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BOARD REVIEW SERIES

SEVENTH EDITION

BRS Neuroanatomy

Douglas J. Gould, PhD Professor and Chair Department of Foundational Medical Studies Oakland University William Beaumont School of Medicine Rochester, Michigan

Author of 1st–4th Editions: James D. Fix, PhD (1931–2010)

Acquisitions Editor: Crystal Taylor Development Editor: Deborah Bordeaux Freelance Development Editor: Maria McAvey Editorial Coordinator: Priyanka Alagar Marketing Manager: Danielle Klahr Production Project Manager: Kirstin Johnson Manager, Graphic Arts & Design: Stephen Druding Art Director: Jennifer Clements Manufacturing Coordinator: Margie Orzech Prepress Vendor: S4Carlisle Publishing Services

Seventh Edition

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Library of Congress Cataloging-in-Publication Data ISBN-13: 978-1-975214-37-1 ISBN-10: 1-975214-37-4 Library of Congress Control Number: 2023912843

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To Laurisa—my support and inspiration. I would be lost without you.

Preface

BRS Neuroanatomy , seventh edition, is a concise review of human neuroanatomy intended for health professions students including medical and dental students preparing for their respective boards and other examinations. It presents the essentials of human neuroanatomy in a concise, tightly outlined, well-illustrated format. There are more than 650 questions with answers and explanations, some in cluded at the end of each chapter and some in a comprehensive examination at the end of the book. NEW TO THIS EDITION ■ 20 new clinical correlates and 44 new clinical vignette–based practice questions ■ Updated content and terminology referencing Terminologia Anatomica and UpToDate ■ Expanded section on referred pain ■ New section on the cranial nerve examination ■ Updated glossary and expanded answer explanations in the chapters and comprehensive examinations To the Student Although this book is usable as a reference tool, to make the most of this book, work your way up the neuroaxis by starting at the beginning with the anatomy and blood supply, embryology and histology, and then proceeding up the spinal cord to higher centers. The illustrations, figures and tables, as well as their legends contain much board-relevant information that complement and inform the extensive question bank.

Acknowledgments

Special thanks to and in respectful memory of Dr. James Fix , for creating the first four editions of BRS Neuroanatomy —the foundation upon which all future editions are based. I thank my students and colleagues for their valuable input as the seventh edition was developed. I also thank the Wolters Kluwer staff and their associates for their contributions to this edition—Crystal Taylor, acquisitions editor; Deborah Bordeaux, development editor; Priyanka Alagar, editorial coordinator; and the stu dent and faculty reviewers, who were invited by the publisher to provide valuable feedback and sug gestions. Special thanks to Shannon Derthick for her contribution of the art for multiple new figures in Chapter 10.

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Contents

Preface vi Acknowledgments vii

1 GROSS ANATOMY OF THE BRAIN 1

Objectives 1

I. Introduction 1 II. Overview 1 III. Divisions of the Brain 2 IV. Atlas of the Brain and Brainstem 11 Review Test 14

2 MENINGES AND CEREBROSPINAL FLUID 18

Objectives 18

I. Meninges 18 II. Ventricles 22 III. Cerebrospinal Fluid 24 IV. Hydrocephalus 24

V. Meningitis 25 VI. Herniation 26 VII. Circumventricular Organs 26 Review Test 30

3 BLOOD SUPPLY OF THE CENTRAL NERVOUS SYSTEM 34

Objectives 34

I. Arteries of the Spinal Cord 34 II. Venous Drainage of the Spinal Cord 35 III. Arteries of the Brain 36 IV. Cerebral Arterial Circle (of Willis) 41

V. Meningeal Arteries 42 VI. Veins of the Brain 42 VII. Venous Dural Sinuses 42 VIII. Angiography 44 IX. Intracranial Hemorrhage 45 Review Test 48

Objectives 52

I. Overview 52 II. Development of the Neural Tube 52

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Contents

III. Neural Crest 53 IV. Placodes 54 V. Stages of Neural Tube Development 55 VI. Spinal Cord (Medulla Spinalis) 57 VII. Medulla Oblongata (Myelencephalon) 58 VIII. Metencephalon 60 IX. Mesencephalon (Midbrain) 61 X. Development of the Diencephalon, Optic Structures, and Hypophysis 62 XI. Development of the Telencephalon 64 XII. Congenital Malformations of the Central Nervous System 65 Review Test 71

5 NEUROHISTOLOGY 74

Objectives 74

I. Overview 74 II. Neurons 74 III. Neuroglia 77 IV. Nerve Cell Degeneration and Regeneration 81 V. Axonal Transport 82 VI. Capillaries of the Central Nervous System 82 VII. Sensory Receptors 84 Review Test 86

6 SPINAL CORD 90

Objectives 90

I. Introduction 90 II. External Morphology 90 III. Internal Morphology 96 IV. Myotatic Reflex 99 Review Test 100

7 TRACTS OF THE SPINAL CORD 102

Objectives 102

I. Ascending Tracts 102 II. Descending Tracts 107

III. Integrative Pathways 110 IV. Clinical Considerations 111 Review Test 112

8 LESIONS OF THE SPINAL CORD 116

Objectives 116 I. Lower Motor Neuron Lesions 116 II. Upper Motor Neuron Lesions 118 III. Sensory Pathway Lesions 118

Contents

IV. Peripheral Nervous System Lesions 119 V. Combined Upper Motor Neuron and Lower Motor Neuron Lesions 119 VI. Combined Motor and Sensory Lesions 120 VII. Intervertebral Disk Herniation 123 Review Test 124

9 BRAINSTEM 129

Objectives 129

I. Overview 129 II. Medulla Oblongata (Myelencephalon) 129 III. Pons 134 IV. Mesencephalon (Midbrain) 138 V. Corticobulbar (Corticonuclear) Fibers 140 Review Test 143

