Electrical Test is sometimes done to assess whether a nerve which has suffered compression is degenerating or not. The nerve is stimulated directly by a short duration stimulus along its course. When it is stimulated it conveys impulses to the muscles it supplies (provided it has fibres to carry them) and the muscles contract. If this is carried out at intervals from the time of injury the nerve will at first be hypersensitive and require a very low intensity.
Later it may require more and, if it is degenerating, it will not conduct after about the 14th day. If, however, it does continue to conduct after 21 days the nerve has not degenerated and the injury is only a neuropraxia. In this case voluntary movement may be difficult or absent temporarily but recovery is likely eventually.
