Abstract
It has been reported that the levator veli palatini muscle of speakers with velopharyngeal incompetence tends to demonstrate muscle fatigue during connected speech. This study examined whether a speech aid prosthesis might reduce the levator muscle fatigue of such speakers.
Eight patients with postsurgical cleft palates served as subjects. Four of the subjects wore a palatal lift prosthesis; the other four wore a bulb-attached palatal lift prosthesis as a speech aid prosthesis. Each subject was asked to pronounce the syllable [p_??_] more than 50 times at a rate of one time per second. Mean power frequency (MPF) of one syllable was obtained from electromyography data of the levator muscle by power spectral analysis. The MPF regression line against the course of syllable repetition was calculated. We interpreted this regression slope as a sign of the degree of fatigue of the levator muscle.
The absolute value of the slopes of the regression lines with speech aid prosthesis were significantly smaller than those without speech aid prosthesis. That is, it was shown that the speech aid prostheses reduced the decrease in MPF during speech.
These results suggested that speech aid prostheses reduce the levator muscle fatigue of postsurgical cleft palate patients with velopharyngeal incompetence during connected speech and the effect is not dependent on the type of speech aid prosthesis worn by the speaker.
