Subarachnoid hemorrhage caused by rupture of a distal anterior inferior cerebellar artery aneurysm--three case reports.

Three female patients, two under 35 years old, presented with ruptured aneurysms of the distal anterior inferior cerebellar artery (AICA) manifesting as subarachnoid hemorrhage. The first patient had a ruptured saccular aneurysm of the meatal loop of AICA, which was treated by direct neck clipping. The second patient had a ruptured aneurysmal lesion that arose from a microvascular anomaly of the dorsolateral portion of the AICA, which was successfully treated by trapping. The third patient was dead on arrival, and autopsy revealed a ruptured saccular aneurysm in the meatal loop of the AICA. The mechanism of development of distal AICA aneurysm remains unclear, and some cases indicate a complicated causal relationship between the aneurysms and vascular anomalies. Neurosurgeons need to carefully evaluate the vascular structure around the aneurysms by preoperative angiography in each case, and select the most appropriate strategy.