Endoscopic View of Crural Cistern. I, The endoscope has been introduced through the opticocarotid triangle and into the carotid cistern to provide this view of the anterior part of the crural cistern. The yellow circle approximates the superficial position of the tip of the endoscope. J, The endoscope has been advanced to provide this view of the intracrural membrane, which extends from the posterior segment of the uncus to the cerebral peduncle. The anterior choroidal artery passes above and the posterior cerebral artery passes below this membrane. (Images courtesy of AL Rhoton, Jr.)