AXIAL CONFIGURATION OF THE VELOPHARYNGEAL VALVE AND ITS VARYING MECHANISM

The variability of the normal velopharyngeal (VP) closure mechanism wa s studied by investigating VP anatomy in relation to its closure mecha nism in 60 patients. The axial configuration of the VP isthmus, as obs erved in axial CT scans at rest, was found to be correlated with VP fu nction in terms of its closure patterns in speech as observed by nasen doscopy, A flat VP isthmus was found to be closed mainly in the antero posterior direction, forming the coronal closure pattern, A deep VP is thmus is closed by movement of the velum and medial movement of the la teral pharyngeal walls, forming the circular closure pattern, A flat V P isthmus occurs when the hamuli are posteriorly located and the muscu lar slings, therefore, open more posteriorly. We conclude that posteri or insertion of the velar muscles on to the skull base results in a fl atter, larger VP axial configuration, whereas an anterior insertion re sults in a VP axial configuration that is deeper and less flat, A flat VP isthmus contracts mainly in an anteroposterior direction, exhibiti ng a coronal closure pattern, while a deep or round VP isthmus contrac ts centripetally, exhibiting a circular closure pattern, Variability o f the VP valving mechanism is of anatomic and not of functional origin .