Sweat function evaluation
Why evaluate sudomotor function?
Sweat glands are innervated by small diameter sympathetic C-fibers. Sudomotor (sweat) dysfunction can be one of the earliest detectable neurophysiologic abnormalities in distal small fiber neuropathies. Quantitative assessment of sweat response has been proposed as an index of the severity and distribution of autonomic failure as well as an early indicator for regeneration of small fibers   .
Diabetes is shown to be the primary cause of small fiber neuropathy. The ADA has identified sudomotor (sweat) dysfunction as one of the major clinical manifestations of diabetic autonomic neuropathy. Furthermore, the assessment of autonomic dysfunction may identify patients at high risk for cardiac autonomic neuropathy, which carries a very high rate of morbidity and mortality .
Peripheral Autonomic Neuropathy and its effect on sweat glands 
Normal sweat gland innervation in a healthy control (left). Reduced sweat gland innervation in a patient with diabetes indicates autonomic neuropathy (right).