Peripheral autonomic surface potential: a quantitative technique for recording autonomic neural function in man.

Using EMG equipment with time-locked recording and standard averaging facilities we were able to record a previously poorly studied skin potential. The potential, termed by us by the peripheral autonomic surface potential (PASP), was recorded from the palmar surface of the hand and the plantar surface of the foot in 20 normal subjects. The PASP consisted of a biphasic potential with an initial negative and a later positive peak. The mean palmar PASP latency was 1.51 +/- 0.19 seconds and the mean plantar PASP latency was 2.09 +/- 0.24 seconds. The mean palmar and plantar PASP amplitudes were 485 +/- 100 microV and 102 +/- 45 microV respectively. A mean central sympathetic conduction velocity was calculated at 1.2 +/- 0.21 m/s. In two patients with unilateral lumbar sympathectomy the ipsilateral plantar PASP was absent in one and of considerably reduced amplitude in the other. Both palmar and plantar PASPs were absent or of reduced amplitude in five patients with diabetes mellitus. The study indicates that the PASP may prove a useful quantitative test of central and peripheral autonomic function.