Endoscopic view of vertebrobasilar artery and anterior pons. The clivus and most of the sphenoid bone have been removed to reveal the right and left vertebral arteries uniting at the pontomedullary junction to form the basilar artery. 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 nerves and from the pons more anterolaterally the large trigeminal nerves. The oculomotor nerves emerge from the midbrain between the superior cerebellar and posterior cerebral arteries. The convoluted course of the internal carotid arteries can be seen as these traverse the carotid canal and cavernous sinus. (Image courtesy of AL Rhoton, Jr.)