Three-dimensional quantification of "still" points during normal facial movement.

This study investigated the 3-dimensional displacement of points on the face that were thought to be still during facial movement. These points are currently used to measure displacement of moving facial regions during assessment of normal facial movement and treatment interventions following facial nerve paralysis. It is, however, unknown if these places are "still" points. The Expert Vision Motion Analysis System was used to collect and analyze data on 42 normal subjects during facial movement. No point on the face was found to be still during facial expression. However, several points were present with very small movements for each individual expression. These were termed "reference" points. These small movements may be the result of system noise, physiological tremor, skin movement, or head-holder movement during facial expressions. Future studies of the displacement of the markers during facial movement in both normal subjects and patients with facial nerve paralysis may take into account the contribution of the "reference" point displacements to the overall facial movement.