A, The left half of the tentorium has been removed while preserving a laterally placed tentorial sinus. A large sinus is seen through the right tentorial surface. B, The right half of the tentorium has been removed to expose a large inferior hemispheric vein from the suboccipital surface and a smaller superior hemispheric vein from the tentorial surface emptying into the large tentorial sinus. The superior hemispheric veins, which drain the tentorial surface, are divided into an anterior group, which empties into the Galenic system, and a posterior group, like the vein shown, which empties into the tentorial sinuses. Smaller veins from both the left tentorial and suboccipital surfaces join the laterally placed tentorial sinus near the junction of the left transverse and superior petrosal sinuses. C, The straight and tentorial sinuses have been removed. The anterior group drains toward the cerebellomesencephalic fissure and the vein of Galen, and the posterior group passes backward to empty into the tentorial sinuses. D, The posterior lip of the cerebellomesencephalic fissure has been removed to expose the veins of the superior cerebellar peduncle, which ascend to unite and form the vein of the cerebellomesencephalic fissure that empties into the vein of Galen. A transverse pontine vein and the vein of the cerebellopontine fissure join to form a superior petrosal vein that empties into the superior petrosal sinus. E, The posterior lip of the cerebellomesencephalic fissure has been removed to expose the tributaries of the vein of the cerebellomesencephalic fissure and the branches of the SCA. The paired veins of the superior cerebellar peduncle unite to form the vein of the cerebellomesencephalic fissure that empties into the vein of Galen. F, The branches of the SCA within the cerebellomesencephalic fissure have been removed. The paired veins of the superior cerebellar peduncle ascend on the superior cerebellar peduncles and join to form the vein of the cerebellomesencephalic fissure. The veins on the surface of the middle cerebellar peduncle course laterally to join the veins emptying into the superior petrosal sinus. (Images courtesy of AL Rhoton, Jr.)