Fig 4.

Basilar artery aneurysm identified on repeat CTA and DSA. A 65-year-old woman who presented with diffuse SAH in the basal cisterns and bilateral Sylvian fissures. Note hydrocephalus (A and D). A maximum-intensity-projection image from a CTA (B) and a DSA (C) performed on the day of presentation demonstrate no evidence of an aneurysm arising from the basilar artery. A follow-up CTA (E) and DSA (F) performed 7 days after presentation demonstrate an aneurysm arising from the posterior aspect of the basilar artery, consistent with a perforator artery aneurysm.