Functional Recovery of Denervated Skeletal Muscle with Sensory or Mixed Nerve Protection: A Pilot Study

Abstract

Functional recovery is usually poor following peripheral nerve injury when reinnervation is delayed. Early innervation by sensory nerve has been indicated to prevent atrophy of the denervated muscle. It is hypothesized that early protection with sensory axons is adequate to improve functional recovery of skeletal muscle following prolonged denervation of mixed nerve injury. In this study, four groups of rats received surgical denervation of the tibial nerve. The proximal and distal stumps of the tibial nerve were ligated in all animals except for those in the immediate repair group. The experimental groups underwent denervation with nerve protection of peroneal nerve (mixed protection) or sural nerve (sensory protection). The experimental and unprotected groups had a stage II surgery in which the trimmed proximal and distal tibial nerve stumps were sutured together. After 3 months of recovery, electrophysiological, histological and morphometric parameters were assessed. It was detected that the significant muscle atrophy and a good preserved structure of the muscle were observed in the unprotected and protective experimental groups, respectively. Significantly fewer numbers of regenerated myelinated axons were observed in the sensory-protected group. Enhanced recovery in the mixed protection group was indicated by the results of the muscle contraction force tests, regenerated myelinated fiber, and the results of the histological analysis. Our results suggest that early axons protection by mixed nerve may complement sensory axons which are required for promoting functional recovery of the denervated muscle natively innervated by mixed nerve.

IGF-1 potentiates sensory innervation signalling by modulating the mitochondrial fission/fusion balance

“…Sensory protection has been suggested as a promising technique when motor nerve repair is delayed or when injury occurs at a proximal point4. However, sensory protection is not sufficient to improve the functional recovery of long-term denervated SKM cells.…”

"Babysitting" procedures in proximal nerve trunk injuries: two case reports and a review

“…However, another consideration is that there is no consensus about the negative influence of sensate fibers. Some authors' [17,18] experience agrees with this last opinion, but several other and more recent experimental experiences [19][20][21][22] do not. In these studies, sensate fibers produce end-to-side regeneration and reinnervation of distal muscle.…”

Sensory protection to enhance functional recovery following proximal nerve injuries: current trends

“…Researchers have also used the end-to-side neurorrhaphy model to study the protective effects of mixed nerve containing both motor and sensory axons. The use of mixed nerve is supported by a recent study by Li et al [33] who compared muscle protection following denervation using the peroneal nerve (mixed protection) or sural nerve (sensory protection). They showed that both the mixed-and sensory-protected groups demonstrated preservation of muscle architecture and better functional recovery following reinnervation compared to the unprotected group.…”

“…Further, the investigators showed that mixed protection was superior to sensory protection in terms of axon structure (more regenerated myelinated axons, larger axonal diameter, thicker myelin sheath) and function (greater contraction force). [33] They controlled for stump reinnervation by the motor component of the mixed nerve by performing end-to-side coaptation and capping the end of the transected motor nerve. In contrast, another study by Michalski et al [27] reported no difference between mixed-and sensory-protected groups in terms of number of regenerating axons, axon diameter, and myelin cross-sectional area in the distal stump.…”

“…Without donor axon, disruption and injury to the recipient nerve, the neurotrophic signals stimulating Schwann cell proliferation and axonal sprouting through nerve bridges are substantially diminished. [33,36,37] As a result, few axons are available downstream for reinnervation or to provide trophic factors. Thus, compared to other techniques, side-to-side neurorrhaphy is a relatively inefficient technique for nerve reconstruction, and it does not result in clinically significant functional recovery or offer sufficient "protection" from muscle atrophy.…”