ELECTRICAL SIGNS IN THE DIAGNOSIS OF CARPAL TUNNEL AND RELATED SYNDROMES*

A common problem in clinical neurology is the differential diagnosis of the cause of tingling or numbness of fingers which may be associated with weakness of the small muscles of the hand. There is general recognition that the syndrome may result from compression of nerve roots or peripheral nerves supplying the hand, or of the blood vessels supplying the affected nerves, and that compression may occur at various sites in the spine (Brain, Northfield, and Wilkinson, 1952), thoracic outlet (Walshe, 1951), and more peripherally. The median nerve is commonly compress.d in the carpal tunnel on the flexor aspect of the wrist (Kremer, Gilliatt, Golding, and Wilson, 1953) and the diagnosis is of considerable importance in view of the efficacy of decompression of the carpal tunnel (Brain, Wright, and Wilkinson, 1947). Electromyographic diagnosis has hitherto depended on the demonstration of evidence of partial denervation confined to the muscles supplied by a particular motor nerve or one of its branches. This method has certain practical disadvantages. It may fail to demonstrate changes at an early stage which