Physiologic assessment of Isshiki type III thyroplasty.

Isshiki type III thyroplasty is a laryngeal framework surgical procedure that lowers a patient's pitch. To objectively assess the procedure, preoperative and postoperative voice recordings, as well as electroglottography and photoglottography were performed. Jitter, shimmer, and glottographic quotients were measured to assess changes in vibratory pattern. The mean and range of frequencies in contextual speech was also determined. Analysis of the preoperative and postoperative data from two patients with over 1 year follow-up showed a decrease in frequency of vibration. Postoperatively, the vocal folds still vibrated in a regular pattern as described by the myoelastic-aerodynamic theory. There was no increase in jitter or shimmer quotient. The Isshiki type III thyroplasty appears capable of lowering fundamental frequency of speech without adversely affecting the vibratory mode of the vocal folds.