Endovascular Management of Dural Arteriovenous Malformations

DAVM are typically classified by location of the involved sinus or shunt as well as by the pattern of venous drainage. [5] The pattern of venous drainage is a key factor predicting the natural history of these lesions and provides the foundation for the widely adopted Borden [7] and Cognard [8] classification systems. Borden type I DAVM are mostly benign lesions that exhibit normal antegrade flow into a dural sinus. Type II lesions exhibit a degree of AV shunting exceeding the capacity of antegrade outflow from the involved sinus resulting in retrograde venous drainage into cortical veins. Type III lesions drain exclusively into cortical veins or a trapped sinus segment (sinus thrombosis at both ends from high-flow venous congestion). The Cognard classification is a modified version of the Djindjian classification and identifies five types of DAVM based on the pattern of venous outflow. Briefly, type I lesions exhibit normal antegrade flow into a dural sinus. Type II DAVM show retrograde venous drainage into the adjacent sinus segments (type IIa), cortical veins (type IIb) or both (type IIa +b). Types III and IV DAVM drain directly into cortical veins, either with (type IV) or without (type III) venous ectasia. Type V DAVM are typically localized to the tentorium or dural coverings of the posterior fossa and are further characterized by drainage inferiorly into spinal perimedullary veins.