Critical Evaluation of the Action of the Posterior Crico-Arytenoid Muscle, Utilizing Direct EMG-Study

Abstract

In the present investigation the electrical activity of the posterior crico-arytenoid muscle has been studied by direct electromyography. In the course of direct laryngoscopy under neurolept analgesia 10 patients, 4 males and 6 females, have been examined for the evaluation of unilateral vocal cord immobility. The normally mobile side was utilized for the study of the action of the posterior crico-arytenoid muscle. This muscle showed a basic resting electrical activity as well as a rhythmic respiratory fluctuation, with an inspiratory rise of electrical activity on deep respiration. During closure of the glottis, as in phonation and sphincteric actions, the posterior crico-arytenoid muscle exhibited a considerable degree of electrical activity. It is suggested that the posterior crico-arytenoid muscle is not solely an abductor muscle, and though it has an abducting effect during forcible inspiration it does not seem to be the sole abductor. Several structural properties of the motor control of the small internal laryngeal muscles are discussed. No evidence can be found as to a specific arrangement for the two antagonistic muscle systems, abductors and adductors.