6 SPINAL CORD: WHITE AND GRAY MATTER

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6



VENTRICLES AND THE

CEREBROSPINAL FLUID



6.1



V

 entricular Anatomy



6.2



V

 entricular Anatomy in Coronal Forebrain Section



6.3



A

 natomy of the Fourth Ventricle:

Posterior View with Cerebellum Removed



6.4



A

 natomy of the Fourth Ventricle: Lateral View



6.5



M

 agnetic Resonance Imaging of the Ventricles: Axial

and Coronal Views



6.6



C

 irculation of the Cerebrospinal Fluid



67



68



Overview of the Nervous System



Ventricles of Brain



Right lateral ventricle

Anterior

(frontal) horn

Body

Inferior

(temporal) horn

Posterior

(occipital) horn



Left

lateral

ventricle



Cerebral aqueduct

(of Sylvius)

4th ventricle



Left lateral aperture

(foramen of Luschka)

Left interventricular

foramen (of Monro)



Left lateral recess



3rd ventricle

Median aperture

(foramen of Magendie)



Optic recess

Interthalamic adhesion

Infundibular recess



CSF Composition



Pineal recess

Suprapineal recess



Na� (mEq/L)



Blood plasma



140–145



135–147



K� (mEq/L)



3



3.5–5.0



Cl� (mEq/L)



115–120



95–105



HCO3� (mEq/L)



20



22–28



Glucose (mg/dL)



50–75



70–110



0.05–0.07



6.0–7.8



7.3



7.35–7.45



Protein (g/dL)

pH



6.1  VENTRICULAR ANATOMY

The lateral ventricles are C-shaped, reflecting their association

with the developing telencephalon as it sweeps upward, back,

and then down and forward as the temporal lobe. The position of the lateral ventricles in relation to the head and body

of the caudate nucleus is an important radiological landmark

in a variety of conditions, such as hydrocephalus, � caudate

atrophy in Huntington’s disease, and shifting of the Â�midline

with a tumor. Cerebrospinal fluid (CSF) flows through the

interventricular foramen of Monro into the narrow third



CSF



�ventricle, then into the cerebral aqueduct and the fourth ventricle. Blockage of flow in the aqueduct can precipitate internal hydrocephalus, with swelling of the ventricles rostral to

the site of blockage. The escape sites where CSF can flow into

expanded regions of the subarachnoid space called cisterns are

the medial foramen of Magendie and the lateral foramina of

Luschka. These foramina are additional sites where blockage

of CSF flow can occur. The choroid plexus, extending into the

ventricles, produces the CSF.



Ventricles and the Cerebrospinal Fluid



69



Corpus callosum

Right lateral ventricle

Body of caudate nucleus

Choroid plexus of lateral ventricle

Stria terminalis

Right thalamostriate vein

Body of fornix

Tela choroidea of 3rd ventricle

Choroid plexus of 3rd ventricle

Thalamus

Putamen _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _

Globus pallidus

(internal [i] and external [e] segments)

e

i



Lentiform nucleus



Internal capsule

3rd ventricle

Hypothalamus

Tail of caudate nucleus

Optic tract

Choroid plexus of lateral ventricle

Inferior (temporal) horn of lateral ventricle

Fimbria of hippocampus



Coronal section of

brain (posterior view;

arrow in left

interventricular foramen)



Hippocampus

Dentate gyrus

Subiculum

Parahippocampal cortex



Ependyma



Pia mater



6.2╇VENTRICULAR ANATOMY IN CORONAL

FOREBRAIN SECTION

A coronal section through the diencephalon shows the bodies

of the lateral ventricles, the narrow interventricular foramina

of Munro, and the midline third ventricle. The flow of CSF is



Entorhinal cortex



from the lateral ventricles into the third ventricle. The choroid

plexus protrudes into both the lateral and third ventricles and

produces CSF. The temporal (inferior) pole of the lateral ventricle and its associated choroid plexus is shown in the temporal lobe.