10 CRANIAL NERVES 145

Objectives 145

I. Overview 145 II. Nervus Terminalis (CN 0) 145 III. Olfactory Nerve (CN I) 145 IV. Optic Nerve (CN II) 146 V. Oculomotor Nerve (CN III) 147 VI. Trochlear Nerve (CN IV) 149 VII. Trigeminal Nerve (CN V) 150 VIII. Abducens Nerve (CN VI) 151 IX. Facial Nerve (CN VII) 151 X. Vestibulocochlear Nerve (CN VIII) 153 XI. Glossopharyngeal Nerve (CN IX) 154 XII. Vagal Nerve (CN X) 155

XIII. Accessory Nerve (CN XI) 157 XIV. Hypoglossal Nerve (CN XII) 157 XV. Cranial Nerve Testing 157 Review Test 161

11 TRIGEMINAL SYSTEM 165

Objectives 165

I. Trigeminal Nerve (CN V) 165 II. Ascending Trigeminothalamic Tracts 166

III. Trigeminal Sensory Nuclei 168 IV. Trigeminocerebellar Fibers 170 V. Trigeminal Reflexes 170 VI. Clinical Considerations 171 Review Test 173

Contents

12 LESIONS OF THE BRAINSTEM 176

Objectives 176

I. Overview 176 II. Vascular Lesions of the Medulla 176 III. Vascular Lesions of the Pons 177 IV. Lesions of the Midbrain 179 V. Decerebrate and Decorticate Rigidity 180 VI. Acoustic Neuroma (Schwannoma) 181

VII. Internuclear Ophthalmoplegia 182 VIII. Subclavian Steal Syndrome 182 Review Test 183

13 DIENCEPHALON: THALAMUS AND HYPOTHALAMUS 188

Objectives 188

I. Overview: The Thalamus 188 II. Boundaries of the Thalamus 188 III. Primary Thalamic Nuclei and their Major Connections 190 IV. Blood Supply of the Thalamus 192 V. Internal Capsule 192 VI. Blood Supply of the Internal Capsule 193 VII. Clinical Considerations 193 VIII. Overview: The Hypothalamus 194 IX. Surface Anatomy of the Hypothalamus 194

X. Hypothalamic Regions and Nuclei 194 XI. Major Hypothalamic Connections 197 XII. Major Fiber Systems 199

XIII. Functional Considerations 200 XIV. Clinical Considerations 201 Review Test 202

14 AUDITORY SYSTEM 207

Objectives 207

I. Overview 207 II. Outer, Middle, and Inner Ear 207 III. Auditory Pathway 209 IV. Efferent Cochlear (Olivocochlear) Bundle 211 V. Hearing Defects 211 VI. Tuning Fork Tests 212 VII. Brainstem Auditory Evoked Response 212 Review Test 214

Objectives 216

I. Overview 216 II. Labyrinth 216

Contents

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III. Vestibular Pathways 218 IV. Efferent Vestibular Connections 219 V. Medial Longitudinal Fasciculus 219

VI. Vestibulo-Ocular Reflexes 219 VII. Clinical Considerations 221 Review Test 222

16 VISUAL SYSTEM 225

Objectives 225

I. The Retina 225 II. Visual Pathway 228 III. Pupillary Light Reflexes and Pathway 230 IV. Pupillary Dilation Pathway 231 V. Convergence-Accommodation Reflex 232

VI. Centers for Ocular Motility 233 VII. Clinical Considerations 234 Review Test 236

17 OLFACTORY, GUSTATORY, AND LIMBIC SYSTEMS 240

Objectives 240

I. Olfactory System 240 II. Gustatory System 241 III. Limbic System 243 Review Test 249

18 BASAL NUCLEI AND THE EXTRAPYRAMIDAL MOTOR SYSTEM 253

Objectives 253

I. Basal Nuclei 253 II. Extrapyramidal Motor System 253 Review Test 260

19 CEREBELLUM 264

Objectives 264

I. Overview 264 II. Major Divisions of the Cerebellum 264 III. Cerebellar Cortex 266 IV. Major Cerebellar Pathways 268 V. Cerebellar Dysfunction 270 VI. Cerebellar Lesions 271 Review Test 273

Contents

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20 AUTONOMIC NERVOUS SYSTEM 277

Objectives 277

I. Overview 277 II. Divisions of the Autonomic Nervous System 277 III. Visceral Afferent Fibers and Pain 281 IV. Autonomic Innervation of Selected Organs 282 V. Clinical Considerations 284 Review Test 285

21 NEUROTRANSMITTERS AND PATHWAYS 289

Objectives 289

I. Overview 289 II. Dopamine 290 III. Acetylcholine 291

IV. Norepinephrine (Noradrenaline) 292 V. Serotonin (5-Hydroxytryptamine) 293 VI. Opioid Peptides 294 VII. Nonopioid Neuropeptides 295 VIII. Amino Acids 296 IX. Nitric Oxide 298 X. Functional and Clinical Considerations 298 Review Test 300

22 CEREBRAL CORTEX 304

Objectives 304

I. Overview 304 II. Neocortex 304 III. Functional Areas of the Cerebral Cortex 305

IV. Cerebral Dominance 310 V. Split-Brain Syndrome 312 VI. Blood Supply to the Major Functional Cortical Areas 313

VII. Apraxia 314 VIII. Aphasia 315 IX. Dysprosodies 316 Review Test 317

Comprehensive Examination 323 Appendix 351 Glossary 353 Index 363

and Hypothalamus 13

Diencephalon: Thalamus

chapter

Objectives Thalamus ■ List the boundaries of the thalamus. ■ List the thalamic nuclei and their primary functions and connections. ■ Describe the blood supply to the thalamus. ■ Describe the internal capsule. Hypothalamus ■ List the boundaries of the hypothalamus.

