A Spinal Epidural Arteriovenous Fistula Treated With Onyx Transarterial and Transvenous Embolization Using the Hemiazygos Vein: A Case Report

A spinal epidural arteriovenous fistula (SEDAVF) often causes dilatation of the epidural venous plexus extending across 1-2 vertebral segments, frequently exhibiting intramedullary venous reflux. Herein, we report a case of SEDAVF characterized by multiple discontinuous dilated epidural venous plexuses extending across seven vertebral segments, accompanied by intradural venous reflux. A 53-year-old woman presented with gait disturbance. Spinal magnetic resonance imaging (MRI) and computed tomography angiography (CTA) revealed spinal cord edema, flow voids, multiple dilated epidural venous plexuses, and intradural venous reflux, leading to a diagnosis of SEDAVF. Treatment was performed based on the assumption that an L2 radiculomedullary vein (RMedV) with intradural reflux was responsible for the symptoms. Accordingly, Onyx transarterial embolization (TAE) was initially administered, but as the patient's symptoms persisted, we performed another intervention, combining Onyx transvenous embolization (TVE) via the azygos and hemiazygos vein with Onyx TAE, which removed reflux into the RMedV and improved symptoms. Thus, in cases of SEDAVF with multiple dilated venous plexuses extending across several vertebral levels, identifying the responsible lesion and fully understanding the vascular anatomy is needed to ensure appropriate treatment. An endovascular treatment strategy focused on eliminating intravertebral reflux may lead to symptomatic improvement. As such, meticulous preoperative imaging interpretation and accurate identification of the symptom-causing lesions are crucial.