Lateral exposure of middle cerebral artery in Sylvian fissure. The left middle cerebral artery, the larger of the two terminal branches of the internal carotid artery, is shown entering the Sylvian (lateral) fissure where it progressively divides into four M segments. The last or M4 segment sends branches into their final cortical territory. The middle cerebral arteries supply most of the lateral surface of the hemisphere, except the superior part of the parietal lobe and inferior part of the temporal and occipital lobes. Elevation of the frontal lobes has put tension on the olfactory bulbs (resting on olfactory fossa of cribriform plate) and the olfactory tracts. (Image courtesy of PA Rubino)