Onyx embolization of a ruptured aneurysm in a patient with moyamoya disease

• Treatment of ruptured aneurysms in moyamoya disease should be strongly recommended to prevent rebleeding which has a high mortality.
• Surgical treatment of collateral vessel aneurysms is challenging because of the complexity and deep location of these aneurysms and conservative management is controversial.
• Endovascular embolization using Onyx can be an effective treatment of collateral vessel aneurysms associated with moyamoya disease that would be difficult to treat surgically.

We report a woman who presented with an intraparenchymal hemorrhage. Her cerebral angiogram showed a middle cerebral artery (MCA) M1 occlusion with multiple collaterals supplying the distal MCA territory, compatible with moyamoya disease. Also, an associated 8 mm dysplastic distal aneurysm fed by a left-sided P2 perforator was seen, collateral from the posterior cerebral artery. The aneurysm was successfully occluded with Onyx (ev3 Endovascular, Plymouth, MN, USA) embolization. The woman had an uneventful postoperative course. Aneurysm formation in patients with moyamoya disease represents a major hemorrhagic risk. Several treatment strategies exist including endovascular and surgical approaches. Patients with moyamoya disease who present with aneurysmal intracerebral hemorrhage should be treated to prevent rebleeding. Onyx embolization can be an effective treatment of aneurysms that are associated with moyamoya disease and would otherwise be difficult to treat surgically.