Application of continuous intraoperative neuromonitoring (C-IONM) for recurrent laryngeal nerve preservation in transoral endoscopic thyroidectomy: a preliminary report from Vietnam

The transoral endoscopic thyroidectomy vestibular approach (TOETVA) eliminates visible scarring but introduces technical challenges for recurrent laryngeal nerve (RLN) preservation. Continuous intraoperative neuromonitoring (C-IONM) provides dynamic assessment of nerve function, potentially reducing injury risk. This study reports the initial Vietnamese experience with C-IONM during TOETVA. Thirty-two patients undergoing TOETVA with C-IONM (NIM Vital system, Medtronic) for benign nodules or differentiated thyroid carcinoma were prospectively enrolled. An Automatic Periodic Stimulation (APS) electrode was placed on the vagus nerve for continuous monitoring. Intraoperative loss of signal (LOS) events were recorded, and all patients underwent postoperative laryngoscopy to assess vocal cord function. C-IONM was successfully established in all 33 nerves at risk. Baseline median amplitude was 645.0 (IQR: 520.0-780.0) µV. Intraoperative LOS events occurred in 3 nerves (9.1%): 2 transient events resolved with maneuver adjustment without postoperative deficit; 1 sustained LOS (3.0%) resulted in temporary vocal cord palsy (full recovery within 3 months). The positive predictive value of sustained LOS for temporary palsy was 100%, and the negative predictive value of stable EMG was 100%. No permanent nerve injuries occurred. C-IONM is feasible during TOETVA and may provide useful real-time functional information to guide surgical decision-making. The two transient loss of signal events successfully reversed through timely surgical adjustments suggest that C-IONM may help prevent nerve injury during this technically demanding approach. Larger comparative studies are needed to confirm these preliminary findings.