Spinal extradural arteriovenous fistula after lumbar epidural injection: CT angiographic diagnosis using 3D-volume rendering.

Spinal extradural arteriovenous fistulas (SEDAVFs) are a rare form of spinal arteriovenous fistulas, the etiology of which has not been completely elucidated. To our knowledge, this is the first reported case of SEDAVF that may have been caused by a spinal procedure. This report describes a 50-year-old female patient who presented with an SEDAVF at the L3/4 level that developed 3 years after a transforaminal epidural block due to disc extrusion, after which she underwent no other operation or trauma. From routine spine magnetic resonance imaging, disc sequestration was considered more likely than vascular malformation. However, on lumbar CT angiography (CTA) and three-dimensional volume rendering images (3D-VRI), the lesion showed good association with arteries of the aortic branches, allowing us to confirm the exact diagnosis of the lesion as SEDAVF. A limitation of 3D-VRI reconstruction is the difficulty in separate visualization of the vertebral body and blood vessels. On follow-up CTA, 3D dual-energy computed tomography (DECT) depicted smaller vascular structures and showed their anatomical relationships to the bone. While spinal angiography has been traditionally known as the gold standard for SEDAVF diagnosis, CTA with 3D-VRI, especially obtained by DECT, allows clinicians to make an accurate diagnosis and treatment plan that are difficult to judge by routine MRI.