Associate Editor, Betty Kim

I. Meninges

A. Meningeal layers

B. Virchow–Robin spaces—a perivascular potential space, between blood vessels and the surrounding sheath of leptomeninges entering the nervous tissue (brain and spinal cord)

C. Cisterns—regions where the meningeal layers (pia and arachnoid) are widely separated

1. Surrounding the midbrain—interpeduncular, crural, ambient (contains the vein of Galen, posterior cerebral [PCAs] and superior cerebellar arteries [SCAs]), and quadrigeminal cisterns; also, cerebello-medullary (cisterna magna), pontine, chiasmatic, sylvian, and lumbar (maximal at L2) cisterns

II. Cerebrospinal Fluid

A. Function: waste removal, carry nutrition to the brain, cushioning of the brain and regulating various brain functions via neurotransmitters, paracrine and endocrine effects. Hypothalamic hormones are secreted into the cerebrospinal fluid (CSF) and transported by the ependymal cells to the hypophyseal portal system.

B. CSF constituents

Abbreviations: CSF, cerebrospinal fluid; PMNs, polymorphonuclear neutrophils; RBCs, red blood cells; WBC, white blood cell

C. CSF production

1. Active process—Na⁺ is actively secreted into the subarachnoid space via Na⁺/K⁺ adenosine triphosphate (ATP) pump with H₂O from vessels following the Na⁺ ions

2. Sites of CSF production

a. 70% Choroid plexus

b. 18% Ultrafiltrate

c. 12% Metabolic H₂O production

3. Control of CSF production

a. Raphe nuclei send axons (serotonin) to the periependymal vessels.

(1) Carbonic anhydrase inhibitors (acetazolamide)

(2) Norepinephrine (NE)

c. Increased production

(1) Volatile anesthetics and CO₂

4. CSF volumes in a 70 kg man

a. 450 mL = CSF production each day. CSF production is 0.3–0.37 mL/minute, 20 mL/h

b. 150 mL = total volume

c. 25 mL = within ventricles

5. Choroid plexus—a single layer of cuboidal epithelial cells surrounding blood vessels, involved in CSF production. Primarily located in

a. Roof of the fourth ventricle

b. Inferior medullary velum and lateral recess to the foramen of Luschka

c. Posterior roof of the third ventricle

Fig. 1.1 Overview of the ventricular system and important neighboring structures. Left lateral view. The ventricular system is an expanded and convoluted tube that is the upper extension of the central spinal canal into the brain. (From THIEME Atlas of Anatomy, Head and Neuroanatomy, © Thieme 2007, Illustration by Markus Voll.)

3. Arachnoid granulations

a. Most abundant at the superior sagittal sinus, contains arachnoid villi

b. A pressure-dependent one-way valve, with collapsing tubules that transmit CSF when intracranial pressure (ICP) is 3–6 cm H₂O greater than the venous pressure

E. Intracranial pressure

1. Monro–Kellie doctrine—the closed skull has a fixed/constant volume with

a. 1500 mL brain tissue

b. 150 mL blood (arteries + veins)

c. 150 mL CSF (total volume)

d. Any added volume (brain swelling due to edema, increased blood volume, increased CSF, tumor, hemorrhage, etc.) forces removal of normal inhabitants of the cranial cavity.

2. Normal ICP values

a. <10–15 mm Hg—adults and older children

b. 3–8 mm Hg—younger children

c. 1.5–6 mm Hg—infants

III. Brain Barriers

A. Blood–brain barrier (BBB) formed by

1. Capillary endothelial tight junctions (mainly)

2. Pinocytic activity in endothelial cells

3. Astrocytic foot processes

B. Molecular movement across the BBB

1. Diffusion

2. Carrier-mediated transport (D-glucose, amino acids)

3. Active transport

C. Permeability across the BBB

1. Highly permeable—H₂O, CO₂, O₂, lipid-soluble (ethanol, barbiturates, heroin, and anesthetics)

2. Slightly permeable—ions (Na⁺, Cl⁻, and K⁺)

3. Impermeable—plasma proteins, protein-bound molecules, large organic molecules, and L-glucose

D. Blood–CSF barrier is formed by the tight junctions of choroid cuboidal epithelium (although blood vessels have fenestrated capillaries).

