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
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