Onyx embolization of extradural spinal arteriovenous malformations with intradural venous drainage

Background: Extradural arteriovenous malformations (AVMs) are uncommon vascular malformations of the spine. They are characterized by an arteriovenous communication (localized in the paraspinal soft tissues and the epidural venous plexus) that may have retrograde intradural venous drainage. Surgical treatment of extradural AVMs can be challenging because of the common location ventral to the dural sac and the presence of arterialized venous lakes. Objective: To assess the effectiveness of embolization with a liquid embolic material (Onyx; ev3 Inc, Irvine, California) in 7 consecutive patients with extradural spinal AVMs and intradural venous drainage. Methods: We retrospectively collected information regarding patient characteristics, clinical presentation, symptom duration, diagnostic imaging, treatment, complications, and clinical and radiological follow-up. Results: Patients were 5 men and 2 women (mean age, 66 years; range, 45-76 years). Symptom duration varied from 2 months to 6 years. Six patients underwent embolization of the AVM as the primary treatment; 1 patient was treated after attempted surgery. Complete obliteration was demonstrated in each patient on completion angiography and was confirmed during follow-up in 6. Three patients had resolution of their preembolization symptoms. Three patients had improvement but not complete resolution of their motor deficits. In 1 patient, the AVM was an incidental finding during an investigation for chronic low-back pain; symptoms were not thought to be related to the AVM, and symptoms were not ameliorated by successful embolization. Conclusion: Our early experience with these uncommon lesions suggests that Onyx embolization is a valuable and effective strategy for extradural spinal AVMs and intradural venous drainage.