Cerebral arterial fenestrations: a common phenomenon in unexplained subarachnoid haemorrhage.

Background: Fenestrations of intracranial arteries are variants resulting from incomplete fusion of vessels during development with unknown clinical significance. They are best visualised with 3D rotational angiography (3DRA).

Objective: In a prospective consecutive series of patients with suspected aneurysms, 3DRA was performed to identify not only the potential bleeding source but also to assess the frequency and location of any fenestrations of intracranial arteries.