FIG 1. 60-year-old male patient who presented with headache and in whom a large unruptured internal carotid aneurysm was found. Pretreatment, treatment, and follow-up images are presented.

A, Large internal carotid aneurysm before treatment.

B, Seal test before treatment of the aneurysm with Onyx. Microcatheter and balloon are in place with gentle contrast material injection into the aneurysm

C, Angiographic result immediately after Onyx treatment.

D, Follow-up angiogram 6 months after treatment, showing complete occlusion and intervening soft thickened tissue between vessel lumen and Onyx cast in the aneurysm