolipids and cholesterol are the most important of these. The remaining 15% to 30% of myelin consists of proteins; among them, myelin basic protein, proteolipid protein, and
F I G U R E 2 .10
Myelin. A. Schematic drawing of axons, myelin sheaths, and oligodendrocytes. B. Light microscopic picture showing longitudinally oriented myelin sheaths (stained blue) along nerve fibers (stained black; Holmes stain). C. Swelling and breaking up of myelin sheaths (LFBeosin). D. Disintegration of myelin into small oil-red O-positive lipid globules.
Chemical Composition of Central Myelin Lipids 70%–85% Sphingolipids: Sphingomyelin: phospholipid Cerebroside: glycolipid (galactose) Sulfatide: cerebroside sulfate ester Cholesterol Proteins 15%–30% Myelin basic protein Myelin proteolipid protein Myelin-associated glycoprotein Myelin oligodendrocyte-glycoprotein
myelin oligodendrocyte-glycoprotein are particularly important because of their antigenic role in autoimmune diseases (Table 2.6). Pathology Degeneration Myelin is primarily involved in immune- and virusmediated diseases, hereditary and acquired metabolic diseases, and various toxic disorders. It is also affected in vascular, infectious, and traumatic disorders, and in wallerian degeneration of the axons. The pattern of myelin degeneration is the same regardless of the cause. The myelin sheath swells, becomes irregular, and breaks
down fi rst into larger, and then smaller and smaller globules, which contain cholesterol ester and triglycerides. These globules are phagocytosed and gradually removed by macrophages to the perivascular and subarachnoid spaces (see Fig. 2.10). Meninges The brain and spinal cord are covered with three membranes: (a) the dura mater, a thick outer fibrous membrane, containing large venous sinuses and separating the cranial cavity into a supratentorial and an infratentorial compartment; (b) the arachnoid, beneath the dura, a thin avascular membrane covered with mesothelial cells; the arachnoid villi (granulations) are tufts of arachnoidal (meningothelial) cells that project into the venous sinuses and veins; and (c) the pia mater, a thin, inner fibrous membrane attached to the surface of the brain and spinal cord and connected to the arachnoid by delicate fibrous trabeculae. The arachnoid and the pia together form the leptomeninges. Between them is the subarachnoid space, fi lled with cerebrospinal fluid (CSF). The CSF is absorbed into the venous sinuses at the arachnoid villi. The pia mater contains blood vessels, accompanying them into the neural parenchyma and forming the perivascular or Virchow-Robin spaces fi lled with CSF. The Virchow-Robin spaces usually end at the
Meninges. A. Schematic drawing of the anatomic relationship between the dura, arachnoid, and pia. B. Leptomeningeal carcinomatosis extends into the cerebral cortex along the VirchowRobin spaces (HE).
Skull Dura Arachnoid Cortex Pia Mater
level of transition of arterioles to capillaries. They provide a route for the extension of inflammation or neoplasm from the subarachnoid space into the parenchyma (Fig. 2.11). Pathology The meninges are involved in traumatic, infectious, hemorrhagic, and neoplastic diseases. The epidural and the subdural spaces are common sites of traumatic hemorrhages. The subarachnoid space is the site of exudate from leptomeningeal inflammation, of hemorrhage from rupture of a berry aneurysm, and of neoplastic infi ltration from primary or metastatic neoplasms. Postinflammatory and posthemorrhagic fibrosis of the leptomeninges and arachnoid villi interferes with the circulation and absorption of CSF, ultimately leading to hydrocephalus. Blood Vessels Vascular supply of the brain and the pathology of arteries are presented in Chapter 4. A few distinct features are mentioned here. Cerebral arteries differ from systemic arteries by having only one elastic layer. Capillaries are distinguished by the presence of (a) tight junctions between endothelial cells, (b) basement membrane, and (c) astrocytic foot-plates attached to the adventitia. These three features provide a barrier between the blood and the brain. This blood– brain barrier (BBB) can prevent harmful substances from reaching the nervous parenchyma, but it can also prevent therapeutic agents from crossing to the parenchyma.
Transsynaptic Atrophy
Retrograde Transsynaptic Atrophy
Types of degenerations in the central nervous system: schematic drawing.
T Y P E S O F D E G E N E R AT I O N S I N T H E C E N T R A L N E RV O U S S Y S T E M Anterograde Degeneration Anterograde (wallerian) degeneration results from transection of the axons commonly by infarcts, hemorrhages, tumors, and trauma. Distal to the injury, fi rst the axons break down into small argyrophilic fragments, then their myelin sheaths break down into neutral lipid globules. The neurons of the injured axons undergo retrograde degeneration: The cytoplasm swells, the dendrites retract, the Nissl bodies dissolve, and the nucleus is peripherally displaced (Figs. 2.12 through 2.14). Trans-Synaptic Degeneration In trans-synaptic degeneration or transneuronal atrophy, those neurons that lose their chief or only afferent connection (that is, their synaptic input) atrophy. Particular sites of trans-synaptic neuronal atrophy are (a) the lateral geniculate bodies following degeneration of the ganglion cells of the retina, optic nerve, or optic tract;
Anterograde or Wallerian degeneration. A. Lacunar infarct in the internal capsule. B. Degeneration of the ipsilateral pyramidal tract in the medulla (myelin stain). C. MRI of a 68-year-old man showing an old infarct in distribution of middle cerebral artery. Note the atrophy of the ipsilateral pedunculus due to wallerian degeneration of the descending corticopontine and pyramidal tracts.
Wallerian degeneration. Degeneration of the fasciculus gracilis from compression of the sensory nerve roots by a metastatic carcinoma in the lumbar spine (myelin stain).
(b) the mammillary body following degeneration of the fornix (Fig. 2.15); and (c) the neurons of the gracile and cuneate nuclei of the medulla following degeneration of the posterior columns in the spinal cord.
Trans-synaptic atrophy of the mammillary body. A 58-yearold known hypertensive man suffered a stroke 7 years prior to his death. A. Transverse section reveals a large infarct in the right Ammon horn, hippocampus, and fusiform gyrus. The right fornix, the most prominent efferent connection to the mammillary body, is degenerated (wallerian degeneration). The right mammillary body, not included in the picture, is severely atrophic (trans-synaptic atrophy; myelin stain).
olivary nuclei atrophy when the Purkinje cells in the contralateral cerebellar cortex have degenerated.
Retrograde Trans-Synaptic Degeneration
Dying-Back Degeneration
Retrograde trans-synaptic degeneration develops in those neurons that project to neurons that have already degenerated. For example, the neurons of the inferior
Degeneration of the axons begins in their distal ends and progresses toward the neurons of their origin. It occurs in systemic degenerative diseases.
Pseudohypertrophic degeneration of the inferior olivary nuclei in a 45-year-old man with bilateral palatal myoclonus and a large malignant glioma infi ltrating the dentate nuclei and the upper midbrain. A. Medulla showing hypertrophy of both inferior olivary nuclei (myelin stain). B. The neurons are enlarged, their cytoplasms vacuolated, and the processes thickened and fragmented (Bodian stain).
Pseudohypertrophic Degeneration of the Inferior Olives Pseudohypertrophic degeneration of the inferior olivary nucleus is a particular type of trans-synaptic degeneration (Fig. 2.16). It is associated with lesions either in the ipsilateral central tegmental tract or the contralateral dentate nucleus of the cerebellum. The olivary neurons enlarge and display cytoplasmic vacuoles, peripherally displaced nucleus, and thick, rich, dendritic arborization.
CEREBR A L EDEM A Cerebral edema is the abnormal accumulation of fluid within brain tissue resulting in an increase in brain volume. Brain edema is always a serious, often life threatening complication of diverse conditions: expanding mass lesion, ischemic or hemorrhagic stroke, head injury, infection, and ischemic-hypoxic, metabolic, toxic, and hypertensive encephalopathies. General Aspects Intracranial pressure (ICP), the pressure of the CSF, remains within physiologic range (90 to 180 mm H 2O) as long as the volume of the brain, circulating blood, and CSF remain constant. An increase in brain volume
initially is compensated for by a decrease in blood flow and CSF volume. When the edema persists and progresses, however, this compensatory mechanism fails; subsequently, the intracranial pressure rises. When it exceeds 200 mm H 2O, clinical symptoms develop: headache, nausea, vomiting, altered mentation, visual impairment, and papilledema. A computed tomography (CT) scan readily reveals the edema, showing obliteration of the sulci and cisterns, hypodensity of the white matter with fi ngerlike projections, and compression of the ventricles. As the brain volume continues to increase, hippocampal and cerebellar tonsillar herniations with brainstem and medullary compressions occur. When the intracranial pressure reaches the level of the systemic blood pressure, the circulation ceases and death occurs. Types of Edema Three types of edema are vasogenic, cellular, and interstitial. Vasogenic edema, the most common, is generally associated with mass lesion, infarction, hematoma, and traumatic and inflammatory lesions. The edema, generalized or focal, results from a breakdown of the blood– brain barrier and escape of fluid and protein into the intercellular space, chiefly into the white matter. Cellular (cytotoxic) edema results from an accumulation of fluid in the cytoplasm of the neurons, glial
cells, and capillary endothelium, which swell and may suffer irreparable damage. Cellular edema develops in a wide range of disorders: ischemic-hypoxic states, hypoosmolality states associated with dilutional hyponatremia, inappropriate antidiuretic hormone secretion, osmotic dysequilibrium syndrome of hemodialysis, head injuries, diabetic ketoacidosis, and Reye syndrome. Interstitial edema is associated with chronic hydrocephalus. Fluid infi ltrates the periventricular white matter around the frontal and occipital horns through a disrupted ependymal layer.
C E R E B R A L C H A N G E S A S S O C I AT E D W I T H I N T R A C R A N I A L E X PA N D I N G MASS LESIONS Vasogenic Edema Intracranial expanding mass lesions, such as neoplasms, abscesses, granulomas, and hematomas, induce a vasogenic edema, which, if not resolved, leads to herniations, vascular lesions, and bony erosions (Table 2.7). Herniations and vascular lesions are particularly important, because they create serious clinical situations, and death can ensue. Initially, the edema surrounds the mass lesion then gradually propagates further along the fiber tracts, ultimately becoming generalized. The severity of edema
is usually proportional to the rate of growth of the mass: It is most extensive around fast-growing lesions. Pathology Grossly, the edematous brain is voluminous and heavy. The convolutions are broadened and flattened, and the sulci are shallow or obliterated (Fig. 2.17). On cut sections, the edematous white matter is soft and yellowish. The ventricle adjacent to the mass lesion is compressed and, in severe edema, the midline is shifted to the opposite side (see Fig. 2.17). TA B L E 2 . 7.
