Evaluation of Voice Change after Thyroidectomy with Kymography and High Speed Stroboscopy

Abstract

Voice change is one of the major factors affecting the quality of life of patients after thyroidectomy. Voice changes after thyroidectomy have been evaluated by stroboscopy and voice analysis. Recently, digital kymography (DKG) and high-speed videostroboscopy (HSV) have been developed, and showed usefulness in evaluating the vocal fold vibration accurately. The aim of this study was to evaluate the vibratory change of vocal folds after thyroidectomy using kymography and high-speed stroboscopy.

We evaluated the voice and vocal fold movement of 24 female patients who underwent thyroidectomy in a single tertiary hospital from December 2018 to October 2019. We obtained a serial data of kymography and high-speed stroboscopy at 1 day before thyroidectomy, 1 week and 1 month after surgery. We analyzed glottal area waveform, amplitude symmetry index, phase symmetry index, and open quotient with the data. These parameters were calculated at three lines of vocal fold position (line 1 = anterior, line 2 = medial, line 3 = posterior). At the same period, we performed voice analysis with multidimensional voice profile (MDVP), and subjective voice assessment with voice handicap index-10 (VHI-10) questionnaire.

Highest frequency (F-high), frequency range (F-range), and fundamental frequency (F0) decreased at 1 week after thyroidectomy (P = 0.003, 0.004, <0.001) compared with preoperative values. The decrease persisted and did not recover at 1 month after thyroidectomy (P = 0.002, 0.015, 0.001). Data obtained by DKG and HSV showed that open quotient at all three lines increased at 1 week after thyroidectomy (P = 0.011, 0.006, 0.032) and recovered to preoperative levels at 1 month (P = 0.189, 0.153, 0.841). Other quantitative measurements did not show significant change between preoperative and postoperative periods. When we performed a correlation analysis between vocal parameters from acoustic analysis and values obtained from DKG and HSV, significant negative correlations were observed between F-high, F-range, and F0 with glottal area waveform at 1 month after surgery (Rho = - 0.589, - 0.529, - 0.708; P = 0.002, 0.008, <0.001). There were positive correlations between phase symmetry index in line 1, line2 with shimmer at 1 week after thyroidectomy (Rho = 0.489, 0.425; P = 0.015, 0.038). However, there was no correlation between the total score of VHI-10 questionnaires and quantitative measurements of vocal fold vibration.

Acoustic parameters related with vocal frequency were impaired till 1 month after thyroidectomy. Open quotient evaluated in the whole vocal fold were increased at 1 week after surgery. Quantitative measurements of vocal fold vibration using DKG and HSV showed good correlation with acoustic parameters including highest frequency, frequency range, fundamental frequency, shimmer, and maximal phonation time. Thus, multifunction examination system for HSV, DKG may provide important information of acoustic parameters and vocal fold vibratory patterns after thyroidectomy.