Electrophysiologic findings and grip strength after nerve injuries in the rat forelimb

We developed electrophysiologic methods for testing the three major forelimb nerves as a tool to evaluate motor and sensory recovery in rats. Median, ulnar, or radial nerves were transected and repaired in Sprague-Dawley rats. Compound muscle action potentials (CMAPs) and somatosensory evoked potentials (SSEPs) were recorded preoperatively and at various postoperative intervals. Correlation between grip strength and CMAPs was investigated. Reliable CMAPs were recorded for all three nerves. Median- or ulnar-nerve-derived SSEPs were reliably recorded; radial SSEPs could not be recorded. CMAPs followed typical regeneration patterns after nerve repair. SSEPs showed a consistent peak latency but fluctuating amplitude. Grip strength and median CMAP amplitude correlated positively. We conclude that it is possible to conduct minimally invasive electrophysiologic testing in rat forelimbs. The CMAP is a valid parameter that shows the typical time course of nerve regeneration and reinnervation.