Axial configuration of the velopharyngeal valve and its valving mechanism.

The variability of the normal velopharyngeal (VP) closure mechanism was studied by investigating VP anatomy in relation to its closure mechanism in 60 patients. The axial configuration of the VP isthmus, as observed in axial CT scans at rest, was found to be correlated with VP function in terms of its closure patterns in speech as observed by nasendoscopy. A flat VP isthmus was found to be closed mainly in the anteroposterior direction, forming the coronal closure pattern. A deep VP isthmus is closed by movement of the velum and medial movement of the lateral pharyngeal walls, forming the circular closure pattern. A flat VP isthmus occurs when the hamuli are posteriorly located and the muscular slings, therefore, open more posteriorly. We conclude that posterior insertion of the velar muscles on to the skull base results in a flatter, larger VP axial configuration, whereas an anterior insertion results in a VP axial configuration that is deeper and less flat. A flat VP isthmus contracts mainly in an anteroposterior direction, exhibiting a coronal closure pattern, while a deep or round VP isthmus contracts centripetally, exhibiting a circular closure pattern. Variability of the VP valving mechanism is of anatomic and not of functional origin.