Influence of time shifting of single muscle fiber potentials (SFPs) on jitter values measured using concentric needle electrode - a simulation study

Abstract

Objectives: The aim of this simulation study was to evaluate the resulting value of jitter measured from a simulated examination recording and to analyze its dependence on both the number of SFPs contributing either to the triggering peak or the non-triggered peak, and time shifting (delays of triggering at the end-plate) of individual SFPs in these paired potentials.

Methods: We simulated potentials recorded using a concentric needle electrode with two well separated peaks, and performed a simulated examination (consisting of 50 trains of 100 discharges) with an assumed number of fibers forming peaks. For each train, fiber diameters were chosen at random within the allowed ranges. For each discharge the delay of triggering for each fiber at the end-plate was selected at random from an assumed range. The mean jitter values were calculated, together with the median and 95% quantile.

Results: The results suggest that jitter is related to the mean of the individual SFP shifts.

Conclusion: These findings extend the understanding of reduced jitter measurements using a concentric needle electrode. If more than one fiber forms the peak, then jitter decreases due to averaging of individual time shifts of potentials constituting the peak, rather than due to detection of the SFP with the earliest peak.

Keywords: Concentric needle electrode; Electromyography; Neuromuscular jitter; Single fiber electromyography; Single fiber potential.