Vibratory Pattern of the Vocal Cord in Unilateral Paralysis of the Cricothyroid Muscle: An Experimental Study

Abstract

The effect of unilateral paralysis of the cricothyroid muscle on the vocal cord position and length and vibratory pattern was investigated in dogs through the use of normal and high speed cameras. After unilateral section of the external branch of the superior laryngeal nerve, the arytenoid on the active side adducts across the midline toward the paralytic side. Unilateral contraction of the cricothyroid muscle elongates both vocal cords conspicuously, though more on the active side than on the inactive side. In the case of unilateral contraction of the cricothyroid muscle, the two vocal cords vibrate at the same frequency, and the vocal cord on the side of active cricothyroid muscle always precedes the opposite cord in vibratory cycle.