Large and deep brain arteriovenous malformations are associated with risk of future hemorrhage

Background and Purpose-The correlation between features present in brain arteriovenous malformations (AVMs) such as size, location, and angioarchitecture at presentation with subsequent risk of hemorrhage may be valuable in predicting the behavior of AVMs and therefore guiding management. Methods-We prospectively followed up 390 patients with brain AVMs at the University of Toronto Vascular Malformation Study Group. Location, size, angioarchitecture details, blood supply, and clinical presentation were recorded at baseline. Intracranial hemorrhages during follow-up were recorded. Significant factors from univariate analyses were used to construct a multivariate model relating the above features to the occurrence of hemorrhage. Results-Thirty-eight patients had bleeding caused by the AVM in a follow-up of 1205 patient-years (mean, 3.1 years per patient). In analyses adjusted for multiple AVM characteristics, large AVMs bled more frequently than small lesions (odds ratio [OR], 2.5; 95% confidence interval [CI], 1.41 to 4.35; P<0.0001). and deep-seated AVMs had more bleeding in follow-up than those located at superficial sites (OR, 5.56; 95% CI, 2.63 to 12.5 P<0.0001). Conclusions-Deep-seated and large AVMs were significantly more prone to hemorrhage during prospective follow-up. The distinction between factors associated with hemorrhagic presentation and the natural history risk of hemorrhage will be emphasized.