Proximal axonal changes after peripheral nerve injury in man.

Peripheral nerve injury leads to changes in the proximal axon. Traumatic nerve injuries in humans were investigated to characterize such electrophysiological changes. Mixed nerve conduction studies (MNCS) and motor conduction studies (MCS) were performed proximal to the injury. Control values were obtained from the uninjured limb. Median (n = 24) and ulnar (n = 35) nerve injuries were studied. The injured nerves had significant mixed nerve action potential (MNAP) amplitude reductions (median: P < 0.0001; ulnar: P < 0.0001). The majority of the MNAP amplitude reductions were severe and early. There was slowing in the mixed nerve conduction velocity (MNCV) (median: P = 0.09; ulnar: P = 0.04) and motor conduction velocity (MCV) (median: P = 0.046; ulnar: P = 0.005). Axonal loss appears to play a significant role in producing the MNCS changes observed, and its early occurrence is noteworthy. Proximal MCV reduction could be secondary to the effects of injury as well as collateral sprouting of uninjured axons. Proximal axonal changes may have an impact on recovery.