MOTOR-NERVE TRANSPLANTATION

The motor nerve transplantation (MNT) technique is used to transfer an intact nerve into a denervated muscle by harvesting a neurovascular p edicle of muscle containing motor endplates from the motor endplate zo ne of a donor muscle and implanting it into a denervated muscle. Thirt y-six adult New Zealand White rabbits underwent reinnervation of the l eft long peroneal (LP) muscle (fast twitch) with a motor nerve graft f rom the soleus muscle (slow twitch). The right LP muscle served as a c ontrol. Reinnervation was assessed using microstimulatory single-fiber electromyography (SFEMG), alterations in muscle fiber typing and grou ping, and isometric response curves. Neurofilament antibody was used f or axon staining. The neurofilament studies provided direct evidence o f nerve growth from the motor nerve graft into the adjacent denervated muscle. Median motor endplate jitter was 13 mu sec preoperatively, an d 26 mu sec at 2 months, 29.5 mu sec at 4 months, and 14 mu sec at 6 m onths postoperatively (p < 0.001). Isometric tetanic tension studies s howed a progressive functional recovery in the reinnervated muscle ove r 6 months. There was no histological evidence of aberrant reinnervati on from any source outside the nerve pedicle. Isometric twitch respons es and adenosine triphosphatase studies confirmed the conversion of th e reinnervated LP muscle to a slow-type muscle. Acetylcholinesterase s tudies confirmed the presence of functioning motor endplates beneath t he insertion of the motor nerve graft. It is concluded that the MNT te chnique achieves motor reinnervation by growth of new nerve fibers acr oss the pedicle graft into the recipient muscle.