Severe Subarachnoid Hemorrhage Due to Fusiform Lateral Anterior (A1) Artery Perforator Aneurysm with "Spontaneous Resolution".

Perforating arteries are thin and long vessels which originate from the main cerebral arteries. Subarachnoidal hemorrhage from a perforator aneurysm is rare. Here, we report on a 70-year-old woman who presented with severe subarachnoid hemorrhage from a fusiform lateral anterior (A1) artery perforator aneurysm. Unexpectedly, digital subtraction angiography was non-diagnostic. MR imaging, however, demonstrated occlusion of the aneurysm secondary to thrombosis. Surgery was performed to remove the associated hematoma, and histopathological examination verified intraaneurysmal thrombosis.