• Lucia Schwyzer, Chun-Po Yen, Avery Evans, Sebastian Zavoian, and Ladislau Steiner.
• Lars Leksell Center for Gamma Surgery, Department of Neurological Surgery, University of Virginia, Charlottesville, Virginia 22908, USA. ls9e@virginia.edu
• Neurosurgery. 2012 Dec 1;71(6):1139-47; discussion 1147-8.

BackgroundThe effectiveness and risk of gamma knife surgery (GKS) in the management of partially embolized cerebral arteriovenous malformations (AVMs) remain to be elucidated.ObjectiveTo evaluate the long-term imaging and clinical outcomes of GKS in AVM patients who had undergone previous partial embolization and compare the results with patients treated with GKS alone.MethodsA total of 215 embolized AVMs were analyzed. The mean patient age was 32.9 years. The mean volume of the nidus was 4.6 mL (range, 0.1-29.4 mL), and the mean prescription dose was 19.6 Gy (range, 4-28 Gy). This group was compared with 729 nonembolized AVMs.ResultsAfter embolization and GKS, angiographically confirmed total obliteration of the AVMs was significantly lower (33%) compared with patients in whom GKS was used alone (60.9%; P < .001). However, the mean nidus size was larger and the Spetzler-Martin grade was higher for the embolized AVMs compared with the nonembolized AVMs. Radiation-induced changes occurred more often in the embolized (43.4%) than the nonembolized (33.4%) AVMs (P = .028). Permanent neurological deficits associated with radiation-induced changes occurred in 2.7% of the embolized compared with 1.3% of the nonembolized patients (P = .14).ConclusionIn our retrospective and historical series, the long-term results suggest that the obliteration rate is significantly lower in embolized AVMs compared with nonembolized AVMs, also because of the fact that the combined treatment is applied to higher grade AVMs; the percentage of grade III-V AVMs was 58.6% and 48.8% for nonembolized AVMs.

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