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Stepwise Fiber Dissection of the Left Cerebral Hemisphere G-M

Surgical Correlation


G, The posterior, but not the anterior, part of the globus pallidus has been removed. Transcapsular bridges of gray matter cross the anterior part of the internal capsule. H, The optic tract proceeds posteriorly toward the lateral geniculate body. Three bundles of the optic radiations are seen: an anterior one that is deeper and loops forward above the temporal horn before turning backward, the middle one passes laterally above the temporal horn, and the third bundle passes backward lateral to the atrium to reach the calcarine sulcus. I, The retrolenticular part of the optic radiations has been removed to expose the tapetum, which separates the optic radiations from the ventricular wall. The lateral ependymal wall of the atrium has been opened. The anterior commissure was transected and the lateral part removed. The middle part of the optic radiation has been elevated on a dissection. J, The optic radiations have been removed to expose the tail of the caudate blending into the amygdala. The optic tract has been exposed further posteriorly. The stria terminalis courses medial to the caudate tail and contains fibers passing from the amygdala to the septal area, thalamus, and mamillary body. K, The lateral ependymal wall of the lateral ventricle has been removed and some bundles of callosal fibers above the ventricle have been preserved. The calcar avis bulges into the medial wall of the atrium and occipital horn. The window in the white matter (yellow arrow) overlying the calcar avis exposes the cortical gray matter in the deep end of the calcarine sulcus. The red pin is positioned lateral to the deep site of the foramen of Monro. The genu of the internal capsule is located directly lateral to the foramen of Monro. The anterior limb of the capsule is located anterior to the red dot and lateral to the caudate head. The posterior limb is located posterior to the foramen of Monro. The internal capsule blends into the cerebral peduncle below the level of the optic tract. L, The head of the caudate has been folded downward to expose the foramen of Monro. The columns of the fornix pass superior and anterior to the foramen of Monro. The septum pellucidum is exposed above the rostrum of the corpus callosum. The amygdala is exposed below the optic tract. M, The tail of the caudate has been elevated to expose the stria terminalis, which arises within the amygdala. The collateral eminence overlies the deep end of the collateral sulcus. The tail of the caudate nucleus blends into the amygdala. (Images courtesy of AL Rhoton, Jr.)