Observation of velopharyngeal closure patterns following isolated stimulation of levator veli palatini and pharyngeal constrictor muscles.

This study, using mongrel dogs, showed the individual movements caused by the levator veli palatini muscle (LVP) and pharyngeal constrictor (PC) contraction, induced by electrical stimulation to each peripheral motor nerve. Each bilateral peripheral motor nerve of the LVP and PC muscles was isolated and stimulated electrically to induce the individual contraction of bilateral LVP and PC muscles. The movements were visualized by use of a fiberscope. Vertical movement of the middle soft palate was observed mainly at LVP contraction. Circular closure in the posterior region of the velopharynx was induced by contraction of the PC muscle. The posterior and lateral wall movements clearly occurred following PC contraction.