Pathologic Consequences of Intracranial Expanding Mass Lesions Herniations
Transtentorial uncal/ hippocampal Central Cerebellar tonsillar Cerebellar transtentorial Subfalcial cingular
Infarcts Mesiotemporal Occipital Frontal Superior cerebellar Brainstem hemorrhage Pituitary necrosis
Bony Erosion Dorsum sellae Post clinoid process
Cerebral edema. A. CT scan showing massive edema and mass effect around a malignant neoplasm with ring-like enhancement. The ipsilateral ventricle is obliterated. B and C. Focal swelling of the white matter around a large temporal lobe glioblastoma: The ipsilateral ventricle is compressed and the third ventricle is shifted to the opposite side. D. Generalized edema associated with a large temporal lobe glioma. Dorsal view shows diffuse enlargement, broadened convolutions, and obliterated sulci.
Histology of vasogenic edema. A. Macrosection of the hemispheric white matter shows loss of affi nity of myelin for Luxol fast blue. The arcuate fibers are relatively preserved. B. Extravasated plasma infi ltrates the white matter and the pericapillary spaces. C. The white matter is vacuolated and spongy, and the myelin sheaths are separated from each other and are broken up (LFBCV). D. Hypertrophied GFAP-positive astrocytes are noted in spaces between the myelin sheaths (immunostains).
Histologically, the edematous white matter stains pale with Luxol fast blue, except for the arcuate fibers, which are relatively well preserved. Lakes of sera fi ll the pericapillary spaces (Fig. 2.18). The myelin sheaths are swollen, beaded, and separated from each other. Hypertrophied astrocytes and a few macrophages are scattered in the spaces between them. Herniations The infant's cranium is expandable; separation of the sutures and enlargement of the head compensate for increasing brain volume. Because the adult's cranium has rigid bony walls, a gradual increase in brain volume displaces certain structures from one compartment into another (Fig. 2.19; see also Table 2.7). Transtentorial Uncal and Hippocampal Herniation A hemispheric mass lesion displaces the uncus and all or part of the hippocampus through the tentorial opening. Subsequently, the oculomotor nerve-roots are pressed against the rigid tentorial edge or the petroclinoid ligament. The rostral brainstem with the aqueduct is compressed and displaced to the opposite side. This displacement allows the tentorial edge to lacerate the pyramidal fibers in the opposite pedunculus, producing the Kernohan's notch (see the section Localizing Features).
Central Herniation Bilateral anterior hemispheric or centrally situated mass lesions displace the diencephalon and/or upper midbrain downward into the tentorial opening. Cerebellar Tonsillar Herniation A mass lesion in the posterior fossa or in the supratentorial compartment thrusts the cerebellar tonsils downward through the foramen magnum, compressing the medulla and obliterating the cisterna magna. The cerebellar tonsils then may undergo necrosis. Cerebellar Transtentorial Herniation A posterior fossa mass lesion displaces the superior vermis and hemispheres upward through the tentorial opening. Subfalcial Herniation A frontocentral mass lesion displaces the cingular gyrus under the falx. Vascular Lesions Herniations, by pressing the cerebral arteries against the surrounding structures, produce pale or hemorrhagic infarcts (Fig. 2.20; see also Table 2.7).
Types of cerebral herniations. A. Anatomic specimen showing the structures in the tentorial opening. Note the relationship between the midbrain, oculomotor nerves, posterior cerebral arteries, uncus, and parahippocampal gyrus. B. Transtentorial herniation of the left uncus and parahippocampal gyrus in an acute subdural hematoma. Note the deep groove around the herniated gyri caused by the rigid tentorial edge. The midbrain and the aqueduct are compressed and displaced to the right. C1. A transverse band of pallor in the myelin-stained left oculomotor nerve likely corresponds to the site of compression against the tentorial edge. C2. The right oculomotor nerve is normal. D. Right peduncular notch associated with a left temporal mass lesion. Displacement of the midbrain to the right pressed the pedunculus against the tentorial edge, which resulted in a notch (Kernohan's notch). Note also the herniation of the cingular gyrus and compression of the ventricle. E. Subfalcial herniation. Dorsal view of herniated cingular gyrus associated with a frontal mass lesion. F. Cerebellar tonsillar herniation associated with a hemispheric carcinoma metastasis. Note the deep groove around the tonsils caused by their downward thrust through the foramen magnum.
FIGURE 2.20
Vascular lesions associated with mass lesions and raised intracranial pressure. A. Massive pontine hemorrhage (Düret hemorrhage). B. Occipital hemorrhagic infarct. A
Mesial temporal and occipital infarct results when the herniated hippocampus compresses the posterior cerebral artery against the tentorial edge. Anterior cerebral artery infarct occurs with the subfalcial herniation of the cingulum, when the artery is pressed against the rigid falx. Superior cerebellar infarct occurs in upward cerebellar herniation and results from compression of the artery against the tentorial edge. Brainstem hemorrhage (Düret hemorrhage) occurs when displacement of the brainstem stretches, angulates, or tears the branches of the basilar artery, thus leading to multiple confluent petechial hemorrhages. Hemorrhages also can result from impairment of venous drainage into the vein of Galen. Pituitary necrosis results from the impairment of circulation in the hypophyseal portal blood vessels. Bony erosions result from long-standing edema. Common sites are the dorsum sellae and the posterior clinoid process. C L I N I C A L M A N I F E S TAT I O N S O F I N T R A C R A N I A L E X PA N D I N G M ASS LESIONS A N D R ISI NG I N T R AC R A N I A L P R E S S U R E Intracranial expanding lesions and a rising intracranial pressure produce characteristic symptoms and signs; some provide important diagnostic clues and others warn of a deteriorating and life threatening situation. They are divided into (a) general features, (b) localizing features, and (c) signs of herniations. General Features Headaches, variable in nature, present often at night or on awakening. Intermittent at onset, they gradually
increase in frequency, severity, and duration. They often are localized to the vicinity of the mass lesion, but with rising intracranial pressure, become more diffuse. Nausea and vomiting occur with or without headaches and are more common with posterior fossa mass lesions. Seizures, partial or generalized, may be the presenting symptom and, for months or even years, the only manifestations of a slow-growing mass. Papilledema is the most important diagnostic sign of increased intracranial pressure, but is not always present. It presents with a gradual decrease of visual acuity, constriction of the visual field, and enlargement of the blind spot. Alteration in level of alertness, progressing from lethargy and obtundation to stupor and coma, indicates rising intracranial pressure and is usually associated with signs of herniation. Mental symptoms are manifold; decline of cognitive functions, loss of spontaneity and initiative, affective disorders, behavioral changes, hallucinations and, occasionally, psychotic behavior have been associated with mass lesions. Some relate to rising intracranial pressure and others are reactions of the personality to an impaired cerebral function. Localizing Features Neurologic symptoms and signs indicate the location of the lesions. Psychiatric symptoms of localizing significance are most likely associated with lesions in the frontal lobe and temporomesial region. A false localizing sign is a hemiparesis on the side of a hemispheric mass lesion, which results from a contralateral peduncular notch associated with hippocampal herniation.
Isolated abducens nerve palsy due to displacement of the brainstem and stretching of the nerve roots has no localizing significance. Signs of Herniations Transtentorial uncal-hippocampal herniation manifests with ipsilateral occulomotor nerve palsy, dilated pupil, nonreactive to light, and ptosis. Central diencephalic-rostral midbrain herniation manifests with small pupils, nonreactive to light and changing to midsize, respiratory changes, and decorticate posturing. Cerebellar tonsillar herniation, or pressure cone syndrome, manifests with rising systolic and diastolic blood pressure, bradycardia, and irregular breathing, culminating in respiratory arrest. Brainstem hemorrhage is a terminal event manifested by coma, small nonreactive pupils, bilateral pyramidal signs, and decerebrate posturing.
Hydrocephalus may result from (a) obstruction to CSF circulation, (b) overproduction of CSF, and (c) failure of CSF absorption at the arachnoid granulations (Table 2.8). Hydrocephalus is classified as obstructive, nonobstructive, and other. Obstructive Hydrocephalus Obstructive hydrocephalus is the most common type. Obstruction to CSF circulation may occur within the ventricles or within the subarachnoid space. If the obstruction is within the ventricles, the hydrocephalus is noncommunicating; that is, the ventricles do not communicate with the subarachnoid space. If the obstruction is within the subarachnoid space, the hydrocephalus is communicating. Common causes of obstructive hydrocephalus are congenital malformations and acquired pathologic lesions. Congenital Obstructive Hydrocephalus
H Y DRO C E P H A LU S Hydrocephalus (Greek hydros, water and cephaly, head) denotes an excessive accumulation of the CSF that considerably enlarges the ventricles.
Obstruction to CSF circulation commonly occurs at the aqueduct of Sylvius due to atresia or severe stenosis. Less often, the obstruction is at the outlet foramina of the fourth ventricle, as occurs in the Arnold-Chiari and the Dandy Walker malformations (see Chapter 12).
