Intervention Outcomes of Two Treatments for Muscle Tension Dysphonia: A Randomized Controlled Trial

Purpose The aim of this study was to test the hypothesis that stretch-and-flow voice therapy (SnF) is noninferior to resonant voice therapy (RVT) for speakers with muscle tension dysphonia. Method Participants with primary muscle tension dysphonia were randomly assigned to 1 of 2 treatment groups. Participants received 6 sessions of either SnF or RVT for 6 weeks (1 session per week). Pretreatment and posttreatment audio recordings of sustained vowels and connected speech were acquired. Response to treatment was assessed using the voice handicap index (VHI) as the primary outcome measure. Secondary outcome measures included the acoustic voice quality index, the smoothed cepstral peak prominence, and scales from the Consensus Auditory-Perceptual Evaluation of Voice instrument. Data were analyzed for 21 participants who completed the study (12 in the SnF group, 9 in the RVT group). Results Direction of change for the primary outcome measure and all 3 secondary outcome measures at posttreatment was in the direction of improvement for both SnF and RVT. Confidence intervals for VHI measures did not cross the null effect line on forest plots, suggesting significant effects for both treatments on the primary outcome measure. The effect sizes for pretreatment to posttreatment changes in VHI were large for both treatment groups. Similar results were found for the secondary acoustic outcome measures. There were statistically significant pretreatment to posttreatment changes in the primary and secondary outcome measures for patients receiving both treatments, indicating significant improvement in response to both RVT and SnF. There were no statistically significant differences in pretreatment to posttreatment changes in the primary outcome measure or any secondary outcome measure between the two groups. The within-group pretreatment to posttreatment changes in Consensus Auditory-Perceptual Evaluation of Voice scales did not reach statistical significance for either RVT or SnF. Conclusions Both SnF and RVT produced positive treatment response in speakers with muscle tension dysphonia, with no statistically significant difference in the outcome measures between the two treatments. This suggests that SnF is noninferior to RVT and that both are effective options for treating vocal hyperfunction. Results from this study also support previous findings documenting the sensitivity of multidimensional acoustic measurements to treatment response.