Table 1.

Classification of dural arteriovenous fistulas

Borden classification
1	Venous drainage directly into dural venous sinus or meningeal vein
2	Venous drainage into dural venous sinus with CVR
3	Venous drainage directly into subarachnoid veins (CVR only)
Cognard et al.
I	Venous drainage into dural venous sinus with antegrade flow
II a	Venous drainage into dural venous sinus with retrograde flow
II b	Venous drainage into dural venous sinus with antegrade flow and CVR
II a + b	Venous drainage into dural venous sinus with retrograde flow and CVR
III	Venous drainage directly into subarachnoid veins (CVR only)
IV	Type III with venous ectasias of the draining subarachnoid veins
V	Direct drainage into spinal perimedullary veins
	(CVR indicates cortical venous reflux)