Infratentorial Supracerebellar Approach. A and B, The venous complex emptying into the vein of Galen blocks access to the pineal region. This complex includes the internal occipital, basal, and internal cerebral veins and the vein of the cerebellomesencephalic fissure (already sectioned). Arteries, including the P3 portions of the PCAs, a tentorial branch of the SCA, and the medial posterior choroidal arteries, cross the exposure. The lower margin of the operative field is the superior colliculus. C, The vein of Galen has been retracted to expose the splenium. The lateral margin of the operative field is the pulvinar. D, The basal vein has been retracted to expose the posterior part of the third ventricle. (Images courtesy of AL Rhoton, Jr.)