抄録
The purpose of this study was to examine whether the levator veli palatini muscle (LVP) in patients with velopharyngeal incompetence who have undergone surgery for cleft palate is more easily fatigued than that of normal subjects during speech. Five patients with postsurgical cleft palate who were identified to have borderline velopharyngeal incompetence on nasopharyngeal fiberscopy were studied. Five normal subjects served as control. Each subject was asked to pronounce/pu/more than 50 times at a rate of one time per second. Electromyograms (EMG) of the LVP were recorded at a sampling rate of 2000/sec. The mean power frequency (MPF) of one syllable was obtained by power spectral analysis with an analytic window 1 second in width. In all normal subjects, the slopes of the regression line relating the MPF of the LVP EMG to the syllable number were slightly, but not significantly negative. However, in all patients with borderline velopharyngeal incompetence, the slopes of the regression line were significantly negative. These findings revealed that the LVP of speakers with borderline velopharyngeal incompetence was more easily fatigued than that of normal speakers during repetition of syllables. This study suggests that the fatigability of the LVP might be one cause of borderline velopharyngeal incompetence after surgery in patients with cleft palate.
