Gamma Knife Radiosurgery of Surgically Partially Resected Cerebral Arteriovenous Malformations

Objective : In this study, we aimed to evaluate flow characteristics in partially resected arteriovenous malformations (AVMs) and identify factors associated with complete obliteration following Gamma Knife radiosurgery (GKRS).Methods : Among 587 patients with AVMs treated with GKRS between August 1992 and October 2024, 31 patients with residual AVMs after microsurgical resection were included. Clinical charts and imaging studies were retrospectively reviewed. AVM flow was categorized as low, moderate, or high based on the number of angiographic frames from nidus visualization to draining vein opacification. Kaplan-Meier survival analysis was used to estimate complete obliteration rates, while univariate and multivariate Cox proportional hazards regression analyses were applied to identify factors associated with complete obliteration. The log-rank test was used to compare actuarial complete obliteration rates among the three AVM flow groups.Results : The median clinical follow-up period after GKRS was 44 months (interquartile range, 35–105). Complete obliteration was achieved in 24 patients (77.4%). The actuarial obliteration rates were 29.0%, 56.7%, and 69.7% at 3, 5, and 10 years, respectively. Complete obliteration occurred in three (37.5%) high-flow, 14 (87.5%) moderate-flow, and all low-flow AVMs. The mean time to obliteration was 131.7 months (95% confidence interval [CI], 92.9–170.6) for high-flow AVMs, 73.0 months (95% CI, 44.2–101.8) for moderate-flow AVMs, and 36.7 months (95% CI, 22.1–51.3) for low-flow AVMs (p=0.004, log-rank test). Prior embolization and lower AVM flow were independently associated with complete obliteration on both univariate and multivariate analyses.Conclusion : GKRS produced favorable outcomes in patients with partially resected AVMs. Slower-flow residual AVMs and prior embolization were independently associated with higher rates of complete obliteration.