Posterior view of midbrain. The cerebellum has been retracted inferiorly to expose the superior and inferior colliculi. The tentorium cerebelli is visible on either side of the midbrain. The great cerebral vein of Galen lies in the quadrigeminal cistern and is formed by the union of the internal cerebral veins and the basal veins of Rosenthal just posterior to the pineal gland. The vein of Galen receives blood from deep cerebral veins as well as the vein of the cerebellomesencephalic fissure, which drains the superior aspect of the cerebellar vermis and adjacent portions of the cerebellar hemispheres. The vein of Galen travels posteriorly and superiorly to drain into the straight sinus, which is located in the junction between the falx cerebri and the tentorium cerebelli. (Image courtesy of AL Rhoton, Jr.)