■ List the regions and nuclei of the hypothalamus and their primary functions and connections. ■ List the major fiber pathways associated with the hypothalamus and include a description of what they connect and the clinical implications if they are damaged.

I. OVERVIEW: THE THALAMUS

■ largest division of the diencephalon. ■ receives precortical input from all sensory systems, except the olfactory system. ■ largest input received is from the cerebral cortex. ■ projects primarily to the cerebral cortex and to a lesser degree to the basal nuclei and hypothalamus. ■ plays an important role in sensory and motor system integration.

II. BOUNDARIES OF THE THALAMUS (Figures 13.1 and 13.2)

A. Anterior: interventricular foramen

B. Posterior: free pole of the pulvinar

C. Dorsal: free surface underlying the fornix and the lateral ventricle

D. Ventral: plane connecting the hypothalamic sulci

F. Lateral: posterior limb of the internal capsule

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Chapter 13 Diencephalon: Thalamus and Hypothalamus

189

Internal medullary lamina

Ant. nuclear group

Mediodorsal nucleus

VPL

VPM

Ventral tier nuclei

Medial geniculate body

Lat. geniculate body

Cingulate gyrus

Mammillothalamic tract Fornix

Prefrontal cortex

Amygdaloid complex Temporal neocortex Substantia nigra Sup. parietal lobe

Globus pallidus Substantia nigra

Area 6 Diffuse frontal cortex

Areas 18 and 19 Inf. parietal lobule

Dentate nucleus Globus pallidus Substantia nigra

Inf. colliculus Lat. lemniscus

Area 4

Areas 41 and 42

Optic tract

Medial lemniscus Spinothalamic tracts

Area 17 Trigeminothalamic tracts and taste pathways

Areas 3, 1, and 2

Motor cortex (area 4)

Internal medullary lamina

Reticular nucleus

VPL

Third ventricle

Striatum

VPM

Zona incerta

Subthalamic nucleus

Copyright © 2023 Wolters Kluwer, Inc. Unauthorized reproduction of the content is prohibited. FIGURE 13.1. Major thalamic nuclei and their connections. (A) Oblique dorsolateral aspect of the thalamus and major nuclei. (B) The major afferent and efferent connections of the thalamus. (C) The transverse section of the thalamus showing the major connections of the centromedian nucleus. CM, centromedian nucleus; MD, mediodorsal nucleus; LD, lateral dorsal nucleus; LP, lateral posterior nucleus; VA, ventral anterior nucleus; VL, ventral lateral nucleus; VPL, ventral posterolateral nucleus; VPM, ventral posteromedial nucleus.

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BRS Neuroanatomy

Ventral lat. nucleus (area 4)

Ventral lat. nucleus (areas 3, 1, and 2)

Ventral ant. nucleus (areas 6 and 8)

Mediodorsal and ventral ant. nuclei

Lat. post. nucleus (areas 5 and 7)

(areas 9–12 and 44–47)

Pulvinar (areas 18, 19, 39, and 40)

Lat. geniculate body (area 17)

Medial geniculate body (areas 41 and 42)

Ventral lat. nucleus (area 4)

Central sulcus

Ventral post. nucleus (areas 3, 1, 2)

Ventral lat. nucleus (area 6)

Lat. dorsal nucleus (areas 5 and 7)

Ant. nucleus group (areas 24 and 31)

Lat. post. nucleus (area 7) Pulvinar

Mediodorsal and ventral ant. nuclei (areas 9–12)

(areas 18 and 19)

Lat. geniculate body

Calcarine fissure (area 17)

Pulvinar (areas 18 and 19)

FIGURE 13.2. (A) Lateral and (B) medial views of the cerebral hemisphere showing the cortical projection areas of the major thalamic nuclei.

III. PRIMARY THALAMIC NUCLEI AND THEIR MAJOR CONNECTIONS

A. Anterior nucleus ■ receives hypothalamic input from the mammillary nucleus via the mammillothalamic tract. ■ receives hippocampal input via the fornix. ■ projects to the cingulate gyrus. ■ part of Papez circuit, a well-described learning and memory circuit. B. Dorsomedial nucleus (mediodorsal nucleus) ■ reciprocally connected to the prefrontal cortex. ■ has abundant connections with the intralaminar nuclei. ■ receives input from the amygdala, the temporal neocortex, and the substantia nigra. ■ part of the limbic and striatal systems.

Chapter 13 Diencephalon: Thalamus and Hypothalamus

191

■ when destroyed, results in memory loss (Wernicke–Korsakoff syndrome). ■ plays a role in the expression of affect, emotion, and behavior (limbic function).

C. Intralaminar nuclei ■ receive input from the brainstem reticular formation, the ascending reticular activating system, and other thalamic nuclei. ■ receive spinothalamic and trigeminothalamic input via the spinal lemniscus.

■ project diffusely to the neocortex. ■ project to the dorsomedial nucleus. 1. Centromedian nucleus

■ largest of the intralaminar nuclei. ■ reciprocally connected to the motor cortex (area 4). ■ receives input from the globus pallidus. ■ projects to the striatum.

■ projects diffusely to the neocortex. ■ plays a role in attention and arousal. 2. Parafascicular nucleus ■ projects to the striatum and the supplementary motor cortex (area 6). ■ plays a role in changing patterns of response to stimuli.