E. Circumventricular organs are midline ventricular system structures of specialized tissues with absent BBB due to fenestrated capillaries.

1. Circumventricular organs (from rostral to caudal)

IV. Blood Supply to the Brain

A. General – The brain constitutes only 2% of body weight (1500 g) but receives 17% of the cardiac output and uses 20% of the body’s oxygen.

B. Cerebral blood flow

C. Origins of great vessels

1. Brachiocephalic (innominate)—bifurcates into the right common carotid artery and left subclavian artery → vertebral artery → internal mammary artery → thyrocervical trunk → costocervical trunk

2. Left common carotid artery

3. Left subclavian artery gives off vertebral, thyrocervical, and costocervical trunks.

a. Vertebral artery dominance

(1) Left side = 50%

(2) Right side = 25%

(3) Nondominance = 25%

b. The left vertebral artery arises from the aorta in 5% of cases; 40% of the population has a hypoplastic vertebral artery.

Fig. 1.2 Overview of arteries of the head. Left lateral view. The common carotid artery divides into internal and external carotid arteries at the carotid bifurcation, which is usually at the level of the fourth cervical vertebra. There are eight branches of the external and none of the cervical internal carotid artery. (From THIEME Atlas of Anatomy, Head and Neuroanatomy, © Thieme 2007, Illustration by Karl Wesker.)

(c) Periosteal arterial branches: Persistent arteries of the petrosal/intraosseous segment:

Fig. 1.3 Branches of the cavernous segment of the internal carotid artery (ICA).

(1) Intracavernous segment of ICA (proximal → distal):

(a) C5: ascending portion—entrance into the cranium to the genu

(b) C4: posterior genu—between C5 and C3 segments

(c) C3: horizontal portion—between the genu

(d) C2: anterior genu

(e) C1—remainder of the ICA segment

(a) Meningohypophyseal trunk (posterior trunk) has three branches:

(i)   Tentorial artery (of Bernasconi and Cassinari)—tentorium

(ii)  Inferior hypophyseal artery—neurohypophysis

(iii) Dorsal meningeal artery (clival branch)—CN VI and part of the clivus

(b) Inferolateral trunk (artery of the inferior cavernous sinus) travels to

(i)   Inferolateral cavernous sinus wall

(ii)  Tentorium (via tentorial branch)

(iii) Foramen ovale and spinosum to supply CN III, IV, VI, and gasserian ganglion

(iv) The most important anastomoses include

• Maxillary artery (via artery of the foramen rotundum)

• MMA and ophthalmic artery

(d) Medial trunk (McConnell’s capsular arteries)—supplies the anterior and inferior pituitary gland, present only in 28% of the population, the most distal branch from the C3 and C2 segment

(i)   Anterior capsular artery—courses medially over the sellar roof

(ii)  Inferior capsular artery—courses inferomedially, supplies the sella floor

(3) Persistent arteries of the intracavernous segment

Fig. 1.4 View of the anterior circle of Willis as it would be seen from a right pterional approach.

(ii) Orbital branches:

• Lacrimal artery—supplies lacrimal gland and conjunctiva. The most significant branch of the lacrimal artery is the recurrent meningeal artery, which turns backward through the superior orbital fissure to anastomose with the MMA.

• Muscular artery—supplies extraocular muscles and the orbital periosteum

(iii) Extraorbital branches—include supraorbital, anterior and posterior ethmoidals, dorsal nasal, medial frontal, palpebral, and supratrochlear arteries. These branches possess extensive anastomoses with the ECA (via ethmoidal and anterior falcine artery) for collateral intracranial flow during proximal ICA occlusion.

Fig. 1.5 Lateral internal carotid artery catheter angiogram.

