• Yuki Shinya, Hirotaka Hasegawa, Masahiro Shin, Mariko Kawashima, Satoshi Koizumi, Atsuto Katano, Yuichi Suzuki, Kosuke Kashiwabara, and Nobuhito Saito.
• Department of Neurosurgery, The University of Tokyo Hospital, Tokyo, Japan.
• Neurosurgery. 2022 Sep 1; 91 (3): 485495485-495.

BackgroundArteriovenous malformations (AVMs) of the diencephalon (DC) and brainstem (BS) are difficult to treat. Stereotactic radiosurgery (SRS) is a reasonable option; however, an optimal radiosurgical dose needs to be established to optimize long-term outcomes.ObjectiveTo evaluate dose-dependent long-term outcomes of SRS for DC/BS-AVMs.MethodsWe retrospectively analyzed the long-term outcomes of 118 patients who had SRS-treated DC/BS-AVMs. The outcomes included post-SRS hemorrhage, AVM obliteration, neurological outcomes, and disease-specific survival. According to margin doses, the patients were classified into low (<18 Gy), medium (18-20 Gy), and high (>20 Gy) dose groups.ResultsSRS reduced the annual hemorrhage rate from 8.6% to 1.6% before obliteration and 0.0% after obliteration. The cumulative hemorrhage rate in the low dose group was likely to be higher than that in the other groups ( P = .113). The cumulative obliteration rates in the entire cohort were 74% and 83% at 5 and 10 years, respectively, and were significantly lower in the low dose group than in the other groups (vs medium dose: P = .027, vs high dose: P = .016). Multivariate analyses demonstrated that low dose SRS was significantly associated with worse obliteration rates (hazard ratio 0.18, 95% CI 0.04-0.79; P = .023).ConclusionSRS with a margin dose of 18 to 20 Gy for DC/BS-AVMs may be optimal, providing a higher obliteration rate and lower risk of post-SRS hemorrhage than lower dose SRS. Dose reduction to <18 Gy should only be optional when higher doses are intolerable.Copyright © Congress of Neurological Surgeons 2022. All rights reserved.

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