Sympathetic skin responses recorded from non-palmar and non-plantar skin sites: their role in the evaluation of thermal sweating

Objective: To characterize the sympathetic skin responses (SSRs) recorded from non-palmar and non-plantar (non-Pa/Pl) skin sites and to evaluate their clinical usefulness.

Methods: SSRs were recorded from 6 non-Pa/Pl sites as well as palmar and plantar (Pa/Pl) sites using magnetic neck stimulation in 33 normal subjects, 17 neurological patients with dysautonomia and one patient with lumbar sympathectomy. A conventional thermoregulatory sweat test (TST) was also carried out in 3 patients.

Results: Clear and reproducible SSRs were obtained from all recording sites in all of the normal subjects when the skin temperatures of the subjects were maintained above 34°C and the subjects drank 100–200 ml of hot water. The distribution of absent SSRs was closely correlated with that of anhidrosis or a sweating delay shown by the TST in the patients. Nine of the 17 neurological patients (53%) showed normal responses at Pa/Pl sites, and abnormal responses at non-Pa/Pl sites.

Conclusions: Recording SSRs from multiple skin sites including non-Pa/Pl sites after magnetic stimulation is more sensitive in detecting sudomotor dysfunction than is the conventional method of recording SSRs from only Pa/Pl sites. In addition, this new method is very useful for the objective clinical evaluation of thermal sweating.