Intraoperative electrophysiological studies to predict the efficacy of neurolysis after nerve injury-experiment in rats.

Compound muscle action potentials (CMAPs) can be used to analyze injury and recovery of nerve. This standardized study evaluates the value of CMAP analysis in predicting the long-term efficacy of neurolysis. CMAP amplitude is also used to determine the optimal extent of neurolysis. The left peroneal nerves of 30 rats were crushed. CMAPs were recorded for both crushed (left) and control (right) nerves. Fifteen rats underwent neurolysis 3 months post crush injury; the remaining 15 were sham controls and did not undergo neurolysis. CMAP measurements were taken after: (1) release of the nerve from the fascia, (2) opening the epineurium, and (3) opening the perineurium. At 3 months post crush injury, opening the epineurium resulted in a statistically significant increase in CMAP. CMAP increase with perineurial neurolysis was greater than with fascial release of the nerve but was not statistically different from that of epineurial release. At 5 months post crush injury, recovery of crushed nerves that underwent neurolysis was 90% and significantly less at 70.5% in rats not treated with neurolysis, according to CMAP analysis. Two conclusions can be made from this study. First, intraoperative neurophysiologic studies can monitor the immediate results of neurolysis and predict long-term results in the injured nerve. Second, epineurotomy is important in neurolysis, improves the function of the nerve, less invasive, and a slightly more effective technique than perineurotomy.