Anterior inferior endoscopic view of the diencephalon and caudal arterial circle of Willis. In this magnified view, the basilar artery apex gives rise to the superior cerebellar arteries before terminating into right and left posterior cerebral arteries. The oculomotor nerve arises from the midbrain and courses between the superior cerebellar and posterior cerebral arteries within the interpeduncular cistern before it enters the lateral wall of the cavernous sinus.   The posterior communicating artery connects the internal carotid artery with the posterior cerebral artery. The midbrain or mesencephalon is largely obscured by the termination of the basilar artery. It represents the rostral end of the brainstem. Rostral to it in this view is the diencephalon featuring the mammillary bodies, tuber cinereum, and hypophysis. The optic chiasm is not visible in this view. (Image courtesy of AL Rhoton, Jr.)