A novel electrodiagnostic assessment of the laryngeal closure reflex.

INTRODUCTION: We describe a novel, clinically applicable conduction study of the laryngeal nerves.
METHODS: Seventeen normal volunteer subjects were included. Activation of the sensory territory of the superior laryngeal nerve was performed by administration of low level brief electrical stimuli. The laryngeal closure reflex (LCR) evoked by this stimulus was recorded by needle electrodes. Mean minimal latencies were calculated for each response, and proposed values for the upper limit of normal were determined.
RESULTS: Uniform, consistent early ipsilateral responses and late bilateral responses, which exhibit greater variation in latency and morphology, were recorded. Significant side-to-side differences in latencies were observed, consistent with the length discrepancy between right and left recurrent laryngeal nerves.
CONCLUSIONS: This technique yields clear, quantifiable data regarding neurologic integrity of laryngeal function, heretofore unobtainable in the clinical setting. This study may yield clinically relevant information regarding severity and prognosis in patients with laryngeal neuropathic injury.