May the Inferior Petrosal Sinus Recanalization During Endovascular Treatment for Carotid-Cavernous Fistulas Increase the Risk of Sixth Nerve Palsy?

Background: Sixth nerve palsy is a common complication of endovascular treatment for carotid-cavernous fistulas (CCF). Two hypotheses are evoked: the spontaneous venous congestion into the cavernous sinus and the direct compression of the nerve by the embolic agent into the cavernous sinus. Nevertheless, the evidence is still uncertain. Knowing the vicinity of the sixth nerve with the inferior petrosal sinus (IPS) in the Dorello canal, we hypothesized that the recanalization of the IPS increased the risk of nerve damage. Methods: We analyzed a prospective database of patients treated for CCFs from March 2009 to April 2016. We excluded patients who did not need treatment, cases of high-flow CCF, and patients lost to follow-up, obtaining a homogeneous population of 82 patients with indirect CCFs. This population was divided in 2 groups: patients without new-onset/worsening of sixth nerve palsy and patients with this postprocedural complication. Results: Our main endpoints were the potential differences between patients with or without recanalization of IPS and between those who underwent or not an embolization with Onyx-18. We did not find any statistically meaningful difference between the 2 groups concerning the necessity of IPS recanalization (P > 0.999, odds ratio 0.97, 95% confidence interval 0.32–2.96) or with the use of Onyx-18 as an embolic agent (P = 0.56; odds ratio 1.41, 95% confidence interval 0.41–2.45). Conclusions: The recanalization of a thrombosed IPS does not increase the risk of procedural sixth nerve damage. The initial injury seems to relate with development/worsening of a sixth nerve palsy.