Sudomotor is controlled by a division of sympathetic system and it is relating to, or being nerve fibers controlling the activity of sweat glands (post sympathetic cholinergic fiber or C-fibers).
Sudomotor dysfunction is using to define a decreased sudomotor activity.
Mainly, Sudomotor function evaluation is performed to detect skin blood flow (microcirculation) and C-fiber density for early detection (first stages) of peripheral distal neuropathy in population at high risk such as diabetic patient.
Sudomotor dysfunction is one of the earliest detectable neurophysiologic abnormalities in distal small fiber neuropathy. Traditional neurophysiologic measurements of sudomotor function include thermoregulatory sweat testing (TST), quantitative sudomotor axon reflex testing (QSART), silicone impressions, the sympathetic skin response (SSR), and the recent addition of quantitative direct and indirect axon reflex testing (QDIRT). These testing techniques, when used in combination, can detect and localized pre- and postganglionic lesions, can provide early diagnosis of sudomotor dysfunction and can monitor disease progression or disease recovery. In this article, we review the common tests available for assessment of sudomotor function, detail the testing methodology, review the limitations and provide examples of test results.