Comparison between median and ulnar sensitive action potential (SAP) obtained with two different stimulation methods.

We studied the sensory action potentials (SAP) of median and ulnar nerves in four groups of 20-30, 30-40, 40-50 and 50-60 years old healthy subjects. In each group ten sensitive ulnar and median nerves were examined stimulating respectively V and III hand digital nerves, with two compared methods. In the former stimulus intensity was 20 mA, with a duration 0.1 msec, and SAP was recorded with averaging technique after 20 stimuli; in the latter the stimulus intensity was supra maximal (100 mA), with a duration 0.1 msec and a single SAP was recorded. The SAP's recording was performed by bipolar surface electrodes at the wrist, following conventional techniques. There was not statistically significant difference between SAP's latencies obtained with the two methods in each group, even if there was a decrease of the latency value obtained with supra maximal stimulus. Otherwise there was a statistically significant increase of SAP's amplitude obtained with supra maximal stimulus, above all in elderly people for median (p < 0.001) and ulnar (p < 0,0005) nerve