Laryngeal ultrasound-guided adhesive transcutaneous electrodes versus conventional endotracheal electrodes for intraoperative neuromonitoring during thyroid and neck surgery.

Introduction: Conventional intraoperative neuromonitoring during thyroid surgery commonly uses electromyography electrodes embedded in endotracheal tubes. Adhesive transcutaneous electrodes may be a novel, noninvasive and low-cost alternative, but its accuracy and limitations remain less known. This prospective study compared the accuracy of adhesive transcutaneous electrodes placed under laryngeal ultrasound guidance to that of conventional endotracheal tube electrodes and assessed the factors associated with success in adhesive transcutaneous electrodes intraoperative neuromonitoring.

Methods: Consecutive patients undergoing open thyroid and neck surgery in a tertiary endocrine surgery unit were prospectively recruited. Before skin incision, the position of vocal cords relative to the thyroid cartilage was marked with laryngeal ultrasonography, and a pair of adhesive transcutaneous electrodes was placed on the overlying skin. Endotracheal tube electrode was used simultaneously. Standardized vagus and recurrent laryngeal nerve stimulation protocol was followed. On each stimulation, electromyography signals were simultaneously recorded by adhesive transcutaneous electrodes and endotracheal tube electrodes and later verified by postoperative flexible laryngoscopy.

Results: From 2023 to 2024, 300 nerves at risk from 216 patients were analyzed. Median age was 59 (50-70) years; 72.7% were female. Adhesive transcutaneous electrode electromyography had lower amplitudes for both recurrent laryngeal nerve and vagus nerve (P < .001). All 4 vocal cord vocal cord paresis (1.33%, transient and unilateral) were detected by adhesive transcutaneous electrodes and endotracheal tube electrodes, that is, 100% sensitivity and negative predictive value for vocal cord vocal cord paresis. Adhesive transcutaneous electrodes had slightly lower specificity (91.6% vs 96.5%) and accuracy (91.8% vs 96.6%), and lower positive predictive value (14.3% vs 28.6%). Signal interference in adhesive transcutaneous electrodes occurred in 6 patients (2.8%). Higher body mass index (BMI) was the only factor associated with false results from adhesive transcutaneous electrodes (P = .002, odds ratio 1.176, 95% confidence interval 1.060-1.305). Accuracy of adhesive transcutaneous electrodes (94.6%) became comparable to endotracheal tube electrodes in patients with body mass index <25. Adhesive transcutaneous electrodes cost less than endotracheal tube electrodes (32 vs 427 US dollars) for each surgery. Two patients with misplaced endotracheal tube electrodes (false endotracheal tube electrodes signal loss) had normal recurrent laryngeal nerve function correctly predicted by adhesive transcutaneous electrodes.

Conclusion: Laryngeal ultrasound-guided adhesive transcutaneous electrode intraoperative neuromonitoring has comparable sensitivity and negative predictive value to endotracheal tube electrodes and may resolve false endotracheal tube electrodes signal loss. Lower body mass index was associated with improved and comparable accuracy to endotracheal tube electrodes. Adhesive transcutaneous electrodes may be a reliable, low-cost replacement to endotracheal tube electrodes in patients with body mass index <25.