Hydrocephalus HYDROCEPHALUS Obstructive Congenital
Malformations Cerebral
Nonobstructive
Neoplasm Inflammation Hemorrhage Metabolic
Excessive Formation of CSF
Defective Absorption of CSF
Plexus papilloma Hypo/hypervitaminosis A
Dural sinus thrombosis
Normal pressure hydrocephalus
Hydrocephalus ex vacuo
Inflammation Hemorrhage Undetermined
Brain atrophy
Acquired Obstructive Hydrocephalus Acquired obstructive hydrocephalus may occur at any age and from various causes. Intracerebral mass lesions, especially tumors, may obstruct the flow of the CSF at any point within the ventricles. The ventricles dilate proximal to the block and remain of normal size distal to it. Acute obstruction within the subarachnoid space results from meningitis and subarachnoid hemorrhage. Chronic obstruction results from postinflammatory and posthemorrhagic fibrosis of the leptomeninges, neoplastic infiltration, and fibrous thickening of the leptomeninges in some neurometabolic diseases (e.g., mucopolysaccharidosis).
appearance of Babinski sign may develop due to stretching of the descending corticospinal fibers around the anterior horns. The clinical diagnosis is supported by magnetic resonance imaging (MRI), which shows markedly enlarged ventricles and a normal or variably obliterated subarachnoid space (Fig. 2.21). NPH is one of the few treatable causes of dementias, provided it is diagnosed early. The removal of a large quantity of CSF by lumbar puncture usually improves the gait. The improvement is considered a good prognostic sign and an indication for shunting the CSF from the lateral ventricle to the jugular vein or peritoneal cavity. Pathologic Features
Nonobstructive Hydrocephalus Nonobstructive hydrocephalus results from an overproduction of CSF by a choroid plexus papilloma or from failure of absorption at the arachnoid villi due to a thrombotic or neoplastic occlusion of the superior sagittal sinus.
The leptomeninges appear normal or variably thickened. The ventricles are markedly enlarged. The ependymal lining often is disrupted, and the subependymal glia is proliferated. The cerebral cortex is normal or mildly atrophic. Hydrocephalus Ex Vacuo
Other Forms of Hydrocephalus Normal Pressure Hydrocephalus Normal pressure hydrocephalus (NPH), a particular form of obstructive hydrocephalus, is distinguished by a progressive enlargement of the ventricles without clinical evidence of raised intracranial pressure. The CSF flow is obstructed in the subarachnoid space or at the arachnoid villi. In a few cases, the history discloses previous head trauma, meningitis, or subarachnoid hemorrhage; however, in a large percentage of cases, no cause is evident.
Hydrocephalus ex vacuo (passive hydrocephalus) results from a reduction of the brain volume, mostly of the hemispheric white matter. It commonly occurs in neurodegenerative diseases, hereditary metabolic diseases, chronic infectious diseases, chronic postanoxic encephalopathies, and following head injuries. On CT scan and MRI, the subarachnoid space is widened due to convolutional atrophy. Grossly, the cerebral cortex is variably thin, and the white matter is reduced in amount. The lateral ventricles and the third ventricle are enlarged, whereas the aqueduct and fourth ventricle usually remain normal (see Fig. 2.21).
Clinical Features NPH occurs in individuals 60 to 70 years of age or older. The clinical criteria include the triad of progressive gait disorder, often the presenting symptom; dementia; and urinary incontinence. The gait disorder manifests with short shuffl ing steps and postural instability (frontal gait apraxia). The dementia has components of frontal lobe dysfunction: psychomotor slowing, loss of initiative, and apathy. Spasticity in the legs and the
CER EBR A L CH A NGES I N P H YS I O L O G I C AG I NG Aging is an inescapable natural biologic process affecting all organ systems of the body. This process, regulated by genetic factors (longevity genes) and influenced by environmental factors, begins after age 50 to 60 years or later. Aging of the central nervous system primarily
F I G U R E 2 . 21
A. Normal pressure hydrocephalus in a 60-year-old man with "gait difficulties over the years" and memory decline. MRI shows enormously enlarged ventricles and only mildly enlarged subarachnoid space. B. Hydrocephalus ex vacuo in a 70-year-old demented patient. CT scan shows enlarged ventricles and significantly widened subarachnoid space. A
FIGURE 2 .22
Cerebral changes in physiologic aging. A. MRI showing periventricular caps around the anterior horns. B. Lipofuscin accumulation in thalamic neuron in the brain of a 73-year-old man (HE). C. Neuritic plaque in hippocampus (Bodian stain). D. Abundance of corpora amylacea in the pia matter (immunostain for ubiquitin). E. Siderocalcinosis of small blood vessel in basal ganglia (HE).
manifests with cerebral atrophy—a reduction of brain volume. The morphologic changes are clinically undiscovered for some time. The appearance of neurologic decline, chiefly motor dysfunction, and of cognitive decline, chiefly memory impairment, varies greatly among individuals.
CT scan and MRI demonstrate the atrophy as a widening of the subarachnoid space and cisterns, reduction of hemispheric white matter, and enlargement of lateral ventricles. Frequent, incidental age-related fi ndings are periventricular caps and rims corresponding to periventricular ischemic demyelination (Fig. 2.22).
Cerebral artifacts. "Swiss cheese" brain showing A. multiple smooth-walled cavities, B. corresponding to empty holes lacking tissue reaction (HE). Artificial histologic changes. C. Dissolution of granule cells in cerebellar cortex. D. Spiky neurons in surgical specimen (HE).
The pathomechanism of cerebral aging is complex. Mitochondria play a central role in the aging process. With advancing age, the amount of mitochondriaderived free oxygen radicals increases, damaging cellular lipids and proteins and the mitochondrial DNA. This oxidative stress is not effectively countered due to a decline in antioxidant defense mechanisms. It is noteworthy that aging increases the risk for neurodegenerative diseases, vascular diseases, and malignancies, all leading causes of death in the elderly. Pathology Grossly, the brain volume diminishes by about 2% to 3% per decade after age 50, resulting in convolutional and white matter atrophy and enlargement of the subarachnoid space and lateral ventricles. The leptomeninges thicken, with prominent arachnoid granulations. Histologically, lipofuscin, a yellowish-brown pigment (the wear-and-tear pigment), accumulates in the perikaryon of the neurons. The neuronal density may be reduced in the hippocampus, the frontal cortex, and the cerebellum. The number of fibrous astrocytes and microglial cells increases. Corpora amylacea accumulate around the blood vessels and beneath the ependyma and pia mater.
The pyramidal neurons of the hippocampus may display a small number of neuritic plaques, neurofibrillary tangles, granulovacuolar degeneration, and Hirano bodies (see Fig. 2.22). The spinal cord may display small, thin calcified plaques attached to the leptomeninges.
A RT I F IC I A L C E R E BR A L C H A NG E S Artificial changes, gross and histologic, result from postmortem autolysis, insufficient fi xation and prolonged histological processing. "Swiss cheese" changes are multiple smooth-walled cavities caused postmortem by gas-producing organisms. Tissue reactions are typically absent, and microorganisms may clog the lumens of small blood vessels (Fig. 2.23). Among histologic changes, the dissolution of granular cells in the cerebellar cortex results from postmortem autolysis. Buscaino bodies—round, mucinous structures in the white matter—result from postmortem myelin degradation. Prolonged histologic processing shrinks the parenchyma, producing dilated perivascular and pericellular spaces. Dark, spiky neurons with corkscrew dendrites are seen at the edge of surgical specimens (see Fig. 2.23).
BIBLIOGRAPHY Kurosinski, P., & Götz, J. (2002). Glial cells under physiologic and pathologic conditions. Arch Neurol, 59, 1524–1528. Ludwin, S. K. (1997). The pathobiology of the oligodendrocytes. J Neuropath Exp Neurol, 56, 111–127. Mattson, M. P. (2001). Molecular biology of the aging nervous system. In S. Duckett, J.C. De La Torre (Eds.), Pathology of the aging human nervous system, 2nd edition (pp. 16–41). New York: Oxford University Press.
Medana, I. M., & Esiri, M. M. (2003). Axonal damage: a key predictor of outcome in human CNS diseases. Brain, 126, 515–530. Norenberg, M. D. (1994). Astrocyte responses to CNS injury. J Neuropath Exp Neurol, 53, 213–220. Sarnat, H. B. (1995). Ependymal reactions to injury. A review. J Neuropath Exp Neurol, 54, 1–15.
1. Neurofibrillary tangles are encountered in: A. B. C. D. E.
Normal aging Down syndrome Postencephalitic parkinsonism None of these All of these
2. Lewy bodies are diagnostic of: A. B. C. D. E.
Amyotrophic lateral sclerosis Idiopathic Parkinson's disease Peroxisomal diseases Progressive supranuclear palsy Arteriosclerotic parkinsonism
3. Axonal spheroids: A. B. C. D. E.
Result from swelling of Golgi type 2 axons Occur in hippocampus Characterize viral diseases Result from shearing injuries of axons Are fi xation artifacts
4. A glial scar is produced by: A. B. C. D. E.
Oligodendrocytes Alzheimer's type 2 astrocytes Fibrillary astrocytes Rosenthal fibers Schwann cells
5. The major function of oligodendrocytes is: A. B. C. D. E.
Phagocytosis of tissue debris Replacement of lost tissue Protection against bacterial invasion Formation of blood–brain barrier Formation of myelin
6. The term Wallerian degeneration in the CNS refers to: A. Degeneration of axons beginning in their distal ends B. Degeneration of axons and their myelin sheaths proximal to transection C. Degeneration of axons and their myelin sheaths distal to transection D. Degeneration of neurons that have lost their synaptic connections E. Degeneration of neurons that project to denervated neurons 7. All of the following statements concerning vasogenic edema are correct except: A. It is associated with dilutional hyponatremia. B. It results from the breakdown of the blood–brain barrier. C. It is associated with expanding mass lesions. D. It causes herniations. E. It affects chiefly the white matter. 8. Increased intracranial pressure associated with a mass lesion can cause all of the following except: A. B. C. D. E.
Cerebellar tonsillar herniation Pituitary necrosis Isolated abducens nerve palsy Hydrocephalus ex-vacuo Hippocampal herniation
9. If a 40-year-old woman, diagnosed with an acute right subdural hematoma, suddenly develops a right ptosis with a dilated pupil nonreactive to light, the most likely cause is: A. B. C. D. E.
Acute hydrocephalus Occipital lobe infarct Laceration of ipsilateral pedunculus Laceration of contralateral pedunculus Transtentorial hippocampal herniation
10. All of the following statements concerning normal pressure hydrocephalus are correct except: A. It manifests with gait disorder. B. It can develop after purulent meningitis. C. It can complicate a subarachnoid hemorrhage. D. MRI shows normal ventricles and enlarged subarachnoid space. E. MRI shows large ventricles and normal or mildly enlarged subarachnoid space.
