Natural course | Borden classification | Cognard classification | |||||
Type | Venous drainage site | CVR | Type | Venous drainage site | Flow pattern in sinus | CVR | |
Benign | I | Dural sinus | No | I | Dural sinus | Antegrade | No |
Benign | IIa | Dural sinus | Retrograde | No | |||
Aggressive | II | Dural sinus | Yes | IIb | Dural sinus | Antegrade | Yes |
Aggressive | IIa+b | Dural sinus | Retrograde | Yes | |||
Aggressive | III | Cortical vein | Yes | III | Cortical vein | Yes without venous ectasia | |
Aggressive | IV | Cortical vein | Yes with venous ectasia | ||||
Aggressive | V | Cortical vein with spinal medullary drainage | Yes |
CVR, cortical venous reflux; dAVF, dural arteriovenous fistula.