Ruptured Distal Middle Cerebral Artery Aneurysms-Characteristics and Strategy

Distal middle cerebral artery (dMCA) aneurysms are very rare. Most ruptured dMCA aneurysms lead to subarachnoid hemorrhage (SAH) coexisting with intracerebral hematoma (ICH), resulting in a deteriorating state. The risk factors of rupture of dMCA aneurysms remain unknown. To elucidate the risk of rupture, we studied differences between 4 ruptured and eleven unruptured dMCA aneurysms.

We retrospectively analyzed patients diagnosed with a dMCA aneurysm according to the maximum size of the aneurysm, aspect ratio, and aneurysm size to vessel size (size ratio).

Four patients presented with SAH coexisting with ICH, resulting in a midline shift, caused by rupture of the dMCA aneurysm. The median aspect ratio of ruptured and unruptured dMCA aneurysms was 2.38 and 1.65, respectively, with no significant difference. The median maximum diameter of ruptured and unruptured dMCA aneurysms was 2.98 and 3.78 mm, respectively, with nonsignificant difference. The median size ratio of ruptured and unruptured dMCA aneurysms was 3.13 and 1.84, respectively, being significant difference (P < 0.02). The outcomes of 4 patients having ruptured dMCA aneurysm were as follows: one patient died due to the initial attack, and the others were severely disabled due to cerebral infarction caused by vasospasm.

Distal MCA aneurysms, even if they are small, may be likely to rupture leading to SAH complicated by ICH and result in a poor neurological state and unfavorable outcomes. We recommend aggressive treatment for dMCA aneurysms considering morphological factors such as the size ratio even if they are small and unruptured.