Delay of the Denervation Process in Skeletal Muscle by Sensory Ganglion Graft and Its Clinical Application

We examined the effects of dorsal root ganglion isografts on the denervation process of skeletal muscle. A segment of sciatic nerve was removed from each of 25 inbred Wistar-Kyoto rats. Fifteen were set aside as controls. In the remaining 10 rats, isogeneic cervical dorsal root ganglia were grafted to the severed distal stump of the common peroneal nerve. Between day 72 and day 286 postoperatively, both controls and recipients were killed after twitch and tetanic tension recording of the extensor digitorum longus was performed. The wet muscle weight and the twitch and tetanic tensions of the denervated extensor digitorum longus in the graft group were significantly greater than those in the control group. The mean area of the denervated tibialis anterior muscle fibers in the graft group also was significantly larger than that in the control group. In electron and light microscopic images, nerve cells along the periphery of each dorsal root ganglion were found surviving with regenerating axons throughout the experimental period. Numerous myelinated axons were observed in the common peroneal nerve of the graft group, and there were significantly more axonal branches in the extensor digitorum longus of the graft group than in the extensor digitorum longus of the control group. Thus sensory nerve fibers from the grafted dorsal root ganglia had certain beneficial effects to slow the denervation process, presumably secreting trophic factors into the denervated muscle. Clinically, we have transferred avulsed dorsal root ganglia in cases of total brachial plexus avulsion directly into denervated skeletal muscle. This procedure, accompanied by nerve crossing procedures, will probably keep denervated skeletal muscle in a better condition until regenerating motor axons from the repair site reach their target muscle.