G, Anterior clinoid process has been removed to expose the clinoid segment of the internal carotid artery defined by the upper and lower dural rings. The upper ring is formed by the dura extending medially from the upper surface of the anterior clinoid. The lower dural ring is formed by the dura, which extends medially from the lower margin of the anterior clinoid and separates the lower clinoid margin from the oculomotor nerve. H, Posterosuperior view of the sella. The dorsum and posterior clinoid have been removed to expose the posterior lobe of the pituitary, which was hidden below the dorsum. The abducens nerve is exposed below the petrosphenoid ligament. The trigeminal nerve has been reflected forward to expose the petrolingual ligament, which extends above the internal carotid artery just proximal to the artery’s entry into the cavernous sinus. I, Enlarged view of the petrolingual and petrosphenoid ligaments. The inferior hypophyseal artery passes to the capsule of the posterior lobe. The greater petrosal nerve courses medially and is joined by the deep petrosal branch of the periarterial carotid plexus to form the vidian nerve. J, Enlarged view. The carotid artery protrudes medially to deform the lateral surface of the anterior lobe of the pituitary gland. A tongue of anterior lobe extends laterally above the intercavernous carotid. (Images courtesy of AL Rhoton, Jr.)