Cross-Facial Nerve Grafting for Facial Reanimation: Effect on Normal Hemiface Motion

 

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ABSTRACT

Reinnervation of the paralyzed hemiface with a cross-facial nerve graft (CFNG) requires division of facial nerve branches on the normal hemiface to serve as axon donors. There is therefore concern about whether any impairment of normal hemiface motion occurs in the postoperative period. To minimize the likelihood of donor-side impairment, donor branches are chosen from the bucco-zygomatic region which has extensive cross branching, as opposed to the single temporal or marginal mandibular branches.

This study chose to determine quantitatively if this practice does, in fact, adversely affect the normal side hemiface motion governed by these branches, viz., eye closure, pucker, and smile. Since surgical procedures near the facial nerve (such as superficial parotidectomy) may leave the patient with transient facial weakness, even in the absence of nerve transection, the hypothesis was that hemiface motion would be impaired on the donor side during the early postoperative period (first month) secondary to edema and/ or neuropraxia. However, based on the clinical observation that donor-side facial motion is not demonstrably impaired late after surgery, a further hypothesis was that any early facial motion impairment would return to normal by 3 months postoperatively.

Seven patients underwent sural CFNG as a primary or secondary component of their facial animation procedure. Their facial motion was quantified preoperatively and in serial postoperative examinations using the Maximal Static Response Assay (MSRA) of facial motion.

Careful selection of redundant bucco-zygomatic branches of the facial nerve on the normal side for CFNG did not ultimately (≥ 3 months postoperative) impair the important motions of eye closure, smile, or pucker. Early postoperative (≤ 1 month) weakness of the smile was seen on both X and Y axes, indicating that both the risorius and zygomatic muscles were transiently weakened. The ability to elevate the lower eyelid was unaffected at any postoperative time point. Movement of the normal hemiface did not appear to be permanently affected by CFNG when a careful choice of redundant bucco-zygomatic donor branches was made.