Retrograde effects of digital nerve severance on somatosensory evoked potentials in man

To determine if retrograde conduction changes might occur long after injury of the most distal peripheral nerves, short-latency somatosensory evoked potentials (SEPs) to median or ulnar nerve stimulation at the wrist were studied in 10 subjects who had sustained traumatic digit amputation 4 months to 15 years previously. SEPs were recorded from Erb's point (N9), the cervical region (N13), and the contralateral scalp hand area (N20). While N9 latency was slightly delayed or not affected, the amplitude was either markedly reduced or undetectable. For N13 and N20 components, latency prolongation and amplitude reduction were mild to moderate, but the central conduction time (N13-N20) remained normal. The present data indicate that even the most distal nerve injury may have profound long-term retrograde effects on parental nerve function which are presumed mainly due to an axonopathy.