Superior Extension of Upper Clival Approach to the Infrasellar Approach. A, Two dural layers, periosteal and meningeal, line the sella below the pituitary gland. A triangular green piece has been inserted between the meningeal layer and pituitary capsule. The double-layer structure of the dura is especially apparent around the intercavernous sinuses, which course between the 2 layers. The left distal carotid dural ring has been divided. B, The sellar part of the medial wall of the cavernous sinus has been separated from the pituitary capsule, and the anterior lobe has been retracted medially to expose the posterior lobe. The medial wall of the cavernous sinus is formed by a thin layer of meningeal dura. The pituitary capsule is tightly attached to the outer surface of the gland. The sellar part of the medial wall of the cavernous sinus covers the lateral surface of the anterior lobe, but the posterior lobe is positioned behind the medial wall of the cavernous sinus in the concavity of the dorsum sellae. C, 45-degree endoscope directed superior. The posterior lobe of the pituitary grand has been retracted upward, and the dorsum sellae has been exposed. The posterior lobe sits in the concave anterior surface of the dorsum sellae. The inferior hypophyseal artery arises from the meningohypophyseal trunk and courses medial to supply the posterior lobe. Care is required to avoid avulsion of the inferior hypophyseal artery during transposition of the gland. D, 45-degree endoscope directed superior. The dorsum sellae has been drilled while preserving the posterior clinoid processes and adjacent part of the dorsum. The mesencephalic leaf of Liliequist’s membrane, which spans the interval between the posterior clinoid process and the pontomesencephalic junction, has been exposed. The mesencephalic membrane is open around the upper the basilar artery. The oculomotor nerves course in the lateral wall of the interpeduncular cisterns and form the pillars to which the leaves of Liliequist’s membrane attach. This specimen has a duplicate left superior cerebellar artery. E, Closer view. The contents of the interpeduncular cistern and the origins of the both posterior cerebral arteries can be seen through the large opening in the mesencephalic membrane. The thalamoperforating arteries arise from the P1 and enter the brainstem by passing through the posterior perforated substance in the area behind the mamillary bodies. F, 70-degree endoscope directed upward showing the anatomic upper limit of the extended upper clival approach. The diencephalic leaf of Liliequist’s membrane has been opened, and the posterior lobe of the pituitary gland has been elevated. The interpeduncular and part of the chiasmatic and carotid cisterns are accessible. The right peduncular vein is exposed lateral to the mamillary bodies. (Images courtesy of AL Rhoton, Jr.)