Carpal tunnel syndrome is frequently accompanied or preceded by certain lesion such as trigger finger or thumb, diabetes mellitus, rheumatoid arthritis, periarthritis-shoulder, etc. It is rather rare and of some interest to observe CTS with dermatomyositis. Recently such a case was seen at SNUH and reported hereby. The electrodiagnostic finding was characteristic of dermatomyositis (or polymyositis) and concomittant CTS:

1. Myopathic pattern, throughout--i.e., short duration motor unit action potential, short duration polyphasic potential, etc.

2. Abundant abnormal spontaneous activity--Fibrillation potentials, positive sharp waves, high frequency bizzare discharge, insertional activity, more marked in proximal group of muscles.

3. Prolonged latency of motor and absent sensory nerve action potential of Rt. median nerve.

4. Normal nerve conduction velocity.