(2) Superior hypophyseal arteries—several small arteries arising from the posteromedial portion of the intradural ICA

(a) They course beneath the optic nerve to supply:

(i)   Pituitary (anterior pituitary lobe, pituitary stalk) and tuber cinereum

(ii)  Optic nerve and chiasm (inferior surface)

(b) These arteries anastomose with the arteries of the contralateral as well as the inferior hypophyseal arteries to form the hypophyseal portal system.

(c) Aneurysms arising from this region point inferiorly and medially.

(a) Perforators— ~ Seven perforators evenly distributed along the PcommA course superomedially to supply the posterior hypothalamus, anterior thalamus, subthalamic nucleus, and posterior limb of the internal capsule (IC). The largest perforator (anterior thalamoperforating artery) terminates between the mamillary bodies and optic tracts.

Fig. 1.6 Branches of the ophthalmic artery. Right orbit, superior view after opening of the optic canal and orbital roof. The ophthalmic artery is a branch of the internal carotid artery. It runs below the optic nerve through the optic canal to the orbit and supplies the intraorbital structures, including the eyeball. (From THIEME Atlas of Anatomy, Head and Neuroanatomy, © Thieme 2007, Illustration by Karl Wesker.)

(b) PcommA variants are observed in 50% of cases, including absent or hypoplastic (30%), fetal origin (20%), duplicated or triplicated:

(i)   Fetal origin of the PCA (“fetal PCA”)—when PcommA diameter is the same as PCA. Failed regression of fetal PCA leads to dominant blood supply of occipital lobes from ICA (via fetal PCA) rather than from the vertebrobasilar system (20% unilateral and 8% bilateral).

(5) Dural artery—a small branch that arises from the ICA 3–5 mm proximal to the bifurcation; courses anteriorly to supply the dura of the anterior clinoid process

(6) Carotid siphon—intracavernous and supraclinoid segments of the ICA

Fig. 1.7 Posterior communicating artery infundibulum. Lateral internal carotid artery angiogram demonstrates the artery arising from the tip of a pyramidal dilation.

a. Course posterosuperiorly through the anterior perforated substance to supply:

(1) Optic nerve (superior surface) and optic chiasm

(2) Anterior hypothalamus

(3) Septum pellucidum

(4) Anterior commissure

(5) Pillars of the fornix and the anteroinferior striatum

b. Note: Medial distal striate artery = recurrent artery of Heubner (RAH)

3. Anterior communicating artery (AcommA)—located in the cistern of the lamina terminalis

a. Two or more perforators arise from the AcommA that supply:

(1) Infundibulum

(2) Optic chiasm

Fig. 1.8 Anterior cerebral artery. The major branches are the orbitofrontal (medial frontobasal), frontopolar (polar frontal), anterior internal frontal (anteromedial frontal), callosomarginal, middle internal frontal (interomedial frontal), posterior internal frontal (posteromedial frontal), paracentral (cingular), superior parietal (paracentral), and inferior parietal (precuneal). (From THIEME Atlas of Anatomy, Head and Neuroanatomy, © Thieme 2007, Illustration by Markus Voll.)

(4) Preoptic hypothalamus

b. Perforators include the subcallosal artery and medial artery of the corpus callosum.

c. Aneurysms usually arise at the point where the dominant A1 bifurcates at the AcommA and point toward the opposite side.

4. Postcommunicating segment (A2)

5. Distal segment (A3)—distal to the pericallosal–callosomarginal junction

Fig. 1.9 Middle cerebral artery. The major terminal branches are the orbital frontal (lateral frontobasal), prefrontal, precentral (artery of the precentral sulcus), central (artery of the central sulcus), anterior parietal (artery of the postcentral sulcus), posterior parietal, angular (parietooccipital branch), posterior temporal, middle temporal, anterior temporal, and temporopolar arteries. (From THIEME Atlas of Anatomy, Head and Neuroanatomy, © Thieme 2007, Illustration by Markus Voll.)

Fig. 1.10 Posterior cerebral artery. View of inferior surface of brain.

