Quantitative electromyography in babies and young children with no evidence of neuromuscular disease

A technique of quantitative EMG suitable for use in babies and young children is described. No specific level of force is required and portions of EMG as short as 100 ms are suitable for analysis. A specially modified Medelec APA6 action potential analyser converted the EMG into two pulse trains representing amplitude pulses and turns pulses with a display on the CRT screen. The ratio of the mean amplitude/turns per second was determined for between 15 and 20 different portions of EMG to produce a Mean Ratio of mean amplitude/turns per second. Ninety-seven children were investigated for neuromuscular disease. Twenty-two had a primary muscle disease, 21 a neurogenic process and 25 no neuromuscular disease. This last group was called the Apparent control group. The problem of obtaining control values is discussed. A 5-year follow-up study found no change in the clinical diagnosis of the patients in the 3 groups. Numerical limits for the Mean Ratio of mean amplitude/turns per second for the Apparent control group are defined.