Natural History of Brain Arteriovenous Malformations

Abstract

INTRODUCTION: Long-term follow-up studies in patients with brain arteriovenous malformations (AVMs) have yielded contradictory results regarding both risk factors for rupture and annual rupture rate. We performed a long-term follow-up study in an unselected, consecutive patient population with AVMs admitted between 1942 and 2005 to the Department of Neurosurgery at the Helsinki University Hospital. METHODS: Patients with untreated AVMs were followed from admission until death, occurrence of AVM rupture, initiation of treatment, or until the end of 2005. Patients with at least 1 month of follow-up time were included in further analysis. Annual and cumulative incidence rates of AVM rupture as well as several potential risk factors for rupture were analyzed using Kaplan-Meier life-table analyses and Cox proportional hazards regression models. RESULTS: We identified 238 patients with a mean follow-up time of 13.5 years (range, 1 mo–53.1 yr). The average annual risk of hemorrhage from an AVM was 2.4%. The risk was highest during the first 5 years after diagnosis and declined thereafter. Risk factors predicting subsequent AVM hemorrhage in univariate analysis were young age, previous rupture, deep and infratentorial locations, and exclusively deep venous drainage. Previous rupture, large AVM size, and infratentorial and deep locations were independent risk factors according to multivariate models. CONCLUSION: According to this long-term follow-up study, AVMs with previous rupture and large size, as well as those with infratentorial and deep location have highest risk of subsequent hemorrhage. This risk is highest during the first few years after diagnosis but remains significant for decades.