11. All of the following statements concerning cerebral changes in physiologic aging are correct except: A. Lipofuscin accumulates in the perikaryon of the neurons. B. A few cortical neurons display neurofibrillary tangles. C. Pyramidal neurons in hippocampus display Hirano bodies. D. Neurons of dentate gyrus display Pick bodies. E. A few neuritic plaques occur in the Ammon's horn. 12. Artificial cerebral changes include all of the following except: A. Dissolution of the granular cell layer in the cerebellar cortex B. Dilated pericellular spaces C. Spiky neurons D. "Swiss-cheese" brain E. Corpora amylacea (Answers are provided in the Appendix.)
Cerebral Hypoxia
Etiology Pathology Clinical Features Permanent Global Ischemia: Brain Death Cerebral Pathology in Chronic Epilepsy
dequate oxygen (O2) supply, approximately 6 mL/100 g/min for the gray matter and less for the white matter, is vital for normal functioning of the nervous tissue; insufficient O2 supply leads to cerebral hypoxia.
ETIOLOGY The major causes of cerebral hypoxia are (a) hypoxemia, (b) anemia, (c) histotoxicity, and (d) ischemia (stagnant cerebral blood flow). Hypoxemic hypoxia develops when the blood oxygen tension falls below 40 mm Hg, which may occur in acute respiratory arrest, chronic obstructive pulmonary disease, alveolar hypoventilation, airway obstruction, near-drowning, diminished oxygen concentration
in the air, weakness of respiratory muscles, and status epilepticus. Anemic hypoxia develops when the oxygencarrying hemoglobin falls to half its normal concentration, as occurs in severe blood loss and chronic anemia. Histotoxic hypoxia is caused by toxic substances, such as carbon monoxide, cyanide, and sulfide, which prevent utilization of oxygen by the neural tissue. Ischemic (stagnant) hypoxia develops when the blood flow falls below 18 mL/100 g tissue/min. This drop may be regional, confi ned to an arterial territory (see Chapter 4), or global, leading to generalized cerebral hypoperfusion. Global cerebral ischemia, transient or permanent, may occur in a variety of clinical settings: cardiac arrest, cardiac arrhythmias, sudden hypotension from myocardial infarct, and severe rise of intracranial pressure. Unlike in hypoxemic and anemic hypoxias, in ischemic hypoxia, the brain is deprived of all blood constituents, most importantly of glucose; moreover, the harmful metabolites such as lactic acid are not eliminated. In certain clinical situations, different types of hypoxias are combined; in cardiopulmonary arrest ischemia and hypoxemia occur concurrently.
Ammon's horn (Cornu Ammonis CA) A. histologic section (LFB-CV). B. Schematic drawing showing the sections of CA.
PAT H O L O G Y General Aspects The severity and extent of the pathologic process depends chiefly on the severity and duration of the hypoxic event, on the body temperature, and on the blood glucose concentration. Hyperglycemia aggravates the ischemic damage whereas hypothermia protects the brain. The cerebral pathology is distinguished by (a) selective neuronal necrosis and (b) selective regional vulnerability. In selective neuronal necrosis, a lack of oxygen from any cause affects fi rst, and usually, only the neurons. Necrosis of the glial cells, axons, and myelin (pannecrosis) occurs in severe and protracted hypoxicischemic events. Selective regional vulnerability determines the anatomic distribution of the lesions. Most vulnerable are the hippocampus, the neocortex, the cerebellar cortex, the thalamus, and the basal ganglia. The hypothalamus, the brainstem, and the spinal cord are the least vulnerable. In the hippocampus, the pyramidal neurons in the CA1 zone (Sommer's sector) are primarily affected (Fig. 3.1); in the neocortex, laminae 3, 5, and 6; in the cerebellum, the Purkinje cells;. in the thalamus, the anterior and dorsomedial nuclei; and, in the basal ganglia, the spiny neurons. Carbon monoxide poisoning has an affi nity for the iron-rich globus pallidus and the reticular zone of the substantia nigra. Gross features range from patchy congestions of gray structures in the very acute stage, through soft, spongy cortex in the subacute stage, to atrophic sclerotic
Acute ischemic–hypoxia. A few days' survival following myocardial infarct and cardiac arrest in a 62-year-old man. Coronal section shows patchy congestion in the cerebral cortex.
cortex in the chronic stage. The deep gray structures and the hemispheric white matter are variably atrophic, and the ventricles are dilated in chronic cases (Figs 3.2. 3.5, 3.7, 3.8 and 3.9 ). Histologic Features Neuronal Necrosis Red neurons, the histologic hallmarks of hypoxicischemic injuries, display bright eosinophilia of the perikaryon, loss of Nissl substance, and shrunken basophilic homogenous nucleus (Fig 3.3). Other neurons appear as ghost neurons, displaying faintly stained perikaryon and nucleus, or as dark neurons, displaying condensed, darkly stained perikaryon and corkscrew-
C E R E B R A L H Y P OX I A
Hypoxic-ischemic neurons in (A) Ammon's horn and (B) cerebellar cortex. The perikaryon, shrunken and devoid of Nissl substance, stains intensely red. The condensed pyknotic nucleus stains deeply blue. C. Chronic mineralized (ferruginated) dead neurons in cerebral cortex, hematoxylin-eosin (HE).
Acute cortical multilaminar necrosis (case in Fig 3.2). A and B. The faintly stained ischemic laminae are sharply demarcated from the relatively spared external laminae and are depleted of neurons and glial cells (LFB-HE; HE).
like dendrites. Irreversibly damaged neurons gradually disintegrate and disappear. Some remaining dead neurons become incrusted with calcium and iron salts (ferrugination) (Fig. 3.3). Death of the cortical neurons, particularly those in the hippocampus, may be delayed hours to days following a short episode of global ischemia. This delayed neuronal death, or maturation phenomenon, may account for a delay in a patient's deterioration, affording a short time for therapeutic intervention.
Cortical Laminar Neuronal Necrosis Neuronal necrosis in the cerebral cortex typically occurs in a laminar fashion, seldom in multiple small foci. The neuronal necrosis may involve one or several laminae, or even the whole width of the cortex. With time, a dense astrocytic fibrillary gliosis forms at the site of lost neurons. In the cerebellum, Bergmann astrocytosis replaces the Purkinje cells.
Cortical Laminar Pan-Necrosis A severe and prolonged hypoxic-ischemic insult affects not only the neurons but also the oligodendrocytes, the astrocytes, the myelin, and the axons, all of which undergo necrosis (infarction). This may occur in one or several laminae, or throughout the entire width of the cortex. The capillaries, least vulnerable to hypoxia, show prominent endothelial swelling and proliferation. Macrophages derived from microglial cells and blood monocytes gradually remove the tissue debris. Meanwhile, at the edge of the necrosis, the astrocytes proliferate into large gemistocytic astrocytes, separating the cortex from the healthy white matter. Ultimately, a loose mesoglial network replaces the cerebral cortex (see Figs. 3.4, 3.5, 3.7, and 3.8). Hypoxic-Ischemic Leukoencephalopathy Hypoxic-ischemic leukoencephalopathy, a rare condition, results from less severe but prolonged hypotension
Subacute cortical pan-necrosis. A 52-year-old man survived 12 days in a coma following a cardiorespiratory arrest of approximately 28 minutes. A. Transverse section of cerebral hemispheres shows reddish-brown discoloration of the cerebral cortex and softening of the white matter. B. The cerebral cortex is outlined by a darkly stained outer and a faintly stained inner layer. C. The outer layer contains necrotic tissue densely packed with macrophages. A few ischemic neurons are entrapped among macrophages (HE).
and cerebral hypoperfusion. It is characterized by multiple small areas of demyelination in the cerebral hemispheric white matter (Fig. 3.6). Within these areas, axonal changes vary in severity, macrophages are absent, and astrocytic reaction is insignificant. Pathomechanism of Hypoxic-Ischemic Neuronal Necrosis Hypoxic-ischemic neurons die of the excitotoxic effects of the neurotransmitter glutamate and its analogs that accumulate in excess in ischemic tissue. These excitatory neurotransmitters depolarize the neuronal membrane, allowing excessive influx of sodium, chloride, water, and calcium into the neuronal compartment. Subsequent swelling, metabolic dysfunction, and disruption of the cellular membrane ultimately lead to the disintegration of the neurons. Why neurons in certain regions are more vulnerable to hypoxia-ischemia than are those in other regions has not been elucidated fully. Regional differences in vascular architecture seem not to be a satisfactory explanation. Regional differences among neurons possessing specific receptors for locally released excitatory neurotransmitters are a more likely explanation. Hence, regions with the highest concentration of neurons that possess glutamate-sensitive receptors are the most vulnerable to hypoxia-ischemia.
Hypoxic-ischemic leukoencephalopathy. Twelve days prior to his death, a 66-year-old man with chronic obstructive lung disease suffered a severe acute exacerbation, which failed to respond to intensive therapy. Macrosection from the cerebral hemisphere shows small focal areas of myelin pallor (LFB-HE).
C L I N I C A L F E AT U R E S Syncope, the momentary loss of consciousness, results from transient global ischemia of a few seconds duration. Hypoxic and ischemic encephalopathy results from a mild to moderate continuous hypoxia that produces a variety of symptoms, including headaches, confusion, memory and cognitive impairment, seizures, myoclonus, and motor and sensory deficits. Severe hypoxia,
when it lasts 10 minutes or more, produces diffuse and profound cerebral damage manifested by alterations of consciousness ranging from lethargy to deep coma, seizures, myoclonic jerks, changes of muscle tone, and pathologic reflexes. Late sequelae comprise a broad spectrum of neurologic and mental symptoms. At one extreme is full recovery and, at the other, irreversible coma, persistent vegetative state, or dementia (Figs. 3.7, 3.8 and 3.9; Tables 3.1 and 3.2). A variety of temporary or permanent symptoms may occur between these extremes: seizures, action myoclonus, parkinsonian features; cerebellar ataxia; visual, motor, and sensory deficits; variable degrees of cognitive and memory impairment; affective disorders; and behavioral changes.
