Q, The opening in the choroidal fissure has been extended back to the area above the posterior commissure by dividing the tenia fornix. The choroid plexus is not disturbed on the thalamic side of the choroidal fissure. Branches of the medial posterior choroidal artery course with the internal cerebral veins. R, An interforniceal approach, in which the body of the fornix is divided longitudinally in the midline, has been completed. The massa intermedia, aqueduct, posterior commissure, pineal recess, and pineal are exposed. S, Superolateral view of the dissection. The velum interpositum, located between the upper and lower layers of tela and in which the internal cerebral veins and medial posterior choroidal arteries course, has been exposed. The lower layer of tela attached to the striae medullaris thalami has not been opened. Both internal cerebral veins are exposed posterior to the foramen of Monro. If a vein at the foramen of Monro is to be sacrificed, it is preferable to sacrifice the anterior septal rather than the thalamostriate vein. T, The exposure has been extended back to the atrium where the choroid fissure has been opened by dividing the tenia fornix along the edge of the crus of the fornix. The medial posterior choroidal arteries pass along the side of the pineal and through the quadrigeminal cistern to reach the roof of the third ventricle. U, The opening in the choroidal fissure has been extended to the temporal horn. The choroidal fissure has been opened by dividing the tenia on the edge of the fimbria of the fornix to expose the posterior cerebral artery and basal veins. The choroid plexus remains attached to the thalamus. V, The choroid plexus in the right lateral ventricle has been removed. The medial atrial vein drains into the internal cerebral veins. The amygdala is exposed below the globus pallidus and just behind the middle cerebral artery coursing in the sylvian fissure. The amygdala forms the anterior wall and anterior part of the roof of the temporal horn and superiorly blends into the lower margin of the lentiform nucleus. The middle cerebral artery courses above the amygdala in the medial part of the sylvian fissure. (Images courtesy of AL Rhoton, Jr.)