An Efficacy Study of Voice Quality Using Cepstral Analyses of Phonation in Parkinson's Disease before and after SPEAK-OUT!®.

Introduction: SPEAK-OUT!® is a behavioral treatment for hypokinetic dysarthria in persons with Parkinson's disease (PD) that has become an alternative to the gold-standard Lee Silverman Voice Treatment (LSVT) in recent years. Acoustic evaluation of the efficacy of SPEAK-OUT!® therapy has focused on prosody. The purpose of this study was to investigate SPEAK-OUT!® efficacy in terms of vocal quality and its impact on quality of life. Vocal quality was measured acoustically using cepstral peak prominence (CPP) analysis and the Acoustic Voice Quality Index (AVQI) and perceptually using clinical ratings of speech performance. Impact on quality of life was measured with the Voice Handicap Index (VHI) and Voice-Related Quality of Life (V-RQOL). An additional goal of this study was to investigate whether dysarthria severity and disease duration were predictive of changes in voice quality due to SPEAK-OUT!®.

Methods: Pre- and post-therapy data included PD participants' acoustic and perceptual ratings of audio recordings. Demographic data included age, sex, diagnosis, duration of PD, and severity of dysarthria.

Results: Participants achieved significant improvement in the vowel and sentence CPP smoothed (CPPS) mean score as well as in their AVQI score post SPEAK-OUT!® treatment. Improvements in AVQI correlated negatively with disease duration and positively with dysarthria severity.

Discussion/conclusion: SPEAK-OUT!® is effective in improving voice quality in patients with hypokinetic dysarthria due to idiopathic PD. Patients with more severe dysarthria and with a shorter disease duration may benefit the most, supporting earlier intervention. As for the type of measurement, AVQI combines acoustics from both vowel and sentence contexts and may therefore be the measure of choice over CPPS (vowel) or CPPS (sentence).