A 66-year-old woman was found unresponsive after complaining of severe headache several days prior. She was comatose upon initial evaluation and a cranial CT revealed diffuse subarachnoid hemorrhage. A right posterior communicating artery aneurysm (figure, A, arrow) was successfully treated with endovascular embolization. Conventional angiography performed 7 days following ventriculostomy placement for hydrocephalus demonstrated interval development of a traumatic arteriovenous fistula (AVF) filling by the middle meningeal artery (figure, C, D, arrow). The AVF was treated with intra-arterial embolization. Ventriculostomy-associated AVF has rarely been reported.(1) Outcomes of untreated iatrogenic AVF are unknown, but could lead to hemorrhagic complications.