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Introduction: The application of intraoperative neural monitoring (IONM) trouble-shooting algorithms procedures in transoral endoscopic thyroidectomy vestibular approach (TOETVA) was investigated. Methods: Loss of signal (LOS) is defined as a loss of the primary electromyographic (EMG) normal biphasic waveform with reduced amplitude response to less than 100μV with a stimulation level intensity of 1–2mA. A systematic review of the IONM system at LOS was covered methodically: (i) correct endotracheal tube verification, (ii) stimulation of the recurrent laryngeal nerve (RLN) at entry point, (iii) ipsilateral or contralateral vagal nerve (VN) stimulation, and (iv) laryngeal twitch (LT). Results: The function of 223 nerves at risk (NAR) was recorded with IONM. Twenty-seven (12%) NAR experienced a suspected LOS. LT could not be appreciated. In 15/27 (55%) cases, the application of the IONM trouble-shooting algorithm revealed upward displacement of the EMG tube (all orotracheal intubations). In 9 (4%) NAR, VN stimulation was not accomplished. In detail, there were n.5 left and n. 4 right VNs. Two VNs were ipsilateral, and 7 VNs contralateral. For EMG tube displacement, because the oral/nasal area is included in the aseptic field, it is less possible to re-check by the laryngoscope or fiberscope. Conclusions: A limit for applying the IONM trouble-shooting algorithm to TOETVA is determined by (a) inability to appreciate the LT, (b) difficulty in stimulating the ipsilateral and contralateral VN, and (c) remodeling EMG endotracheal tube position. A modified IONM trouble-shooting algorithm for TOETVA is proposed. [ABSTRACT FROM AUTHOR]

Continuous intraoperative neural monitoring (C-IONM) is a promising technology used to decrease recurrent laryngeal nerve (RLN) damage during thyroid surgery. However, C-IONM use is limited due to its challenging application. C-IONM requires dissection of the carotid sheath and placement of an electrode around the vagus nerve (VN). In our study, we simultaneously stimulated and monitored the proximal RLN trans-tracheally using surface electrodes that were positioned solely on the endotracheal tube. We described the design, implementation, and testing of a pre-prototype, combined stimulating and recording endotracheal tube (SRET) that continually delivered current from tube edge, and tested the function of the RLN at the vocal cords (VC). The SRET was tested in vivo on 10 RLNs using 5 pigs as animal models. The SRET was capable of the following, delivery of continuous trans-tracheal stimulation to the proximal RLN, continuous trans-tracheal stimulation-induced VC movement, and standard ipsilateral RLN biphasic waveforms with latency and amplitude; and recording evoked responses were recorded in the ipsilateral RLN. The pre-prototype SRET represents a possible advancement in technology because it simplified the C-IONM. Thus, the SRET provides a minimally invasive, alternative application to the C-IONM vagal nerve cuff electrodes. [ABSTRACT FROM AUTHOR]

Continuous intraoperative neural monitoring (C-IONM) during thyroid surgery is a useful tool for preventing recurrent laryngeal nerve (RLN) injury. The present study aims to analyze the tensile strength tolerance of C-IONM electrodes on the vagal nerve (VN). A C-IONM wire was enclosed in a hand-held tensile testing system. The probe displacement on the VN was continuously monitored by positioning a second probe far-up/proximally in a piglet model, and an automatic periodic stimulation (APS) accessory was used. The 3-mm and 2-mm APS accessory has a mean tensile strength of 20.6 ± 10 N (range, 14.6–24.4 N) and 11.25 ± 8 N (range, 8.4–15.6 N), respectively (P = 0.002). There was no difference between bilateral VNs. The mean amplitude before and during electrode displacement was 1.835 ± 102 μV and 1.795 ± 169 μV, respectively (P = 0.45). The mean percentage of amplitude decrease on the electromyography (EMG) was 6.9 ± 2.5%, and the mean percentage of latency increase was 1.9 ± 1.5%. No significant amplitude reduction or loss of signal (LOS) was observed after > 50 probe dislocations. C-IONM probe dislocation does not cause any LOS or significant EMG alterations on the VN. [ABSTRACT FROM AUTHOR]

Background: Adoption of continuous intraoperative neural monitoring (C-IONM) in endoscopic thyroid surgery is limited due to the uneasy application of C-IONM electrode. Feasibility for transcutaneous vagal nerve stimulation was tested. Materials and Methods: Vagus nerve (VN) and recurrent laryngeal nerve (RLN) were mapped and stimulated in different neck sites by (1) transcutaneous monopolar intermitted stimulation; (2) prototype for continuous transcutaneous stimulating electrodes (TSEs), that is, suction ball C-IONM electrode remodeled; (3) stimulation subsequently to neck CO2 insufflation; (4) direct stimulation of surgical exposed nerves. Electromyographic (EMG) parameters were compared. Results: Six anterior neck locations evoked EMG signals of VNs and RLNs. Location Nos. 3 and 6 according to our scheme were over the VNs, confirmed by ultrasonography and subsequent dissection. Other locations did not correspond to nerves sites. Transcutaneous thresholds were higher than surgical exposed ones to produce a consistent and satisfactory EMG response. TSE recorded solely in location No. 5 with amplitude values 256-9 μV. It was not possible to stimulate and monitor the RLN and VN after neck CO2 insufflation. Conclusion: Transcutaneous C-IONM is unfeasible for endoscopic thyroidectomy. [ABSTRACT FROM AUTHOR]