Orthodromic sensory action potentials from palmar stimulation in the diagnosis of carpal tunnel syndrome.

It is known that the major slowing of nerve conduction in the carpal tunnel syndrome occurs in the palm to wrist segment. A technique exploiting this fact and easily applicable in the routine laboratory would be useful in diagnosing early examples of the condition. To this end, orthodromic sensory potentials from stimulation of digits II and V, and of the palmar branches of the median and ulnar nerves were recorded at the wrist in 53 healthy hands, 72 hands with a tentative diagnosis of carpal tunnel syndrome and in 20 hands of patients with unrelated neurological conditions. Using conventional criteria, 53% of the 72 hands from those suspected of carpal tunnel syndrome were thought to have median nerve compression. When conduction velocity in median palm wrist fibres was taken into account, 67% of hands were then considered abnormal. It is concluded that orthodromic sensory action potentials from palmar stimulation provide a rapid, sensitive and acceptable method of diagnosing the carpal tunnel syndrome.