Introduction/purpose Spinal epidural arteriovenous fistulas (SEDAVF) with intradural venous drainage are a rare and poorly understood vascular malady of the spine – one that is both potentially neurologically devastating as well as potentially curable. Several theories have been postulated as to their nature and causative incidents, but they remain a mystery. These types of fistulae are broadly differentiated into two categories: post-traumatic (usually in the cervical spine) and atraumatic (usually lumbar spine).

Materials/methods Retrospective search of imaging and clinical data including patient demographics, angiographic findings, surgical results (where applicable), and follow up clinical information was performed in patients who had conventional spinal angiography over the past 10 years.

Results We report a series of 14 patients with atraumatic spinal epidural arteriovenous fistula with intradural drainage treated at our institution. Eleven had intradural drainage of the epidural fistula. All of these patients presented with insidious onset of lower extremity weakness mimicking SDAVF both in presentation and on imaging. All patients underwent diagnostic spinal angiogram, and 12/14 (85.7%) had at least one endovascular intervention. Seven of the 15 patients underwent open surgery for their fistula. Ten of the patients (71.4%) had fistulae in the lumbar spine, with 2 patients presenting with an atraumatic SEDAVF in the thoracic spine and 2 in the cervical spine. Eleven of the patients (including all of the patients with cervical and thoracic level SEDAVF) had disc bulges resulting in greater than 25% spinal canal stenosis at an adjacent level. 50% of patients were cured from endovascular methods alone, 14.3% cured purely surgically, and 35.7% cured with a combined approach.

Conclusion Because of the variability in venous anatomy and the nature of the circuitous drainage pathway some of these fistulae take, the atraumatic fistulae with intradural venous drainage (a high-risk feature) can be missed if one hasn’t already thought of the diagnosis. All of the patients with intradural drainage had adjacent disc bulges, which may be contributory to the intradural routing of the venous drainage. The epidural space is significantly narrowed by the disc bulge resulting in increased resistance to venous outflow in the epidural space necessitating the drainage to reroute intradurally. Eleven patients with intradural drainage of an epidural fistula in patients presenting with myelopathy is the largest series of such patients reported to date. We also discuss embolization resulting in cure or partial cure in over 85% of the patients in our series, demonstrating the importance of a thorough knowledge of this entity on the part of the neurointerventionalist.

Disclosures A. Nicholson: None. M. Amans: None. F. Settecase: None. S. Hetts: None. D. Cooke: None. C. Dowd: None. R. Higashida: None. M. Lawton: None. V. Halbach: None.