Investigation on EMG Profiles of the Superior Laryngeal Nerve in a In Vivo Porcine Model

Background. We investigate the electromyographic (EMG) profiles of the external branch of superior laryngeal nerve (EBSLN). Materials. Laryngeal EMG was simultaneously recorded by endotracheal tube surface electrodes and needle electrodes using monopolar stimulation probe in 12 piglets (22 EBSLNs). Vagal nerve (VN), recurrent laryngeal nerve (RLN) and EBSLN were excite to record and compare EMG tracings. VN, RLN and EBSLN were stimulated from 0.1-1.0mA. Cmin and Cmax were defined as minimum and maximal stimulation to evoke an EMG response. Results. Stimulation resulted in a dose-response curve. Cmin were 0.19mA (0.04-0.4), 0.19mA (0.08-0.3), 0.21mA (0.1-0.4), respectively for EBSLN, RLN and VN (p>0.05). Cmax were 0.6 mA with 396±330μV amplitude values, 0.5 mA and 1058±382 μV, 0.8 mA and 870±382 μV, for EBSLN, RLN and VN (p>0.05). There was no difference between amplitudes of response per side for EBSLN, RLN and VN (P=0.317, P=0.203, P=0.468). EBSLN amplitudes were significantly lower than RLNs and VN (i.e., 42% of RLN and 50% of VN amplitudes values). Conclusions. Cmin and Cmax of EBSLN were similar to those of RLN and VN. RLN and VN, EBSLN amplitude stimulus-response curve were highly variable. We recommend using 1.0mA stimulation and visual appreciation of CTM twitch for EBSLN identification, function verification and prognostication.