Ruptured intrameatal AICA aneurysm associated with a cerebellar pial arteriovenous shunt: a case report.

Intrameatal anterior inferior cerebellar artery (AICA) aneurysms associated with distal arteriovenous shunts are extremely rare. We report a ruptured intrameatal AICA aneurysm associated with a cerebellar pial arteriovenous shunt, most consistent with a pial arteriovenous fistula. A 68-year-old woman presented with posterior fossa subarachnoid hemorrhage. Digital subtraction angiography demonstrated a small intrameatal AICA aneurysm and a distal cerebellar arteriovenous shunt supplied by the AICA, brainstem perforators, and superior cerebellar artery. No definite nidus was identified, and contrast-enhanced magnetic resonance imaging suggested a focal shunt point at the brainstem-cerebellar junction; however, a tiny cerebellar or brainstem arteriovenous malformation could not be completely excluded. The aneurysm was considered flow-related. Segmental AICA parent artery occlusion and limited embolization of a brainstem perforating feeder were performed, followed by Gamma Knife radiosurgery for the residual shunt. Follow-up angiography confirmed complete obliteration without recurrent hemorrhage.