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.
['Woollard|A C S|ACS|', 'Lichtman|J W|JW|', 'Rolfe|K|K|', 'Grobbelaar|A O|AO|']
D000818:Animals D001369:Axons D005152:Facial Muscles D051379:Mice D009046:Motor Neurons D009416:Nerve Regeneration D009417:Nerve Tissue D016067:Nerve Transfer D009431:Neural Conduction D009469:Neuromuscular Junction D012107:Research Design D013518:Surgery, Plastic D046608:Synkinesis D016378:Tissue Transplantation
YFP Synkinesis Nerve regeneration Targeted muscle reinnervation