Abstract
This study is an investigation of the efficacy of voice therapy for patients with Parkinson's disease. Intensive voice therapy designed to target the underlying laryngeal and respiratory patho-physiologies accompanying disordered speech in patients with idiopathic Parkinson's disease was administered to 40 patients; 12 patients served as control subjects. Microphone recordings were made of all subjects before and after therapy or at one month intervals in order to measure the following variables: maximum duration sustained vowel phonation (seconds), maximum fundamental frequency range (ST), mean fundamental frequency (Hz) and fundamental frequency variability (STSD) in reading, and forced and slow vital capacities (L). In addition, subjects, spouses and speech pathologists made perceptual ratings of the subjects before and after treatment. Statistically significant differences (p less than .05) were measured on the following variables after therapy in the treated group: maximum duration sustained phonation, maximum fundamental frequency range, mean fundamental frequency and fundamental frequency variability in reading. No statistically significant differences on these variables were measured in the control group. Corresponding changes in the perceptual variables of loudness, monotonous speech and intelligibility were measured as well. These findings support the effectiveness of intensive voice therapy for patients with Parkinson's disease and should be viewed as an initial step in documenting treatment effectiveness in this population.

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