The Early Risk of Hemorrhage in Patients with Unruptured Brain Arteriovenous Malformations: A Prospective Cohort Study

Background: This study aims to identify factors indicative of an increased risk of hemorrhage for patients with unruptured brain arteriovenous malformations (bAVMs).

Methods: From a total of 769 cases, 385 with untreated unruptured bAVMs were followed from referral until treatment, bAVM rupture, death or last review. Cox proportional hazards regression models and Kaplan-Meier life table analyses were generated assessing nine potentials risk factors and calculating bAVMs first rupture rates after referral.

Results: No risk factor for bAVM hemorrhage could be found from regression analyses. The cumulative risk of first bAVMs hemorrhage was 1.5%, 2.6%, and 7.0% at 2 months, 6 months and 12 months. More than two thirds of those experiencing bAVM hemorrhage after presentation had an adverse outcome (mRS>2). Age, sex, mode of presentation (seizure and/or neurological deficit), location (deep or infratentorial), presence of aneurysm and presence of exclusive deep venous drainage had no observable association with an increased risk of future hemorrhage.

Conclusion: No factor was significantly associated with the risk of subsequent bAVMs hemorrhage. The hemorrhage rate after diagnosis is not inconsequential and should influence early decision making of management. The application of complex risk assessment paradigms incorporating bAVMs presentation modalities or morphological variables is inappropriate.