Standardized Intraoperative Neuromonitoring Procedure is Feasible in Transoral Endoscopic Thyroidectomy

Abstract

Background: Intraoperative neuromonitoring in thyroid surgeries has become popular, but the standardized manner of intraoperative neuromonitoring during transoral endoscopic thyroidectomy vestibular approach (TOETVA) is not well established. This study evaluated the feasibility of using a standardized intraoperative neuromonitoring method for TOETVA.

Methods: Medical records of consecutive patients who underwent TOETVA with intraoperative neuromonitoring were retrospectively reviewed. Patients were positioned before intubation to prevent tube migration, then intubated using video laryngoscopy. The electromyography amplitudes of the vagal nerves and the recurrent laryngeal nerves were checked before (V1, R1) and after (V2, R2) thyroid resection. V1 and V2 signals were evaluated using a long ball tip stimulator with a stimulus current of 3 mA. R1 and R2 signals were obtained using the stimulus current of 1 to 3 mA.

Results: Forty-two patients (3 males and 39 females) were included. Lobectomy was performed in 40 patients (95.2%) and total thyroidectomy in 2 (4.8%). Pathologic diagnoses were 30 papillary thyroid carcinomas, 2 follicular thyroid carcinomas, and 9 benign diseases. Conversion to open surgery occurred in 1 patient due to bleeding. Thus, 43 nerves at risk in 41 patients were analyzed. V1 and R1 signals were detected from all nerves. The mean V1 and R1 amplitudes were 738.7±391.4 μV and 804.4±347.5 μV, respectively, and 38 (88.3%) and 39 (90.7%) nerves had R1 and V1 amplitudes of more than 500 μV. There were 2 cases (4.6%) of transient recurrent laryngeal nerve injury. R2 and V2 signals were detected in the 41 remaining nerves. The mean R2 and V2 amplitudes were 917.2±505.2 μV and 715.7±356.2 μV, respectively, and 36 (87.8%) and 32 (78.0%) nerves had respective R2 and V2 amplitudes of more than 500 μV.

Conclusions: Intraoperative neuromonitoring could be performed in a standardized manner in TOETVA, and the quality of intraoperative neuromonitoring was excellent. Further studies are needed to verify the feasibility of the current approach.