Transtracheal/transesophageal stimulation of the recurrent laryngeal nerve

A new technique is described which allows stimulation of the recurrent laryngeal nerve (RLN) through intact tracheal and esophageal mucosa. In ten anesthetized dogs, the posterior-lateral tracheal wall and the anterior-lateral esophageal wall were stimulated by a 1 to 2 mA current with a probe placed just distal to the edge of the cricoid cartilage. The tracheal mucosa was approached through a tracheostomy stoma and the esophageal mucosa through the mouth. The resultant vocal cord motion was frequency dependent, with graded abduction occurring below 30 Hz and adduction above 40 Hz. By stimulating the posterior laryngeal mucosa proximal to the cricoid edge, the RLN branch to the posterior cricoarytenoid muscle was activated, causing ipsilateral vocal cord abduction independent of frequency. Monitoring of cardiopulmonary parameters demonstrated no alterations at these amperages. There were no mucosal abrasions noted. The transtracheal and transesophageal approaches to RLN stimulation appear promising as diagnostic techniques for evaluating vocal cord function during laryngoscopy and, possibly, as methods of glottic airway control.