Effects of the Lee Silverman Voice Treatments (LSVT) on prosody in speakers suffering from Parkinson's disease

Background: Dysarthrophonia in speakers suffering from Parkinson's disease affects all parameters of speech and is not easily influenced by medication or surgery. The Lee Silverman Voice Treatment (LSVT) was developed specifically to target hypokinetic dysarthrophonia. It has not yet been investigated whether the LSVT influences intonation patterns of speech. Methods: Using a single case Study design, a female and two males suffering from idiopathic Parkinson's disease were treated with a word finding placebo therapy prior to application of the LSVT. 18 test sentences (6 neutral declaratives, 6 neutral questions, 6 angry utterances) were investigated acoustically. Intonation patterns were transcribed, the timing of maximum fundamental frequency (F0) in relation to the accented syllable was described and the rise in F0 was measured oil the basis of narrow-band spectrograms. Participants also underwent laryngoscopic and stroboscopic examination. Speech rate, maximum intensity, maximum phonation time, minimum and maximum F0, intelligibility, and naturalness were also monitored. Results: Few unequivocal effects were observed. After LSVT treatment speakers produced more pronounced intonation patterns in neutral utterances, increased the number of peaks in angry utterances, aligned the F0 maximum more often to the stressed syllable in angry utterances and produced higher F0 rises in neutral Utterances. The laryngoscopic and stroboscopic investigations revealed high variability within subjects. One speaker improved in maximum phonation time. The other maximum performance measures and intelligibility were not influenced by the LSVT, mainly due to ceiling effects. Conclusions: The participants of this study showed fewer differences to unaffected speakers in the parameters measured than was expected. This may be due to the discrepancy between spontaneous speech and read sentences observed in hypokinetic dysarthria. The study discusses ways in which speech parameters might influence each other.