Intraoperative electrophysiologic monitoring of the recurrent laryngeal nerve was performed with a commercially available device consisting of an endotracheal tube with integrated stainless-steel-wire surface EMG electrodes positioned at the level of the true vocal cords. Forty-two recurrent laryngeal nerves were successfully monitored with this system in 31 patients undergoing thyroidectomy or parathyroidectomy. In all cases, evoked EMG responses were elicited by direct electrical recurrent laryngeal nerve stimulation. Stimulus thresholds for evoked responses ranged from 0.2 to 0.6 mA (mean 0.3 mA) for the 37 nerves with preoperative ipsilateral normal vocal cord mobility. Mechanically evoked potentials with acoustic signals were also detected during the surgical procedures related to recurrent laryngeal nerve manipulation. It may be concluded that surface electrode monitoring of the recurrent laryngeal nerve with this system provides a simplified, noninvasive technique that is as sensitive as monitoring with intramuscular laryngeal electrodes.
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