Vascular Relationships of the Anterior Segment of the Medial Temporal Region. A, Right transsylvian approach (inset) to the basal cisterns. The carotid branches and bifurcation have been exposed. The temporopolar artery arising from the M1 has been sectioned near its origin (green arrow) and folded downward (yellow arrow) to better expose the uncal region. An anterior uncal artery arises from the choroidal segment of the carotid and irrigates the semilunar gyrus. In this specimen, the AChA does not give any branches to the semilunar gyrus. B, Same view as in part A in another specimen. Two anterior uncal arteries arise from the choroidal segment of the carotid and supply the semilunar gyrus. The anterior uncal artery that arises from the proximal M1 and irrigates the ambient gyrus has been sectioned near its origin (green arrow) and folded downward (yellow arrow) to facilitate the exposure of the uncal region. C, Right anterior subtemporal approach (inset) to the entorhinal area and basal cisterns. The branches of the carotid artery and P2a have been exposed. An anterior parahippocampal artery arises from the AITA, and an anterior hippocampal-parahippocampal artery arises from P2a segment (the anterior hippocampal branch enters the uncal sulcus and is not visualized). D, Lower surface of another MTR. The entorhinal area is irrigated medially by the parahippocampal branch of the anterior hippocampal-parahippocampal artery that arises from the P2a, and laterally by a large anterior parahippocampal artery that originates from the AITA. (Images courtesy of AL Rhoton, Jr.)