Onyx HD-500 embolization of intracranial aneurysms: Modified technique using continuous balloon inflation under conscious sedation

The conventional technique of intracranial aneurysm embolization using Onyx HD-500 (ev3 Neurovascular, Irvine, CA, USA) involves repetitive balloon inflation-deflation cycles under general anesthesia. By limiting parent artery occlusion to 5 minutes, this cyclic technique is thought to minimize cerebral ischemia. However, intermittent balloon deflation may lengthen procedure time and allow balloon migration, resulting in intimal injury or Onyx leakage. We report our experience using a modified technique of uninterrupted Onyx injection with continuous balloon occlusion under conscious sedation. All Onyx embolization procedures for unruptured aneurysms performed by the senior author (A.J.R.) between September 2008 and April 2010 were retrospectively reviewed. Demographic, clinical, angiographic, and procedural data were recorded. Twenty-four embolization procedures were performed in 21 patients with 23 aneurysms, including four recurrences. Twenty aneurysms (87%) involved the paraclinoid or proximal supraclinoid internal carotid artery. Size ranged from 2.5 to 24 mm and neck diameter from 2 to 8 mm. The modified technique was employed in 19 cases. All but one patient (94.4%) tolerated continuous balloon inflation. Complete occlusion was achieved in 20 aneurysms (83.3%) and subtotal occlusion in three (12.5%). Stable angiographic results were seen in 85%, 94%, 94%, and 100% of patients at 6, 12, 24, and 36 months, respectively. There were no deaths. Permanent non-disabling neurological morbidity occurred in one patient (4.2%). Minor, transient, and/or angiographic complications were seen in three patients (12.5%), none related to the technique itself. Onyx embolization of unruptured intracranial aneurysms can be safely and effectively performed using continuous balloon inflation under conscious sedation.