Dural Relationships and Ligaments in the Cavernous Sinus, Endocranial View. A, Superolateral view; the left anterior clinoid has been removed. The proximal and distal dural rings in the lateral wall of the carotid artery delimit the clinoid segment of the carotid artery. These rings typically fuse at the posterior aspect of the carotid artery medial to the tip of the anterior clinoid process. B, Ligaments of the cavernous sinus, superior view. The dura mater forming the superior wall of the left cavernous sinus has been removed along with the posterior half of the distal dural ring to show the interclinoid ligament between the anterior and posterior clinoid processes and the anterior and posterior petroclinoid ligaments between the petrous apex and the anterior and posterior clinoids, respectively. C, The left anterior clinoid has been removed. The carotidoculomotor membrane forms the proximal dural ring when it meets the carotid medially. Blue silicon, representing the venous filling in the cavernous sinus, has been partially removed below the distal dural ring posteriorly. The proximal dural ring is not evident in the posterior and medial aspect of the carotid. In some specimens, there is a caroticoclinoid ligament between the anterior clinoid and middle clinoid (when present) or medial border of the carotid sulcus at the level of the anterior bend of the carotid artery (when the middle clinoid is absent). D and E, Further removal of blue silicon of the left cavernous sinus. This ligament blends into the carotidoculomotor membrane and is directed to the periosteal layer covering the middle clinoid process or medial aspect of the carotid sulcus. It may have adherences to the internal carotid artery and to the meningeal layer of the dura mater covering the pituitary, F, The left half of the pituitary gland has been removed to show the meningeal layer covering the gland and the periosteal layer covering the sellar wall of the sphenoid sinus. Both of them form part of the medial wall of the cavernous sinus. (Images courtesy of AL Rhoton, Jr.)