PER M A N E N T GLOBA L ISC H E M I A: B R A I N D E AT H The difference between the mean systemic arterial blood pressure and the intracranial pressure (ICP) (pressure of the CSF) maintains the cerebral perfusions pressure (CPP). A drop in arterial blood pressure or an increase in ICP depresses blood perfusion. When the CPP suddenly drops below a critical value (about 40 mm Hg), cerebral circulation gradually ceases. If blood flow is not restored, the nonperfused brain suffers total and irreversible damage, eventually leading to irreversible cessation of all functions of the brain, in both the cerebral
hemispheres and the brainstem. Brain death is defi ned clinically as irreversible coma, apnea, and loss of all brainstem reflexes. Cardiorespiratory functions can be temporarily maintained with mechanical support and vasopressor agents. Pathologic Features The term respirator brain is considered inappropriate, because the pathologic changes relate not to the use of mechanical ventilation but to permanent nonperfusion. The changes due to in vivo autolysis become noticeable within 12 to 24 hours. Grossly, the brain is congested, swollen, soft, and mushy (Fig. 3.10). The hippocampus and the cerebellar tonsils are herniated and necrotic. The cortex is dusky, and the white matter pinkish and soft due to incomplete fi xation. Histologically, the neural tissue stains faintly: The neurons are pale, ghost-like, or brightly eosinophilic; the glial nuclei are shrunken; the astrocytes and the blood vessels show no reactive changes; and the pituitary gland is necrotic (Fig. 3.10).
C E R E B R A L PAT H O L O G Y I N C H RON I C E P I L E P S Y Hypoxic-ischemic lesions often are encountered in the brains of patients who suffer from epilepsy with generalized tonic-clonic seizures and status epilepticus. The lesions result from respiratory and circulatory
Prolonged coma following cardiac arrest. Chronic cortical pan-necrosis. Three-month survival in a 69-year-old man. A. Transverse section of the cerebral hemispheres shows thinning and sponginess of the cortex, necrosis of the basal ganglia, and focal softening of the white matter. The cerebral cortex shows (B) ischemic necrosis of the entire width of the cortex (LFB-CV) and (C) intense perinecrotic astrocytic reaction (GFAP).
Persistent vegetative state following cardiac arrest with 4.5-year survival. Chronic cortical pan-necrosis. At 7 months of age, a previously healthy baby girl suffered a cardiac arrest for 10 minutes during anesthesia for repair of a diaphragmatic hernia. After 40 minutes, the heart rate returned to normal. The child remained in a permanent vegetative state until her death at age 5 years. A. On examination, at 5 years of age, her eyes were open and moved around but she did not react to visual or verbal stimuli and made no spontaneous movements. Her extremities were spastic, atrophic, and deformed. She slept through the night and also for a few hours during the day. B. On transverse section, the cerebral cortex is thin and spongy, the gray structures are atrophic, the hemispheric white matter is reduced, and the ventricles are enlarged. C. The cortex from the frontal to the occipital lobes underwent cystic necrosis (HE). D. It is replaced by a glial mesodermal network (van Gieson), E. which contains lipid-laden macrophages (oil-red O). F. The hemispheric white matter is devoid of myelin (Weil stain). G. Schematic representation of the sites of the surviving neurons: hypothalamus, brainstem, and parts of hippocampus. H. The cerebellar cortex is totally depleted of Purkinje cells, basket fibers and granule cells; it is outlined by a prominent Bergmann astrocytic layer (Bodian stain).
Post-hypoxic dementia. Following resuscitation from ventricular fibrillation and cardiac arrest, a 23-year-old man became severely demented. Thirteen years later, at age 36 years, he died. A. Multifocal thinning of the cerebral cortex, atrophy of the white matter, and enlargement of the anterior horns. B. Loss of neurons in hippocampal gyrus.
Comparison Between Clinical Presentation of Prolonged Coma and Persistent Vegetative State
Comparison Between Anatomic Sites of Pathology in Prolonged Coma and Persistent Vegetative State
Prolonged Coma
Persistent Vegetative State
Awareness of self and environment lost, wakefulness retained Markedly reduced Reduced to sound, screaming, moaning, groaning Retained Intact Retained
Motor activity Speech
Lost Lost
Sleep-wake cycle Respiration Autonomic functions
Lost Altered Altered
Anatomic Sites of Pathology Prolonged Coma
Widespread bi-hemispheric cortical and/or white matter Diencephalon Rostral brainstem
Widespread bi-hemispheric cortical and/or white matter Bi-thalami
Permanent global ischemia: Brain death. A 72-year-old man suffered a cardiopulmonary arrest and survived 11 days with the assistance of mechanical ventilation. A. Transverse section of the cerebral hemispheres shows break-up of neural tissue in the basal ganglia and white matter and patchy, dusky discoloration of the cortex. B. Ghost neurons in the brainstem and lack of glial and vascular reactions (HE).
Ammon's horn sclerosis in a 28-year-old woman with generalized tonic-clonic seizures. A. The Ammon's horns are atrophic, and the temporal horns are enlarged. B. Thinning of the Sommer's sector from neuronal losses and dense diffuse astrogliosis in another chronic epileptic patient (Holzer stain).
impairments that occur during and after the seizures. Two characteristic lesions are Ammon's horn sclerosis and cerebellar cortical atrophy. Ammon's Horn Sclerosis Grossly, the Ammon's horn is atrophic, gray, and fi rm, and the adjacent temporal horn is variably dilated. Histologically, severe or total loss of pyramidal neurons and astrocytic gliosis are present in CA1 zone (Sommer's sector). The lesion may extend beyond the Sommer's sector to involve the entire Ammon's horn (hippocampal sclerosis) and also may extend into the parahippocampal regions and amygdala (mesial temporal sclerosis) (Fig. 3.11).
Cerebellar cortical lobular atrophy in a child with intractable tonic-clonic seizures. Loss of Purkinje cells and granule cells. The cortex is outlined by a prominent Bergmann astrocytic layer (cresyl violet).
Cerebellar Cortical Atrophy
Ammon's Horn Sclerosis in Temporal Lobe Epilepsy
Grossly, the cerebellar folia are atrophic, often in a lobular pattern, the atrophy being more prominent at the depth and walls of the folia than at the crest. Histologically, the cortex shows Purkinje cell losses and replacement Bergmann astrocytosis. The lobular pattern results from edema that develops during the seizures and compromises the blood flow, fi rst at the depths of sulci (Fig. 3.12). Scattered laminar and small focal neuronal losses and astrogliosis in the neocortex, amygdala, and thalamus variably occur.
Ammon's horn sclerosis has been identified in a significant number of surgically resected mesio-temporal lobes from patients with a history of intractable or drug-resistant complex partial seizures. Some patients also suffered from generalized tonic-clonic seizures (Fig. 3.13). A causal relationship between Ammon's horn sclerosis and temporal lobe seizures has often been raised. Ammon's horn sclerosis may develop in a variety of clinical conditions complicated by severe hypoxia: birth injuries, febrile seizures, and vascular, infectious, and
BIBLIOGRAPHY Bernat, J. L. (1997). Systemic hypoperfusion brain injury In K. M. A. Welch, D. J. Caplan, et al. (Eds.) Primer on cerebrovascular diseases (pp. 289–292). San Diego: Academic Press. Ginsberg, M. D., Hedley–Whyte, E. T., & Richardson, E. P., Jr. (1976). Hypoxic-ischemic leukoencephalopathy in man. Arch Neurol, 33, 5–14. Hogan, R. E. (2001). Mesial temporal sclerosis Clinicopathological correlations. Arch Neurol, 58, 1484–1486. Kinney H. C., Samuels, M. A. (1994). Neuropathology of the persistent vegetative state. A review. J Neuropathol Exp Neurol, 53, 548–558.
Ammon's horn sclerosis in temporal lobe epilepsy (cresyl violet stain). Surgically resected right temporal lobe specimen from a 28-year-old woman. At age 11 years, she had a few generalized tonic-clonic seizures. Temporal lobe seizures began at age 23 years.
traumatic injuries. It is conceivable that Ammon's horn sclerosis, when acquired early in life, may, in time, become epileptogenic, capable of triggering complex partial seizures.
Leestma, J. E. (2001). Neuropathology of brain death. In E. F. M. Wijdicks (Ed.). Brain death (pp. 45–60). Philadelphia: Lippincott–Wilkins. Multi-Society Task Force on PVS, The. Medical aspects of the persistent vegetative state. (1994). N Engl J Med, 330, 1499–1508. Plum, F. & Posner, J. B. (1980). The diagnosis of stupor and coma, 3rd ed. Philadelphia: FA Davis Company.
1. Ischemic neurons reveal: A. Swollen cytoplasm B. Pale staining with eosin C. Bright eosinophilia in hematoxylin-eosin– stained sections D. Enlarged nucleus E. Bluish discoloration of cytoplasm in hematoxylin-eosin–stained sections 2. The characteristic pattern of cortical neuronal losses in cerebral hypoxia is: A. B. C. D. E.
Haphazard Laminar Perivascular None of these All of these
3. The neural tissue elements most vulnerable to hypoxia are: A. B. C. D. E.
Oligodendrocytes Astrocytes Neurons Axons Myelin
4. The cerebral regions most vulnerable to hypoxia are: A. B. C. D. E.
Hippocampus Neocortex Purkinje cells All of these None of these
5. In delayed death from carbon monoxide, the site of cerebral pathology is the: A. B. C. D. E.
Putamen Pallidum Ammon's horn Thalamus Red nucleus
6. All of the following statements concerning brain death are correct except: A. It is caused by permanent cerebral global ischemia. B. Lack of response to noxious stimuli is present. C. Brainstem reflexes are present. D. EEG is isoelectric. E. Patient is apneic. 7. The zone of the hippocampus most vulnerable to hypoxia is: A. B. C. D.
CA1 (Sommer's sector) of Ammon's horn CA2 zone CA4 zone Presubiculum
8. Cerebral changes encountered in the brains of patients who had suffered from chronic epilepsy are: A. B. C. D. E.
Purkinje cell degeneration Ammon's horn sclerosis Astrocytic gliosis in cerebral cortex None of these All of these
9. All of the following statements concerning cerebral hypoxia are correct except: A. It develops during an acute cardiorespiratory arrest. B. Histotoxic hypoxia can be caused by cyanide. C. Ischemic hypoxia develops when the blood flow falls below 18 mL/100 g/min. D. Hypothermia aggravates ischemic brain damage. E. Hyperglycemia aggravates ischemic brain damage. 10. The brains of patients kept for some time on mechanical ventilation show all of the following except: A. B. C. D. E.
