Posterior Perspective of the Partially Dissected Cerebellum. The left cerebellar hemisphere has been partly dissected to reveal the dentate nucleus and middle cerebellar peduncle. The left trochlear nerve is seen exiting the dorsal surface of the midbrain caudal to the inferior colliculus of the quadrigeminal plate. Further superiorly, the basal veins of Rosenthal run posteriorly and medially through the ambient cistern to drain into the great cerebral vein of Galen. (Image courtesy of AL Rhoton, Jr.)