New velopharyngeal measurements at rest and during speech: implications and applications

To make proper management decisions, it is important to understand the cause of velopharyngeal inadequacy (VPI) in individual patients. Previous studies suggest that abnormal velar and pharyngeal structures as well as their ratios may contribute to VPI after primary palatal repair in some patients. The aim of the current study was to develop a new protocol to evaluate the velopharyngeal (VP) mechanism and the levator veli palatini muscles at rest and during speech production. A secondary goal was to investigate the correlations among VP measurements and craniofacial structures that may predict velopharyngeal motions during speech production.

Seventeen healthy adults were scanned with magnetic resonance imaging (MRI) techniques. Multiple MRI scans covered the craniofacial region, the VP mechanism, and the levator veli palatini muscles at rest and during sustained phonations of /a/, /i/, /z/, /m/, and /f/. Measurements of craniofacial and VP structures at rest and during speech productions were obtained using image analysis software.

The maximal effective VP ratio, maximal pharyngeal constriction ratio, maximal velar stretch ratio, maximal velar height, and maximal levator shortening ratio were selected to represent the functional properties of the VP mechanism. The following predictors were found to partially explain the variances of corresponding measurements: rest effective VP ratio for the maximal effective VP ratio, maximal pharyngeal constriction for the maximal pharyngeal constriction ratio, and rest and maximal effective VP ratios for the maximal velar stretch. These predicting effects had implications in VP surgery and in understanding VP physiology.

This study developed a practical imaging protocol to measure the VP mechanism at rest and during speech productions. New measurements such as the effective VP ratio, pharyngeal constriction ratio, velar stretch ratio, and levator shortening ratio may help to identify the cause of persistent VPI after palatal repair. Implications on the VP surgery were discussed.