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Objective: The aim of this study was to report a method that quantifies axon reflex sweating from individual sweat glands with nanoliter precision. Measurement of the axon reflex is generally expressed as a single variable (e.g., the flare area or total sweat volume). High-definition videography enables precise measurement of sweating from single, axon reflex-stimulated sweat glands (SGs).Methods: The sudomotor axon reflex was activated in healthy subjects and subjects with peripheral neuropathy by iontophoresis of 10% acetylcholine. Sweating was simultaneously imaged for 5 min in a 2.5-cm2 area of iodine-coated skin to one side of the stimulus, using a customized high-resolution camera with starch-coated transparent tape over a rigid viewing screen. A second video then imaged the directly stimulated sweating. The indirect sweat response was quantified in terms of sweat gland number and distance from the stimulation site (radius), sweat rate per gland, and total sweat.Results: Fifty-two healthy control and twenty subjects with neuropathy underwent testing at the foot, calf, thigh, and hand. Normal ranges were calculated for SG density, mean sweat rate per SG, and total sweat volume. Neuropathy subjects demonstrated reduced sweating, and values differed between body sites.Interpretation: The described method precisely measures the total and individual sweat output of hundreds of SGs in response to a standard, axon reflex-mediated stimulus, and quantifies alterations in axon reflex sweating seen in peripheral neuropathy. [ABSTRACT FROM AUTHOR]

Sudomotor dysfunction is common in many subtypes of neuropathy but is one of the earliest detectable neurophysiologic abnormalities in distal small fiber neuropathy. Clinical assessments of sudomotor function include thermoregulatory sweat testing (TST), quantitative sudomotor axon reflex testing (QSART), silicone impressions, the sympathetic skin response (SSR), the acetylcholine sweat-spot test and quantitative direct and indirect axon reflex testing (QDIRT). These testing techniques, when used in combination, can detect and localize pre- and postganglionic lesions, can provide early diagnosis of sudomotor dysfunction and can monitor disease progression or disease recovery. In this article, we describe many of the common clinical tests available for evaluation of sudomotor function with focus on the testing methodology and limitations while providing concrete examples of test results. [ABSTRACT FROM AUTHOR]