Radiation-Induced Imaging Changes and Cerebral Edema following Stereotactic Radiosurgery for Brain AVMs

BACKGROUND AND PURPOSE: T2 signal and FLAIR changes in patients undergoing stereotactic radiosurgery for brain AVMs may occur posttreatment and could result in adverse radiation effects. We aimed to evaluate outcomes in patients with these imaging changes, the frequency and degree of this response, and factors associated with it. MATERIALS AND METHODS: Through this retrospective cohort study, consecutive patients treated with stereotactic radiosurgery for brain AVMs who had at least 1 year of follow-up MR imaging were identified. Logistic regression analysis was used to evaluate predictors of outcomes. RESULTS: One-hundred-sixty AVMs were treated in 148 patients (mean, 35.6 years of age), including 42 (26.2%) pediatric AVMs. The mean MR imaging follow-up was 56.5 months. The median Spetzler-Martin grade was III. The mean maximal AVM diameter was 2.8 cm, and the mean AVM target volume was 7.4 mL. The median radiation dose was 16.5 Gy. New T2 signal and FLAIR hyperintensity were noted in 40% of AVMs. T2 FLAIR volumes at 3, 6, 12, 18, and 24 months were, respectively, 4.04, 55.47, 56.42, 48.06, and 29.38 mL Radiation-induced neurologic symptoms were encountered in 34.4%. In patients with radiation-induced imaging changes, 69.2% had new neurologic symptoms versus 9.5% of patients with no imaging changes (P ¼ .0001). Imaging changes were significantly associated with new neurologic findings (P, .001). Larger AVM maximal diameter (P ¼ .04) and the presence of multiple feeding arteries (P ¼ .01) were associated with radiation-induced imaging changes. CONCLUSIONS: Radiation-induced imaging changes are common following linear particle accelerator–based stereotactic radiosurgery for brain AVMs, appear to peak at 12 months, and are significantly associated with new neurologic findings.