Comparison of a Sole Embolic Agent in the Treatment of Cavernous Sinus Fistulas: Onyx versus Coils.

Abstract

Transvenous coil embolization is a standard treatment for cavernous sinus fistulas (CSFs). Although Onyx is widely used for shunts, its use as a sole embolic agent for CSFs remains limited because of concerns regarding dimethyl sulfoxide (DMSO)-related toxicity. This study compared the safety and efficacy of endovenous Onyx embolization with transvenous coil embolization for CSFs. Between 2009 and 2023, 57 CSFs were treated endovascularly at a single institution. Twenty-five patients (22 cavernous sinus dural arteriovenous fistulas and 3 direct carotid cavernous fistulas) underwent endovenous Onyx embolization without adjunctive coils and were compared with 25 patients treated with transvenous coil embolization alone. Outcomes included complete immediate occlusion (CIO), long term occlusion, symptom aggravation, unintended migration to vein or artery, and DMSO-related toxicity. Baseline characteristics were comparable between groups, and embolization was initiated on the venous side in all patients. The rate of symptom aggravation or newly developed neurologic symptoms was identical in both groups (20%). Venous migration occurred only in the Onyx group (8%), and no DMSO-related toxicity was observed. CIO was achieved in 60% of the coil group and 84% of the Onyx group, without a statistically significant difference. Higher CIO rates with Onyx were observed in female patients and in late restrictive-type fistulas. However, the long-term occlusion rates were similar. Endovenous Onyx embolization achieved a numerically higher rate of CIO than coil embolization without increasing complication rates. These subgroup findings should be interpreted cautiously given the limited sample size, and larger confirmatory studies are needed.