Poor fi xation Dusky discoloration Myelin pallor Pituitary necrosis Leukocytic infiltration (Answers are provided in the Appendix.)
Etiology, Pathology, and Clinical Aspects of Stroke Various Stroke Etiologies: Stroke in the Young Cerebral Pathology in Arteriolosclerosis: Vascular Dementia
E T I O L O G Y, PAT H O L O G Y, A N D C L I N I C A L A S P E C T S OF S T ROK E The incidence and mortality of stroke are high. An estimated 500,000 to 700,000 new cases occur every year. Despite early identification and treatment of risk factors, it remains the third leading cause of death in Western countries. The most disabling neurologic disease of the elderly, stroke commonly affects individuals over 55 years of age, and the incidence increases with advancing age. It is more common among men and among African Americans. Importantly, stroke also occurs among younger subjects, even children, in whom etiologies comprise a broader spectrum. Stroke presents with a sudden onset and rapid progression of focal neurologic symptoms and signs, culmi-
nating within minutes or hours—at most within 24 to 48 hours. It results from a sudden alteration of cerebral blood flow in an arterial territory (regional cerebral blood flow, rCBF). This alteration occurs in one of two ways: A reduction of rCBF causes ischemia and eventually an infarction, or B bleeding into the brain parenchyma or into the subarachnoid space causes a massive intracerebral hematoma or a subarachnoid hemorrhage. Thus, a stroke is either ischemic or hemorrhagic; its pathologic substrate is either an infarct or a hemorrhage. Ischemic Stroke Cerebral Infarction The brain requires a constant and adequate blood flow to supply oxygen and glucose essential for its high energy metabolism. A constant blood flow is assured by an autoregulatory mechanism of arteries and arterioles; they constrict in response to rising systemic blood pressure and dilate in response to falling systemic blood pressure. This mechanism operates while the arterial pressure remains between 50 and 160 mm Hg. One-
Atherosclerosis of cerebral arteries. A. Severe atheromatosis of basal arteries. Confluent yellow atheromatous plaques occur in the arterial walls. The basilar artery is elongated and stiff, and the lumen is distended. The sclerotic right carotid presses on the optic nerve. B. The atheromatous basilar artery displays focal dilation and narrowing of the lumen and presses on the pontine basis. The rigid walls of the carotids press on the optic nerves. C. Atheromatous plaque in the wall of the basilar artery shows focal subintimal cholesterol clefts, disruption of the elastic lamina, and marked intimal proliferation severely reducing the lumen (van Gieson).
fourth of the cardiac output is to the brain—an average blood flow of 700 to 800 mL/min (55 to 65 mL/100 g/ min). A reduction of blood supply to 15 to 20 mL/100 g/ min for a few minutes produces ischemia and neurologic deficits. A prolonged fall to 8 to 10 mL/100 g/min results in ischemic necrosis, that is, an infarction. Etiologies Arteriosclerosis of the cervicocranial arteries and diseases of the heart are primary causes of infarctions in the elderly. A group of less common but important etiologies affect chiefly younger individuals and are presented in the section, Various Stroke Etiologies. Arteriosclerosis of cervicocranial arteries. Atherosclerosis affects chiefly the large arteries: the extracranial cerebral arteries and their major intracranial branches. Preferential sites are the bifurcations of common carotid arteries, origins of internal carotids, and vertebral arter-
ies. Intracranially, atheromatosis commonly develops in the cavernous segment and syphon of carotids, and at the points of junction, proximal segments, and bifurcations of major arteries. The atherosclerotic artery is rigid, elongated, or tortuous. The lumen is distended or reduced, and the wall contains multiple, often confluent yellow atheromatous plaques (Fig. 4.1). Potential consequences of atherosclerosis. Atherosclerosis promotes infarction in several ways (Fig. 4.2): (a) It predisposes to local thrombus formation and luminal occlusion; (b) it is a potential source of fibrinoplatelet and cholesterol emboli to the brain; and (c) it can critically reduce the vascular lumen by 70% or more, thus rendering the arterial territory vulnerable to systemic circulatory insufficiency. Arteriolosclerosis affects the small parenchymal arteries and arterioles. Several pathologic forms exist, such as fibrosis, hyalinosis, mural lipid deposits, micro-
C E R E B ROVA S C U L A R D I S E A S E S
Consequences of atherosclerosis. A. Thrombotic occlusion of MCA in the Sylvian fissure causing a large infarct. B. Cholesterol embolus in a small leptomeningeal artery overlying a cortical infarct, hematoxylin-eosin (HE) C. Hemodynamically significant (greater than 75%) stenosis in a carotid endarterectomy specimen.
Pathologic forms of arteriolosclerosis. A. Fibrohyalinosis with mural thickening and luminal stenosis (HE), B. Mural lipid deposits (oil-red-O). C. Eccentric microatheroma (LFB-HE). D. Markedly thickened, structureless fibrotic wall and virtually nonexisting lumen (HE).
atheroma, and fibrinoid necrosis (Fig. 4.3). These changes are commonly associated with chronic hypertension and are important in the etiology of lacunar infarcts.
Diseases of the heart. Most cardiac diseases are potential sources of emboli to the brain. The most important are chronic atrial fibrillation, sick sinus syndrome, mitral and aortic valvular diseases, and myocardial
Arterial supply of the brain. Schematic drawings of territorial supplies of major cerebral arteries on (A) lateral, median, and basal surfaces; (B) and (C) on transverse planes; and (D) on horizontal plane. Blue, anterior cerebral artery (ACA); red, middle cerebral artery (MCA); yellow, posterior cerebral artery (PCA); green, anterior choroidal artery (AchA).
infarct with overlying thrombus. Arrhythmias are apt to dislodge platelet or fibrin fragments and calcium flecks from a mural thrombus or from the valves. A left atrial myxoma is a rare source of emboli. An atrial septal defect (right–left shunt) opens the way to emboli from deep venous thrombi to the brain (paradoxical emboli). Heart failure with systemic hypotension or hypovolemia is another important cause of focal ischemia in the territory of a severely stenotic artery. Less common etiologies. This group comprises various vasculopathies and vasculitis, hematologic diseases, iatrogenic complications, illicit substance abuse–related diseases, and some inherited metabolic diseases (see section, Various Stroke Etiologies).
Pathology Gross features. The assessment should include the type, age, size, and arterial territory (Fig. 4.4; Table 4.1): • Type of infarct. A bland infarct is pale over the entire area, and a hemorrhagic infarct contains confluent petechial hemorrhages in the cortex and subcortical gray structures (Fig. 4.5). Emboli are an important cause of a hemorrhagic infarct. The bleeding occurs through damaged capillary walls, following fragmentation and migration of the embolus. Bleeding distally to the occlusion through retrograde collateral circulation is an alternative mechanism. A sudden rise in blood pressure can precipitate such a situation. • Age of infarct. An infarct evolves through three stages: necrosis, liquefaction, and cavitation (Fig. 4.6). During
the acute stage, which occurs approximately the fi rst week following stroke, the ischemic tissue undergoes necrosis. During the fi rst 24 hours, it swells, appears somewhat pale, and is slightly soft. After 24 to 48 hours, it becomes friable, breaks up, and is demarcated from the surrounding healthy tissue by artificial cracks. • During the acute stage, ischemic necrosis invariably is associated with edema (cellular and vasogenic), which reaches its peak by the fi fth or sixth day. Cellular edema affects chiefly the gray matter, and vasogenic edema affects the white matter. Importantly, extensive edema, by increasing the brain volume, leads to herniations with brainstem and medullary compression. These subject the patient to serious risk of deterioration and even death. • By the end of the fi rst week, the subacute stage begins, as the necrotic tissue breaks down and lique-
fies, which may take 2 to 3 weeks. Gradually, the edema resolves, the tissue debris is removed, the infarcted area shrinks, and ultimately is transformed into a cystic cavity. This chronic stage of cavitation may take several weeks or months, depending on the size of the infarct. • Size and arterial territories. Infarcts are situated within territorial boundaries of the arteries subjected to ischemic insults. A large infarct occupies all or part of the supply territory of a cervical or large intracranial artery; a large infarct is commonly caused by atherothrombotic or thromboembolic occlusion. It is more common in the carotid than in the vertebral arterial territory (Figs. 4.7 through 4.10). The most common site is the territory of the middle cerebral artery (MCA).
A watershed or border-zone infarct is situated between the terminal branches of adjacent major arteries (Fig. 4.11). Likely causes are embolus or a sudden drop in blood pressure, which fi rst compromises the blood flow in the terminal branches (hemodynamic failure). A small or lacunar infarct is a cystic cavity with irregular margins, measuring 0.5 to 1 cm (rarely, 1.5–2 cm [giant lacune]), which results from the removal of necrotic tissue. It is associated with arteriolosclerosis of the deep penetrating basal arteries and the cortical (medullary) arteries, and it occurs commonly in the basal ganglia, internal capsule, thalamus, and pons (Fig. 4.12). In the white matter, the site of predilection is the watershed zone between the cortical and basal penetrating arteries—the corona radiata, the outer angle of the
Gross Assessment of Arterial Infarcts Type: Pale Hemorrhagic Arterial territory: Carotid Vertebrobasilar Size: Large—macrovessels Lacune—microvessels Age: Acute—ischemic necrosis Subacute—liquefaction Chronic—cavitation
Types of infarcts. A. Pale, bland infarct in carotid territory (MCA and ACA). B. Hemorrhagic infarct in MCA territory. Petechial hemorrhages are confi ned to the gray structures.
Morphologic evolution of infarcts in MCA territory. A. Ischemic necrosis. Note the swelling of ischemic territory and compression of adjacent ventricle. B. Liquefaction of ischemic tissue. C. Cavitation following removal of tissue debris. Note the enlargement of adjacent ventricle, indicating chronicity of the lesion.
Infarcts in carotid arterial territories. MCA infarcts: A. cortical (parietal artery). B. basal ganglia (lenticulostriate artery). C. ACA infarct. D. AchA infarct. E. MCA and ACA infarct.