D. Dorsal tier nuclei

1. Lateral dorsal nucleus ■ a posterior extension of the anterior nuclear complex. ■ receives mammillothalamic input. ■ projects to the cingulate gyrus. ■ has reciprocal connections with the limbic system. ■ plays a role in spatial learning and memory. 2. Lateral posterior nucleus ■ located between the lateral dorsal nucleus and the pulvinar. ■ has reciprocal connections with the superior parietal cortex (areas 5 and 7). ■ plays a role in visual and spatial attention. ■ often considered with the pulvinar as part of the pulvinar-LP complex. 3. Pulvinar ■ the largest thalamic nucleus (actually a series of interconnected subnuclei). ■ has reciprocal connections with the association cortex of the occipital, parietal, and pos terior temporal lobes. ■ receives input from the lateral and medial geniculate bodies (MGBs) and the superior colliculus. ■ concerned with visual attention and appropriate motor activities in coordination with oculomotor function. ■ lesions of the dominant side may result in sensory aphasia. ■ receives input from the globus pallidus and the substantia nigra. ■ projects diffusely to the prefrontal and orbital cortices. ■ projects to the premotor cortex (area 6). ■ functions in conjunction with the basal nuclei. 2. Ventral lateral nucleus ■ receives input from the globus pallidus, substantia nigra, and the cerebellum (dentate nucleus). ■ projects to the motor cortex (area 4) and to the supplementary motor area (area 6). ■ influences somatic motor mechanisms via the striatal motor system and the cerebellum. ■ destruction reduces Parkinsonian tremor. 3. Ventral posterior nucleus ■ the nucleus of termination of general somatic afferent (pain and temperature) and spe cial visceral afferent (SVA; taste) pathways.

E. Ventral tier nuclei ■ include primarily specific relay nuclei: 1. Ventral anterior nucleus

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BRS Neuroanatomy

■ contains three subnuclei : a. Ventral posterolateral (VPL) nucleus

■ receives the spinothalamic tracts and the medial lemniscus. ■ projects to the somesthetic (sensory) cortex (areas 3, 1, and 2). ■ lesion results in contralateral loss of pain and temperature sensation as well as loss of tactile discrimination in the trunk and extremities.

b. Ventral posteromedial (VPM) nucleus ■ receives the trigeminothalamic tracts.

■ receives taste from the solitary and parabrachial nuclei. ■ projects to the somesthetic cortex (areas 3, 1, and 2). ■ lesion results in contralateral loss of pain and temperature sensation, and loss of tactile discrimination in the head; results in ipsilateral loss of taste. c. Ventral posteroinferior nucleus

■ receives vestibulothalamic fibers from the vestibular nuclei. ■ projects to the vestibular area of the somesthetic cortex.

F. Lateral geniculate body (LGB) ■ a visual relay nucleus. ■ receives retinal input via the optic tract. ■ projects to the primary visual cortex (area 17, the lingual gyrus, and the cuneus) via the optic (retrolenticular) radiations.

G. Medial geniculate body

■ an auditory relay nucleus. ■ receives auditory input via the brachium of the inferior colliculus. ■ projects to the primary auditory cortex (areas 41 and 42) via the auditory (sublenticular) radiations.

IV. BLOOD SUPPLY OF THE THALAMUS

A. Posterior communicating artery ■ gives rise to the anterior thalamoperforating arteries. B. Posterior cerebral artery ■ gives rise to the posterior choroidal arteries. ■ gives rise to the posterior thalamoperforating arteries.

C. Anterior choroidal artery

■ primarily serves the LGB.

V. INTERNAL CAPSULE (Figure 13.3)

■ a layer of white matter (myelinated axons) that separates the caudate nucleus and thalamus medi ally from the lentiform nucleus laterally. ■ consists of three divisions:

B. Genu

■ contains corticobulbar fibers.

Chapter 13 Diencephalon: Thalamus and Hypothalamus

193

Anterior limb

Caudate nucleus

Genu

Globus pallidus

Corticobulbar fibers

Putamen

Posterior limb

Corticospinal fibers

Thalamus

Auditory radiation (sublenticular part of internal capsule) to superior temporal gyrus (areas 41 and 42)

Sensory radiations from VP nucleus to areas 3, 1, 2

Medial geniculate body (audition)

Lateral geniculate body (vision)

Visual radiation (retrolenticular portion of internal capsule) to striate cortex of occipital lobe (area 17)

FIGURE 13.3. Horizontal section of the right internal capsule showing the major fiber projections. Lesions of the internal capsule result in contralateral hemiparesis and contralateral hemianopia. VP, ventral posterior. (Modified with permission from Fix JD. High-Yield Neuroanatomy . 3rd ed. Lippincott Williams & Wilkins; 2005:118.)

C. Posterior limb ■ located between the thalamus and the lentiform nucleus. ■ contains the sensory radiations (pain, temperature, and touch). ■ contains the corticospinal fibers. ■ includes the retrolenticular (visual) and sublenticular (auditory) radiations.

VI. BLOOD SUPPLY OF THE INTERNAL CAPSULE (See Figure 3.6)

A. Anterior limb ■ irrigated by the medial striate branches of the anterior cerebral artery and by the lateral striate branches (lenticulostriate) of the middle cerebral artery. B. Genu ■ perfused either by direct branches from the internal carotid artery or by pallidal branches of the anterior choroidal artery. C. Posterior limb ■ supplied by branches of the anterior choroidal artery and lenticulostriate branches of the mid dle cerebral arteries.

VII. CLINICAL CONSIDERATIONS

A. Infarction of the internal capsule ■ most frequently results from occlusion of the lenticulostriate branches of the middle cerebral artery and results in the following contralateral conditions:

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BRS Neuroanatomy

1. Tactile hypesthesia 2. Anesthesia 3. Hemiparesis (with Babinski sign)

4. Lower facial weakness 5. Homonymous hemianopia

B. Thalamic syndrome (Dejerine and Roussy) ■ usually caused by occlusion of a posterior thalamoperforating artery.

■ classic signs: contralateral hemiparesis; contralateral hemianesthesia; elevated pain threshold; spontaneous, agonizing, burning pain (hyperpathia); and athetotic posturing of the hand (tha lamic hand).

