A Pilot Study of Muscle‐Nerve‐Muscle Grafting for Facial Reanimation in Rats

Abstract

Objectives: (1) Describe the muscle-nerve-muscle (MNM) reinnervation technique, which involves implanting a graft to serve as a conduit between an innervated donor muscle and a denervated recipient muscle. (2) Analyze the effects of MNM reinnervation with and without electrical stimulation and exogenous testosterone on functional recovery following rat facial nerve injury. Methods: A prospective controlled animal study. Facial nerve branches to the whisker pads of 24 adult male Sprague Dawley rats were harvested and each rat was then randomly assigned to 1 of 3 treatment groups of 8 rats each: no graft (control), MNM grafting alone (MNM), or MNM grafting + electrical stimulation (ES) and testosterone propionate (TP) (MNM+). MNM grafts were implanted from the functioning to the nonfunctioning whisker pads in the experimental groups. One experimental group underwent an ES and TP protocol. Whisker movement was assessed by behavioral observations, electromyographic recordings, and video analysis. Results: Recovery of coordinated movement was displayed at 16 weeks by 0% of the control animals, 71% of the MNM animals, and 85% of the MNM+ animals. Electromyographic recordings demonstrated electrical conductance across grafts in both MNM and MNM+ animals. Histologic analysis of the MNM grafts demonstrated growth of myelinated fibers across nerve grafts in both MNM and MNM+ animals. Conclusions: This study demonstrated not only that reinnervation following MNM grafting can improve tone and movement in a selected muscle following a facial nerve injury, but also that therapy with electrical stimulation and exogenous gonadal steroids further enhances the recovery of these functional measures.