Fig 3.

Supraclinoid internal carotid artery aneurysm identified on repeat DSA. A 72-year-old man who presented with perimesencephalic SAH that is localized near the right clinoid process (A). An initial CTA performed on the day of presentation did not identify a lesion responsible for the SAH (B). DSA performed on the day after presentation demonstrates relative narrowing of the right supraclinoid internal carotid artery, the right middle cerebral artery, and the right anterior cerebral artery in the anteroposterior (C) and lateral (D) projections, which was thought to represent early vaspospasm. A follow-up DSA was performed 7 days after presentation, which demonstrates an irregular saccular outpouching (arrows) arising from the supraclinoid internal carotid artery in the anteroposterior (E) and lateral (F) projections, consistent with a dissecting aneurysm.