Pattern identification requires gold-standard 4-vessel cerebral angiography to definitively establish the presence of cortical venous reflux (CVR).
Angiographic Sentinel Probe
Identify the venous drainage pattern of the dAVF to establish the natural history Cognard Grade and determine the haemorrhagic probability.
Guidelines & Evidence
Clinical Details
Section 1
When to Use
When to Use
Classifying dural arteriovenous fistulas (dAVFs) based on cerebral venous drainage.
Predicting the risk of intracranial haemorrhage or non-haemorrhagic neurological deficits.
Determining the urgency and modality of treatment (embolization vs. surgery).
Section 2
Literature
Development
Developed by Cognard and colleagues in 1995, this classification expanded on the Borden system by incorporating the direction of flow (antegrade vs. retrograde) and the presence of cortical venous reflux (CVR). It remains the global reference for neurovascular risk stratification.
Section 3
Pearls/Pitfalls
The Danger of Reflux
Cognard types IIb through IV are considered "aggressive" lesions. The presence of cortical venous reflux (CVR) exposes thin-walled pial veins to high-pressure arterialized flow, leading to a massive increase in annual haemorrhage risk (up to 15-20% in some series). These lesions mandate prompt neurointerventional or surgical closure.
Section 4
Evidence Appraisal
Primary Reference
Cerebral dural arteriovenous fistulas: clinical and angiographic correlation with a revised classification of venous drainage
