2018 年 46 巻 2 号 p. 97-103
Anterior clinoidectomy (ACD) is an essential technique that is of utmost importance in direct surgery for paraclinoid aneurysm. ACD is usually performed using an extradural or intradural procedure. As for the choice between extradural and intradural clinoidectomy, 24 cases of paraclinoid internal carotid artery (IC) aneurysm were reviewed. These cases were categorized according to the Al-Rodhan classification. As a matter of principle, we chose extradural ACD for unruptured cases that require more decompression of the optic nerve and mobilization of the IC artery and intradural ACD for ruptured cases. Nine cases (ruptured, 1 case; un-ruptured, 8 cases) of group III aneurysm (carotid cave) and a relatively large unruptured case of group Ia aneurysm (superior hypophyseal), were treated with external ACD. In group III, ruptured in 1 case; group Ib (ventral paraclinoid), 4 cases (ruptured in 3 and unruptured in 1); group II (ophthalmic), unruptured in 1 case; group Ia, unruptured in 4 cases; and IC lateral (C2C3), unruptured in 2 cases, intradural ACD was performed. In a ruptured large case of group Ia, combined (extradural and intradural) ACD and multi-clipping using a suction and decompression method were performed. Aneurysm clipping was performed in all the cases except for 2 unruptured cases of wrapping after each ACD. Postoperative optic nerve injury occurred in 2 unruptured cases of group III. Each ACD was not thought to be a direct factor of postoperative optic nerve injury. Removal of the anterior clinoid process and optic unroofing, and circumferential dissection of the distal dural ring are key surgical procedures for ACD. The benefit of intradural ACD is the early exposure of the lesion and tailored anterior clinoid process resection. If an unintended event occurs during surgery, surgeons would be more able to control that event. The advantage of extradural ACD is minimal brain retraction. Extradural ACD will leave the dura intact until ACD is completed. Thus, the dura provides a natural protective barrier from neurovascular injury on drilling. Knowledge of the characteristics of each procedure is required in direct surgery for paraclinoid aneurysm. In conclusion, extradural ACD is appropriate for unruptured cases that require more decompression of the optic nerve and more mobilization of the IC artery, and intradural ACD is adequate for other unruptured cases. For ruptured cases, intradural ACD is safer than extradural ACD.