Abstract
Twelve cases of spinal extramedullary arteriovenous malformation (AVM) were studied clinically and radiologically. They were classified into four types: premedullary type, retromedullary type, AVM in the conus region, and radiculomeningeal type. In the premedullary type, an arteriovenous fistula (AVF) rather than nidus existed between the anterior spinal artery and vein. Similarly, a fistula rather than nidus was found between the posterior spinal artery and vein in the retromedullary type. AVM in the conus region was intradural extramedullary around the conus medullaris. Radiculomeningeal AVM or AVF has been considered as the “single-coiled” type of spinal cord AVM. The nidus or fistula in this type fed by branches of the dorso-spinal artery existed around the intervertebral foramen, and was drained reversely through the radiculomedullary vein into the posterior spinal venous system. In all types of extramedullary AVM, congestion of the spinal venous system contributed as a pathogenetic mechanism. Vascular steal, mass effect, or adhesive arachnoiditis were also important pathogenetic factors. Artificial embolization was the treatment of first choice in principle. However, operative indication existed not infrequently according to the type or the site of AVM such as radiculomeningeal type.
