A rare and symptomatic Cavernous Donut-shaped Aneurysm treated by Flow Diverter Deployment.

•A 62-year-old lady was admitted for acute diplopia secondary to a left III cranial nerve palsy.•She had left eyelid swelling and ptosis and mild ipsilateral retroorbital pain.•CTA and DSA showed a 25-mm left intracavernous aneurysm with a central intrasaccular thrombus.•It had an intrasaccular “swirling” flow with a donut-shaped appearance.•A flow-diverter stent was deployed to bridge the aneurysmal neck, and 12 months later the patient totally recovered.