Long-term side effects of radiosurgery for arteriovenous malformations

In this report, our experiences with 181 consecutive patients who underwent Gamma Knife radiosurgery (GKRS) for arteriovenous malformations (AVMs) during an approximately quarter century period from 1978 to 2002 will be summarized along with much of what we have learned from a wealth of already published data. During the mean post-GKRS follow-up period of 10.2 years (range, 5.4-30.6), 15 (8.3%) of our 181 patients experienced stereotactic radiosurgery-related, symptomatic complications. Among these 15 patients, 12 manifested complications 5 years or more after GKRS. Furthermore, in 5 of these 12, the complications were seen 10 or more years after GKRS. In the present series, the actuarial complication rates computed using the Kaplan-Meier method were 2.3% at the fifth, 8.2% at the tenth, 15.2% at the fifteenth and 31.1% at the twentieth post-GKRS year. AVM volumes, Pollock-Flickinger AVM scores, the initial presentation of bleeding and centrally located AVMs were demonstrated to be significantly associated with the risk of delayed complications after GKRS (p<0.05). There was a significant difference in complication rates between two patient groups, based on whether dose planning was performed using the older (Kula) or the modern (Gamma Plan) system (18.0 vs. 4.6%, χ2 p=0.0002). Although GKRS is undoubtedly an alternative to microsurgical resection for appropriately selected AVMs, we must weigh treatment results against complication risks which are not negligibly low.