Right anterolateral view of Sylvian fissure and terminal branches of internal carotid artery. Retraction of frontoparietal and temporal lobes has opened the Sylvian (lateral) fissure to demonstrate the bifurcation of the internal carotid artery into its anterior and middle cerebral arteries. The anterior cerebral artery courses medially around the optic nerve to enter the longitudinal interhemispheric fissure. The larger middle cerebral artery enters the Sylvian (lateral) fissure. Its M1 (horizontal) segment quickly gives rise to its M2 segment, which divides into a superior and inferior trunk. The posterior cerebral artery, the terminal branch of the basilar artery, curves around the cerebral peduncle (within the crural cistern between the cerebral peduncle and uncus of the temporal lobe) and courses in a supratentorial direction to supply the posteromedial portion of the temporal lobe and occipital lobe. The oculomotor nerve is visible having emerged from the medial wall of the interpeduncular fossa and coursing forward within the interpeduncular cistern to the dura overlying the roof of the cavernous sinus. (Image courtesy of AL Rhoton, Jr.)