The Medial Temporal Region and Adjacent Vascular Structures. a, Medial view of the anterior segment of the medial temporal region (MTR) and adjacent vascular structures. The anterior choroidal artery (AChA) passes above the semiannular sulcus and uncinate gyrus to reach the lower end of the choroidal fissure, where it enters the temporal horn through the inferior choroidal point. The posterior cerebral artery (PCA) courses medial to the uncal sulcus that divides the posterior segment of the uncus into upper and lower parts. b, The PCA has been removed. An imaginary line (yellow dashed line), referred to as the carotid-choroidal line, drawn from the bifurcation of the internal carotid artery or the M1 segment of the middle cerebral artery (MCA) to the inferior choroidal point is a reliable landmark to determine the superior extent of the amygdalar resection. c, The PCA is the main arterial supplier of the MTR and typically has a proximal bifurcation situated adjacent to the middle segment of the MTR and a distal bifurcation formed by the posterior inferior temporal artery and the parietooccipital arterial trunk (P2p). The PCA gives off the anterior inferior temporal artery, from which the anterior parahippocampal artery arises, just before the proximal bifurcation. In this case, the middle inferior temporal artery and the posterior parahippocampal artery arise from the posterior inferior temporal artery. The medial posterior choroidal artery and the quadrigeminal artery arise from the proximal part of P2a. d, The branching pattern of the PCA in another case. A trifurcation into the middle and posterior inferior temporal arteries and the parietooccipital trunk (P2p) was seen instead of the distal bifurcation. The posterior parahippocampal artery arises from the middle inferior temporal artery and the medial posterior choroidal artery from the parietooccipital trunk (P3). e, The frontal lobe and the central core of the right cerebral hemisphere have been removed to expose the temporal horn, atrium, and the basal cisterns. The M1 segment of the MCA courses on the upper surface of the temporal pole, the M2 segment crosses the insular surface, and the M3 travels on the opercular surfaces. The PCA passes posteriorly in the crural and ambient cisterns (P2a and P2p segments, respectively) to reach the quadrigeminal cistern (P3 segment). f, Enlarged view of e. The AChA enters the choroidal fissure at the inferior choroidal point located at the posterosuperior edge of the uncus. (Images courtesy of AL Rhoton, Jr.)