Geometry of Saccular, Side-branch Cerebral Aneurysms: Implications for Treatment

Background Saccular, side-branch aneurysms are cerebral aneurysms that occur at the junction between a major intracranial artery and a smaller vessel that originates from this parent artery. The geometry of this group of aneurysms was investigated to determine the location of the side branch in relation to the parent vessel or aneurysm neck. Methods From a series of microsurgically clipped cerebral aneurysms, 121 side-branch aneurysms had detailed imaging studies and operative records that could be analyzed to determine side-branch vessel origin in relation to the aneurysm neck. Results The distribution of aneurysms (N) and the number in which the side-branch originated from the parent artery (PA) were: internal carotid ophthalmic (N = 37; PA = 11); internal carotid-superior hypophyseal (N = 2; PA = 2); internal carotid-posterior communicating (N = 28; PA = 11); internal carotid-anterior choroidal (N = 5; PA = 1); main stem of the middle cerebral artery (N = 13; PA = 6); main stem of the anterior cerebral artery (N = 7; PA = 6); secondary branch of the middle cerebral artery (N = 8; PA = 7); secondary branch of the anterior cerebral artery (N = 1; PA = 0); vertebral-posterior inferior cerebellar artery (N = 11; PA = 5); basilar-anterior inferior cerebellar artery (N = 2; PA = 1); and basilar-superior cerebellar artery (N = 7; PA = 5). Conclusions Regardless of whether these observations reflect the universe of cerebral aneurysms, a certain percentage of this group of aneurysms will have the side-branch vessel originate from the aneurysm neck. This incidence will likely be influenced by aneurysm location and other factors. Protection of these important vessels from occlusion during endovascular management will require sophisticated endovascular techniques. If these measures are either unavailable or prove unsuccessful, then clipping will be needed if the side-branch vessel originates from the aneurysm neck and its preservation is critical.