Ann Otol Rhinol Laryngol100:1991 VOCAL FOLD MEDIALIZATION BY SURGICAL AUGMENTATION VERSUS ARYTENOID ADDUCTION IN THE IN VIVO CANINE MODEL DAVID C. GREEN, MD GERALD S. BERKE, MD PAUL H. WARD, MD Los ANGELES, CALIFORNIA There are a variety of methods for treating unilateral vocal cord paralysis, but to date there have been few studies that compare these phonosurgical techniques by using objective measures of voice improvement. Vocal efficiency is an objective voice measure that is defined as the ratio of the acoustic power produced by the larynx to the subglottic air power. Vocal efficiency has been found to decrease with glot- tic disorders such as vocal cord paralysis and carcinoma. This study compared the effects of vocal fold medialization by surgical augmenta- tion to those of arytenoid adduction on the vocal efficiency, videostroboscopy, and acoustics (jitter, shimmer, and signal-to-noise ratio) of a simulated unilateral vocal cord paralysis in an in vivo canine model. Arytenoid adduction was superior to surgical augmentation in vocal efficiency, traveling wave motion, and acoustics. KEY WORDS - flaccid laryngeal paralysis, laryngoplasty, phonosurgery, recurrent laryngeal nerve, stroboscopy, vocal efficiency. noid muscle contraction plays a greater role in in- tensity control during normal phonation than later- al cricoarytenoid contraction by changing cord stiffness and shape, while lateral cricoarytenoid contraction plays a greater role in pathologic cases with incomplete glottic closure by enhancing cordal adduction. Clinically, vocal efficiency has been shown to decrease with some forms of laryngeal dis- ease, such as invasive carcinoma and vocal cord pa- ralysis.t"" Although vocal efficiency is a useful objective measure of voice, it does have its shortcomings. This measure may not correspond with vocal quality. The voice may be quite harsh with a normal vocal efficiency. Also, vocal efficiency does not indicate the degree of control the patient has over the glottis. Typically, vocal efficiency increases with intensity, and an early vocal abuser may have a higher vocal efficiency despite actively abusing his or her voice. 9 INTRODUCTION There are a variety of methods for treating uni- lateral vocal cord paralysis. These include Teflon injection;' thyroplasty, 2 arytenoid adduction," and nerve" and nerve-muscle pedicle transfer. 5 Most of these methods have been reported to improve the voice. However, recently, a theoretical paper com- paring effects of the above treatment modalities on laryngeal vibration found significant differences among them." Unfortunately, to date there have been few studies that compare these phonosurgical techniques by using objective measures of voice im- provement. Most authors simply describe the voice as improved over the paralyzed state. Vocal efficiency is an objective measure of the voice that was first studied by van den Berg" in 1956. He defined the efficiency of the voice as the ratio of the acoustic power of the voice to the sub- glottic power. The subglottic air power can be esti- mated as the product of the mean glottic airflow rate and the mean subglottic pressure. The physio- A number of acoustic measures of voice quality logic control of vocal efficiency has been studied by have been used clinically. These include jitter, shim- several investigators. Koyama et al," using an in vi- mer, and signal-to-noise ratio. Jitter is defined as vo canine model, found higher levels of vocal effi- the fluctuation in the time interval between succes- ciency when cricothyroid contraction was added to sive peaks of the fundamental frequency. Shimmer recurrent laryngeal nerve stimulation. Tanaka and is the cycle-to-cycle variation in the amplitudes of Tanabe," also using an in vivo canine model, found the peaks. Signal-to-noise ratio is the ratio of the that increased contraction of the thyroarytenoid or sound energy in the acoustic signal to the noise in cricothyroid muscle increased glottic resistance (the the voice signal. 12.13 Lieberman':' was the first to re- ratio of glottic airflow to subglottic pressure), while port an increased jitter in pathologic phonation. vocal efficiency remained constant. They further Lieberman':' and Koike et al 15 found, using high- observed that contraction of the lateral cricoaryte- speed cinematography, that pitch perturbations re- noid muscle increased both glottic resistance and fleeted variations in the glottic area and periodicity. vocal efficiency. They postulated that thyroaryte- Koike et aIlS and Zyski et al 16 found increased jitter From the Division of Head and Neck Surgery, University of California-Los Angeles, and the Department of Head and Neck Surgery, West Los Angeles Veterans Administration Medical Center, Los Angeles, California. This study was performed in accordance with the PHS Policy on Humane Care and Useof Laboratory Animals, the NIH Guide for the Care and Useof Laboratory Animals, and the Animal Welfare Act (7 U.S.C. et seq.): the animal use protocol was approved by the Institutional Animal Care and Use Committee (IACUC) of the University of California. Presented at the meeting of the American Laryngological Association, Palm Beach, F1orida, April 28-29, 1990. REPRINTS - Gerald S. Berke, MD, Division of Head and Neck Surgery, UCLA, 10833 Le Conte Ave, Los Angeles, CA 90024. 280