Effect of placement of a speech appliance on levator veli palatini muscle activity during blowing

We have observed clinically that some speakers wearing a speech appliance for correction of velopharyngeal incompetence can blow with variable intensity without nasal air escape. This clinical finding suggests that tightness of velopharyngeal closure may be regulated in accordance with oral air pressure during blowing. The purposes of this electromyographic study were (1) to examine whether levator vell palatini muscle activity can be changed in relation to oral air pressure during blowing when the speech appliance is removed, (2) to clarify whether or not the change is related to the severity of velopharyngeal incompetence, and (3) to examine whether placement of a speech appliance can alter levator muscle activity into the equivalent of that of normal speakers during blowing.

Eight patients with repaired cleft palate, who routinely wear a palatal lift prosthesis (PLP) or a hybrid speech appliance of a pharyngeal bulb and palatal lift (bulb-PLP), served as subjects. Subjects were classified into one of two groups according to their speech appliance (PLP group and bulb-PLP group). Electromyography of the levator veli palatini muscle was recorded with a speech appliance in place and then with the speech appliance removed as the subject blew through a tube at three different effort levels.

In the removed condition, the change in levator activity in relation to oral air pressure was variable across subjects in the bulb-PLP group, whereas levator activity changed in relation to oral air pressure change for all subjects in the PLP group. However, levator activity changed in relation to oral air pressure with either speech appliance in place for all subjects irrespective of their speech appliance types.

The severity of velopharyngeal incompetence might be related in part to change in levator activity in association with oral air pressure. The effect of a speech appliance to correct velopharyngeal incompetence might consist not only of mechanical obturation of the velopharynx but also of alteration of velopharyngeal function to become similar to normal speakers. Moreover, it is likely that the velopharyngeal system could be well regulated so as to exhibit a consistent outcome of velopharyngeal function.