A, Infratentorial supracerebellar approach. The approach has been directed between the lower surface of the tentorium and the tentorial cerebellar surface. The large venous complex draining into the vein of Galen is in the central part of the exposure and the PCA and SCA are exposed laterally. A large vein of the cerebellomesencephalic fissure blocks access to the pineal and limits access to the cerebellomesencephalic fissure. This approach is selected for lesions located in the midline below the vein of Galen and not extending deeply into the cerebellopontine fissure. The SCA branches looping around the lip of the cerebellomesencephalic fissure may extend upward and limit access to the pineal region. B, The vein of the cerebellomesencephalic fissure has to be divided to expose the pineal. The medial posterior choroidal arteries are intertwined with the veins in the region. C, The occipital transtentorial approach has been directed along the medial side of the right occipital lobe. The tentorium behind the quadrigeminal cistern has been divided. The approach provides access to the splenium and the upper part of the cerebellomesencephalic fissure and has been extended forward to the lateral surface of the cerebral peduncles. Both the superior and inferior colliculi can be exposed and the arteries can be followed forward into the ipsilateral ambient cistern. In addition, the veins joining the vein of Galen can be elevated to expose the pineal. The trochlear nerve is exposed just distal to its brainstem exit below the inferior colliculus. D, Combined supra and infratentorial exposure with the division of the transverse sinus and tentorium. Division of the transverse sinus, if it is small and well collateralized, provides an exposure that combines both the supra- and infratentorial approaches. (Images courtesy of AL Rhoton, Jr.)