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A lower-pitched voice is one of the most common voice alterations after thyroidectomy without laryngeal nerve injury. The aim of this study was to evaluate the acoustic and stroboscopic changes and the treatment outcomes in patients with a lower-pitched voice with the goal of eventually establishing a therapeutic guideline. Patients with a lower-pitched voice were selected according to the results of acoustic analysis among thyroidectomized patients. According to their pitch-gliding ability, patients were classified into a “gliding group” and “nongliding group,” and direct voice therapy was performed. For those who did not respond, indirect voice therapy with subsequent identical direct voice therapy was performed. Video-stroboscopy, acoustic and perceptual analysis, and subjective analysis using a questionnaire were performed before and after treatment. The results of the two groups were compared. Fifty patients were enrolled. Decreased vocal cord tension was the most common stroboscopic finding in these patients. After direct voice therapy, 87 % of patients in the gliding group showed restoration of pitch 2 months after thyroidectomy. None of the patients in the nongliding group showed improvement. After indirect voice therapy and subsequent direct voice therapy, these nonresponders finally showed improvement 4.5 months after thyroidectomy. Several characteristic stroboscopic findings of the nongliding group were identified. The pitch-gliding ability and several specific stroboscopic findings were predictive of a response to direct voice therapy. Based on these findings, an individualized therapeutic approach could be applied, and the pitch of patients with a lower-pitched voice after thyroidectomy was restored earlier than expected.

The objectives of this study were to emphasize the importance of preoperative laryngeal examination before thyroidectomy by investigating the incidence of coincident abnormal laryngeal conditions that impair the quality of voice, and evaluate the usefulness of the "thyroidectomy-related voice questionnaire" as a screening tool.Five hundred consecutive patients scheduled to undergo thyroidectomy underwent preoperative laryngeal examination and voice analysis and completed the questionnaire. According to the laryngeal examination results, patients were classified into normal and abnormal groups. Acoustic-analysis results and questionnaire scores were compared between the two groups, and correlations between acoustic parameters and questionnaire scores were evaluated. The cutoff score of the questionnaire that can effectively discriminate between the two groups was also determined.The incidence of abnormal laryngeal conditions was 35.8%. The most common finding was laryngopharyngeal reflux (27.2%) followed by vocal nodule (4.8%), vocal polyp (1.8%), vocal cord palsy (1.2%), Reinke's edema (0.4%), vocal cyst (0.2%), and vocal sulcus (0.2%). The perceptual grade of voice quality (0.33 ± 0.49 for normal group vs. 0.65 ± 0.62 for abnormal group, P = 0.000) and the questionnaire scores (3.21 ± 5.47 for normal group vs. 13.41 ± 11.67 for abnormal group, P = 0.000) of the two groups were significantly different, and there was a significant correlation between objective voice parameters and questionnaire scores. A questionnaire score of 5 showed the best sensitivity (74%) and specificity (71%) in discriminating between the two groups.The incidence of coincident abnormal laryngeal conditions is relatively high; therefore, voice screening before thyroidectomy is important. The "thyroidectomy-related voice questionnaire" is a simple and effective screening tool to detect preexisting laryngeal disorders that can affect the quality of voice.