The clinical presentation of dural arteriovenous fistulas (DAVFs), in particular 
the associated risk of intracranial hemorrhage, shows a strong correlation with 
their pattern of venous drainage. The two most commonly used and clinically 
accepted DAVF classifications are the Merland-Cognard classification and the 
Borden classification, both based on the morphology of the venous drainage. A 
revised classification that grades DAVFs through a combination of angiographic 
and clinical features has also been proposed. This article offers a review of 
these various classification schemes, and discusses their application to 
treatment decision making.