Assessing the clinical utility of the magnetic stimulator for measuring response latencies in the laryngeal muscles.

Our purpose was to assess the use of magnetic stimulation for measuring conduction time of the recurrent and superior laryngeal nerves In 10 normal volunteers (7 male, 3 female). Subjects underwent laryngeal electromyography and magnetic stimulation of the vagus nerve bilaterally at the mastoid tip with a figure 8 coil. Mean muscle response latencies were measured and examined for consistent differences. Thyroarytenoid muscle response latencies were consistently longer than those in the cricothyroid muscle. Left thyroarytenoid muscle latencies were consistently longer than those on the right in agreement with bilateral asymmetry of these nerves. No appreciable differences were observed in cricothyroid muscle latencies when the right side was compared with the left. Results were consistent and reproducible within a broad range, but appreciable intersubject variability was observed. The limited sample size was unable to support a correlation with anthropometric variables, although an association was indicated. Magnetic stimulation with this technique has great potential for use in neurolaryngologic studies.