C A
Infarcts in vertebrobasilar arterial territories. A. PCA infarct. B and C. Bilateral midbrain infarcts (LFB-CV) (peduncular branches of PCA and BA).
Basilar artery infarcts. A. Extensive thrombotic infarct involves the basis and tegmentum of the pons. B. Pontine basis infarct (myelin stain). C. Cerebellar infarct (SCA territory).
Vertebral artery infarcts. A and B. Gross and histologic picture of lateral medullary infarct (LFB-CV), the territory of the posterior inferior cerebellar artery, (PICA).
Watershed infarcts. A. Cortical infarct in the border zone between ACA and MCA showing B. laminar cortical pannecrosis (the external cortical layer is spared (HE). C. Bilateral cortical– subcortical infarcts in the border zones between ACAs and MCAs. D. Cortical–subcortical infarct in the border zone between MCA and PCA.
lateral ventricle, and the subinsular region (Fig. 4.13). Systemic hypoperfusion due to cardiac failure, hypotension, or hypovolemia, plays a primary role in the pathogenesis. Alternate mechanisms are atheromatous occlusion, microembolus, and, less often, stenosis of extracranial or large intracranial arteries. Multiple infarcts may occur within the carotid or vertebrobasilar territories, or within both. Concomitant infarct and hemorrhage. It is not unusual to fi nd within one brain recent or old infarcts and hemorrhages together (Fig. 4.14). Histologic Features Ischemia elicits a chain of interrelated events: necrosis, edema, inflammatory reaction, macrophage activation, and marginal astrocytic proliferation (Table 4.2).
Ischemic necrosis. During the fi rst 24 to 48 hours, the ischemic tissue appears vacuolated, spongy, and stains faintly with eosin (Fig. 4.15). The distribution is patchy; faintly stained hypoperfused areas alternate with hyperemic areas (luxury perfusion) due to loss of autoregulation and early venous fi lling. The hypoperfused but potentially viable tissue around the ischemic core, the so-called penumbra, provides the rationale for instituting therapy to rescue it from being incorporated into the infarction. The neurons, most vulnerable to ischemia, are fi rst to succumb. Red neurons are the hallmark of ischemia; they shrink and show bright eosinophilia of the perikaryon, dissolution of the Nissl substance, and homogenization of the nucleus (see Fig. 4.15). Other neurons appear as dark neurons with shrunken peri-
Lacunar infarcts. A. Basal ganglia (lenticulostriate artery). B. Thalamus (thalamoperforating artery). C. Pons (paramedian branches of BA).
F I G U R E 4 .14 F I G U R E 4 .13
Giant white-matter lacunar infarct in the border zone between cortical and deep penetrating arteries.
Approximate Timetable of Histologic Events in Ischemic Necrosis 1. Tissue Necrosis Neurons Myelin Glial cells Axons 1 hr — 3–4 days 2. Edema Cytotoxic 3 hrs
3. Inflammation; PNL 24–72 hrs 4. Macrophage Activation 48–72 hrs 5. Capillary Proliferation 48 hrs 6. Marginal Astrocytosis 48 hrs–days
Vasogenic 72 hrs
PNL, polymorphonuclear leukocytes.
Concomitant hemorrhagic and ischemic strokes in a 75-yearold hypertensive woman. She developed ballistic movements in her right extremities, followed 4 days later by left hemiparesis. Gross section shows a fresh hemorrhage in the left subthalamic nucleus and a recent right MCA infarct.
karyon, or as ghost neurons with pale perikaryon and nucleus. As the neurons undergo necrosis, changes also occur in the myelin, nerve fibers, and glial cells. The myelin fi rst loses its affi nity for Luxol fast blue. Then, by about the third day, the myelin gradually disintegrates into neutral lipid globules. Along with the myelin, the nerve fibers break into small fragments, and residual axonal retraction balls may remain at the margin of the infarct. Within the severely affected ischemic areas, the oligodendrocytes and astrocytes also disintegrate. The capillaries, least vulnerable to ischemia, show endothelial hypertrophy and hyperplasia (see Fig. 4.15).
Histologic evolution of infarcts. Ischemic necrosis. A. Ischemic tissue stains faintly with eosin, is vacuolated and spongy. B. Ischemic (red) neurons display a strongly eosinophilic, shrunken perikaryon and a homogenous dark basophilic nucleus (HE). C. Myelin disintegrates into small lipid globules (LFB-CV) and (D) the axons into small fragments (Holmes stain). E. Capillaries are prominent (reticulin stain).
Edema. Two types of edema develop in ischemic tissue: cellular and vasogenic. In cellular (cytotoxic) edema, swelling of the neurons and astrocytes develops within a few hours after the ischemic insult. This swelling results from the opening of the ion pump and the excessive inflow of sodium, chloride, and water into the intracellular compartment and outflow of potassium into the extracellular compartment. Vasogenic edema develops 2 to 3 days after the ischemic insult and reaches its peak by the fifth or sixth day. It results from breakdown of the blood–brain barrier and the escape of fluid and protein into the extracellular space, chiefly into the white matter. The white matter swells and stains faintly with Luxol fast blue. The myelin sheaths are separated from each other, and the pericapillary spaces are filled with plasma fluid (Fig. 4.16). Inflammatory reaction. During the fi rst 24 to 38 hours, the ischemic tissue is invaded by polymorphonuclear
leucocytes (Fig. 4.17). This inflammatory reaction, mediated by cytokines, aggravates the ischemic injury by producing toxic substances and obstructing the microcirculation. Macrophage activation. By about the third day, the leucocytes are replaced by macrophages derived from blood monocytes and activated microglial cells. The macrophages phagocytose the tissue debris and remove it to the blood vessels and subarachnoid space (Fig. 4.18). So, gradually, the infarcted tissue is transformed into a cystic cavity, the lumen of which is traversed by a fi ne fibrous meshwork derived from surviving capillaries (Fig. 4.19). Marginal astrocytic proliferation. At the margin of the ischemic tissue, the astrocytes proliferate into large gemistocytic astrocytes, forming a transition zone between the infarct and the healthy tissue (see Fig. 4.19).
Histologic evolution of infarcts. Vasogenic edema. A. Plasma fluid fi lls the perivascular space (LFB-CrV-E).
Histologic evolution of infarcts. Inflammatory reaction. Polymorphonuclear leukocytes invade the ischemic tissue during the fi rst 24 hours (HE).
Histologic evolution of infarcts. Macrophage activation. A. By the second and third day, macrophages invade the necrotic tissue. B. Cytoplasms of macrophages are fi lled with tissue debris, which is then removed to the perivascular spaces. C. Collection of macrophages around a blood vessel (LFB-CV-E).
Histologic evolution of infarcts. Marginal astrocytic proliferation. A. Chronic cavitated infarct contains a few remaining capillaries and macrophages within the lumen. B. The margin consists of proliferated gemistocytic astrocytes (HE).
Pathomechanism Reduction or cessation of rCBF, by disrupting the oxygen and glucose supply to the nervous tissue and by preventing elimination of harmful metabolites, induces a chain of deleterious processes leading fi rst to neuronal death and ultimately destroying all tissue. Glutamate-
mediated excitotoxicity and lactic acidosis play key roles in ischemic necrosis. Excitotoxicity. Ischemia initiates the release and excessive accumulation of the excitatory neurotransmitters glutamate and aspartate and related amino acids in the
extracellular space. By exciting the neuronal membrane receptors, these neurotransmitters depolarize the synaptic membranes, allowing ionic and water exchange; the inflow of sodium, chloride, and water into the neurons; and the outflow of potassium into the extracellular space. Most important, they promote the entry of calcium into the neurons. Intracellular overload of calcium interferes with mitochondrial and metabolic functions and eventually destroys the neurons.
Lactic acidosis. Ischemia leads to anaerobic glycolysis and the formation of lactic acid and free radicals. The harmful effects of lactacidosis and free radicals, along with some other toxic metabolites, culminate in the breakdown of all components of neural tissue.
Clinical Aspects Presentation. Ischemic stroke accounts for about 80% of all strokes. The clinical presentation is determined by the severity of the ischemic attack and its cause, and also by the adequacy of the collateral circulation and the presence of any stroke risk factors (Table 4.3).
Transient ischemic attack (TIA). A mild and short ischemic attack produces transient impairment of neuronal function. Focal neurologic symptoms and signs develop suddenly, progress rapidly, and usually resolve within
Stroke Risk Factors Age, gender, race Hypertension Arteriosclerosis Cardiac diseases Hyperlipidemia Diabetes mellitus Oral contraceptive use Illicit substance abuse Cigarette smoking Chronic alcohol abuse Obesity Migraine Sedentary lifestyle
less than 24 hours. Clinical features of TIAs in the carotid and vertebrobasilar arterial territories are summarized in Table 4.4. Completed stroke. A severe ischemic attack lasting approximately from thirty minutes to 1 hour produces an infarction: The neurologic deficits remain prolonged or permanent. Classification. There are three subtypes of ischemic strokes based on their pathomechanism (Table 4.5): • Thrombotic stroke, accounting for about 50% of ischemic strokes, is often preceded by TIAs. The symptoms worsen steadily or stepwise during the fi rst 24 to 48 hours (evolving stroke). • Embolic stroke, accounting for about 30% of ischemic strokes, has a very abrupt onset and rapid evolution of neurologic deficits that are maximal from the onset. The source of the embolus—heart, aorta, cervicocranial arteries—is usually evident, and the infarct is often hemorrhagic. • Hemodynamic stroke, accounting for 10% to 30% of ischemic strokes, results from systemic hypoperfusion in the territory of a severely stenotic artery. Cardiovascular diseases that affect the systemic circulation are present, and the infarcts are preferentially located in watershed regions and terminal arterial fields.
Transient Ischemic Attacks Carotid Territory Transient monocular blindness *Hemiparesis *Hemisensory deficit Aphasia (D) Vertebrobasilar Territory Diplopia Binocular visual loss Vertigo Ataxia
Dysarthria Bilateral motor/ sensory deficits Loss of consciousness
*Contralateral. D, dominant hemisphere.
