An accurate and specific diagnosis of myopathy is essential for at least three reasons; for prognosis, for genetic counselling with the family and for treatment planning.

Therefore this study reviewed one hundred and eighty-six cases on myopathy received by the EMG laboratory of Severance Hospital Yonsei University from January of 1972 to August of 1983. The age distribution varied from 13 months to 68 years and the male-female sex ratio was 2.8:1.

Cases were clinically classified in 6 groups such as progressive muscular dystrophy(PMD), myotonia, inflammatory myopathy etc., the most common being PMD. EMG examination showed characteristic features such as low amplitude and short duration motor unit action potentials with full interference pattern upon minimal or moderate effort in all cases.

Although the above EMG findings generally served to categorize the myopathies, there were no significant differences distinguishing one type from another.

Therefore it was essential that accurate diagnosis with various diagnostic studies including electrodiagnostic studies be made in order to plan the care of the patient and to properly counsel with parents.

Keywords :Myopathy, Electrodiagnosis, Progressive muscular dystrophy