Elektromyographische Untersuchung bei Myopathien

Needle electromyography is the most helpful clinical test in a situation where physical examination and serum creatine kinase activity point towards a myopathy. In typical patients, a decrease of mean motor action potential amplitude and duration and an increased number of polyphasic potentials along with the early recruitment of an inappropriately large number of motor units are the hallmark of myopathies. Myotonic discharges indicate the specific group of myotonic disorders with or without clinical myotonia. Inflammatory myopathies are often characterized by spontaneous activity (fibrillation potentials and positive sharp waves) uncommon in chronic degenerative myopathies. Quantitative myography is best performed according to the Buchthal analysis but may be replaced or favourably supplemented by the outlier analysis. Sophisticated automated analysis programs have not proved superior in diagnosing myopathies.