Right Occipital Transtentorial Approach. A, The occipital transtentorial approach is directed between the medial surface of the occipital lobe and the falx. This occipital lobe is commonly free of bridging veins to the superior sagittal sinus. The first vein encountered is the internal occipital vein, which passes from the anterior part of the medial occipital lobe to the vein of Galen. B, The tentorium has been opened lateral to the straight sinus, and the vein of Galen has been retracted to expose the pineal body from above. The exposure of the contralateral internal cerebral and basal veins is limited. C, The internal cerebral vein has been retracted to expose the posterior part of the third ventricle. D, The exposure has been directed laterally along the side of the brainstem to the ambient cistern, where the lateral margin of the cerebral peduncle and the P2p segment are exposed. (Images courtesy of AL Rhoton, Jr.)