Abstract
Spontaneous dissecting aneurysms in the anterior circulation are extremely uncommon. The natural course of this entity is far from being understood, and the treatment is still debated. In this paper, we report a case of cerebral infarction caused by the dissecting aneurysm of the left anterior cerebral artery (ACA). A 45-year-old male developed an acute right hemiparesis with severe headache. CT scan showed a cerebral infarction at the left ACA territory. Consecutive cerebral angiography revealed a double lumen of A2 with an intimal flap immediately distal to the anterior communicating artery (Acom). Under conservative treatment, his motor weakness was gradually improved. However, the second angiography two weeks after admission revealed aneurysmal dilatation of distal A2 with marked stenosis of A3. The rapid growth of the aneurysm during the short period necessitated curative treatment. The patient underwent a left frontal craniotomy. Through an interhemispheric approach, the bilateral distal A3 portion, which seemed intact, was first dissected. Following the A3-A3 side-to-side anastomosis, the proximal left ACA was dissected. In front of genu of corpus callosum, a 1.2cm-sized fusiform aneurysm was observed. Further dissection of A2 to the proximal side revealed an abnormally thin portion of the arterial wall immediately distal to the Acom, which was compatible with the entry point based on the angiographical finding. The outer appearance of the A2, which proved to have a double lumen on the angiogram, seemed relatively thin but almost normal in color. The left AC was trapped from the entry point to the anastomosis. The postoperative course was uneventful, and angiography showed the left peripheral region was supplied from the anastomosis. We believe the best surgical treatment for the dissecting aneurysm is trapping with bypass. Although the dissection causing infarction has scarcely been considered to rupture in the literature, this case suggests the possibility of rupture that might be fatal. Thus, the rapid growth of aneurysm may be a good surgical indication. Surgical treatments for this type of lesion are discussed.
