Protocol for Neurophysiological Studies of the Superior and Recurrent Laryngeal Nerves and of the Cricothyroid and Thyroarytenoid Muscles. Clinical Utility

Objective This study describes a protocol for laryngeal neurophysiological studies and presents reference values for motor nerve conduction with percutaneous stimulation Electroneurography ENG and muscle function using laryngeal Electromyography EMG Methods We obtained motor nerve conduction values for superior laryngeal and recurrent laryngeal nerves using an external approach with percutaneous stimulation for both nerves We also obtained normal values of the motor unit action potentials MUAPs of the twenty cricothyroid and the twelve thyroarytenoid muscles in healthy subjects and conducted a statistical analysis of mean Results Mean latency of the superior laryngeal nerve was plusmn ms mean amplitude of Potential Action Muscular Compound CMAP was plusmn mV Mean Latency and amplitude of the recurrent laryngeal nerve were plusmn ms and plusmn mV respectively Mean duration of cricothyroid motor unit action potentials MUAP was plusmn ms amplitude was plusmn mu V In the thyroarytenoid muscle mean duration of MUAP was plusmn ms amplitude plusmn mu V and the interference pattern had an amplitude of mu V for both Conclusions This survey of healthy subjects establishes laryngeal nerve and muscle reference values which are essential for assessing anomalies at these locations