Sudomotor dysfunction is known to be common in patients with amyotrophic lateral sclerosis (ALS). Q-Sweat (Quantitative Sweat Measurement System; WR Medical Electronics Co., Stillwater, Minnesota) is modeled on quantitative sudomotor axon reflex test, which is estimated by the latency to the start of sweat secretion and the amount of sweat. The aim of this study is to find correlation between sudomotor dysfunction and functional status in patients with ALS.

Medical records of 17 patients with ALS were reviewed. Functional status of subjects was scored using ALS functional rating scale (ALS-FRS). Volume of sweat at 4 different points of body (i.e. both forearms and thighs) was detected at Q-Sweat. We obtained mean value of volume measured in both upper and lower limbs, respectively, and subtracted the age-adjusted normal lower limit from those values. The difference value was called ‘SCORE’ of upper limbs and lower limbs each. In case that the SCORE measured in a patient was in normal range, it was recorded as 0 point, what means normal response of diaphoresis.

Age, gender and duration from onset to the time of the test were not statistically associated with degree of sudomotor dysfunction. Negative linear correlation between ALS-FRS and SCOREs of upper (r=−0.485, P=0.049) and lower limbs (r=−0.509, P=0.037) were elicited. There was no significant difference between bulbar-dominant and limb-dominant type groups in ‘SCORE’ in both upper and lower limbs.

The study showed that the sudomotor dysfunction represented by Q-Sweat is statistically correlated with functional status of patients with ALS. Patients have decreased function of regulating sweat responses as the disease progresses and are susceptible to skin damage or aspiration by saliva. Sudomotor dysfunction can deteriorate functional status of patients and the degree of this issue can be easily quantified by Q-Sweat.