Microsurgical and Endovascular Treatments of Spinal Extradural Arteriovenous Fistulas with or without Intradural Venous Drainage

OBJECTIVE: To present treatment strategies for spinal extradural arteriovenous fistulas (AVFs) in relation to angioarchitecture. METHODS: A retrospective analysis comprising 14 patients treated at 2 hospitals was performed. RESULTS: The 14 AVFs included 4 cervical, 1 thoracic, and 9 lumbosacral lesions. Three key angiographic features were observed: the feeding artery, an enlarged extradural venous plexus, and intradural retrograde venous drainage. In 3 patients (3 cervical AVFs) with compressive myelopathy owing to an enlarged venous plexus, the treatment goal was mass reduction of the venous plexus. Combined endovascular and microsurgical treatments may be curative for a large venous lake with multiple feeders. No intradural procedure was required because of the absence of intradural venous drainage. In contrast, in the other 11 patients (1 cervical, 1 thoracic, and 9 lumbosacral AVFs) with congestive myelopathy owing to intradural retrograde venous drainage, the goal of treatment was occlusion of the intradural proximal vein. Microsurgery or endovascular treatment may be curative by itself for a small venous pouch with a single intradural draining vein. Extradural procedures were not required in most patients treated by microsurgery because the extradural venous plexus was small. In all 14 patients, neurologic deficits improved or stabilized, and no recurrence was noted in the follow-up period (29 months). CONCLUSIONS: Spinal extradural AVFs consist of 2 subtypes-type A with intradural drainage and type B without intradural drainage-characterized by regional differences at each spinal level in angioarchitecture, causes of myelopathy, and treatment goals.