Ischemic Stroke Causes and Presentation Thrombus
Embolus
Cardiogenic Stepwise Fluctuating Hx of TIA
Hemodynamic failure
Arterial
Sudden Rapid progression Hemorrhagic infarct
Clinical Features Clinical features of ischemic stroke greatly depend on the size and location of the infarcts. Large hemispheric and brainstem infarcts present with depression of alertness ranging from somnolence through lethargy to coma. During the acute stage, ischemic edema when severe, aggravates the clinical course and may endanger the patient's life. Seizures may occur during the acute stage or several weeks or months later. Mortality rate ranges from 10% to 20% during the fi rst month. Cardiac and pulmonary complications account for about half the deaths. Neurologic deficits, particularly motor, remain in about 50% of survivors. Behavioral changes, depression, and cognitive decline add to the clinical picture. Multiple cortical or subcortical infarcts, depending on their locations, are the substrates of multiinfarct dementia.
Stroke Syndromes Ischemic strokes produce distinct syndromes for each arterial territory. Table 4.6 summarizes the common clinical manifestations of carotid territory infarcts. The occlusion of the internal carotid artery presents chiefly with features of a middle cerebral artery (MCA) territory infarct; contralateral motor and sensory deficits, visual field defect, and aphasia when the lesion is in the dominant hemisphere. If the occlusion extends beyond the point of origin of the ophthalmic artery, ipsilateral blindness occurs. Anterior cerebral artery (ACA) territory infarct is distinguished by motor and sensory deficits, predominantly in the leg. Neuropsychological dysfunctions are associated with infarcts in the
Systemic hypoperfusion Local arterial stenosis Watershed infarct
territories of cortical branches of the MCA and the ACA. Infarcts in the territories of the vertebrobasilar arteries produce a great variety of syndromes (Table 4.7). Posterior cerebral artery syndromes generally present with various combinations of visual, sensory, and neuropsychological deficits. Large brainstem infarcts are the most detrimental, causing either a sudden loss of consciousness with extensive neurologic deficits or a "locked-in" syndrome with consciousness intact. It is important to differentiate between coma and conditions that superficially may be mistaken for coma (Table 4.8). Cross syndromes of unilateral brainstem infarcts manifest with ipsilateral cranial nerve deficits (3rd to 12th) and contralateral motor and sensory deficits.
Diagnostic Evaluation Specific diagnostic tests are aimed at defi ning the cerebral lesion and identifying any vascular and cardiac pathology. Neuroimaging using structural and functional magnetic resonance imaging (MRI) and computed tomography (CT) scan are most valuable in eliminating diseases that can mimic a stroke, differentiating between an ischemic and a hemorrhagic stroke, and monitoring progression of edema and hemorrhagic complications (Table 4.9): 1. From about 8 to 24 hours after the onset of symptoms, CT scan shows the infarct as a low-density area within an arterial supply territory (Fig. 4.20). Earlier indirect signs, however, are present as loss of differentiation between the cortex and the white
TA B L E 4 . 6 ( A ) .
Internal Carotid Territory Infarcts Syndromes of Middle Cerebral Artery (1) Clinical Features
Cortical and Deep Branches
*Homonymous hemianopia
Conjugate horizontal gaze
Paresis to opposite side
*Hemiplegia face, arm → leg
*Hemisensory deficit
Global aphasia (D)
Expressive aphasia (D)
Receptive aphasia (D)
Agraphia (D), Alexia (D) Gerstmann syndrome; agraphia, acalculia, fi nger agnosia, right-left confusion
Constructional apraxia (nD) Dressing apraxia (nD) Agitated delirium
Neuropsychological dysfunction
Superior Division
Inferior Division
Lenticulostriate Artery
Homonymous hemianopia/ upper quadrantanopia
None/Minimal
*Hemiparesis *Hemisensory deficit
*Contralateral, (D) dominant hemisphere, (nD) nondominant hemisphere. KEY: 1, MCA; 2, superior division; 3, inferior division; 4, lenticulostriate artery.
TA B L E 4 . 6 ( B ) .
Syndromes of Branches of Internal Carotid Artery (2) Clinical Features
Anterior Cerebral Artery
Anterior Choroidal Artery
Ophthalmic Artery
*Homonymous hemianopia quadrantanopia
Amaurosis fugax Partial/total blindness
*Paresis of leg, minimal of arm bilateral: Central paraplegia
*Hemiparesis
*Deficit over leg
Transcortical motor aphasia (D)
Frontal lobe: abulia Bilateral: akinetic mutism, Gait apraxia
*Grasp reflex Sucking reflex Urinary incontinence
*Contralateral; D, dominant hemisphere. KEY: 1, ACA; 2, MCA; 3, AchA.
Subclavian Steal Syndrome An occluded or stenosed subclavian artery, proximal to the origin of the vertebral artery, steals the blood flow from the vertebral artery by reversing its direction. Ipsilateral to stenosis Delayed radial pulse Reduced BP Supraclavicular bruit Exercise of the arm can induce TIAs in posterior circulation
matter, and effacement of sulci. A large infarct, by the second or third day, is surrounded by edema, which produces a mass effect with ventricular compression and midline shift (Fig. 4.21). 2. From about 1 to 3 weeks, a subacute infarct often shows peripheral enhancement due to neovascularity (luxury perfusion). Sometimes, by the second week, the infarct is poorly visualized, a phenomenon referred to as fogging. 3. From 3 to 4 weeks on, a chronic infarct appears as a well-delineated, low-density lesion with a dilated ipsilateral ventricle due to tissue loss. MRI demonstrates the infarction earlier than does the CT scan, within a few hours after the ictus, and is particularly useful in diagnosing lacunar infarcts. An acute infarct appears as a hyperintense (bright) lesion with a
VA, vertebral artery; SA, subclavian artery.
Posterior Cerebral Artery Infarcts Occipitotemporobasal Syndromes Occipitotemporal artery *Homonymous hemianopia Visual agnosias; inability to recognize objects, colors, faces (prosopagnosia) (D) Alexia without agraphia (inability to read—ability to write) (D) Spatial disorientation (nD).
Calcarine artery Unilateral *Homonymous hemianopia
**Bilateral Cortical blindness (pupillary light reflex is present) Denial or unawareness of blindness
Thalamic Syndromes Thalamogeniculate artery Sensory loss for all modalities Dysesthesias Spontaneous pain Athetotic hand posturing Intention tremor Choreoathetosis Homonymous hemianopia
Thalamoperforating artery Unilateral Hemiataxia Tremor Choreoathetosis
Bilateral Hypersomnia Korsakoff amnestic syndrome Subcortical dementia Vertical gaze abnormalities
*Contralateral; D, dominant hemisphere; nD, nondominant hemisphere; **Anton syndrome. KEY: 1, occipitotemporal atery; 2, calcarine artery; 3, thalamogeniculate artery; 4, thalamoperforate artery.
TA B L E 4 . 7 ( C ) .
Midbrain Syndromes *Peduncular Arteries Weber Syndrome Ipsilateral 3rd nerve palsy Contralateral Hemiplegia
Basilar Artery Benedikt Syndrome Ipsilateral 3rd nerve palsy Contralateral Intention tremor
Top of the Basilar Syndrome Vertical gaze palsy Skew deviation of eyes Pupillary changes Somnolence Hallucinosis Confusion Visual field defect
*Branches of PCA and BA. KEY: 3, oculomotor nerve.
TA B L E 4 . 7 ( D ) .
TA B L E 4 . 7 ( E ) .
Pontine Syndromes
Medullary Syndromes
Basilar Artery Infarcts *Locked-in syndrome Quadriplegia Facial diplegia Anarthria, Dysphagia Consciousness; intact
**Pontine tegmentum and basis syndrome Unilateral Bilateral Ipsilateral Coma Cranial nerve 6th, 7th palsy Quadriplegia Gaze palsy Bulbar paralysis Contralateral Facial diplegia Hemiparesis Hemihypesthesia *Paramedian arteries. **Circumferential branches of superior and anterior inferior cerebellar arteries. KEY: BA, basilar artery; Py, pyramids.
Lateral Medullary Syndrome Posterior inferior cerebellar artery (PICA) Ipsilateral Contralateral Loss of pain and Loss of pain and temperature sensations temperature sensations over the face over the body and Loss of cornea reflex extremities Horner syndrome Ataxia Paralysis of soft palate, pharynx, larynx
Medial Medullary Syndrome Anterior spinal artery/Vertebral artery Ipsilateral Contralateral 12th nerve palsy Hemiparesis Loss of position and vibration sensations
KEY: 1, Spinotrigeminal tract; 2, sympathetic tract; 3, spinothalamic tract; 4, pyramids; 5, medial lemniscus; 6, acoustic/vestibular nucleus; 7, vagus motor nucleus; 8, hypoglossus nucleus.
TA B L E 4 . 7 ( F ) .
Cerebellar Syndromes Ataxia of gait, trunk, and ipsilateral limbs Variable midbrain, pontine, medullary deficits
KEY: SCA, superior cerebellar artery, midbrain; AICA, anterior inferior cerebellar artery, pons; PICA, posterior inferior cerebellar artery, medulla; BA, basilar artery.
Comparison Between Coma, Locked-In Syndrome, and Akinetic Mutism Clinical Features
Locked-in Syndrome
Consciousness Motor activity Speech Autonomic functions Brain Stem reflexes Anatomical sites
Lost None None Altered Altered Brain stem Diencephalon Bihemispheric Cortex/white matter
Intact None; due to quadriplegia None; due to anarthria Retained Retained Pontine basis
Intact None/severely reduced Mute/reduced to yes–no Retained Retained Fronto-orbital-cingular regions Diencephalon
TA B L E 4 .9 ( A ) .
TA B L E 4 .9 ( B ) .
CT Appearance of Cerebral Infarct and Hemorrhage
MRI Appearance of Cerebral Infarct and Hemorrhage
Hyperacute 1–24 h Acute 24 h–3 days Subacute 4 days+
Sulcal effacement
Hyperdense
Hypodense Edema Hypodense Mass effect Ventricular compression Ring-enhancement Hypodense Ventricular dilatation
Hyperdense Edema Hyperdense
Chronic 14 days+ weeks
Isodense Hypodense Ring-enhancement
Hyperacute:
Identifier: 1,888,799,978