An analysis on aerodynamic and acoustic changes after thyroidectomy

Abstract

The purpose of this study was to investigate the aerodynamic and acoustic changes after thyroidectomy without laryngeal nerve injury by using objective methods. Voice samples of sustained /a/ recorded from 44 adults preoperatively and nearly 1 week and 3 months after thyroidectomy were analyzed for mean vocal fundamental frequency (Mean Fo, Hz), maximum fundamental frequency (Max Fo, Hz), minimum fundamental frequency (Min Fo, Hz), jitter, shimmer, glottal to noise excitation ratio (GNE), irregularity, noise, overall severity, S time, Z time, S/Z ratio, and maximum phonation time (MPT). Voice samples were analyzed using the lingWAVES software. The comparisons of preoperative and early and late postoperative acoustic parameters revealed significant differences in Mean F0, Max F0, MPT, and S Time between the early and late postoperative periods. The voice changes after thyroidectomy were not affected by age, sex, or surgical procedure, but they differed between the benign and malignant nature of the tumor. Patients with malignant tumors showed a greater decrease in Mean F0 and Max F0 compared with the patients with benign tumors, and this difference was statistically significant. Voice changes may occur after thyroidectomy even in the patients with no evidence of laryngeal nerve damage, and these changes can be assessed with objective measurement methods. This information should be explained to the patients during the preoperative counseling, and proper informed consent is ethically and legally required for all planned thyroidectomies.