What is a sweat test?
Sweat tests evaluate a particular part of the autonomic nervous system. The brain increases sweating by directing an increase in sympathetic nervous system traffic to sweat glands in the skin. The chemical messenger, acetylcholine, is released, which acts on the sweat glands to stimulate the production of sweat. The QSART is a special form of sweat test. It tests the ability of sympathetic nerve terminals in the skin to release acetylcholine and increase sweat production. A drug is applied to a nearby patch of skin. This evokes sweating at the site, but it also allows the body to release its own acetylcholine, resulting in sweat production. If a person had a loss of sympathetic nerve terminals that release acetylcholine, applying the patches would not lead to increased sweating. By this sort of neuropharmacologic test, doctors can distinguish sympathetic cholinergic failure due to loss of cholinergic terminals from failure due to abnormal regulation of sympathetic nerve traffic to inta
