Comparison of sympathetic skin response and digital infrared thermographic imaging in peripheral neuropathy

It is well known that the SSR (sympathetic skin response) is to evaluate the function of sudomotor activity and Digital infrared thermal imaging (DITI) is to evaluate the function of vasomotor activity of the sympathetic nerve. To assess the sympathetic nerve impairment in the patients with peripheral neuropathy, the SSRs and DITIs were tested in 35 cases. Twenty-four (68.6%) patients were abnormal on SSR test and twenty-nine (82.9%) patients were abnormal on DITI test. In the relationship between DITI and SSR, 19 (54.3%) cases were abnormal and 1 case was normal finding in both of these two tests. And the remaining 25 (42.9%) patients were abnormal on only either one of both tests. Frequency of abnormal SSR and DITI findings were correlated with severity of axonal involvement in peripheral nerve lesion. The results of this study revealed DITI to be more sensitive test in assessing sympathetic dysfunction in peripheral neuropathy than the SSR. However DITI has very limited values in the patients with symmetrically involved peripheral neuropathy because thermal asymmetry is considered as abnormal on DITI. Therefore, in assessing the function of sympathetic nerve in peripheral neuropathy, combined tests of SSR and DITI are useful.