Neuromuscular reinnervation efficacy using a YFP model

Introduction: The gold standard reconstruction for facial reanimation is the functional muscle transfer. The reinnervation of a muscle is never complete, and clinical results are variable with 20% not achieving a satisfactory outcome. We hypothesise that this may be due to a mismatch between the characteristics of the donor nerve and transferred muscle. Method: 81 YFP-16 and 14 YFP-H mice were studied in three intervention groups over three time periods. Two parameters were investigated: the number and surface area of reinnervated neuromuscular junctions and regenerating axons. An assessment was made of motor unit proportions. Results: All cases of nerve repair and nerve graft, the neuromuscular junctions (NMJ) were completely reinnervated by regenerating axons. The number and calibre of the regenerating axons were significantly different from controls for both intervention groups. The motor units were smaller in both intervention groups. Discussion: Reinnervation occurs after nerve repair or graft; however, the arbour was reinnervated by large numbers of much smaller axons. These axons showed some evidence of remodelling in the repair group, but not in the graft group. Neither group achieved the parameters of the control group. There were persistent qualitative changes to the morphology of both axons and junctions. Imaging documented both synkinesis and alterations that resemble those seen in ageing. Conclusion: Overall, the efficacy of reinnervation is very high with all NMJ reoccupied by regenerating axons. The way small axons are remodelled is different in the nerve repairs compared with the nerve grafts. Crown Copyright (C) 2020 Published by Elsevier Ltd on behalf of British Association of Plastic, Reconstructive and Aesthetic Surgeons. All rights reserved.

Automated summary

The study found that reinnervation occurs after nerve repair or graft, but the number and calibre of regenerating axons can vary, leading to smaller motor units. While all NMJ were reoccupied by regenerating axons, there were significant differences in the way small axons are remodelled between nerve repair and nerve graft groups.