Advancing frameless stereotactic navigation for precise targeting of the foramen ovale during radio-frequency thermal ablation (RFTA) for trigeminal neuralgia in anesthetized patients using triggered electromyography.

PURPOSE: Radio-frequency thermal ablation (RFTA) is an effective method for treating trigeminal neuralgia (TN). However, challenges persist in locating the foramen ovale (FO) and awake surgery has its limitations. Here we evaluate a novel neurophysiologic technique using dynamic mapping with triggered electromyography (T-EMG) to guide surgeons in identifying the FO under general anesthesia.

METHODS: We prospectively collected clinical data from all patients undergoing RFTA for TN with dynamic T-EMG between September 2022 and December 2024. We subsequently reviewed the data within this database. We placed needle electrodes in the masseter muscle and converted a Tew trigeminal needle to a monopolar stimulator. With the assistance of stereotactic navigation and fluoroscopy, we guided the needle to the predicted border of the FO and delivered a current until a response was elicited by the masseter muscle. Based on this motor response, we made real-time trajectory adjustments to identify the FO and ablate the appropriate trigeminal branch.

RESULTS: Twenty-six consecutive patients underwent 27 RFTA procedures under general anesthesia. In 26 out of 27 procedures (96%), the FO was successfully identified. All patients awoke with intact mastication functionality. Sixteen patients (61.5%) had improvement in their facial pain, two (7.7%) had worse pain, and eight (30.8%) had no change in their pain at last follow-up. There were no major complications.

CONCLUSION: Dynamic mapping using T-EMG for identifying the V3 motor branch of the trigeminal nerve during RFTA procedures under general anesthesia is a reliable and practical method for identifying the FO. This technique demonstrates the potential to enhance the precision of RFTA and improve patient outcomes.