Hypofractionated Gamma Knife Radiosurgery for High-Grade Intracranial Arteriovenous Malformations: Functional and Radiological Outcomes from a Retrospective Cohort Study.

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BACKGROUND: High-grade intracranial arteriovenous malformations (AVMs, Spetzler-Martin grades 4-5) remain among the most formidable challenges in neurosurgical practice, given their high risk of hemorrhage, complex angioarchitecture, and frequent eloquent brain involvement. Hypofractionated Gamma Knife radiosurgery (hf-GKRS) has emerged as a promising alternative, aiming to increase obliteration rates and reduce complications by spreading dosing over several sessions. This study critically evaluates the safety, efficacy, and outcome predictors for hf-GKRS in treating high-grade AVMs. Specifically, the predictive utility of radiosurgery grading scales, including the modified Pollock-Flickinger (mPF) and modified radiosurgery-based AVM scale (mRBAS), is examined. METHODS: A retrospective single center observational cohort of 36 patients with SMG 4-5 AVMs, treated between 2009 and 2020, was analyzed. Selection criteria included symptomatic bleed or progressive neurological decline and >2 years post-GKRS follow-up. Treatment comprised 2-5 fraction GKRS protocols (mean total dose 27 Gy, mean nidus volume 15.58 cc) with multidisciplinary input. Outcomes measured included AVM obliteration rates (complete/partial), functional status (pre- and post-GKRS mRS), complications, medication requirements, and the role of radiosurgery grading scales. RESULTS: After a median 38.6 months follow-up, complete AVM obliteration was achieved in 50%, with 91% experiencing >50% nidus reduction. Functional outcomes improved significantly (mean mRS reduction from 1.47 to 0.53, p=0.026), with minimal procedure-related disability. Radiological changes occurred in 55%, but only 13.8% were symptomatic. Interval hemorrhage and mortality rates were low (8.3% and 2.8%, respectively). Any mMedication requirement use post-GKRS was significantly linked to larger nidus volumes (p=0.009). No clinical or dosimetric variable significantly predicted time to obliteration or risk of complications in multivariate analysis. Comparative discussion highlights similar or better functional results and complication profiles relative to volume-staged radiosurgery strategies cited in literature. CONCLUSION: hf-GKRS may be considered as one of the treatment option for symptomatic high-grade AVMs, with reasonable functional recovery and acceptable complication rates. Judicious candidate selection and use of radiosurgery grading scales are essential for optimizing outcomes.

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