C H A P T E R 1 9

Cross-Sectional Anatomy

of the Brain

Objective

1.Identify the major structures of the brain from the three orthogonal planes, including sagittal, coronal, and axial sections.

IIntroduction. Thick, stained brain slices in this chapter are accompanied by

corresponding magnetic resonance imaging scans. Together they represent a mini-atlas of brain slices in the three orthogonal planes (i.e., midsagittal, coronal, and axial). An insert on each figure shows the level of the slice. The most commonly tested structures are labeled.

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Central sulcus

Precuneus

Pineal body

Parieto-occipital sulcus

Figure 19-1 Midsagittal section of the brain with meninges and blood vessels intact. Arachnoid granulations are seen along the crest of the hemisphere. The posterior commissure, decussation of the superior cerebellar peduncles, and medial longitudinal fasciculus are well demonstrated. (Modified from Roberts M, Hanaway J, Morest DK. Atlas of the Human Brain in Section. 2nd ed. Philadelphia, PA: Lea & Febiger; 1987:85.)

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Figure 19-3 Midsagittal magnetic resonance imaging section through the brain and brain stem showing the important structures surrounding the third and fourth ventricles. This is a T1-weighted image. The gray matter appears gray (hypointense), whereas the white matter appears white (hyperintense).

Figure 19-4 Midsagittal magnetic resonance imaging section through the brain stem and diencephalon. Note the cerebrospinal fluid tract: lateral ventricle, cerebral aqueduct, fourth ventricle, cerebellomedullary cistern (cisterna magna), and spinal subarachnoid space. Note also the relation between the optic chiasm, infundibulum, and hypophysis (pituitary gland).

Figure 19-6 Coronal section through the anterior commissure, amygdala, septal nuclei, and optic chiasm. (Modified from Roberts M, Hanaway J, Morest DK. Atlas of the Human Brain in Section. 2nd ed. Philadelphia, PA: Lea & Febiger; 1987:9.)

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Figure 19-7 Coronal magnetic resonance imaging section through the amygdala, optic chiasm, infundibulum, and internal capsule. The cavernous sinus encircles the sella turcica and contains the following structures: cranial nerves (CN) III, IV, VI, V1, and V2; postganglionic sympathetic fibers; and the internal carotid artery. This is a T1-weighted image.

Figure 19-8 Coronal section through the posterior limb of the internal capsule, mammillothalamic tract, mammillary body, and hippocampal formation. The optic tracts are visible bilaterally. (Modified from Roberts M, Hanaway J, Morest DK. Atlas of the Human Brain in Section. 2nd ed. Philadelphia, PA: Lea & Febiger; 1987:19.)

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Caudate nucleus

Internal capsule

Claustrum

VPL

Putamen

VPM

Globus pallidus

Red nucleus

Caudate nucleus

Hippocampal formation

Figure 19-10 Coronal section through the thalamus, ventral posteromedial nucleus (VPM) and the ventral posterolateral nucleus (VPL), posterior limb of the internal capsule, substantia nigra, and red nucleus. (Modified from Roberts M, Hanaway J, Morest DK. Atlas of the Human Brain in Section. 2nd ed. Philadelphia, PA: Lea & Febiger; 1987:23.)

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Lateral ventricle

Pineal gland

Superior colliculus

Pulvinar nucleus

Fornix

Caudate nucleus (tail)

Hippocampal formation

Figure 19-12 Coronal section through the pulvinar, pineal gland (epiphysis), superior and inferior colliculi, and trochlear nerve (CN IV). (Modified from Roberts M, Hanaway J, Morest DK. Atlas of the Human Brain in Section. 2nd ed. Philadelphia, PA: Lea & Febiger; 1987:29.)

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Figure 19-14 Axial magnetic resonance imaging section at the level of the internal capsule and basal nuclei (ganglia). Note that the caudate nucleus bulges into the frontal horn of the lateral ventricle. In Huntington’s disease, there is a massive loss of γ-aminobutyric acid (GABA)-ergic neurons in the caudate nucleus that results in hydrocephalus ex vacuo. A lesion of the genu of the internal capsule results in a contralateral weak lower face with sparing of the upper face. This is a T1-weighted image.

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Figure 19-17 Axial magnetic resonance imaging (MRI) section at the level of the midbrain and mammillary bodies. Because of the high iron content, the red nuclei, mammillary bodies, and substantia nigra show a reduced MRI signal in T2-weighted images. Flowing blood in the cerebral vessels stands out as a signal void. Cerebrospinal fluid produces a strong signal in the ventricles and cisterns.

Figure 19-18 Axial magnetic resonance imaging section at the level of the optic chiasm, mammillary bodies, and midbrain. This patient has neurofibromatosis type 1 and an optic nerve glioma. Note the size of the right optic nerve. The infundibulum is postfixed. This is a T1-weighted image.

Figure 19-19 Axial magnetic resonance imaging section at the level of the uncal incisure, oculomotor nerve.