Activities of the muscles involved in swallowing in patients with cleft lip and palate.

This study was designed to examine the nature of the activity of swallowing muscles in patients with cleft lip and palate (CLP). The electromyographic activity of the thyrohyoid muscle (TH), the geniohyoid muscle (GH), and the myohyoid muscle (MH) of patients with CLP (CLP group) was analyzed and compared with noncleft subjects (control group) during swallowing and drinking water with and without artificial nasal obstruction. In the normal situation without nasal obstruction, a significant (p < 0.01) difference in muscle activity between the two groups was found only for TH. In the control group, the duration and magnitude of muscle activity were significantly (p < 0.01) larger in all the muscles when a nasal obstruction was applied. Meanwhile, in the CLP group these values exhibited a significant (p < 0.05) increase in GH and MH only. With nasal obstruction, the burst durations of GH and MH became significantly (p < 0.01) longer in the control group than in the CLP group. The amplitude of GH activity during swallowing was significantly (p < 0.05) larger in the control group than in the CLP group. These results suggest that in CLP patients during swallowing, TH working from the pharyngeal stage compensates for the weakness of GH and MH working in the oral phase. This may cause a premature transfer of the bolus to the pharynx before making it properly into the oral cavity.