3. P1 segment

5. P3 segment

Abbreviations: ChAs, choroidal arteries; IC, internal capsule; ICA, internal carotid artery; LV, lateral ventricles; PCA, posterior cerebral artery; VL, ventrolateral

Fig. 1.11 The circle of Willis with the arteries including main perforating arteries of the brain (A) viewed from inferior and left in situ showing posterior circulation and (B) close-up view of circle of Willis itself. 1. Pontine arteries. 2. Circumferential pontine arteries. 3. Vertebral artery. 4. Posterior spinal artery. 5. Meningeal branches of vertebral artery. 6. Anterior spinal artery. 7. Posterior inferior cerebellar artery. 8. Labyrinthine artery. 9. Anterior inferior cerebellar artery. 10. Basilar artery. 11. Superior cerebellar artery. 12. Mesencephalic arteries. 13. Arteries to optic chiasm. 14. Thalamotuberal artery. 15. Hypothalamic branch. 16. Mammillary arteries. 17. Posterior thalamoperforating arteries. 18. Branch to oculomotor nerve. 19. Posterior communicating artery. 20. Artery of tuber cinereum. (From Dauber W. Pocket Atlas of Human Anatomy. Stuttgart, Germany: Thieme; 2007. Reprinted by permission.)

L. Vertebral artery

1. Course—arises from the subclavian artery, enters the foramina transversarium at C6 in 90%, turns lateral at C2, travels posteriorly along the atlas, entering the skull via foramen magnum

2. Anastomoses—ECA, thyrocervical and costocervical trunks

3. Supply—pyramids inferior olivary nucleus, CNs X and XII, and the reticular formation

Abbreviations: CN, cranial nerve; ECA, external carotid artery; PICA, posterior inferior cerebellar artery

M. Basilar artery

1. Union of two vertebral arteries near the pontomedullary junction, extends along the ventral pons and terminates as paired PCAs (within the interpeduncular cistern)

2. Basilar artery branches

Abbreviations: ACA, anterior cerebral artery; AICA, anterior inferior cerebellar artery; ChA, choroidal artery; CN, cranial nerve; ICA, internal carotid artery; MCA, middle cerebral artery; PCommA, posterior communicating artery; PCA, posterior cerebral artery; PICA, posterior inferior cerebellar artery; RAH, recurrent artery of Heubner; SCA, superior cerebellar artery

Fig. 1.12 Venous anatomy on lateral catheter angiogram. 1. Septal vein. 2. Anterior caudatevein. 3. Terminal vein. 4. Thalamostriate vein. 5. Atrial vein. 6. Basal vein of Rosenthal. 7. Vein of Galen. 8. Internal cerebral vein. 9. Venous angle. (From Alleyne Jr. CH. Neurosurgery Board Review. New York, NY: Thieme;1997. Reprinted by permission.)

Fig. 1.13 Dural sinus tributaries from the cerebral veins (after Rauber and Kopsch). Right lateral view. Venous blood collected deep within the brain drains to the dural sinuses through superficial and deep cerebral veins. The red arrows in the diagram show the principle directions of venous blood flow in the major sinuses. (From THIEME Atlas of Anatomy, Head and Neuroanatomy, © Thieme 2007, Illustration by Markus Voll.)

V. Blood Supply to the Spinal Cord

Fig. 1.14 Blood vessels supplying the spinal cord. Thoracic vertebra viewed from above. The spinal branches arise from the posterior branches of segmental arteries and divide into an anterior and posterior radicular artery. The radicular arteries supply the dorsal and ventral roots, and peripheral portions of the dorsal and ventral horns. They also communicate with the vasocorona. These arteries have a better developed connection with the anterior spinal artery at some levels and with the posterior spinal artery at other levels. (From THIEME Atlas of Anatomy, Head and Neuroanatomy, © Thieme 2007, Illustration by Karl Wesker.)

