Assessment of Sudomotor Function

This chapter focuses on several sudomotor function tests, such as thermoregulatory sweat test (TST), quantitative sudomotor axon reflex test (QSART), and sweat imprint test (SIT). The TST is a sensitive qualitative test of sudomotor function that provides important information on the pattern and degree of sweat loss. The test can be rendered semiquantitative by estimating the percent of anterior-surface anhidrosis. The QSART specifically evaluates the functional status of postganglionic sympathetic axons. Current is applied through the anode of a constant current generator within one compartment of a multicompartmental sweat cell and the sweat response is recorded from a second compartment with a sudorometer. TST and QSART can be combined to provide information on the distribution of anhidrosis (percentage of anhidrosis), whereas QSART can define the volume of sweat loss. SIT yields information on the diameter distribution of sweat droplets. Combined with QSART, it is possible to determine the volume per sweat droplet.