An experimental model for complex dynamic control of the reinnervated face.

None of the standard approaches to facial paralysis has been able to reinstate active dynamic symmetry. This ultimate goal can be now envisioned by using the intact side as a source of information for mobilization of the impaired musculature along physiological principles. Facial expression results from intricate relationships between forces along different vectors which are exquisitely integrated by the central nervous system. When, for whatever reason, connections are severed between the midbrain facial nucleus and the muscles under its command, these missing circuits must somehow be reestablished. This entails both afferent and efferent connections, in lieu of proprioceptive input and motor output, both of which are indispensable to normal facial motility.