A comparison of concentric needle electromyography, quantitative EMG and single fibre EMG in the diagnosis of neuromuscular diseases.

Conventional concentric needle electromyography, quantitative electromyography using automatic analysis (Quant-EMG) and single fibre electromyography (SFEMG) were compared in the right biceps muscle of 10 patients with anterior horn cell disease and 20 patients with primary muscle disease. Abnormalities were demonstrable by all 3 techniques in the majority of cases irrespective of whether the biceps was weak. SFEMG was found to be more sensitive than Quant-EMG in neurogenic cases and it also provided an indication of disease activity. In cases of myopathy Quant-EMG was of more diagnostic help and was easier to perform than SFEMG. Large amplitude potentials found in some cases of myopathy were associated with increase in the mean amplitude on Quant-EMG and these probably emanate from hypertrophied muscle fibres.