Levator Veli Palatini Muscle Fatigue during Phonation in Speakers with Cleft Palate with Borderline Velopharyngeal Incompetence

Abstract

Objective This study examined whether the levator veli palatini muscle in speakers with borderline velopharyngeal incompetence (BVP) with surgically treated cleft palate might be more fatigable during speech than that in speakers without clefts. Design Each subject was asked to pronounce the syllable /pu/ more than 50 times at a rate of one time per second. Mean power frequency (MPF) of one syllable was obtained from electromyogram data of the levator muscle by power spectral analysis. Participants Five patients with postsurgical cleft palates, who were identified as having BVP by nasopharyngeal fiberscopy, served as subjects, and five participants without clefts served as the control group. Results In all participants without clefts, the slopes of the regression line relating MPF to the course of syllable repetition were negative but not significant. However, in all participants with BVP, the slopes of the regression line were significantly negative. Conclusions These findings demonstrated that the levator muscle of speakers with BVP was more fatigable than that of speakers without clefts during repetition of syllables. This study suggests that the fatigability of levator muscle contributed to mild hypernasality in patients with BVP.