Anatomic Dissection via Subfrontal Exposure of the Chiasmatic Cistern. E, The coronal section of the skull base shown in B has been extended posteriorly to the level of the interpeduncular cistern just in front of the basilar artery. The oculomotor nerves pass between the posterior cerebral and superior cerebellar arteries. F, The right anterior choroidal artery and perforating branches have been retracted laterally to expose the crural cistern located between the posterior part of the uncus and the cerebral peduncle. The intracrural membrane extends from the posterior part of the uncus to the upper part of the cerebral peduncle and separates the crural cistern into upper and lower parts. G, Endoscopic view of the intracrural membrane and the crural cistern shown in F. The anterior choroidal artery courses above and the posterior cerebral artery courses below the intracrural membrane. H, Endoscopic view of the intracrural membrane in another specimen. The anterior choroidal artery courses above the intracrural membrane, which separates the intracrural cistern into upper and lower parts. (Images courtesy of AL Rhoton, Jr.)