Endoscopic anterior inferior perspective of the basilar artery and pons area. The clivus and most of the sphenoid bone have been removed to reveal the basilar artery (formed by right and left vertebral arteries uniting at the pontomedullary junction) ascending on the pons midline. From the basilar artery arise the anterior inferior cerebellar arteries, several pontine arteries (not labeled), and the superior cerebellar arteries before terminating with the posterior cerebral arteries. Near the pontomedullary junction arise the abducens nerve and from the pons more anterolaterally the large trigeminal nerve. Within the cavernous sinus, the abducens nerve courses along the lateral surface of the ICA. Rostral to the terminal basilar artery are the mammillary bodies, brainstem nuclei associated with the hypothalamus and involved with recollective memory function. The sigmoid sinus is visible as it approaches the jugular foramen. (Image courtesy of AL Rhoton, Jr.)