The correlation between compound nerve action potential and the number of the regenerated nerve fibers

Objective To explore the correlation between compound nerve action potential and the number of regeneratod nerve fibers in rat median nerve at the different time points after transection and repair.Methods The rat median nerve was transected at mid-upper arm level and repaired with six types of sutures.Compound nerve action potentials (CNAPs) were recorded 2 or 8 weeks postoperatively and its parameters analyzed.Median nerve samples from normal nerves,proximal to suture site and distal to suture site were harvested and fixed. Semi-thin sections were stained with toluidine blue, luxol fast blue and immunohistochemistry staining.Myelinated nerve fiber counts were obtained.Finally,the correlation between CNAP parameters and the number of regenerated nerve fibers was analyzed by linear regression analysis method.Results CNAP could be recorded at 2 and 8 weeks after nerve repair.CNAP amplitude and area were significantly lower than those of the control group ( P ＜ 0.01).The recovery rates of myelinated nerve fiber count among the various suture groups were significantly different ( P ＜ 0.05).CNAP amplitude and tbe myelinated nerve fiber count had a linear correlation.The linear fitting line equation was y =250.859x + 27.826 for 2-week data and y =265.584x + 2721.462 for 8-week data. Conclusion There is a positive linear correlation between CNAP amplitude and myelinated nerve fiber count at the early regeneration period and the maturation period following median nerve transection and repair.And the slope of the linear equation fitted between CNAP amplitude and myelinated nerve fiber count was similar,except for the different intercepts.The number of myelinated nerve fibers distal to the injury and repair site can be calculated via CNAP amplitude using the linear regression equation,thus the extent of injury and regeneration can be estimated. Key words: Median nerve;  Electrodes;  Amplitude;  Compound nerve action potential; Myelinated nerve fiber count