A new noninvasive method for determination of laryngeal sensory function.

Abstract

We report a new surface technique for studying sensory conduction in the superior laryngeal nerve (SLN). Prospective controlled cohort study at an academic tertiary care hospital. Surface stimulation of the vagus nerve 7-10 cm proximal to a surface electrode placed over the cricothyroid muscle was performed in controls and in subjects with needle electromyographic-confirmed laryngeal neuropathy. Cathodal stimulation was applied below the mastoid process behind the sternocleidomastoid muscle. Nerve conduction parameters were determined. Noninvasive SLN evoked potential studies were performed on healthy volunteers (n = 28) as well as neuropathic subjects (n = 27). Compared to controls, the neuropathic subjects had statistically significant differences in baseline-to-peak amplitude, conduction velocity, and intrasubject side-to-side amplitude ratio (P <.01) of their surface evoked laryngeal sensory action potential (SELSAP). Laryngeal sensory nerve conduction can be determined noninvasively by evaluating SELSAP waveform. This study provides a reproducible method for electrophysiologic evaluation of a sensory branch of the SLN.