We have recently demonstrated the feasibility of artificial agonist/antagonist coupling between intact facial and reinnervated strap muscles in the rabbit. The present study broadens this principle to involve bi-level cross-facial innervation. After severing the facial innervation unilaterally in four dogs, a nerve pedicle from a cervical motor nerve was implanted into the orbicularis oris and from the deep temporal nerve into the orbicularis oculi. After neurotization (5.6 months), the pedicles were electrically stimulated to verify muscular response. Graded contraction on the intact side was induced by stimulating the ipsilateral facial nerve with currents of various pulse widths. The resulting compression of a strain gauge on the intact face triggered a two-channel, opto-isolated, pulse width-modulated stimulator to produce agonistic graded contraction at one level of the reinnervated side (e.g., oral) and reciprocal relaxation in its reinnervated counterpart (e.g., ocular). The sophistication of the present model - as compared to the original pilot study - brings us one step closer to dynamic human facial rehabilitation.
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