Double-peak response in orthodromic sensory nerve conduction of the median nerve

To understand the neural generator of double-peak potentials and the change of latency and amplitude of double peaks with aging.

In 50 healthy subjects made up of groups of 10 people per decade from the age of 20 to 60, orthodromic sensory nerve conduction studies were performed on the median nerves using submaximal stimulation. Various stimulus durations and interstimulation distances were used to obtain each double peak in the different age groups. The latency and amplitude of the second peak were measured. Statistical analyses included one-way ANOVA and correlation tests. p-values<0.05 were considered significant.

When the cathode moved in a proximal direction, the interpeak intervals increased. Second peak amplitudes decreased, and second peak latencies were delayed with aging (p<0.05). In some older people, second peaks were not obtained.

Our experiments indicate that the double-peak response represented the two stimulation sites under the cathode and anode. The delayed latency and decreased amplitude of the second peak that occurs with aging represented peripheral nerve degeneration in aging, which starts at the distal nerve.