Cognard classification

Dural arteriovenous fistulae (DAVF)

Type I

Normal anterograde flow into a dural venous sinus

Type IIa

Drainage into a sinus with retrograde flow within the sinus

Type IIb

Drainage into a sinus with retrograde flow into cortical vein(s)

Type II a+ b

Drainage into a sinus with retrograde flow within the sinus and cortical vein(s)

Type III

Direct drainage into a cortical vein without venous ectasia

Type IV

Direct drainage into a cortical vein with ectasia >5mm and 3x larger than the diameter of the draining vein

Type V

Direct drainage into spinal perimedullary veins

Reference

Adams and Whitfield. Intracranial Dural Arteriovenous Fistulae. ACNR (2007) vol. 7 (3) pp. 10-12