Functional voice outcomes after thyroidectomy: an assessment of the Dsyphonia Severity Index (DSI) after thyroidectomy.

Background: The Dysphonia Severity Index (DSI) is an objective multiparametric acoustic calculation of vocal function; however, its changes after thyroidectomy have not yet been described.

Methods: Patient-reported symptoms, as well as auditory perceptual, acoustic, and videolaryngostroboscopic (VLS) data, were collected prospectively before and after thyroidectomy. Voice outcomes (normal versus negative voice outcome [NVO]) at 6 months after thyroidectomy were based on a combination of voice symptoms and objective findings. The DSI was assessed over the peri-operative course, and differences were determined with Wilcoxon signed rank tests. The DSI was compared between study groups (normal versus NVO) using t tests, analyses of variance (ANOVAs), or rank sum tests as appropriate. The predictive value of DSI for long-term voice dysfunction was assessed by an area under the receiver operating characteristics curve analysis. Correlations between DSI and Consensus Auditory Perceptual Ratings of Voice (CAPE-V) and the patient reported Voice Handicap Index (VHI) were determined with Pearson's correlation coefficients.

Results: In all, 62 patients were evaluated before, 1-4 weeks after, and 6 months after thyroidectomy. Eight (13%) patients were diagnosed with NVO at 6 months. The DSI was different postoperatively between NVO and normal voice (P=.005, repeated measures [RM]-ANOVA), with the NVO group demonstrating a lesser DSI value and greater change from pre-operative assessment at the first postoperative visit when compared with the normal group (P<.006 each). The DSI differed significantly for pre-operative and 6-month assessments according to sex, smoking status, and age. Short-term postoperative DSI (area under the curve [AUC]=0.795) and DSI change from baseline to 1-4 weeks (AUC=0.835) were highly predictive of 6-month NVO. DSI measurements over the post-thyroidectomy course were correlated poorly to moderately (maximum r = -0.62) with CAPE-V and VHI assessments for the same time points.

Conclusion: The DSI is decreased in the early post-thyroidectomy period, mostly in persons who were ultimately found to have a long-term NVO. Early postoperative DSI and change of DSI from baseline at 1--4 weeks postoperation predict long-term post-thyroidectomy voice dysfunction. The modest correlations between the DSI and other vocal assessments point to the utility of DSI as an independent predictor of voice dysfunction after thyroidectomy, which can select patients who may benefit from voice therapy.