Interval analysis of repetitive denervation potentials of human skeletal muscle

Abstract

SUMMARY Interval analyses of denervation potentials (fibrillation-potentials and positive sharp waves) in human skeletal muscles were performed using a DEC PDP-12 computer. Extremely small differences between consecutive intervals (usually less than 1 %) and slow up and down drifts in the spontaneous discharge frequency were found to be characteristic of repetitive denervation potentials. These two findings are safe criteria for the clinical diagnosis of denervation and they may be superior to the more commonly used criteria based upon the shapes, amplitudes, and durations of the potentials. Physiological data from the literature as well as hypotheses relating to spontaneous activity are reviewed. Generator potentials across the muscle fibre membrane, lowered firing threshold, and constant-sized after-potentials are considered the basic factors relevant to spontaneous and rhythmical firing and to the slow drift observed in the firing frequency.

Different Types of Fibrillation Potentials in Human Needle EMG

“…Also a sequence of rhythmic fibrillation potentials had to proceed several seconds in order to be accepted. Rhythmic fibrillations were usually elicited by needle insertion and they showed a gradual shift of interpotential intervals during the recording time (Conrad et al 1972). A short-lasting burst of insertion activity was not accepted.…”

“…My experience in clinical ENMG work is that irregular fibrillations are most common 1 -3 months after axonal injury and in extreme cases only a number of irregular fibrillation sequences may be present with no regular fibrillations at all (unpublished personal observation). There may also be mixed forms of fibrillations, with mainly regular rhythm but sudden changes of the interval (Partanen & Danner 1982, Conrad et al 1972). …”

“…Rhythmic fibrillation potentials are the hallmark of denervated muscle fibres in needle EMG of a striated muscle (Conrad et al 1972, Heckmann & Ludin 1982. They are readily activated by the insertion of an EMG needle electrode (Kugelberg & Petersén 1949).…”

Spontaneous high-frequency action potential

“…A large number of early studies reported that the spontaneous discharges were caused by the various denervations [101][102][103][104][105][106][107][108][109][110][111]. These spontaneous discharges that manifested fibrillation potentials were also termed "denervation potentials" in some reports.…”

“…These spontaneous discharges that manifested fibrillation potentials were also termed "denervation potentials" in some reports. The spontaneous and rhythmical repetitive discharges were originated in skeletal muscles due to the denervation process [101][102][103][104][105], and the spontaneous firing activity of muscle fiber that manifested fibrillation potentials was regarded as the safe criteria for the clinical diagnosis of denervation. The spontaneous depolarizing excitations of striatal neurons were observed after the denervation caused by 6-hydroxydopamine-induced lesions of the nigrostriatal dopaminergic system [106][107][108][109][110][111].…”