Regional Anatomy of the Parasellar Region. G, Sagittal view directed through the sphenoid sinus to the medial wall of the cavernous sinus showing the pituitary gland sitting in the sella above the sphenoid sinus. The anterior intercavernous sinus crosses the anterosuperior aspect of the gland. The basilar sinus, the largest communication between the cavernous sinuses, crosses the back of the dorsum sellae and opens into both cavernous sinuses. H, Enlarged view showing the pituitary gland removed to expose the medial wall of the right cavernous sinus. The anterior intercavernous sinus courses between the meningeal layer of dura facing the gland and the endosteal layer lining the osseous sellar wall. I–L, Photographs illustrating the stepwise exposure of the medial wall of the left cavernous sinus. I, View showing the roof and lateral wall of the cavernous sinus exposed. The clinoidal space has been exposed by removing the anterior clinoid process. The carotidoculomotor membrane, which forms the anterior part of the roof of the cavernous sinus and the carotid collar, has been folded forward to expose the clinoidal segment of the carotid. The oculomotor nerve enters the roof of the cavernous sinus through the oculomotor triangle located on the medial side of the anterior petroclinoid dural fold. A microdissector placed below the diaphragma sellae and lateral to the pituitary gland can be observed through the thin medial wall of the cavernous sinus. J, Enlarged view showing the microdissector through the thin medial sinus wall that separates the cavernous sinus from the pituitary gland. K, View showing the intracavernous carotid and nerves removed to expose the medial wall of the cavernous sinus. The microdissector, placed below the diaphragma sellae and pituitary gland, can be observed through the thin semitransparent medial wall. L, View showing the medial wall of the cavernous sinus opened, with the leaves of the sellar portion of the medial wall folded outward to expose the lateral surface of the gland. The sphenoidal portion of the medial wall is exposed along the anterior and lower edges of the gland. (Images courtesy of AL Rhoton, Jr.)