Microsurgery: Transplantation and Replantation by Harry J. Buncke, MD, et al.
  Table of Contents / Chapter 22:
Facial Paralysis
  The ultimate goal of all surgery for the correction of facial paralysis is the restoration of spontaneous animation and the creation of a balanced, natural smile. This can be accomplished only by reinnervating the paralyzed muscles with seventh-nerve fibers from the same side, proximal to the level of injury or from the opposite seventh nerve when ipsilateral repair is not possible. The reconstruction of the surgically or traumatically injured seventh nerve with interpositional autogenous grafts is the most physiologic approach and can be performed extracranially 1 or, less often, intracranially to extracranially.2,3 Such grafts must be inserted early because the degree of facial muscle functional return is inversely proportional to the period of denervation and the age of the patient. After a year of paralysis, the muscles seldom reinnervate1,4 and other approaches have to be used. Smith 5 and Anderl 6 were the first to attempt reinnervation of the paralyzed facial muscles with grafts from the uninvolved opposite side. Because it takes 6 to 8 months for axons to go through the crossfacial nerve graft, the window for success becomes narrower with the passage of time. Even if such crossfacial nerve grafts fail, they can still be used to innervate muscles transplanted to the paralyzed side, provided axon regeneration has occurred through the graft.7 Frozen section biopsies of the crossfacial nerve graft at the time of contemplated muscle transplantation can confirm the intraneural anatomy and the existence of new axons.8  

Other nerves from the same side as the injury have been transferred to the distal facial nerve to reinnervate the muscles. These include the hypoglossal,9,10 the lingual,11 the phrenic,12,13 the greater auricular,14 the spinal accessory,15,l6 and the ansa- hypoglossal.17,18 Muscle contraction, however, is not spontaneous and a synthetic smile must be learned and practiced. These nerve transfers do preserve the end plates and muscle bulk and can serve as "baby tenders" if a crossfacial nerve graft is considered later.l9 Other experimental techniques using implanted electrodes have been used with some promise to preserve the facial muscle bulk and contractility.20-22

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