Myasthenic syndrome studied with single fiber electromyography.

A patient with the myasthenic syndrome was investigated with single fiber electromyography (SFEMG). It was found that 35 of 36 potential pairs had increased "jitter" and that 29 of these demonstrated impulse blockings. There was improvement in neuromuscular transmission with higher rates of innervation. Transmission worsened following rest. The SFEMG findings at the motor end-plate level correlate well with the results of repetitive stimulation and in vitro studies.