Near-Fibre Electromyography

Abstract

Near fibre electromyography (NFEMG) is the use of specifically high-pass filtered motor unit potential (MUPs) (i.e. near fibre MUPs (NFMs)) extracted from needle-detected EMG signals for the examination of changes in motor unit (MU) morphology and electrophysiology caused by neuromuscular disorders or ageing. The concepts of NFEMG, the parameters used, including NFM duration and dispersion, which relates to fibre diameter variability and/or endplate scatter, and a new measure of neuromuscular junction transmission (NMJ) instability, NFM segment jitter, and the methods for obtaining their values are explained. Evaluations using simulated needle-detected EMG data and exemplary human data are presented, described and discussed. The data presented demonstrate the ability of using NFEMG parameters to detect changes in MU fibre diameter variability, end plate scatter, and neuromuscular transmission time variability. These changes can be detected prior to alterations of MU size, numbers or muscle recruitment patterns.

A scoping review of current and emerging techniques for evaluation of peripheral nerve health, degeneration, and regeneration: part 1, neurophysiology

“…For instance, near-fiber EMG (NFEMG) [32] is the novel approach of representing an E-MU as a near fiber MUP (NFMUP), which more clearly presents the relative contributions of individual muscle fibers near to the electrode recording surface. Suitably large and symmetric peaks within NFMUPs are associated with propagating MU fiber action potentials of single or small groups of near MU muscle fibers [45]. NFMUP duration and dispersion are related to the temporal dispersion across propagating MU fiber action potentials and if increased can reflect increased MU fiber diameter, axonal branch demyelination and/or increased axonal sprouting.…”

“…Traditionally, this is done by calculating MUP jiggle [47] across a set of isolated MUPs selected from a MUPT. However, an emerging and potentially more precise technique involves measurement of NFMUP jiggle and NFMUP segment jitter [45,46] across a set of isolated NFMUPs selected from a MUPT. NFMUP jiggle is measured using the same formulation as MUP jiggle and like MUP jiggle focuses on NFMUP shape stability, while NFMUP segment jitter focuses on temporal stability by measuring temporal differences between matched segments of temporally-adjacent isolated NFMUPs, similar in concept to fiber pair SFEMG jitter measurement.…”

“…Proxies for fiber density might be reported concurrently with standard EMG using lowpass-double differentiation filtered MUPs (i.e. near fiber MUPs) [45].…”