VIII. OVERVIEW: THE HYPOTHALAMUS

■ a division of the diencephalon. ■ lies within the floor and ventral part of the walls of the third ventricle. ■ functions primarily in the maintenance of homeostasis . ■ subserves three systems: the autonomic nervous system ( ANS ), the endocrine system , and the lim bic system .

IX. SURFACE ANATOMY OF THE HYPOTHALAMUS (See Figure 1.5)

■ visible only from the inferior aspect of the brain. ■ lies between the optic chiasm and the interpeduncular fossa (posterior perforated substance).

■ the hypothalamic sulcus forms superior border. ■ includes the following ventral surface structures :

A. Infundibulum

■ the stalk of the hypophysis. ■ contains the hypophyseal portal vessels. ■ contains the supraopticohypophyseal and tuberohypophyseal tracts. B. Tuber cinereum ■ the prominence between the infundibulum and the mammillary bodies. ■ includes the median eminence , which contains the arcuate nucleus .

C. Mammillary bodies ■ contain the mammillary nuclei.

D. Cerebral arterial circle (of Willis) ■ surrounds the inferior surface of the hypothalamus and provides its blood supply.

X. HYPOTHALAMIC REGIONS AND NUCLEI

Copyright © 2023 Wolters Kluwer, Inc. Unauthorized reproduction of the content is prohibited. ■ the hypothalamus is divided into a lateral area and a medial area separated by the fornix and the mammillothalamic tract.

A. Lateral hypothalamic area ■ traversed by the medial forebrain bundle.

Chapter 13 Diencephalon: Thalamus and Hypothalamus

195

■ includes two major nuclei: 1. Lateral preoptic nucleus

■ the anterior telencephalic portion. 2. Lateral hypothalamic nucleus (Figure 13.4) ■ when stimulated, induces eating. ■ lesions cause anorexia and starvation.

B. Medial hypothalamic area (Figure 13.5) ■ includes the periventricular area that borders the third ventricle. ■ divided into four regions, from anterior to posterior: 1. Preoptic region ■ the anterior telencephalic portion.

Thalamus Mammillothalamic tract Dorsal hypothalamic area Dorsomedial nucleus Lateral hypothalamic area Ventromedial nucleus Supraoptic nucleus

F X

Lesions (black) in ventromedial nuclei

Lesions (black) in extreme lateral part of hypothalamus

Voracious appetite (and rage)

Loss of appetite

Third ventricle

F X

Medial nuclei Intralaminar nuclei Of thalamus Lateral nuclei

Reticular nucleus of thalamus

Mammillothalamic tract

Stimulation of this region (dorsomedial nucleus) or Destruction of this region (ventromedial nucleus)

Internal capsule

Dorsal hypothalamic area

Third ventricle Fornix (column) Lateral nucleus Arcuate nucleus Median eminence

Produces

Rage

FIGURE 13.4. Coronal section through the hypothalamus at the level of the dorsomedial, ventromedial, and lateral hypo thalamic nuclei. The column of the fornix separates the medial from the lateral hypothalamic areas. FX, fornix; MD, medial dorsal nucleus of thalamus; OT, optic tract; VL, ventral lateral nucleus of thalamus; VP, ventral posterior nucleus of thalamus.

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BRS Neuroanatomy

Paraventricular and supraoptic nuclei • regulate water balance • produce ADH and oxytocin • destruction causes diabetes insipidus • paraventricular nucleus projects to autonomic nuclei of brainstem and spinal cord Anterior nucleus • thermal regulation (dissipation of heat) • stimulates parasympathetic NS • destruction results in hyperthermia Preoptic area • contains sexually dimorphic nucleus • regulates release of gonadotropic hormones

Dorsomedial nucleus • stimulation results in obesity and savage behavior Posterior nucleus • thermal regulation (conservation of heat) • destruction results in inability to thermoregulate • stimulates the sympathetic NS

Lateral nucleus • stimulation induces eating • destruction results in starvation Mammillary body • receives input from hippocampal formation via fornix • projects to anterior nucleus of thalamus

Midbrain

• contains hemorrhagic lesions in Wernicke encephalopathy Ventromedial nucleus • satiety center • destruction results in obesity and savage behavior

Suprachiasmatic nucleus • receives input from retina • controls circadian rhythms

CN III

Pons

Arcuate nucleus • produces hypothalamic-releasing factors • contains DOPA-ergic neurons that inhibit prolactin release

FIGURE 13.5. Major hypothalamic nuclei and their functions. ADH, antidiuretic hormone; DOPA, dihydroxyphenylalanine; NS, nervous system. (Modified with permission from Fix JD. High-Yield Neuroanatomy . 3rd ed. Lippincott Williams & Wilkins; 2005:132.)

