Bipolar radiofrequency ablation of mandibular branch for refractory V3 trigeminal neuralgia

Background: Percutaneous trans-foramen ovale (FO) radiofrequency ablation (RFA) of Gasserian ganglion (GG) is commonly used to treat V3 trigeminal neuralgia (TN). However, this intracranial approach is less selective and safe. Objectives: To report a novel percutaneous within-FO RFA of the V3 under CT-guidance and outcomes with both bipolar and monopolar techniques. Patients and methods: Twenty-six patients with isolated V3 primary TN and FO >6 mm in diameter underwent either monopolar (n=12) or bipolar RFAs (n=14) based on their preference. Successful analgesia over V3, residual pain, recurrent pain, and complications were compared between the two groups. The ex vivo egg albumen model was used to demonstrate the size difference in the thermocoagulation lesion created by monopolar vs bipolar electrodes. Results: In the bipolar group, there were more cases of masticatory atonia as compared to the monopolar (P=0.104), but no residual pain was observed. In the monopolar group, there were two cases of residual pain found, which led to immediate repeat RFAs. Therefore, during the immediate post-operative period, both groups obtained 100% complete V3 analgesia with a similar risk of facial hematoma (P=0.641). During up to 27-months of post-operative follow-up, in the bipolar group, complete pain relief persisted in all patients; in the monopolar group, 1 case of recurrent pain was found at 14 months. Ex vivo study demonstrated that, at 90 °C/90 seconds of RFA, the width of lesions is significantly larger by the 6-mm spacing parallel-tip bipolar electrodes compared to the monopolar electrode (9.5±0.567 vs 5.5±0.07 mm). Conclusion: In treating patients with isolated V3 TN and FO >6mm in diameter, this percutaneously within-FO RFA of the V3 under CT guidance is both clinically practical and effective, while bipolar RFA is associated with a lower incidence of residual and recurrent pain likely due to larger lesion sizes.