Abstract
We recently classified non-atherosclerotic cerebral aneurysms unrelated to the branching zones into 4 types based on the status of the internal elastic lamina (IEL) and the intima (10). In the present study, we focused on Type 1-3 non-atherosclerotic cerebral aneurysms (10) without symptoms and with trivial symptoms. Type 1 corresponds to classic dissecting aneurysms, the pathogenesis of which is characterized by acute widespread disruption of IEL without intimal thickening. Patients with Type 1 aneurysms usually have an ominous course. We experienced 95 patients with 99 Type 1 aneurysms. Of the 99 aneurysms, 6 were asymptomatic and 1 presented with minor headache. Initial angiographical findings of the 7 patients were irregular stenosis and all of them “cured” or improved during the follow-up period of 1-4 years.
Type 2 aneurysms are segmental ectasias that have extended and/or fragmented IEL with intimal thickening. Weakness of the arterial wall due to damaged IEL is assumed to be compensated by the intimal thickening. Angiogram of the Type 2 aneurysm shows fusiform appearance with smooth contour. Type 2 aneurysms have no luminal thrombus. The patients with Type 2 aneurysms usually have a placid clinical course. Sixteen patients with Type 2 aneurysms were included, and 15 patients were asymptomatic throughout the follow-up periods of 1-6 years. The other patient presented with facial spasm 6 years after the initial diagnosis due to growing of the aneurysm.
Type 3 aneurysms are dolichoectatic dissecting aneurysms, pathologically characterized by IEL fragmentation, multiple dissections of thickened intima and organized thrombus in their lumen. Angiographically, they have fusiform appearance with irregular contour. Most of them progressively enlarge over time. We experienced 9 patients with Type 3 aneurysm. Of the 9 patients, 4 were diagnosed with trivial symptoms. Of these 4, 3 died of aneurysm enlargement.
