Anterolateral view of retracted Sylvian fissure. Retraction of the left 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 internal carotid artery enters the cranial cavity just inferolateral to the optic nerve near the optic canal where it gives rise to the ophthalmic artery that accompanies the nerve into the orbit. The anterior cerebral artery courses medially around the optic nerve and tract 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 usually divides into a superior and inferior trunk. M3 segmental branches arise from these trunks and course laterally along the frontoparietal and temporal operculum and then terminate at the external surface of the Sylvian fissure. From these branches arise M4 segmental branches, which radiate onto and penetrate cortical areas along the lateral convexity of the cerebrum. The superior Sylvian vein (or superficial middle cerebral vein, not labeled) courses along the Sylvian fissure posteriorly. It drains cortical areas along the lateral sulcus and connects to the vein of Labbe (or inferior anastomotic vein). The latter is usually the largest venous channel on the lateral surface of the brain. It crosses the temporal lobe and empties into the transverse sinus. (Image courtesy of PA Rubino)