The Cavernous Sinus and Meckel’s Cave. A, The outer layer of the dura of the right cavernous sinus has been peeled away from the lateral wall of the cavernous sinus and Meckel’s cave. This exposes the oculomotor and trochlear nerves entering the roof of the cavernous sinus and passing forward through the superior orbital fissure. The superior petrosal sinus passes above the ostium of Meckel’s cave and joins the posterior part of the cavernous sinus. B, The remaining dura covering the lateral wall of the cavernous sinus has been removed. The trochlear nerve courses along the inferior aspect of the oculomotor nerve to the base of the anterior clinoid process. C, After the anterior clinoid process has been removed, the clinoid segment of the internal carotid artery is exposed. The oculomotor nerve enters a short cistern in the sinus roof and does not become incorporated into the lateral wall until it reaches the lower margin of the anterior clinoid process. The tentorial artery courses along the inferior surface of the trochlear nerve and runs with it to the superior orbital fissure. D, Overview. The posterior wall of the cavernous sinus extends laterally from the dorsum sellae to the medial edge of the ostium of Meckel’s cave. The floor of the middle fossa has been removed to expose the infratemporal fossa, which contains the branches of the maxillary artery and the mandibular nerve, the pterygoid venous plexus, and the pterygoid muscle. The trochlear nerve courses around the cerebral peduncle just above the pons, between the posterior cerebral and superior cerebellar arteries. It pierces the dura below the free edge of the tentorium cerebelli, just behind the posterior clinoid process, and then passes forward in the lateral wall of the cavernous sinus below the oculomotor nerve and above the ophthalmic division of the trigeminal nerve. The trochlear nerve crosses the oculomotor nerve at the level of the optic strut, entering the orbit by the superior orbital fissure above the annular tendon and medial to the frontal nerve. (Images courtesy of AL Rhoton, Jr.)