Incident hemorrhage risk of brain arteriovenous malformations located in the arterial borderzones

Background and Purpose-We sought to assess the relative risk of hemorrhagic presentation of brain arteriovenous malformations (AVMs) located in the ar terial borderzone territories. Methods-The 464 consecutive, prospectively enrolled patients from the New Y ork AVM Databank were analyzed. AVM borderzone location was coded positive when the malformation was supplied by branches of at least 2 of the major c ircle of Willis arteries (anterior, middle, and/or posterior cerebral arter ies). AVMs fed by branches of only 1 major pial or any other single artery served as a comparison group. Clinical presentation (diagnostic event) was categorized as (1) intracranial hemorrhage, proven by brain imaging, or (2) seizure, focal neurological deficit, headache, or other event with no sign s of AVM hemorrhage on brain imaging. Results-In 48% (n=222) of the patients, AVMs were located in the arterial b orderzone territories; in 52% (n=242) a non-borderzone location was found. Hemorrhage was the presenting symptom in 44% (n=205); 28% (n=132) presented with seizures, 11% (n=52) with headaches, 7% (n=34) with a neurological de ficit, and 9% (n=41) with other or no AVM-related symptoms. The frequency o f incident AVM hemorrhage was significantly lower in borderzone AVMs (27%, n=61) than in non-borderzone malformations (60%, n=144; P<0.001). This diff erence remained significant in a multivariate model controlling for age, se x, AVM size, deep venous drainage, and presence of aneurysms (odds ratio, 0 .4; 95% CI, 0.25 to 0.66). Conclusions-Our findings suggest that borderzone location is an independent determinant for a lower risk of AVM hemorrhage at initial presentation.