Embolization of arteriovenous malformations with onyx: Clinicopathologicalexperience in 23 patients

OBJECTIVE: To report our experience in treatment of arteriovenous malformat ions (AVMs) using a new liquid embolic agent, Onyx (Micro Therapeutics, Inc ., Irvine, CA). METHODS: Between January 1998 and May 1999, 23 patients (8 men and 15 women ) were treated. The patients' average age was 40 years, with seizure being the most common presenting symptom (39%). The average Spetzler-Martin grade on presentation was 3. The average AVM volume before embolization was 14.5 cm(3). RESULTS: We observed an average 63% reduction in AVM volume after 129 arter ial feeders were embolized. There were four adverse events. Two patients ex perienced ischemia because of inadvertent occlusion of an arterial feeder. One of these patients made a full recovery, but the other patient had a per manent deficit. Two other patients experienced transient neurological defic its that resolved within 1 week of embolization. Permanent morbidity was th us 4% (1 of 23 patients). There were no deaths. Twelve patients underwent s ubsequent radiosurgery, and 11 patients had surgery that resulted in comple te resection of their AVMs. Histopathological examinations showed mild acut e inflammation in specimens resected 1 day after embolization. Chronic infl ammatory changes were observed in specimens resected more than 4 days after embolization. In two patients, angionecrosis of the embolized vessels was noted. No evidence of parenchymal hemorrhage was observed in these patients , and vessel wall integrity was maintained as well. CONCLUSION: Onyx is a new nonadhesive liquid embolic agent that has been us ed to treat 23 patients at our institution with good results. Its nonadhesi ve nature and ease of use make it a promising agent in the future treatment of AVMs.