Object: Spinal extradural (epidural) arteriovenous fistulas (AVFs) are uncommon vascular lesions of the spine with arteriovenous shunting located primarily in the epidural venous plexus. Understanding the complex anatomical variations of these uncommon lesions is important for management. The authors describe the different types of spinal extradural AVFs and their endovascular management using Onyx.
Methods: Eight spinal extradural AVFs in 7 patients were studied using MR imaging, spinal angiography, and dynamic CT (DynaCT) between 2005 and 2009. Special consideration was given to the anatomy, pattern of venous drainage, and mass effect upon the nerve roots, spinal cord, and vertebrae.
Results: The neuroaxial location of the 8 spinal extradural AVFs was lumbosacral in 1 patient, lumbar in 4 patients, thoracic in 2 patients, and cervical in 1 patient. Spinal extradural AVFs were divided into 3 types. In Type A spinal extradural AVFs, arteriovenous shunting occurs in the epidural space and these types have an intradural draining vein causing venous hypertension and spinal cord edema with associated myelopathy or cauda equina syndrome. Type B1 malformations are confined to the epidural space with no intradural draining vein, causing compression of the spinal cord and/or nerve roots with myelopathy and/or radiculopathy. Type B2 malformations are also confined to the epidural space with no intradural draining vein and no mass effect, and are asymptomatic. There were 4 Type A spinal extradural AVFs, 3 Type B1s, and 1 Type B2. Onyx was used in all cases for embolization. Follow-up at 6-24 months showed that 4 patients experienced excellent recovery. Three patients with Type A spinal extradural AVFs attained good motor recovery but experienced persistent bladder and/or bowel problems.
Conclusions: The current description of the different types of spinal extradural AVFs can help in understanding their pathophysiology and guide management. DynaCT was found to be useful in understanding the complex anatomy of these lesions. Endovascular treatment with Onyx is a good alternative for spinal extradural AVF management.