Osseous Relationship of the Carotid Cave. A, Osseous relationship of the carotid cave, superior view. The clinoid segment of the ICA, the segment passing medial to the anterior clinoid process, is nearly encased by the anterior clinoid process laterally, the optic strut anteriorly, and carotid sulcus of the sphenoid bone medially. The carotid cave is located along the ICA wall facing the carotid sulcus. The base of the anterior clinoid is attached laterally to the medial end of the sphenoid ridge, formed by the lesser sphenoid wing, and attached medially to the anterior and posterior roots of the lesser wing. The anterior root of the lesser wing extends medially from the base of the anterior clinoid to the body of the sphenoid and forms the roof of the optic canal. The posterior root, called the optic strut, extends medially below the optic nerve to the body of the sphenoid bone and forms the floor of the optic canal. B, Enlarged superior view. The chiasmatic sulcus, a shallow depression between the paired optic canals, is bounded posteriorly by the tuberculum sellae and anteriorly by the planum sphenoidale. The tuberculum sellae is located in the midline along the ridge forming the posterior margin of the chiasmatic sulcus. The middle clinoid process projects upward on the medial side of the terminal part of the carotid sulcus toward the tip of the anterior clinoid process. An osseous bridge may extend from the middle clinoid to the anterior clinoid, thus creating a bony ring, referred to as a caroticoclinoidal foramen, through which the ICA passes. The dura lining the upper margin of the anterior clinoid extends medially above the optic nerve to form the falciform ligament (blue arrow) and slightly downward to line the upper margin at the optic strut and form the anterior part of the distal dural ring (green line). The margins of the left carotid sulcus are shown (interrupted lines). C, Oblique posterior view. The carotid sulcus (interrupted lines) begins below and lateral to the dorsum sella, turns forward in a shallow groove below the lateral edge of the sellar floor, and turns upward to end medial to the anterior clinoid process. D, Oblique posterior view of the right optic strut, the bridge of the bone that extends from the inferomedial aspect of the base of the anterior clinoid to the body of the sphenoid bone and separates the optic canal from the superior orbital fissure. The clinoid segment of the ICA rests against the posterior margin of the strut. The dura lining the upper margin of the anterior clinoid extends medial above the optic nerve to form the falciform ligament (blue arrow) and slightly downward to line the upper margin at the optic strut and form the anterior part of the distal dural ring (green arrow). The posterior surface of the strut widens as it slopes medially. E, Superior view. The lesser sphenoid wing and the base of the left anterior clinoid, have been removed to unroof the optic canal and upper and posterior margin of the optic strut. The posterior margin of the optic strut is shaped to accommodate the anterior surface of the anterior bend of the intracavernous carotid. The pneumatization of the sphenoid sinus may extend through the strut into the anterior clinoid. The lateral wall of the sphenoid sinus forms the medial wall of the optic canal. F, Superior view of specimen with bilateral caroticoclinoidal foramen and interclinoidal osseus bridges. An osseous bridge connects the tips of the anterior and middle clinoid processes bilaterally, thus creating a bony ring around the artery called a caroticoclinoidal foramen, on each side. There are also interclinoidal osseus bridges connecting the anterior and posterior clinoid processes on both sides. (Images courtesy of AL Rhoton, Jr.)