Cerebral Aneurysms Arising from Unbranched Site of Intracranial Arteries

혈관가지가 없는 두개강내 혈관에서 발생한 뇌 동맥류

Objective : In general, most of saccular aneurysms arise at arterial divisions, but those arising at unbranched site are rare. These aneurysms might impose neurosurgeons a formidable surgical challenge, due to uncommon features and a difficult surgical technique. Methods : Between the period of Jan. 1996 and Dec. 1998, a total of 110 cases of aneurysms were operated. Among them, five cases of unbranched site aneurysms were retrospectively analyzed through medical records, angiographic and operative findings. Results : The incidence of aneurysms unrelated to arterial branches was 4.5%. All cases presented with subarachnoid hemorrhage(SAH) ; three(60%) were at internal carotid artery(ICA) and two(40%) at middle cerebral artery (MCA). Two had a history of hypertension and three showed atherosclerotic changes in the arterial wall. One ICA and one MCA aneurysms proved to be a blood blister-like aneurysm(BBA) in their shape. Strikingly, a rapid neurological deterioration was shown in two ruptured ICA variants, which resulted in death and another two aneurysms left with morbidity. Conclusion : The preoperative neurological status in most cases was relatively poor compared to that of aneurysms arising at a branched site. Regarding its pathogenesis, atherosclerosis as well as hemodynamic factors may play an important role in formation of these variant aneurysms among various etiological factors. The overall prognosis of unbranched site aneurysms was worse than that of branched site aneurysms. In cases of BBAs, special attention was requisite to handle them during clipping and/or wrapping due to an easy fragile, thin aneurysmal wall.