To perform nerve conduction studies, surface electrodes are first fastened to the hand and wrist. Small electric shocks are then applied to the nerves in the fingers, wrist, and forearm to measure the speed of conduction of sensory and motor nerve fibers. To perform electromyography, a fine sterile, wire electrode is inserted briefly into a muscle and the electrical activity is displayed on a viewing screen. Certain conditions, such as obesity and anxiety, can slow the speed of conduction and skew the results. Women and the elderly normally have slower conduction times than younger adult men.
Temperature also affects nerve conduction speed.
Some experts urge that room temperature be strictly controlled and that physicians take into consideration any climatic conditions that might affect outcome. They can also detect causes of symptoms that mimic CTS but should be attributed to other problems, such as pinched nerves in the neck or elbow or thoracic outlet syndrome. These tests are not useful for predicting development of CTS in workers who have abnormal results but no symptoms. Physicians who perform them should be certified by the American Board of Electrodiagnostic Medicine, which uses rigorous standards in qualifying doctors. It is too expensive, even now, for routine use, but it may be effective for detecting any internal injuries that might be causing the problem.