Stereotactic radiosurgery after embolization for arteriovenous malformations.

We sought to define the long-term benefits and risks of stereotactic radiosurgery (SRS) for arteriovenous malformation (AVM) patients who underwent prior embolization. Between 1987 and 2006, we performed Gamma Knife® SRS on 120 patients with AVM who underwent embolization followed by SRS. Sixty-four patients (53%) had at least 1 prior hemorrhage. The median number of embolizations varied from 1 to 5. The median target volume was 6.6 cm3 (range, 0.2-26.3 cm3). The median margin dose was 18 Gy (range, 13.5-25 Gy). After embolization, 25 patients (21%) developed symptomatic neurological deficits. The overall rates of total obliteration documented by either angiography or magnetic resonance imaging were 35, 53, 55 and 59% at 3, 4, 5 and 10 years, respectively. Nine patients (8%) had a hemorrhage during the latency interval and 7 patients died due to hemorrhage. The actuarial rates of AVM hemorrhage after SRS were 0.8, 3.5, 5.4, 7.7 and 7.7% at 1, 2, 3, 5 and 10 years, respectively. Permanent neurological deficits due to adverse radiation effects developed in 3 patients (2.5%) after SRS. Using a case-match control technique, we found that embolization prior to SRS was associated with a lower rate of total obliteration (p=0.028) in comparison to radiosurgery alone. In this 20-year experience, we found that prior embolization reduced the rate of total obliteration after SRS and latency interval hemorrhage risks were not affected by prior embolization. In the future, the role of embolization after SRS should be explored.