Dural arteriovenous fistula (DAVF) are a heterogeneous collection of conditions that share arteriovenous shunts from dural vessels. They make up 10-15% of all cerebral vascular malformations. The natural history of aggressive (Borden 2 and 3) cranial dural arteriovenous fistulas (DAVFs) is not well described. Reported annual mortality and hemorrhage rates vary widely and range up to 20% per year. A consecutive single-center cohort of 236 cases that presented with a cranial DAVF between June 1984 and May 2001 was reviewed for the consequences of long-term persistent cortical venous reflux (CVR).