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 provides high specificity and sensitivity capable of detecting evidence of regeneration early after injury.
Keywords: CMAPs; electrophysiology; nerve injury; peroneal nerve; tibialis anterior.
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