ObjectiveTo investigate the effects of medical vs interventional management on functional outcome in A Randomized Trial of Unruptured Brain Arteriovenous Malformations (ARUBA).MethodsWe used the initial results of a nonblinded, randomized, controlled, parallel-group trial involving adults ≥18 years of age with an unruptured brain arteriovenous malformation (AVM) to compare the effects of medical management (MM) with or without interventional therapy (IT) on functional impairment, defined by a primary outcome of death or symptomatic stroke causing modified Rankin Scale (mRS) score ≥2. ARUBA closed recruitment on April 15, 2013.ResultsAfter a median of 33.3 months of follow-up (interquartile range 16.3-49.8 months), of the 223 enrolled in the trial, those in the MM arm were less likely to experience primary outcomes with an mRS score ≥2 than those who underwent IT. The results applied for both those as randomized (MM n = 109 vs IT n = 114) (hazard ratio [HR] 0.25, 95% confidence interval [CI] 0.11-0.57, p = 0.001) and as treated (MM n = 125 vs IT n = 98) (HR 0.10, 95% CI 0.04-0.28, p < 0.001). Functional impairment for the outcomes showed no significant difference by Spetzler-Martin grade for MM but was more frequent with increasing grades for IT (p < 0.001).ConclusionDeath or stroke with functional impairment in ARUBA after a median follow-up of 33 months was significantly lower for those in the MM arm both as randomized and as treated compared with those with IT. Functional severity of outcomes was lower in the MM arm, regardless of Spetzler-Martin grades.Clinicaltrialsgov identifierNCT00389181.Classification of evidenceThis study provides Class II evidence that for adults with unruptured brain AVMs, interventional management compared to MM increases the risk of disability and death over ≈3 years.