Fig. 1.15 Blood supply to the spinal cord segments. In each spinal cord segment, the anterior spinal artery gives off several (5–9) sulcal arteries that course posteriorly in the anterior median fissure. Typically, each sulcal artery enters one half of the spinal cord, supplying the anterior horn, base of the posterior horn, and anterior and lateral funiculi (approximately ⅔ of the total area) in that half; the sulcal arteries tend to alternate direction (left or right) to supply both halves of the spinal cord segment. The paired posterior spinal arteries provide the blood supply to the posterior third of the cord, including the posterior horn and funiculus. All three spinal arteries contribute numerous delicate anastomosing vasocorona on the pial surface of the spinal cord, which in turn send branches into the periphery of the cord. The sulcal arteries are end arteries within the spinal cord and their occlusion may produce clinical symptoms. (From THIEME Atlas of Anatomy, Head and Neuroanatomy, © Thieme 2007, Illustration by Karl Wesker.)

a. Derived from segmental vessels from the aorta, which includes the ascending cervical, deep cervical, intercostals, lumbar, and sacral arteries

b. Passes through the intervertebral foramina to divide into the anterior and posterior radicular arteries to supply the thoracic, lumbar, sacral, and coccygeal spinal segments

c. The anterior ramus of the segmental artery supplies the cord while the posterior ramus branches in the foramen supply the dorsal root ganglion (DRG) and nerve roots via anterior and posterior radicular branches

d. A single thoracic radicular artery (artery of Adamkiewicz) arises from the aorta at T7 (most vulnerable to low flow); 75% arise from T9–T12; 80% arise from the left

2. Posterior arterial system

a. Paired posterior spinal arteries form a leptomeningeal perimedullary network that anastomoses with the anterior system, most prominently at the level of the conus where the anastomotic loop is located.

b. Blood from the posterior medullary arteries flows centripetally in the perforating branches from the leptomeningeal system of the spinal cord surface to the posterior columns and posterior horns.

3. Anterior arterial system

a. Single midline artery that feeds into the anterior medullary artery in the anterior median fissure

b. Flows centrifugally via penetrating branches to the anterior and intermediate gray and via pial radial network to the white matter of the anterior and lateral funiculi

B. Regional arterial supply of the spinal cord

1. Segmental arteries → spinal branches (lies ventral to the root) pass through the intervertebral foramina → anterior or posterior radicular arteries → anterior or posterior spinal arteries.

D. Spinal cord ischemia

1. Most vulnerable at transitional regions where the arterial supply is derived from >1 source

2. Border zone region is especially vulnerable at T1–T4 and L1 (e.g., with an intercostal artery occlusion or an aortic dissection) anterior aspect of the spinal cord. Also vulnerable are areas between the anterior and posterior medullary arteries (between the intermediate and dorsal horns and lateral and posterior fasciculi).

E. Venous drainage of the spinal cord—highly variable, typically follows the arterial system

1. Both anterior spinal veins (located in the anterior sulcus) and the posterior spinal veins lie adjacent to the spinal arteries, which eventually drain into the intervertebral veins exiting the spinal canal via intervertebral foramina.

2. Anterior and posterior radicular veins

VI. Intracranial–Extracranial Anastomoses

A. Occipital artery ↔ vertebral (C1 and C2)

B. Ascending pharyngeal artery ↔ vertebral

C. Ascending pharyngeal artery ↔ ICA via petrous and cavernous branches

D. Facial artery (angular branch) ↔ ICA via angular branch of the facial artery to the orbital branch of the ophthalmic artery

E. Posterior auricular artery ↔ ICA via stylomastoid artery

F. Maxillary artery branch ↔ ICA via

1. MMA ↔ ethmoidal branch of the ophthalmic artery

2. Artery of foramen rotundum ↔ inferior lateral trunk

3. Accessory meningeal artery ↔ inferior lateral trunk

4. Vidian artery ↔ petrous ICA

5. Pharyngeal artery ↔ cavernous ICA

6. Temporal branches ↔ ophthalmic artery

7. Infraorbital artery ↔ ophthalmic artery

Fig. 1.16 Persistent fetal anastomoses between the anterior and posterior circulations.

Fig. 1.17 (A) Lateral and (B) anteroposterior catheter angiograms, and (C) axial T1-weighted magnetic resonance image of a persistent trigeminal artery.

