Removal of the anterior clinoid process for exposure of the proximal intracranial carotid artery.

The anatomy of the carotid artery at the level of the anterior clinoid process was studied in autopsy specimens and at surgery. Marking clips placed at surgery were used to correlate anatomical and angiographic findings. Removal of the anterior clinoid process permits visualization of approximately 6 mm more of the proximal internal carotid artery without entering the cavernous sinus. The exposure reaches just to the hairpin bend of the carotid siphon, but the bend is not seen. The curve in the carotid artery which is observed after anterior clinoid removal is distal to the hairpin turn and corresponds to a bend seen on the anteroposterior projection of the angiogram. Temporary occlusion of the carotid artery proximal to a paraclinoid aneurysm is possible after clinoid removal. Complications of the removal include trauma to the third nerve and cerebrospinal fluid rhinorrhea.