Spinal dural arteriovenous fistula (SDAVF) variant with dual perimedullary and epidural drainage.

Abstract

A spinal dural arteriovenous fistula (SDAVF) is an abnormal connection between a radiculomeningeal artery and a radiculomedullary vein (RMV) characteristically draining into the perimedullary venous system. We present an observation of SDAVF draining simultaneously into the perimedullary and epidural venous systems. A 67-year-old man presented with lower extremity weakness and sphincter dysfunction. MRI documented a longitudinally extensive myelopathy with parenchymal enhancement and flow-voids on T2-weighted images. Spinal angiography revealed the presence of two SDAVFs, at left T9 and right L1. The right L1 SDAVF was treated endovascularly. Superselective angiography of the main feeder, a right T12 radiculomeningeal branch, documented an unusual drainage pattern, with contrast flowing both retrogradely towards the perimedullary venous system and antegradely into the epidural plexus. The meningeal branch was embolized using a liquid embolic agent with adequate penetration of the embolic material into the proximal segment of the draining vein. The left T9 SDAVF was surgically resected, as the radicular artery supplying the fistula also provided the artery of Adamkiewicz. Dual drainage of the right L1 SDAVF into the perimedullary and epidural venous systems allowed to locate the site of the arteriovenous shunt at the point of transdural passage of the RMV, a narrowed segment also known to represent an anti-reflux mechanism. The potential role played by the topographical relationship between the shunt and the anti-reflux mechanism of the RMV in the formation and clinical expression of SDAVFs is discussed.