Study on Normal Laryngeal Electromyography of Thyroarytenoid Muscle, Cricothyroid Muscle, and Posterior Cricoarytenoid Muscle.

OBJECTIVE: The aim of this study was to investigate the physiological activity of intrinsic laryngeal muscle under different functional states of larynx by measuring the normal laryngeal electromyography parameters.

METHODS: Laryngeal electromyography (EMG) was performed in 112 patients with unilateral vocal cord movement disorder. The duration and amplitude of the motor unit potential (MUP) of the thyroarytenoid muscle (TA), posterior cricoarytenoid muscle (PCA), and cricothyroid muscle (CT) were measured when patients were asked to make a deep inspiration and phonate /i/. The normal side of the patients' vocal chords was used as the research object.

RESULTS: (1) The motor unit potential of TA, CT, and PCA were measured when inspiration and phonating /i/. Waveforms were normal. (2) There were significant differences in duration of TA between inspiration and phonating /i/ in comfortable tone. (3) When comparing the duration and amplitude of any 2 of TA, CT, and PCA during inspiration and phonating /i/, there were significant differences in duration between CT and PCA when phonating /i/ only. There were no significant differences in any other comparisons.

CONCLUSIONS: Under either deep inspiration or pronunciation, the TA, CT, and PCA muscles were activated. The TA may play a major role in phonating. The PCA may play a major role in the action of deep inspiration.