Eustachian tube cartilage and medial movement of lateral pharyngeal wall on phonation.

Several authors have demonstrated the importance of medial movement of the lateral pharyngeal wall in velopharyngeal closure upon phonation. However, it remains controversial what muscle is responsible for lateral pharyngeal wall movement and where is the main site of this movement. The purpose of this study was to address the above two unanswered questions. In 22 subjects (12 normal volunteers, 10 patients with cleft palate), lateral pharyngeal wall movement upon phonation was evaluated by using rapid magnetic resonance imaging (MRI). Before rapid MRI, their lateral pharyngeal wall movements were classified into three groups: the poor, moderate, and good, according to the findings of nasopharyngoscopy. Inward displacement of the eustachian tube cartilages upon phonation, which was quantified as distance ratio in the transverse plane of MR images, was compared with nasopharyngoscopic findings. In addition, the level of lateral pharyngeal wall movement was observed in the plane 5 mm lateral to the mid-sagittal plane of MR images. Inward displacement of the eustachian tube cartilage in the transverse plane of MR images was coincident with medial movement of lateral pharyngeal wall observed by nasopharyngoscopy in all 22 subjects. By using one-way analysis of variance, a statistically significant correlation was found between nasopharyngoscopic classification and distance ratio. The sagittal plane of MR images revealed that the main site of movement occurred at the level of the hard palate and above. It is concluded that medial movement of the lateral pharyngeal wall consists of inward displacement of the eustachian tube cartilage, which is caused by contraction of the levator veli palatini muscle, and that the primary site of this movement is at the level of the hard palate and above, where the eustachian tube, but not the superior constrictor muscle, exists.