Development of radiofrequency ablation devices with neuromonitoring system to detect recurrent laryngeal nerve in thyroid nodule

Abstract

Background Radiofrequency ablation (RFA) is an emerging minimally invasive treatment modality of benign thyroid nodule and limited small papillary thyroid cancer. Among the RFA related complications, the recurrent laryngeal nerve (RLN) damage is one of the most concerned complications. To reduce the RLN injury during RFA, we developed a RFA device with intraoperative neuromonitoring system (IONM) to detect recurrent laryngeal nerve. Furthermore, to avoid a use of EMG tube requiring general anesthesia, we developed an accelerometer sensor that can be attached on the anterior neck skin. In this study, we examined the feasibility of neuromonitoring system to detect RLN during RFA in thyroid gland. Methods Three beagles (six thyroid glands) underwent the RFA under general anesthesia. Tip of the RF electrode acted as a neurostimulator probe and its location was ultrasonographically monitored. Stimulation current was set based on NIM-Response 3.0 system. During the procedure, nervemonitoring was performed simultaneously using NIM® standard EMG reinforced tube, needle electrode and accelerometer. Results When the tip of the RF electrode was placed near the tracheoesophageal groove, RLN was successfully identified with EMG tube, needle electrode and accelerometer sensor. After RFA near the tracheoesophageal groove, nerve injury was detected in EMG tube, needle electrode and accelerometer sensor. Conclusion Neuromonitoring system to detect RLN using RF electrode was feasible in the animal study. Like both EMG tube and needle electrode, the accelerometer sensor can detect laryngeal muscle twitching during RLN stimulation. Accelerometer sensor for detecting RLN is expected to make the RFA procedure safer without any invasive monitoring system.