EFFECT OF DELAY OF INNERVATION ON RECOVERY OF MUSCLE AFTER NERVE LESIONS

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Abstract
The recovery of muscle, as indicated by onset and degree of motor function and by the changes of muscle fiber size and wt., has been studied after immediate re-innervation following crushing, after delayed re-innervation achieved by repeated crushing, and after immediate and delayed re-innervation following suture of the peroneal nerve. After a single crush the original fiber size and wt. were recovered about 12 weeks after the onset of functional recovery, i.e., about 5 months after crushing the nerve. Increase of collagenous tissue due to denervation was reversible. After periods of de-nervation of 6 and 8 months, the onset of functional recovery was only slightly delayed. However, the degree of recovery of function was clearly deficient. The recovery of muscle fiber size and wt. was only slightly impaired even after a delay of re-innervation of 8 months. Repeated recoveries and longer periods of denervation have been achieved by successively crushing the nerve at intervals of 3 months. Six and 8 successive recoveries were observed and the functional recovery became progressively worse. Recovery of muscle fiber size and wt. was clearly deficient. Recovery of muscle fiber size after delayed suture was more defective than after delayed re-innervation following nerve crushing. It is concluded that up to a period of 8 months of denervation, the poor degree of functional recovery following re-innervation is due to deficient maturation of the nerve fibers and to deficiency of the newly formed contact between nerve and muscle fibers. After longer periods of denervation, recovery of muscle fibers becomes more deficient, the degree of muscle atrophy being then apparently the decisive factor in limiting functional recovery.