Galvanic Skin Response (GSR) studies, also known as sympathetic skin response, evaluate the autonomic nervous system, and in particular the small C Fibers. It allows you to evaluate patients that have symptoms of a neuropathy but have normal nerve conduction studies. That is because routine nerve conduction studies evaluate large nerve fibers whereas GSR evaluate small nerve fibers. Small nerve fibers are commonly involved early in Diabetics, overweight patients and patients with a demyelinating condition. The GSR test is simple to perform and usually takes only a few minutes. Typically, small disposable surface electrodes are placed on the hand and foot at the same time and a small electrical shock is delivered to record the GSR. It is reimbursable by Medicare!