■ contains the medial preoptic nucleus , which regulates the release of gonadotropic hor mones from the adenohypophysis. The medial preoptic nucleus contains the sexually dimorphic nucleus, whose development is dependent on testosterone levels. 2. Supraoptic region ■ lies superior to the optic chiasm. a. Suprachiasmatic nucleus ■ receives direct input from the retina. ■ plays a role in the control of circadian rhythms . b. Anterior nucleus ■ plays a role in temperature regulation. ■ stimulates the parasympathetic nervous system. ■ destruction results in hyperthermia. c. Paraventricular nucleus ■ neurosecretory cells synthesize and release antidiuretic hormone ( ADH ), oxyto cin , and corticotropin-releasing hormone ( CRH ). ■ regulates water balance (conservation of water). ■ gives rise to the supraopticohypophyseal tract, which projects to the neurohypophysis. ■ destruction results in diabetes insipidus . d. Supraoptic nucleus ■ synthesizes ADH and oxytocin . ■ projects to the neurohypophysis via the supraopticohypophyseal tract. 3. Tuberal region ■ lies superior to the tuber cinereum. a. Dorsomedial nucleus (see Figure 13.4) ■ results in rage when stimulated. b. Ventromedial nucleus (see Figure 13.4) ■ satiety center . ■ when stimulated, inhibits the urge to eat. ■ bilateral destruction involved with hyperphagia, obesity, and savage behavior. c. Arcuate (infundibular) nucleus ■ located in the tuber cinereum.

Chapter 13 Diencephalon: Thalamus and Hypothalamus

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■ a periventricular nucleus. ■ contains neurons that produce hypothalamic-releasing factors and gives rise to the tuberohypophyseal tract, which terminates in the hypophyseal portal system of the infundibulum. ■ effects, via hypothalamic-releasing factors, the release or nonrelease of adenohy pophyseal hormones into the systemic circulation. ■ contains dopaminergic neurons; dopamine is the prolactin-inhibiting factor ( PIF ). a. Mammillary nuclei ■ lies superior to the mammillary bodies. ■ receive input from the hippocampal formation via the fornix . ■ receive input from the dorsal and ventral tegmental nuclei and the raphe nuclei via the mammillary peduncle. ■ project to the anterior nucleus of the thalamus via the mammillothalamic tract. ■ contain hemorrhagic lesions in Wernicke encephalopathy. b. Posterior nucleus ■ plays a role in thermal regulation (ie, conservation and increased production of heat). ■ lesions result in poikilothermia , the inability to thermoregulate.

4. Mammillary region

XI. MAJOR HYPOTHALAMIC CONNECTIONS (Figures 13.6 and 13.7)

■ characterized by mostly reciprocal connections.

A. Afferent connections to the hypothalamus ■ derive from the following structures:

1. Septal area and nuclei and orbitofrontal cortex ■ via the medial forebrain bundle.

Mediodorsal nucleus

Medial forebrain bundle

Fornix

Orbitofrontal cortex Septal nuclei

Periaqueductal gray

Mammillary peduncle

Septal area

Medial forebrain bundle

Dorsal tegmental nucleus Ventral tegmental nucleus

Corticohypothalamic fibers

Amygdaloid body

FIGURE 13.6. Major afferent (input) connections of the hypothalamus. The fornix projects from the hippocampal formation to the mammillary bodies. The medial forebrain bundle conducts both afferent and efferent fibers.

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BRS Neuroanatomy

Mediodorsal Anterior

Thalamic nuclei

Mammillothalamic tract

Septal n.

Pineal gland

Orbitofrontal cortex

Medial forebrain bundle

Septal area

Dorsal tegmental nucleus Ventral tegmental nucleus

Medial forebrain bundle

Dorsal longitudinal fasciculus

Neurohypophysis

Mammillary peduncle Mammillary body Tuber cinereum

FIGURE 13.7. Major efferent (output) connections of the hypothalamus. The medial forebrain bundle conducts afferent and efferent fibers. The hypothalamus projects directly to the autonomic visceral nuclei of the brainstem and spinal cord.

2. Hippocampal formation ■ via the medial forebrain bundle. ■ primarily from the subiculum via the fornix. 3. Amygdaloid nuclear complex ■ via the stria terminalis and ventral amygdalofugal pathway.

4. Primary olfactory cortex (area 34) ■ via the medial forebrain bundle. 5. Mediodorsal nucleus of the thalamus ■ via the inferior thalamic peduncle. 6. Brainstem nuclei

a. Tegmental nuclei (dorsal and ventral) ■ project via the mammillary peduncle. b. Raphe nuclei (dorsal and superior central) ■ project serotonergic fibers via the medial forebrain bundle and the mammillary peduncle (see Figure 21.5). c. Locus ceruleus ■ projects noradrenergic fibers via the medial forebrain bundle (see Figure 21.4).

B. Efferent connections from the hypothalamus ■ project to the following structures: 1. Septal area and nuclei

■ via the medial forebrain bundle. 2. Anterior nucleus of the thalamus ■ via the mammillothalamic tract. 3. Mediodorsal nucleus of the thalamus ■ via the inferior thalamic peduncle. 4. Amygdaloid nuclear complex ■ via the stria terminalis and the ventral amygdalopetal pathway.

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5. Brainstem nuclei and spinal cord ■ via the dorsal longitudinal fasciculus and the medial forebrain bundle. 6. Adenohypophysis ■ via the tuberohypophyseal tract and hypophyseal portal system. 7. Neurohypophysis ■ via the supraopticohypophyseal tract.

XII. MAJOR FIBER SYSTEMS

A. Fornix (see Figures 1.4, 1.5, 17.3, and 17.6) ■ has five parts: the alveus , fimbria , crus , body , and column . ■ projects from the hippocampal formation to the mammillary nucleus, anterior nucleus of the thalamus, and septal area. ■ the largest projection to the hypothalamus. ■ bilateral transection results in an acute amnestic syndrome. B. Medial forebrain bundle (see Figures 13.6 and 13.7) ■ traverses the lateral hypothalamic area. ■ interconnects the septal area and nuclei, the hypothalamus, and the midbrain tegmentum. D. Mammillary peduncle (see Figure 13.6) ■ conducts fibers from the dorsal and ventral tegmental nuclei and the raphe nuclei to the mam millary body. E. Mammillotegmental tract (see Figure 13.7) ■ conducts fibers from the mammillary nuclei to the dorsal and ventral tegmental nuclei. F. Stria terminalis (see Figure 17.3) ■ the most prominent pathway from the amygdaloid nuclear complex. ■ interconnects the septal area, the hypothalamus, and the amygdaloid nuclear complex. ■ lies in the sulcus terminalis between the caudate nucleus and the thalamus. C. Mammillothalamic tract (see Figure 17.3) ■ projects from the mammillary nuclei to the anterior nucleus of the thalamus.

