The influence of skin temperature on latency and amplitude of the sympathetic skin response in normal subjects.

The influence of skin temperature on latency and amplitude of the sympathetic skin response (SSR) was studied in 10 normal subjects. SSRs were elicited in all four limbs of each subject by electrical stimulation after cooling of the right arm and after cooling of the right hand only. At low skin temperature, the latency was prolonged and the amplitude decreased. Latency and amplitude were linearly correlated with skin temperature of the right arm. There were no changes in the left arm and the legs, which basically excludes involvement of central pathways in these response parameters. With regard to the skin temperature of the arm, a temperature correction factor of 0.088 s/degrees C was calculated for latency. With regard to the skin temperature of the hand, latency prolongation was significantly greater after cooling of the whole arm. This suggests that not only the neuroglandular junction, but also the postganglionic sympathetic C fibers were responsible for latency modifications. In contrast, amplitude was reduced similarly after cooling of the whole arm and the hand only, suggesting that mainly the neuroglandular junction is responsible for amplitude modifications. We conclude that skin temperature is a mandatory measurement in the study of the SSR.