Neurovascular Relationships of the Medial Temporal Region. A, Inferior view of the basal surface of the temporal lobe. The anterior segment of the MTR (yellow bracket) is related to the proximal sylvian and carotid cisterns anteriorly, and the crural cistern posteriorly. The middle segment (green bracket) is related to the ambient cistern, and the posterior segment is related to the quadrigeminal cistern (red bracket). The anterior segment of the medial temporal lobe is supplied by the carotid, MCA, AChA, and PCA. Both the middle and posterior segments of the medial temporal lobe are supplied predominantly by the PCA. B, Basal surface of the temporal lobe. The left parahippocampal gyrus and hippocampus have been removed to better expose their cisternal and vascular relationships. The T1-weighted axial MRI (inset) shows the segments of the MTR to be correlated with the anatomic dissection. C, Anterior-superior view. The anterior and middle segments of the medial temporal lobe have an upper surface. The upper surface of the anterior segment of the medial temporal lobe is constituted of the upper surface of the uncus, which has an anterior segment containing the amygdala that faces the carotid and MCA, an apex that faces medially toward the oculomotor nerve, and a posterior segment that faces the cerebral peduncle across the crural cistern. The anterior segment of the MTR, formed by the uncus, receives its arterial supply from the carotid artery, AChA, MCA, and PCA. The middle segment of the MTR has an upper surface formed by the upper surface of the parahippocampal gyrus and the dentate gyrus and fimbria, and is supplied by the PCA. The anterior choroidal arteries arise from the ICA and pass around the anterior segment, apex, and posterior segment of the uncus to reach the inferior choroidal point where they enter temporal horn. The basal veins course through the crural, ambient, and quadrigeminal cisterns. D, Enlarged view of the upper surface of the anterior part of the medial temporal lobe formed by the uncus. The AChA passes around the uncus and enters the choroidal fissure at the inferior choroidal point located at the posterior edge of the anterior segment of the medial temporal lobe. The upper surface of the anterior segment of the uncus is formed by the semilunar and ambient gyri, and the upper surface of the posterior part is formed by the upper surface of the hippocampal head, which folds medially into the posterior segment of the uncus. (Images courtesy of AL Rhoton, Jr.)