[Electromyographic rest-activity. Unusual forms of spontaneous discharge in healthy and sick skeletal muscle]

The forms of spontaneous activity termed as "benign fibrillation potentials" and "benign positive sharp waves" differ from the denervation potentials of the same wave form in the discharge pattern. Fibrillation potentials and positive sharp waves due to a denervation process show a characteristic rhythmical discharge sequence. "Benign fibrillation potentials" and "benign positive sharp waves", on the other hand, display a big difference in the duration of the time intervals between successive waves. It is important to be aware of the frequent occurrence of these benign fibrillations in normal muscles, in order to avoid erroneously diagnosing a denervation process. As in the case of malign fasciculations, "proximal fasciculations" generally occur in lesions of the proximal segment of the lower motoneuron, and have the same diagnostic significance. Unlike malign fasciculations, however, they do not originate in the region of the terminal nerve branches, but at the site of the lesion in question. Local reduction in the stimulus threshold and in the accommodation ensure that a spontaneous impulse will occur. "Low frequency bizarre discharges" and "periods of grouped and serial-discharges" occur mainly in the late phase of a neuromuscular disease and are found especially after traumatic lesions or lesions due to entrapment. We are able to demonstrate that the "low-frequency bizarre discharges" are of myogenic origin, whereas the "periods of grouped and serial-discharges" more than likely originate in the course of the peripheral motoneuron from an active focus.