Intraoperative Problems with Unruptured Large Internal Carotid-posterior Communicating Artery Aneurysm Adhered with Anterior Choroidal Artery: Evaluation of ICA Route and Aneurysmal Projection

Neck clipping of large internal carotid-posterior communicating artery (IC-PC) aneurysms is generally difficult, especially when the anterior choroidal artery adheres to the aneurysm. We report 2 cases with premature rupture during the dissection of the anterior choroidal artery adhering to aneurysmal dome. The rupture point was not from the dissecting area, but from the medial wall of the aneurysmal dome, which also adhered to optic nerve. The traction force seemed to be the cause of tearing of the medial aneurismal wall. One patient successfully underwent clipping with temporary occlusion of the internal carotid artery, and another developed mild hemiparesis due to the cerebral infarction. Large IC-PC aneurysms sometimes adhere to the optic nerve located to the medial side of the aneurysm, because the dome projects medially and the internal carotid artery runs medially, too. To avoid the premature rupture, it is essential to check whether the dome wall adheres to the optic nerve before dissecting the anterior choroidal artery from the dome of aneurysm.