THE SUPERIOR WALL OF THE CAVERNOUS SINUS - A MICROANATOMICAL STUDY

The superior wall of the cavernous sinus was studied in 30 specimens o btained from 15 cadaver heads fixed in formalin. Trapezoidal in shape, the superior wall of cavernous sinus is limited laterally by the ante rior petroclinoid ligament, medially by the dura of the diaphragma sel lae, anteriorly by the endosteal dura of the carotid canal, and poster iorly by the posterior petroclinoid ligament. An interclinoid ligament bisects the wall, dividing it into two triangles: the carotid trigone anteromedially and the oculomotor trigone posterolaterally. Similar t o the lateral wall of the cavernous sinus, the superior wall is formed by two layers: a smooth superficial dural layer and a thin, less defi ned deep layer. In the area of the carotid trigone, both layers separa te to wrap the anterior clinoid process. The removal of this process w ill reveal a ''clinoid space'' medial to which the internal carotid ar tery can be identified. This clinoid segment of the artery, still extr acavernous, is surrounded by two fibrous rings: a distal ring formed b y fibers of the superficial dural layer and a proximal ring related to the deep dural layer. Below the proximal ring, the internal carotid a rtery becomes intracavernous; above the distal ring, the artery is con tinuous with its supraclinoid segment. The complex dural anatomy of th e superior wall, its fibrous rings, and the clinoid space in relation to a superior surgical approach to the cavernous sinus are discussed.