Dural arteriovenous malformation of the major venous sinuses: an acquired lesion.

Arteriovenous malformations of the dura are thought to be congenital. However, arteriographic investigations of four patients who, after a head injury, developed dural arteriovenous fistulae with features of congenital malformations suggest that these abnormal communications may also be acquired. Thrombosis or thrombophlebitis in the dural sinus or vein may be the primary event in their formation. The pathogenesis is probably "growth" of the dural arteries normally present in the walls of the sinuses during the organization of an intraluminal thrombus. This may result in a direct communication between artery and vein or sinus, establishing an abnormal shunt. Ultimate fibrosis of the sinus wall and intraluminal thrombus may be the factors responsible for the spontaneous disappearance of such malformations.