70



Overview of the Nervous System



Posterior View



3rd ventricle



Habenular trigone



Pulvinar



Lateral

Medial



Pineal gland

Superior colliculus



Superior cerebellar peduncle



Inferior colliculus



Median sulcus



Trochlear (IV) nerve



Locus ceruleus area



Superior medullary velum



Medial eminence



Superior

Cerebellar peduncles



Geniculate bodies



Sulcus limitans



Middle



Facial colliculus



Inferior



Vestibular area



Lateral recess



Dentate nucleus



Superior fovea



Tenia of 4th ventricle



Striae medullares

Hypoglossal nerve trigone



Obex



Inferior fovea



Gracile tubercle

Tuberculum cinereum (spinal tract of trigeminal nerve)

Cuneate tubercle

Vagal trigone



6.3╇ANATOMY OF THE FOURTH VENTRICLe:

POSTERIOR VIEW WITH �CEREBELLUM

�REMOVED

The rhomboid-shaped fourth ventricle extends through the

pons and medulla. The foramina of Magendie and Luschka

must remain patent for proper flow of the CSF into the cisterns. Bilaterally symmetrical protrusions, depressions, and

sulci on the floor of the fourth ventricle define the underlying

anatomy of brain stem regions, such as the hypoglossal, vagal,



Posterior median sulcus

Fasciculus cuneatus

Fasciculus gracilis



and vestibular areas. Vital brain stem centers for cardiovascular, respiratory, and metabolic functions just below the floor

of the fourth ventricle can be damaged by tumors in the region. The lateral margins of the fourth ventricle are embraced

by the huge cerebellar peduncles interconnecting the cerebellum with the brain stem and diencephalon. These anatomical

relationships are important when interpreting imaging studies in the compact brain stem regions where the diagnosis of

tumors and vascular lesions is challenging.



71



Ventricles and the Cerebrospinal Fluid

Median Sagittal Section

Habenular commissure



Body of fornix

Choroid plexus

of 3rd ventricle



Pineal gland

Splenium of corpus callosum



Interventricular

foramen (of Monro)



Great cerebral vein (of Galen)



Thalamus

Anterior

commissure



Cerebral aqueduct (of Sylvius)



Lamina terminalis



Lingula



Posterior

commissure



Central lobule

Culmen



Mammillary body



Vermis



Declive



Optic chiasm



Folium



Oculomotor

(III) nerve



Tuber



Superior colliculus



Superior

medullary

velum



Inferior colliculus

Pons



Inferior

medullary

velum



Medial longitudinal fasciculus

4th ventricle



Choroid

plexus

of 4th

ventricle



Medulla (oblongata)

Tonsil

Median aperture (of Magendie)

Pyramidal decussation



Pyramid

Uvula



Vermis



Nodule



Central canal of spinal cord



6.4╇ANATOMY OF THE FOURTH VENTRICLE:

LATERAL VIEW

In a midsagittal section, the rhomboid shape of the fourth ventricle is shown. Rostrally, the narrow cerebral aqueduct leads

into the fourth ventricle; caudally, the foramen of Magendie

provides for escape of CSF into a cistern of the subarachnoid

space. CSF normally does not flow through the central canal of

the spinal cord. The dorsal surface of the brain stem is on the

floor of the fourth ventricle; the cerebral peduncles form the

lateral boundaries; and the medullary velum and cerebellum

form the roof of the fourth ventricle. The choroid plexus is

present in the fourth ventricle. In the diencephalon, the shallow depression of the third ventricle and the interventricular

foramen of Munro are shown.

CLINICAL POINT

The choroid plexus is the site of production of CSF in the lateral, third,

and fourth ventricles. Even subtle changes in equilibrium between

CSF production and absorption can result in altered �intraventricular



pressure and intracranial pressure. Hydrocephalus is most commonly caused by obstruction of outflow (internal hydrocephalus) or

failure of appropriate absorption into the venous sinuses ―external

�hydrocephalus). Occasionally, alterations in CSF production by the

choroid plexus may occur. Inflammation of the choroid plexus or

a papilloma can lead to hypersecretion hydrocephalus. In contrast,

damage to the choroid plexus by radiation, trauma, or meningitis or

secondary to lumbar puncture may result in diminished CSF production (hypoliquorrhea), with resultant long-lasting and persistent

headache that is responsive to change in posture.

The CSF escapes from the ventricular system from the medial

�foramen of Magendie and the lateral foramina of Luschka of the

fourth ventricle. These apertures must remain unobstructed in order

to allow CSF to escape into the subarachnoid space, bathe the CNS,

and then be absorbed into the venous sinuses through the arachnoid

granulations. The foramen of Magendie is the most important of these

apertures; it may become obstructed by tonsillar herniation into the

foramen magnus as the result of Arnold-Chiari malformation; by a

cerebellar tumor; or by an intraventricular tumor that obstructs the

lower portion of the fourth ventricle. Such an obstruction at this lower

level results in expansion of the entire ventricular system, including

the fourth, third, and lateral ventricles.