Stepwise Dissection of the Right Middle Fossa. E, The part of the trigeminal nerve between the posterior root and the 3 divisions have been removed to expose an ossified petrolingual ligament, which extends from the petrous apex to the lingual process of the sphenoid bone. The upper edge of the petrolingual ligament is located at the junction of the petrous and cavernous carotid. The greater wing of the sphenoid bone has been drilled to expose the lateral walls of the sphenoid sinus and the vidian nerve passing forward in the vidian canal. The floor of the middle fossa has been removed to expose the infratemporal fossa and the temporalis muscle in the temporal fossa. F–H, Stepwise lateral and medial exposure of the petrolingual ligament. F, Another right trigeminal nerve and middle fossa. The petrolingual ligament is located at approximately the level of a line extending posteriorly along the upper surface of the second division. G, The first trigeminal division has been reflected downward to expose the upper part of the petrolingual ligament. A branch of the carotid neural plexus ascends to join the abducens nerve after the nerve has passed around the lateral margin of the cavernous carotid. H, View through the sphenoid sinus side of the dissection shown in F and G. The cavernous carotid and the anterior genu and anterior vertical segments of the petrous carotid have been exposed by removing part of the lateral wall of the sphenoid sinus. The upper edge of the petrolingual ligament, positioned on the lateral and not the medial side of the artery, is marked with a yellow interrupted line. A branch of the carotid neural plexus ascends and joins the abducens nerve (arrow). The abducens nerve passes around the lateral margin of the cavernous carotid. The vidian nerve has been exposed by removing bone along in the floor of the sphenoid sinus. (Images courtesy of AL Rhoton, Jr.)