Objectives: The aim was to compare voice outcomes over time in patients treated with Imitation Model voice therapy and Verbal Instructions Model voice therapy.
Methods: A prospective clinical trial was performed with 56 consecutive patients diagnosed with a primary or secondary functional voice disorder. Thirty-one patients were included for voice therapy following the Imitation Model and 25 patients for the Verbal Instructions Model. Assessments included a self-rated Voice Handicap Index, self-perceived hoarseness and vocal fatigue, perceptual voice evaluation by a Speech Language Pathologist, and maximum Voice Range Profiles. All assessments were completed before therapy, at end of therapy, at six-months posttherapy follow-up and 12-months posttherapy follow-up. For maximum Voice Range Profiles group differences were also compared for effects from end-of-treatment to follow-up assessments. Linear mixed models were used for analysis.
Results: Comparison between treatment groups showed significantly larger long-term improvement from the baseline, for verbal instructions model as compared to imitation model for Voice Handicap Index total, and also the physical and emotional subscales, while there was no difference between groups for the functional subscale. Also, voice quality improved more after verbal instructions model, as compared to imitation model, at end of therapy. Results from self-rated hoarseness and vocal fatigue showed no difference between groups. There was no difference between treatment groups in the change of maximum Voice Range Profile from end-of-treatment to follow-up assessments.
Conclusions: The study showed that both Imitation Model voice therapy and Verbal Instructions Model voice therapy improved voice function. Compared to Imitation Model, the Verbal Instructions model showed larger long-term effect on physical and emotional aspects of voice function in everyday life. The two approaches for voice therapy might have different impacts on patients’ learning.