The effects of graft source and orientation on outcomes after ablation of a branched peripheral nerve

Electrode configurations for sensitive and specific detection of compound muscle action potentials to the tibialis anterior muscle after peroneal nerve injury in rats

BACKGROUND

Quantifying peripheral nerve regeneration via electrophysiology is a commonly used technique, but it can be complicated by spurious electrical activity. This study sought to compare electrode configurations for measuring compound muscle action potential (CMAP) of the tibialis anterior (TA) muscle in a rat model for specific and sensitive detection of regeneration of peroneal nerve to the TA.

NEW METHOD

10 Sprague-Dawley rats underwent a peroneal nerve transection with direct microsuture repair. CMAPs were conducted with different placements and types of electrodes. Compound action potentials (CAPs) and gait analysis were regularly collected up to 70 days (d) post operation (PO). Nerve sections were harvested at 49 d (n = 4) and 70 d (n = 6) PO and stained with toluidine blue to assess nerve morphometry.

RESULTS

Of the tested configurations for CMAPs, a concentric recording/reference electrode in combination with stimulation from the sciatic notch showed the least background and highest sensitivity, while some configurations showed significant noise and did not detect changes in CMAPs within the 70 d recording period following injury. CAPs, gait analysis, morphometry, and muscle mass support the extent of regeneration indicated by CMAPs collected with concentric electrodes.

CONCLUSION

Collateral innervation patterns can complicate CMAP recordings as signals from adjacent muscles can be detected and misinterpreted as regeneration. The outcome of this study shows how differences in configurations and electrodes have significant effects on CMAP for the TA. The results identify methods using concentric electrodes that provide high specificity and sensitivity capable of detecting evidence of regeneration early after injury.

Repair and regeneration of peripheral nerve injuries that ablate branch points

The peripheral nervous system has an extensive branching organization, and peripheral nerve injuries that ablate branch points present a complex challenge for clinical repair. Ablations of linear segments of the PNS have been extensively studied and routinely treated with autografts, acellular nerve allografts, conduits, wraps, and nerve transfers. In contrast, segmental-loss peripheral nerve injuries, in which one or more branch points are ablated so that there are three or more nerve endings, present additional complications that have not been rigorously studied or documented. This review discusses: (1) the branched anatomy of the peripheral nervous system, (2) case reports describing how peripheral nerve injuries with branched ablations have been surgically managed, (3) factors known to influence regeneration through branched nerve structures, (4) techniques and models of branched peripheral nerve injuries in animal models, and (5) conclusions regarding outcome measures and studies needed to improve understanding of regeneration through ablated branched structures of the peripheral nervous system.