Introduction: We present the largest US case series with long-term follow-up using Onyx in the endovascular management of complex intracranial aneurysms with high rate of incomplete occlusion and recanalization.

Methods: Nineteen patients with 21 complex intracranial aneurysms were treated. Fifteen aneurysms were in the anterior circulation (7 ophthalmic sidewall, 5 cavernous ICA, 1 petrous ICA, 1 superior hypophyseal and 1 MCA). Six were in the posterior circulation (4 PICA, 1 vertebral, 1 basilar). Four presented with SAH. All were complex aneurysms (e.g. wide-neck, large or giant, fusiform, dissecting-type, or associated to an AVM). Four were treated in the past with other materials. Onyx HD-500 was used in 17 aneurysms, Onyx 34 and 18 in 2 patients each. Coils and stents were used in 5 and 4 patients respectively. Embolization of the feeding vessel was necessary in 2 patients. Clinical and angiographic follow-up was obtained at 2.6 years (6 months – 10 years) and 1.3 years (6 months -5 years), respectively.

Results: Twenty aneurysms were completely occluded on immediate post-embolization angiogram, 1 had a small residual neck. Onyx migration was observed in 4 aneurysms with no radiographic or clinical consequences. Angiographic follow-up showed recanalization in 1 large aneurysm requiring additional Onyx obliteration of the parent vessel. No peri-procedural mortality was observed. Two patients with cavernous ICA aneurysm had a transient third nerve palsy after embolization. Two patients with SAH died of disease-relate complications.

Conclusions: Onyx embolization of complex intracranial aneurysms is feasible, safe and effective. Onyx is a good option in the management of aneurysms recurrences, fusiform and dissecting-type aneurysms. Morbidity and mortality rates are similar to other endovascular techniques. Onyx provides durable aneurysm occlusion at mid- and long-term follow-up.

Patient Care: Patients with aneurysm recurrence and complex intracranial aneurysms have another alternative of endovascular embolization other than platinium coils. Onyx is a good alternative with durable and stable oblitaration rate at long-term follow-up.

Learning Objectives: Describe the importance of the liquid embolic agent Onyx as alternative of the endovascular embolization of complex intracranial aneurysms.

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