Cerebral dural arteriovenous fistulas: clinical and angiographic correlation with a revised classification of venous drainage.

To review the symptoms and progression of dural arteriovenous fistulas (AVFs) and correlate the findings with various angiographic patterns. Patterns of venous drainage allowed classification of dural AVFs into five types: type I, located in the main sinus, with antegrade flow; type II, in the main sinus, with reflux into the sinus (IIa), cortical veins (IIb), or both (IIa + b); type III, with direct cortical venous drainage without venous ectasia; type IV, with direct cortical venous drainage with venous ectasia; and type V, with spinal venous drainage. Type I dural AVFs had a benign course. In type II, reflux into the sinus induced intracranial hypertension in 20% of cases, and reflux into cortical veins induced hemorrhage in 10%. Hemorrhage was present in 40% of cases of type III dural AVFs and 65% of type IV. Type V produced progressive myelopathy in 50% of cases. This classification provides useful data for determination of the risk with each dural AVF and enables decision-making about the appropriate therapy.