G. Ventral amygdalofugal pathway (see Figure 17.3) ■ interconnects the amygdaloid nuclear complex and the hypothalamus.

H. Supraopticohypophyseal tract (Figure 13.8) ■ conducts fibers from the supraoptic and paraventricular nuclei to the neurohypophysis . I. Tuberohypophyseal (tuberoinfundibular) tract (see Figure 13.8) ■ conducts fibers from the arcuate nucleus to the hypophyseal portal system of the infundibulum.

J. Dorsal longitudinal fasciculus (see Figure 13.7) ■ extends from the hypothalamus to the caudal medulla. ■ projects to the parasympathetic nuclei of the brainstem.

Copyright © 2023 Wolters Kluwer, Inc. Unauthorized reproduction of the content is prohibited. K. Hypothalamospinal tract ■ contains direct descending autonomic fibers that influence preganglionic sympathetic neurons of the intermediolateral cell column and preganglionic neurons of the sacral parasympathetic nucleus. ■ interruption above T1 results in Horner syndrome.

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Paraventricular nucleus

Third ventricle

Arcuate (tuberal) nucleus

Supraoptic nucleus

Optic chiasm

Tuberohypophyseal tract

Supraopticohypophyseal tract

Superior hypophyseal artery

Infundibulum

Hypophyseal portal veins

Sinusoids of infundibular stem

Oxytocin ADH

Anterior lobe (adenohypophysis)

Posterior lobe (neurohypophysis)

Hypophyseal vein

Inferior hypophyseal artery

FIGURE 13.8. Hypophyseal portal system. The paraventricular and supraoptic nuclei produce ADH and oxytocin and transport the substances via the supraopticohypophyseal tract to the capillary bed of the neurohypophysis. The arcu ate nucleus of the infundibulum transports releasing hormones via the tuberohypophyseal tract to the sinusoids of the infundibular stem, which drain into the secondary capillary plexus in the adenohypophysis. ADH, antidiuretic hormone. (Modified with permission from Fix JD. High-Yield Neuroanatomy . 3rd ed. Lippincott Williams & Wilkins; 2005:133.)

XIII. FUNCTIONAL CONSIDERATIONS

A. Autonomic function

1. Anterior hypothalamus ■ The ANS is regulated by hypothalamic nuclei. 2. Posterior hypothalamus

■ has a stimulatory effect on the parasympathetic nervous system. ■ has a stimulatory effect on the sympathetic nervous system.

B. Temperature regulation

1. Anterior hypothalamus ■ helps regulate and maintain body temperature. ■ destruction causes hyperthermia. 2. Posterior hypothalamus ■ helps produce and conserve heat. ■ destruction causes the inability to thermoregulate.

C. Water balance regulation

■ ADH controls water excretion by the kidneys.

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D. Food intake regulation

1. Ventromedial nucleus ■ two hypothalamic nuclei play a role in the control of appetite: ■ satiety center. ■ destruction is involved in overeating and obesity.

2. Lateral hypothalamic nucleus ■ the hunger or feeding center . ■ destruction causes starvation and emaciation .

E. Hypothalamic-releasing and release-inhibiting factors ■ produced in the arcuate nucleus of the median eminence. ■ transported via the tuberohypophyseal tract to the hypophyseal portal system. ■ effect the release or nonrelease of adenohypophyseal hormones. ■ with the exception of dopamine, they are all peptides , which include:

1. thyrotropin-releasing hormone. 2. gonadotropin-releasing hormone. 3. somatostatin (growth hormone–inhibiting hormone). 4. growth hormone–releasing hormone. 5. corticotropin-releasing hormone. 6. prolactin-inhibiting and prolactin-releasing factor.

XIV. CLINICAL CONSIDERATIONS

A. Craniopharyngioma ■ originates from embryonic pituitary gland tissue. ■ usually calcified. ■ the most common supratentorial tumor found in children.

■ pressure on the optic chiasm results in a bitemporal hemianopia . Pressure on the hypothalamus causes hypothalamic syndrome , with adiposity, diabetes insipidus, disturbance of temperature regulation, and somnolence. B. Pituitary adenoma ■ constitutes 10% to 20% of all intracranial tumors; 1:10 people will get in lifetime. ■ pressure on the chiasm results in a bitemporal hemianopia (most cases show asymmetry of field defects). Pressure on the hypothalamus may cause hypothalamic syndrome . C. Wernicke encephalopathy ■ results from thiamine (vitamin B 1 ) deficiency. ■ characterized by the triad: ocular palsies , ataxic gait , and mental confusion . ■ lesions are found in the hypothalamus (primarily in the mammillary bodies) and in the periaq ueductal gray of the midbrain.

