Benign fibrillation potentials in normal muscle and their correlation with endplate and denervation potentials.

Fibrillation potentials in normal muscle are identical in origin with the 'spikes' in the endplate zone. The difference in shape is due to the site of the electrode. Both potential types are characterised by a high average maximal frequency and a very irregular discharge pattern. These properties distinguish them from the typical fibrillation potentials of the denervated muscle which show lower maximal discharge frequency, very small differences between consecutive time intervals, and slow up and down drifts in the discharge frequency. Less commonly, irregularly discharging fibrillation potentials are also observed in denervated muscle, which are exactly the same as those in the normal muscle, and which, therefore, may be assumed to have the same origin. It is only the rhythmically discharging fibrillation potentials which indicate a denervating process. The irregular fibrillation potentials, on the other hand, are of no pathological significance. The term benign fibrillation potentials is suggested for the latter.