Periosteal Branches of the Petrous Carotid. A, Right middle fossa and cavernous sinus. B–D are oriented as shown in A. The dura has been elevated from the middle fossa floor and the trigeminal nerve has been reflected forward to expose the petrolingual ligament, the terminal part of the petrous carotid, and the trigeminal impression. The junction of the petrous and cavernous segments of the carotid artery is located at the upper edge of the petrolingual ligament. The greater petrosal nerve is directed anteriorly as it passes across the upper surface of the petrous carotid. The abducens nerve passes below the petrosphenoid (Gruber’s) ligament and through Dorello’s canal and is joined by a branch (green arrow) of the carotid sympathetic plexus. B, A segment of a petrous carotid has been removed to expose the foramen lacerum. A short segment of the medial arterial wall has been preserved to show the origin of 2 periosteal branches that course along the periosteum lining of the carotid canal. The anterior branch passes through the foramen lacerum and the posterior branch ends in the periosteum. C, A short segment of another petrous carotid has been removed to expose a periosteal artery that passes along the lining of the carotid canal and through the fibrocartilage filling the foramen lacerum. D, Superior view. A segment of another petrous carotid, just below the petrolingual ligament, has been excised while preserving the inferior wall of the proximal segment to show the ostium of a periosteal artery that passes forward and medially to penetrate the fibrocartilaginous tissue filling the foramen lacerum. (Images courtesy of AL Rhoton, Jr.)