Third Place .. Resident Basic Science Award 1992 Effect of asymmetric vocal fold stiffness on traveling wave velocity in the canine larynx STEVEN H. SLOAN, MD, GERALD S. BERKE, MD, and BRUCE R. GERRATT, PhD, Los Angeles. California The vocal fold (VF) traveling wave is essential to normal voice production. The present investigation describes a new method to determine traveling wave velocity (TWV) in the in vivo canine phonatory model. This method synchronizes photoglottographlc and electroglottographlc waveforms with videostroboscopic images to determine the du- ration of time the traveling wave moves between two tattoos placed a known distance apart between the upper and lower margins of each VF. Using this method, we com- pared the TWV of a paralyzed VF with the TWV of the contralateral, electrically stim- ulated VF during phonation in two canines. In addition, the presumed VFstiffness asym- metry in the simulated acute recurrent laryngeal nerve paralysis state was confirmed by measuring Young's modulus of each VF. The results indicated that the TWV of the paralyzed VF averaged 55% of the TWV of the normal, stiffer VFwhen the glottal gap was small and entrainment occurred. This study demonstrated the feasibility of quan- tifying traveling wave motion In asymmetric VF stiffness disorders. The potential use of TWV in human beings as a target to optimize the phonosurgical results in asymmetric VFstiffness disorders is discussed. (OTOlARYNGOL HEAD NECK SURG 1992;107:516.) The increasing interest in laryngostroboscopy as a clin- ical and research tool has recently focused attention on mucosal wave movement in the vocal fold during pho- nation. The vocal folds (VF) exhibit a wavelike motion that consists of vertical as well as horizontal compo- nents. The mucosal wave, propagated by the force of subglottic airflow, travels from the lower margin to the upper margin of the VF and then moves laterally, re- From UCLA Head and Neck Surgery. Supported by an NIH/NS grant (ROI DC00855-0l) and a VAMerit Review Grant. Presented at the Annual Meeting of the American Academy of Oto- laryngology-Head and Neck Surgery, Washington, D.C., Sept. 13-17, 1992. Received for publication May 29, 1992; accepted June 29, 1992. Reprint requests: Gerald S. Burke, MD, UCLA Head and Neck Surgery, CHS 62-132, 10833 Le Conte Ave., Los Angeles, CA 90024-1624. 23/1141107 516 sembling a wave breaking on the shoreline. The lower margins of the VF separate first and, before the upper margins separate, an elliptical volume of air is formed in the subglottic vault, confined by the upper margins superiorly and the lower margins laterally. As the upper margins move laterally, a puff of air is released (i.e., the glottal puff or pulse). 1 The lower margins then return to the midline to close the glottis, followed by the return to the midline of the upper margins as a new glottic vibratory cycle begins. The phase delay between the opening of the lower margins and the opening of the upper margins has been termed the mucosal traveling wave, because of its fluid-like movement when viewed on high-speed film or stroboscopy. The specific char- acteristics of this wave, such as its amplitude and ve- locity, modify the glottal air puffs. These puffs or pulses of air form the vocal source, influence the final acoustic signal emitted, and determine vocal quality. Conse- quently, the characteristics of the traveling wave are most important in determination of voice production.