Electrophysiologic studies of the pattern of lesions of mimetic muscles in Bell's palsy

Abstract

This paper reports on 379 investigations of patients with the diagnosis of Bell's palsy. The computerized analysis was carried out retrospectively with the programme FANDOS (6). In most electrophysiological measurements five standard muscles (frontalis muscle, orbicularis oculi muscle, levator labii muscle, zygomaticus muscle, orbicularis oris muscle) were investigated with electromyography (EMG); further, neuromyography was performed. In 77.3% of the cases electromyographically incomplete and 22.7% complete palsies were found. The distribution of the reduced innervation patterns and the degeneration of the muscles did not show a preferred lesion of certain muscles. In about sixty per cent of all cases in at least four muscles a homogeneous electromyographic pattern of the lesion in the mimic musculature could be detected. Degeneration potentials, however, were mostly found in one muscle only. In order to provide a differentiated analysis of the electromyographical state of a facial paresis an "EMG-index" was introduced that allows a general judgement of the "degree of palsy" in all five investigated muscles. An analysis of the time dependence of the "EMG-index" over the course of two weeks following onset of the palsy showed no variation during this time period. This proves that the complete status of the palsy is reached early after onset and that a deterioration or improvement is rarely seen within this time interval.