The refractory period of an axon is the time during which the ability to conduct an action potentials is altered following initiation and propagation of a nerve impulse. A refractory period is demonstrable in peripheral motor and sensory nerves in response to repetitive stimulation.

Many factors, both physiologic and pathologic, influence the excitability cycle of a normal nerve. For the applicability of refractory period determination to the evaluation of peripheral neuropathies, absolute (ARP), relative (RRP) and true relative refractory period (TRRP) of the median sensory nerve was determined in 31 healthy subjects.

Recovery of latency to normal in response to the second stimulus was used to define RRP. A true RRP was calculated by substracting ARP from measured RRP.

The results are as follows;

1)The absolute, relative and true relative refractory period are 0.72±0.16, 2.84±0.44 and 2.12±0.48 msec, respectively.

2) There is no significant difference related to the sexes and the dominance of the extremity.

3) The refractory period determination is useful in the early diagnosis of polyneuropathy and may be useful in the differential diagnosis of demyelinating disease and axonal degenerative disease.

Keywords :Absolute refractory period, Relative refractory period, True relative refractory period