Roles of the Facial, Glossopharyngeal and Vagus Nerves in Velopharyngeal Movement

Abstract

The present study was designed to clarify the role of the motor nerves in velopharyngeal movements, Experiments were carried out on 15 anesthetized rhesus monkeys on the assumption that their velopharyngeal structures are similar to those of human beings. The pattern and degree of velopharyngeal movements with stimulation to the facial, glossopharyngeal, and vagus nerves in the petrosal area were analyzed by means of fiberscopic observations. The results obtained were as follows: 1. Velopharyngeal movements were most active with stimulation to the vagus, then the glossopharyngeal, and, finally, the facial nerve. 2. Complete closure by unilateral stimulation was elicited only by the vagus nerve and not the facial or glossopharyngeal nerves. 3. The pattern of velopharyngeal movements observed when stimulating the facial nerve was quite different from those seen when the glossopharyngeal or the vagus nerve was stimulated That is, movements in a plane at the upper part of the nasopharynx were observed on stimulating the facial nerve while upward movements from all of the velopharyngeal structures were seen when the glossopharyngeal or vagus nerve was stimulated. 4. Combined stimulation to the nerves sometimes resulted in additive effects on velopharyngeal movements, but these could be recognized in only a few cases. This study reveals that the motor nerves innervating the velopharyngeal muscles play different roles in velopharyngeal movements.