Diagnosing carpal tunnel syndrome--clinical criteria and ancillary tests.

Damage to the median nerve within the carpal tunnel gives rise to carpal tunnel syndrome (CTS), which is associated with a wide spectrum of symptoms. The predominant classic symptoms are nocturnal pain of the hand, and sensory disturbances within the distribution of the median nerve, both of which are characteristically relieved by hand movements. Ancillary tests, including nerve conduction studies (NCS) and imaging techniques, are mainly indicated when the classic defining features are absent. NCS are less accurate in the early stages of CTS, and in younger patients. Imaging tests (ultrasound and MRI), while still having a lower diagnostic accuracy than NCS, are proving to be useful for explaining persistence of symptoms following surgical relief. Supplementary tests of small nerve fiber function and measurement of intracarpal pressure might, in the future, improve early recognition of CTS, especially in the absence of well-defined symptoms.