Review Test

1. Which of the following thalamic nuclei has a motor function? (A) Lateral dorsal (B) Lateral posterior

left facial weakness, tongue deviation to the left side, and plantar extensor on the left side? (A) Left internal capsule (B) Left pulvinar (C) MGB (D) Right internal capsule (E) Right pulvinar 7. A capsular stroke is most commonly caused by occlusion of the following artery/arteries: (A) anterior cerebral artery. (B) direct branches of the internal carotid artery. (C) lateral striate arteries. (D) posterior communicating artery. (E) recurrent artery of Heubner. Questions 8 to 13 The response options for items 8 to 13 are the same. Select one answer for each item in the set. (A) Anterior nucleus (B) Centromedian nucleus (C) Lateral geniculate nucleus (D) Mediodorsal nucleus (E) Pulvinar (H) VPL nucleus (I) VPM nucleus Match each of the following descriptions with the appropriate thalamic nucleus. 8. Receives input from the ipsilateral central tegmental tract (F) Ventral anterior nucleus (G) Ventral lateral nucleus

2. To which of the following thalamic nuclei do the spinothalamic fibers project? (A) Anterior nucleus (B) Pulvinar (C) Ventral anterior nucleus

(D) VPL nucleus (E) VPM nucleus

3. To which of the following thalamic nuclei do the cerebellar fibers project? (A) Anterior nucleus (B) Lateral dorsal nucleus

4. To which set of thalamic nuclei does the glo bus pallidus project? (A) Centromedian, lateral dorsal, and lateral ventral nuclei (B) Centromedian, ventral anterior, and ven tral lateral nuclei (C) Mediodorsal, VPL, and VPM nuclei (D) Ventral anterior, ventral lateral, and ante rior nuclei (E) Ventral lateral, lateral dorsal, and lateral posterior nuclei 5. Tritiated leucine [( 3 H)-leucine] is injected into the medial mammillary nucleus for an terograde transport; radioactive label would be found in the: (A) anterior nucleus thalami.

9. Has reciprocal connections with the inferior parietal lobule

10. Receives input from the contralateral lateral spinothalamic tract

(B) arcuate nucleus hypothalami. (C) dorsomedial nucleus thalami. (D) supraoptic nucleus. (E) ventral anterior nucleus thalami.

11. Projects to the putamen

13. Plays a role in the expression of affect, emo tion, and behavior (limbic function)

6. Which structure’s infarction can give rise to left hypesthesia, left homonymous hemianopia,

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22. Which of the following is a hypothalamic structure?

Questions 14 to 18 The response options for items 14 to 18 are the same. Select one answer for each item in the set. (A) Anterior nucleus (B) Medial geniculate (nucleus) body

(A) Alveus (B) Arcuate (C) Column (D) Crus (E) Fimbria

23. Spring fever is a seasonal change in mood and behavior, coinciding with longer days and more sunshine. One possible anatomical substrate for this phenomenon involves the in creased sunlight projecting posteriorly from the retina to which hypothalamic nucleus?

Match each pathway with the appropriate nu cleus to which it gives input. 14. Brachium of the inferior colliculus

(A) Anterior (B) Arcuate

15. Thalamic fasciculus (H 1 )

16. Mammillothalamic tract

17. Dentatorubrothalamic tract

24. A 30-year-old woman presents to her pri mary care physician with a series of concerns, including chronic headaches, visual alterations, irritability, inconsistent menstrual periods, and a recently developed insatiable appetite. Neuroimaging is ordered and a pituitary gland tumor is revealed. Compression of which of the following hypothalamic nuclei may be causing the lack of appetite? (A) Anterior (B) Dorsomedial (C) Mammillary bodies (D) Supraoptic (E) Ventromedial The response options for items 25 to 31 are the same. Select one answer for each item in the set. (F) Dorsal longitudinal fasciculus (G) Fornix (H) Medial forebrain bundle (I) Mammillary peduncle (J) Stria terminalis Match each description below with the struc ture it best describes. 25. Extends from the posterior hypothalamic nucleus to the caudal medulla Questions 25 to 31

18. Gustatory (taste) pathway

19. The sexually dimorphic nucleus is located in the:

(A) anterior nucleus. (B) arcuate nucleus. (C) medial preoptic nucleus. (D) posterior nucleus. (E) ventromedial nucleus.

20. A 40-year-old woman who has taken birth control pills has a 4-month history of amenor rhea and a bitemporal hemianopia that began as a bitemporal quadrantanopia. What is the most likely cause of these deficits? (A) Aneurysm of the anterior communicating artery (B) Cavernous sinus meningioma (C) Optic glioma (D) Pituitary adenoma (E) Sella turcica meningioma 21. Which of the following statements concern ing the hypothalamus is correct? (A) It is a division of the subthalamus. (B) It contains the tuberculum cinereum. (C) Its suprachiasmatic nucleus receives input from the retina. (D) It is not related to the limbic system. (E) Its dorsomedial and the ventromedial nu clei are separated by the striae medullares.

26. Interconnects the hypothalamus and the amygdaloid nuclear complex

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BRS Neuroanatomy

27. Is the largest projection to the hypothalamus

Match each description below with the appro priate clinical condition. 32. Amenorrhea and galactorrhea

28. Connects the septal area to the midbrain tegmentum

33. Hemorrhagic lesions in the mammillary bodies

29. Conducts fibers from the hippocampal for mation to the mammillary nuclei

34. Associated with the Rathke pouch

30. Lies between the caudate nucleus and the thalamus

35. Destruction of the anterior hypothalamic nuclei

31. Separates the medial hypothalamus from the lateral hypothalamus

36. Stimulation of the ventromedial nuclei

Questions 32 to 40 The response options for items 32 to 40 are the same. Select one answer for each item in the set. (A) Anorexia

37. Bilateral lesions of the ventromedial hypo thalamic nuclei

38. Bilateral lesions of the posterior hypotha lamic nuclei

(B) Craniopharyngioma (C) Diabetes insipidus (D) Hyperthermia (E) Inability to thermoregulate (F) Obesity and rage (G) Pituitary adenoma (H) Wernicke encephalopathy

39. Destruction of the supraoptic and paraven tricular nuclei

40. Results from thiamine (vitamin B 1 ) deficiency

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