Fig. 1.18 Brain surface anatomy, superior view. 1. Longitudinal fissure of cerebrum. 2. Superior margin of cerebrum. 3. Frontal pole. 4. Superior frontal sulcus. 5. Inferior frontal sulcus. 6. Precentral sulcus. 7. Central sulcus. 8. Postcentral sulcus. 9. Intraparietal sulcus. 10. Parietooccipital sulcus. 11. Transverse occipital sulcus. 12. Occipital pole. 13. Superior parietal lobule. 14. Inferior parietal lobule. 15. Postcentral gyrus. 16. Paracentral lobule. 17. Precentral gyrus. 18. Inferior frontal gyrus. 19. Middle frontal gyrus. 20. Superior frontal gyrus. (From Frick H, Leonhardt H, Starck D. Human Anatomy 2. New York, NY: Thieme, 1991. Reprinted by permission.)

Fig. 1.19 Brain surface anatomy, right lateral view. 1. Central sulcus. 2. Precentral gyrus. 3. Precentral sulcus. 4. Superior frontal gyrus. 5. Superior frontal sulcus. 6. Middle frontal gyrus. 7. Middle frontal sulcus. 8. Frontal pole. 9. Orbital gyri. 10. Olfactory bulb. 11. Olfactory tract. 12–14. Lateral sulcus. 12. Anterior ramus. 13. Ascending ramus. 14. Posterior ramus. 15. Frontal operculum. 16. Frontoparietal operculum. 17. Superior temporal gyrus. 18. Middle temporal gyrus. 19. Superior temporal sulcus. 20. Inferior temporal sulcus. 21. Inferior temporal gyrus. 22. Preoccipital notch. 23. Occipital pole. 24. Transverse occipital sulcus. 25. Inferior parietal lobule. 26. Intraparietal sulcus. 27. Superior parietal lobule. 28. Postcentral sulcus. 29. Postcentral gyrus. 30. Supramarginal gyrus. 31. Angular gyrus. 32. Pons. 33. Pyramid (medulla oblongata). 34. Olive. 35. Flocculus. 36. Cerebellar hemisphere. (From Frick H, Leonhardt H, Starck D. Human Anatomy 2. New York, NY: Thieme;1991. Reprinted by permission.)

Fig. 1.20 Coronal section through the brain. 1. Longitudinal fissure of cerebrum. 2. Cingulate sulcus. 3. Cingulate gyrus. 4. Sulcus of corpus callosum. 5. Corpus callosum. 6. Lateral sulcus. 7. Claustrum. 8–9. Corpus striatum. 8. Caudate nucleus. 9. Putamen. 9–10. Lentiform nucleus. 10. Globus pallidus. 11. Thalamus. 12. Subthalamic nucleus. 13. Mamillary body. 14. Amygdala. 15. Optic tract. 16. Third ventricle and choroid plexus. 17. Body of fornix. 18. Lateral ventricle and choroid plexus. 19. Cortex of insula. (From Frick H, Leonhardt H, Starck D. Human Anatomy 2. New York, NY: Thieme; 1991. Reprinted by permission.)

Fig. 1.21 Brain surface anatomy, view of medial surface of right hemisphere. 1. Frontal pole of frontal lobe. 2. Medial frontal gyrus. 3. Cingulate sulcus. 4. Sulcus of corpus callosum. 5. Cingulate gyrus. 6. Paracentral lobule. 7. Precuneus. 8. Subparietal sulcus. 9. Parietooccipital sulcus. 10. Cuneus. 11. Calcarine fissure. 12. Occipital pole of occipital lobe. 13–16. Corpus callosum (cut surface). 13. Rostrum. 14. Genu. 15. Body. 16. Splenium. 17. Lamina terminalis (cut surface). 18. Anterior commissure (cut surface). 19. Septum pellucidum. 20. Fornix. 21. Tela choroidea of third ventricle. 22. Choroid plexus of third ventricle (cut edge). 23. Transverse cerebral fissure. 24. Thalamus. 25. Interthalamic adhesion (cut surface). 26. Interventricular foramen of Monro. 27. Hypothalamus. 28. Suprapineal recess and pineal body (cut surface). 29. Vermis of cerebellum (cut surface). 30. Cerebellar hemisphere. 31. Choroid plexus of fourth ventricle. 32. Medulla oblongata (cut surface). 33. Fourth ventricle. 34. Pons (cut surface). 35. Tectal lamina (cut surface) and mesencephalic aqueduct of Sylvius. 36. Mamillary body. 37. Oculomotor nerve. 38. Infundibular recess. 39. Temporal lobe lateral occipitotemporal gyrus. 40. Rhinal fissure. 41. Hypophysis (cut surface) with adenohypophysis (anterior lobe) and neurohypophysis (posterior lobe) of pituitary gland. 42. Optic chiasm (cut surface). 43. Optic nerve. 44. Olfactory bulb and tract. (From Frick H, Leonhardt H, Starck D. Human Anatomy 2. New York, NY: Thieme; 1991. Reprinted by permission.)

