Effects of the Number of Muscle-Nerve-Muscle Grafts on Rat Facial Nerve Functional Recovery

Introduction: Facial nerve denervation can be devastating for patients. Primary neurorrhaphy and interposition (IP) nerve grafting are common reinnervation techniques. Muscle-nerve-muscle (MNM) grafting is a lesser known alternative. After previously demonstrating significant return of function using MNM grafting in a rat facial nerve model, the authors compare the use of multiple MNM nerve grafts with that of single MNM and IP nerve grafts. Methods: Thirty-six male rats were randomized into 4 groups: (1) repair with IP grafts, (2) 1 MNM graft, (3) 3 MNM grafts, and (4) control with no intervention. All groups had the lower zygomatic, buccal, and marginal mandibular branches of the right facial nerve removed. Return of movement and snout symmetry was measured over 16 weeks. Axonal regeneration and muscle atrophy were assessed and quantified. Results: All intervention groups had significantly improved movement and snout symmetry compared with control. Rats in the IP group had significantly increased axon density compared with those in the MNM groups but with smaller axonal diameter than control rats. No difference in axon density or diameter was observed between MNM groups. Use of 3 MNM grafts and IP grafts resulted in preservation of similar muscle mass compared with the control and 1-MNM groups. Conclusion: MNM grafting may be an alternative when other reanimation techniques are not possible. Level of Evidence: NA.