CSF-Venous Fistula Transvenous Onyx Embolization: Evaluation of Onyx Migration into the CSF and Potential One-Way Physiology.

Background and purpose: CSF-venous fistulas (CVFs) are abnormal connections between the subarachnoid space and a paraspinal vein. Transvenous Onyx embolization is a recently adopted treatment method for CVF closure, however no studies have specifically evaluated for Onyx migration into the CSF. The purpose of our study was to evaluate patients who underwent transvenous CVF embolization for Onyx migration into the CSF.

Materials and methods: We evaluated 100 patients who underwent transvenous CVF embolization with posttreatment CT of the spine. Images were reviewed for Onyx migration into the CSF at the level of the embolization as well as distally in the lumbar spine. Basic demographic information including age and sex were recorded.

Results: The mean age was 59.2 years (±10.9, 28-88). Sixty-eight patients were women. Forty-eight patients had postembolization imaging of the treated level, and none had Onyx migration into the CSF at the level of the CVF. Thirty-four patients had imaging of the lumbar spine, and none had Onyx migration distally in the lumbar spine.

Conclusions: Our study did not find any cases of unintended Onyx migration into the subarachnoid space in patients who underwent transvenous CVF embolization. This speaks to the safety profile of transvenous CVF embolization and suggests possible one-way physiology of CVF that allows for egress from the CSF to the veins only.