Fig. 1.22 Isocortex layers. 1. Molecular layer. 2. External granular layer. 3. External pyramidal layer. 4. Internal granular layer. 5. Internal pyramidal layer. 6. Multiform layer. 1–3. External principle zone. 4–6. Internal principle zone. (From Frick H, Leonhardt H, Starck D. Human Anatomy 2. New York, NY: Thieme; 1991.)

Fig. 1.23 Brodmann areas in the neocortex. (From THIEME Atlas of Anatomy, Head and Neuroanatomy, © Thieme 2007, Illustration by Markus Voll.)

1. Main sensory areas—somatosensory area (areas 3, 1, 2), visual area (area 17), auditory area (areas 41, 42), gustatory area (area 43), and olfactory area (multiple Brodmann areas, not distinctly localized)

2. Sensory cortex

Abbreviations: IC, internal capsule; LGB, lateral geniculate body; MGB, medial geniculate body; ML, medial lemniscus; STT, spinothalamic tract; VPLc, ventroposterolateral pars caudalis; VPM, ventroposteromedial; VPMpc, ventroposteromedial pars compacta

Fig. 1.24 Motor homunculus. Coronal section anterior view of the left hemisphere. Axons for the head area are the corticonuclear fibers and the corticospinal fibers split into lateral and anterior corticospinal tracts below the diencephalon. (From THIEME Atlas of Anatomy, Head and Neuroanatomy, © Thieme 2007, Illustration by Markus Voll.)

1. Main motor areas—primary motor (area 4), premotor (area 6a), supplemental motor (areas 6a), frontal eye fields (area 8)

2. Motor cortex

Abbreviations: CN, cranial nerve; MLF, medial longitudinal fasciculus; VA, ventroanterior; VL, ventrolateral

F. Input to the motor area

1. Ipsilateral thalamic VL and ventrolateral pars oralis (VLo) → M1

2. Contralateral cerebellum → M1

3. Medial globus pallidus (GP) → ipsilateral thalamic ventroanterior pars compacta (VApc), VLo, centromedial (CM) → M2 and premotor cortex (not M1)

5. M2 → M1 and premotor cortex

6. Motor cortex has reciprocal fibers with the thalamus (except for thalamic reticular nuclei, which receives afferent fibers from the entire cortex but does not send them back.

G. Cerebral dominance

H. Cerebral topography

Fissure

Surface marking

Sylvian fissure

Localization: 1. Mark a point ¾ of the way on a line over the superior sagittal sinus from the nasion to the inion. Only gold members can continue reading. Log In or Register to continue Share this: Click to share on Twitter (Opens in new window) Click to share on Facebook (Opens in new window) Related Related posts: Neurosurgery Neurology Physiology Critical Care Pathology and Radiology Mild Traumatic Brain Injury: An Overview Stay updated, free articles. Join our Telegram channel Join Tags: Comprehensive Neurosurgery Board Review Jun 20, 2016 | Posted by admin in NEUROSURGERY | Comments Off on Anatomy Full access? Get Clinical Tree Get Clinical Tree app for offline access Get Clinical Tree app for offline access