Introduction: Spetzler-Martin grade I and II arteriovenous malformations (AVM) are associated with lower surgical morbidity rates than higher grade lesions. We present the outcomes for a large cohort of low grade AVMs treated with radiosurgery.

Methods: From an institutional radiosurgery database comprising 1400 AVM patients, we identified all patients with Spetzler-Martin grade I and II lesions. All patients with less than 2 years radiologic follow-up except those with complete AVM obliteration were excluded yielding 502 patients harboring low grade AVMs for analysis. The median age was 35 years, 50% of patients were male, and the most common presentation was hemorrhage in 47%. Median AVM volume and prescription dose were 2.4 cc and 23 Gy. The median radiologic and clinical follow-up intervals were 48 and 62 months, respectively. Univariate and multivariate Cox proportional hazards and logistic regression analyses were used to determine factors associated with obliteration, radiation-induced changes (RIC), and hemorrhage following radiosurgery.

Results: The cumulative obliteration rate was 76%. The median time to obliteration as 40 months, and the actuarial obliteration rates were 66% and 80% at 5 and 10 years, respectively. Independent predictors of obliteration were no pre-radiosurgery embolization (P<0.001), decreased volume (P=0.005), single draining vein (P=0.013), and lower Virginia Radiosurgery AVM Scale (P=0.001). The annual post-radiosurgery hemorrhage rate was 1.4% with increased volume (P=0.034) and lower prescription dose (P=0.006) as independent predictors. Symptomatic and permanent RIC were observed in 8.2% and 1.4% of patients, respectively. No pre-radiosurgery hemorrhage (P=0.011), decreased prescription dose (P=0.038), and higher Virginia Radiosurgery AVM Scale (P=0.001) were independently associated with post-radiosurgery RIC.

Conclusions: Spetzler-Martin grade I and II AVMs are very amenable to successful treatment with stereotactic radiosurgery. While patient, physician, and institutional preferences frequently dictate the final course of treatment, radiosurgery offers a favorable benefit to risk profile for the management of low grade AVMs.

Patient Care: Spetzler-Martin grade I and II arteriovenous malformations are amenable to intervention, but the optimal management of these lesions is under intense debate in light of the recently published randomized controlled trial, ARUBA, which reported superior outcomes of medical therapy over intervention. Our retrospective analysis shows that stereotactic radiosurgery affords a favorable risk to benefit profile for grade I and II AVMs, with relatively high obliteration rates and reasonably low incidences of RIC and latency period hemorrhage.

Learning Objectives: By the conclusion of this session, participants should be able to 1) Describe the outcomes of stereotactic radiosurgery as a treatment approach for Spetzler-Martin grade I and II arteriovenous malformations, 2) Discuss, in small groups the patient, arteriovenous malformation and treatment characteristics which predict obliteration and radiation-induced changes following radiosurgery, and 3) Identify an effective treatment for grade I and II arteriovenous malformations.

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