Improved functional recovery of denervated skeletal muscle after temporarysensory nerve innervation

Prolonged muscle denervation results in poor functional recovery after nerv e repair. The possible protective effect of temporary sensory innervation o f denervated muscle, prior to motor nerve repair, has been examined in the rat. Soleus and gastrocnemius muscles were denervated by cutting the tibial nerve, and the peroneal nerve was then sutured to the transected distal ti bial nerve stump either immediately or after two, four or six months. In ha lf of the animals with delayed repair, the saphenous (sensory) nerve was te mporarily attached to the distal nerve stump. Muscles were evaluated three months after the peroneal-to-tibial union, and were compared with each othe r, with unoperated control muscles and with untreated denervated muscles. A fter four to six months of sensory "protection", gastrocnemius muscles weig hed significantly more than unprotected muscles, and both gastrocnemius and soleus muscles exhibited better preservation of their structure, with less fiber atrophy and connective tissue hyperplasia. The maximum compound acti on potentials were significantly larger in gastrocnemius and soleus muscles following sensory protection, irrespective of the delay in motor nerve uni on. Isometric force, although less than in control animals and in those wit h immediate nerve repair, remained reasonably constant after sensory protec tion, while in unprotected muscles there was a progressive and significant decline as the period of denervation lengthened. We interpret these results as showing that, although incapable of forming e xcitable neuromuscular junctions, sensory nerves can nevertheless exert pow erful trophic effects on denervated muscle fibers. We propose that these fi ndings indicate a useful strategy for improving the outcome of peripheral n erve surgery. (C) 2001 IBRO. Published by Elsevier Science Ltd. All rights reserved.