Introduction The natural history of intracranial dural arteriovenous fistulas (DAVFs) with cortical venous drainage is unfavorable, and treatment is recommended in most cases. Early reports have documented excellent initial clinical and radiographic outcomes after Onyx embolization of DAVFs but little evidence is available regarding the long term durability of this technique.

Methods We retrospectively reviewed a database of 63 DAVFs in 53 consecutive patients who underwent Onyx embolization of a DAVF between 2001 and 2012 at our institution. Cognard types I and III were seen most commonly.

Results A total of 72 Onyx embolization procedures were successfully completed during the study period, resulting in complete or near complete occlusion by the end of the study period in 58 (92.1%) DAVFs. For DAVFs in which complete or near complete obliteration was attained, stability of obliteration at 6, 12, 24, and 46 months was 100%, 95.4%, 93.8%, and 92.3%, respectively. DAVF recanalization/regrowth was discovered on delayed follow-up angiography in only five instances in which immediate post-embolization angiography revealed complete obliteration. Complications were seen in seven embolization procedures and included cranial nerve palsies (n=3), embolic infarcts (n=2), intraparenchymal hemorrhage (n=1), and unintentional stent deployment (n=1).

Conclusions Early evidence has indicated that endovascular Onyx embolization is safe and effective at achieving an initial angiographic cure. Results of our series suggest that angiographic and clinical outcomes of Onyx embolization remain relatively stable at mid and long term follow-up.