A Comparison of Four Selected Acoustic Measures in Detecting Voice Quality Changes With Botulinum Toxin Treatment in Adductor-Type Laryngeal Dystonia.

[PURPOSE] Adductor-type laryngeal dystonia (AdLD) is a voice disorder with substantial negative effects. The current standard treatment is botulinum toxin (BoNT) injections, with novel treatments on the horizon. The aim of this study was to determine the sensitivity of selected acoustic measures to measure voice quality change from pre-BoNT to the participants' perceived maximum benefit from BoNT.

[METHOD] Twenty-three participants with AdLD underwent acoustic recordings at pre-BoNT and a subset of 12 participants during the participants' perceived maximum benefit from BoNT. Four acoustic measures were employed: (a) cepstral peak prominence-smoothed (CPPS) estimated in Praat, (b) the cepstral spectral index of dysphonia (CSID), (c) percent creak (%creak), and (d) sharpness (a measure of vocal strain). The four measures were also compared with listener ratings and Voice Handicap Index (VHI-10) scores.

[RESULTS] The CPPS, CSID, and %creak measures showed significant treatment-related change ( < .001). Effect sizes were large for CPPS (.97) and moderate for CSID (.68) and %creak (.62). Correlations with listener ratings were strong for CPPS (-.66), moderate for CSID (.58) and %creak (.48), and very weak for sharpness (.19). Correlations with VHI-10 were moderate for CPPS (-.53), weak for %creak (.36) and CSID (.33), and very weak for sharpness (.19).

[CONCLUSIONS] Based on these results, CPPS, CSID, and %creak showed utility in assessing voice quality change from pre- to post-BoNT treatment in those with AdLD, with some differences across measures. Future research with novel treatments for AdLD may benefit from utilization of these measures including comparison of effect sizes with degree of improvement from BoNT outcomes.