Evolution of a Stump Aneurysm That Transformed From a Fusiform Aneurysm in the Middle Cerebral Artery.

Abstract

A spontaneous fusiform aneurysm in the middle cerebral artery (MCA) can present with both ischemic and hemorrhagic symptoms, but this aneurysm's clinical course and prognosis are unclear because of its rarity. An asymptomatic fusiform-shaped aneurysm was found in a branch of the right middle cerebral artery (MCA) incidentally during a medical check-up in a 51-year-old woman with no medical history. This aneurysm was followed by annual magnetic resonance imaging with no medical treatment. A distal side of the branch of the MCA harboring the fusiform aneurysm gradually narrowed, and finally occluded 6 years after initial detection. The stump of the branch transformed into an aneurysmal dilatation, which grew for 2 years. To prevent future subarachnoid hemorrhage, surgical intervention was performed. An aneurysmal dilation with a thin wall was found to originate between an intact branch and a funicular occluded branch, which was obliterated with clip application. At 3-year follow-up, no regrowth or de novo aneurysm could be seen. This is the first case report in which serial images demonstrate the stepwise occlusion of an artery with fusiform change and the evolution of a stump aneurysm in the MCA over an extended period.