Extramedullary arteriovenous fistula of the spinal canal with spinal cord venous drainage. Apropos of 2 cases

The authors report two cases of extramedullary arteriovenous fistulas in the spinal canal with venous return into the spinal cord veins. Both patients were middle-aged men who presented with multiple nerve root involvement of the lower extremities for one year and three months respectively. Myelography demonstrated an indentation at the level of the conus medullaris by a dilated vein in both cases. Arteriography of the spinal cord demonstrated an arteriovenous malformation from the dura mater with venous return into the ascending spinal cord veins, located in both cases at T11. Unlike typical angiomas of the spinal cord, these arteriovenous fistulas do not arise from spinal cord arteries. Only the venous return is into the spinal cord system. Initial clinical manifestations are progressive and often misleading, with pseudoradicular pain of the lower extremities or intermittent claudication which was observed in both patients. Only good quality myelography enabled visualization of the dilated vein at the level of the conus medullaris which lead to localization of the arteriovenous malformation and its afferent arteries outside of the spinal cord itself. Treatment is either surgical, or neuroradiological (embolization). Similar results are obtained by both methods, in a condition which would otherwise progress to paraplegia.