Cavernous Carotid and Carotid Cave. A, Anterior view. Coronal section anterior to the sella and optic chiasm. The distal dural rings have been preserved. The walls of the sphenoid sinus has been removed to expose the anterior sella wall and the ICAs. The opticocarotid recess extends into the optic strut. The right proximal dural ring extends medially below the opticocarotid recess and does not form as distinct a proximal ring on the medial side of the artery as does the distal ring. The basilar venous plexus is the largest communicating channel between the cavernous sinuses. B, Enlarged view of right parasellar area and the opticocarotid recess that extends into the optic strut. The dura lining the lower margin of the optic strut continues posteriorly to form the proximal dural ring. The dura on the upper surface of the optic strut extends around the ICA to form the distal dural ring. The abducens nerve passes around the lateral surface of the carotid and ascends medial to the ophthalmic nerve in the cavernous sinus. C, Enlarged view after removing the dura in the sellar region and along the medial wall of the right cavernous sinus. The opticocarotid recess, a pneumatized diverticulum of the sphenoid sinus extends laterally into the optic strut, which separates the optic nerve in the optic canal from the nerves passing through the superior orbital fissure. The dura forming the proximal dural ring does not form as distinct a ring on the medial side of the artery adjacent the carotid sulcus as it does along the anterior and lateral surface of the artery. D, Enlarged view. The distal dural ring encases the carotid artery just below the level of the origin of the ophthalmic artery. The proximal ring blends into the dura surrounding the artery on the side of the carotid sulcus. E, A triangular piece of green material has been inserted into the carotid cave located between the dura forming the collar around the artery and the outer wall of the ICA. The proximal ring is not as distinct on the medial side of the artery as is the distal ring. F, The distal dural ring and upper medial part of the carotid collar has been incised and retracted with black sutures to expose the arterial wall in the carotid cave. G, Transnasal exposure of the left parasellar region in another specimen. One superior hypophyseal artery arises in the carotid cave proximal to the distal ring and ascends to exit the cave and pass to the pituitary stalk. Another superior hypophyseal artery arises above the level of the distal dural ring. A triangular piece of green material has been placed inside the cave. H, The carotid collar, below the level of the distal ring, has been opened to expose the origin of the superior hypophyseal artery in the carotid cave. The proximal ring is not as distinct on the medial side of the ICA as is the distal ring. (Images courtesy of AL Rhoton, Jr.)