Venous drainage pattern classification in intracranial dAVFs

	Classification of Borden et al³		Classification of Cognard et al²
Benign venous drainage patterns	I	Drains to dural sinus	I	Drains to dural sinus
		No CVR		No sinus reflux
				No CVR
			IIa	Drains to dural sinus
				Sinus reflux present
				No CVR
Aggressive venous drainage patterns	II	Drains to dural sinus	IIb	Drains to dural sinus
		CVR present		No sinus reflux
				CVR present
			IIa+b	Drains to dural sinus
				Sinus reflux present
				CVR present
	III	Direct drainage to cortical veins	III	Direct drainage to cortical veins
		Or		No venous ectasia
		Drainage to an isolated segment of dural sinus	IV	Direct drainage to cortical veins
				Venous ectasia present
			V	Spinal perimedullary venous drainage