Effect of type 4 thyroplasty on unilateral cricothyroid muscle paralysis

Abstract

Type 4 thyroplasty (cricothyroid approximation) is a surgery that increases the tension of the vocal folds and elevates the speaking fundamental frequency. We performed type 4 thyroplasty in a patient with pitch disorders caused by unilateral cricothyroid paralysis. Stroboscopy, an acoustic analysis and an electromyogram were used to obtain adiagnosis. The lowest pitch was not changed, but both the speaking fundamental frequency and the vocal range were improved by surgery. These findings suggest that not only the cricothyroid muscle, but also the thyroarytenoid muscle, play important roles in the pitch control.