Fine control of reinnervated muscle. Dynamic rehabilitation of facial paralysis.

Satisfactory rehabilitation of the paralyzed face has yet to be achieved. Ideally, both mobility and symmetry should be restored. In five rabbits, motion signals were picked up from the intact side by miniature strain gauges and channeled by means of an electronic circuit to electrodes placed around nerve pedicles previously implanted into the paralyzed side. An analog current produced in response to muscular contraction (afferent limb) resulted in graded and sustained contraction of the reinnervated side (efferent limb). In six animals, the tension of reinnervated strap muscles could be adjusted by varying the pulse width (0.1-10 msec) of a constant (0.5 mA) current applied to the nerve pedicles. Contraction (strain-gauge compression) of the intact face was followed by reciprocal graded relaxation of the reinnervated straps. Conversely, facial relaxation (elongation) induced graded strap contraction. An agonist-antagonist relationship was, thus, created between the two effectors. This approach may allow the paralyzed face to be electrically reanimated from the intact side in a symmetrical fashion closer to the physiologic state.