Faculty Collaboration Database

An Artifact in Concentric Needle EMG Recordings. Muscle Nerve 2025 Feb;71(2):216-222

Date

12/13/2024

Pubmed ID

39668641

DOI

10.1002/mus.28312

Scopus ID

2-s2.0-85211784134 (requires institutional sign-in at Scopus site)   5 Citations

Abstract

INTRODUCTION/AIMS: In healthy subjects, we observed high amplitude motor unit potential (MUP) waveforms that resembled the cannula potential (CP) with a positive sharp wave (PSW)-like waveform. We analyzed the source of this signal, its prevalence, and its effects on the analysis of electromyographic waveforms.

METHODS: Three channel recordings were performed to explore the contribution of the needle core and cannula to the MUP. In 7 control subjects with no neuromuscular disease, the EMG interference pattern was quantified for the amplitude asymmetry (AASM) of its positive and negative going peaks.

RESULTS: The large amplitude MUP resembling a CP with a PSW-type waveform is recorded by the needle core, not the cannula. With a slight change in needle position, its amplitude decreased and the waveform had a normal appearance. Thus, it is an artifact. Such potentials (AASM > 150%) are commonly encountered (frequency 7%) and occur in all muscles and subjects in this study.

DISCUSSION: The artifact is an enigma and appears related to the interaction between the needle and muscle fiber(s) similar to that in PSW signals. Failure to recognize these waveforms may result in a false impression of abnormality. AASM calculations can help confirm this artifact in automated analysis algorithms to preclude false positive neurogenic patterns.

Author List

Nandedkar SD, Barkhaus PE

Author

Paul E. Barkhaus MD Adjunct Professor in the Neurology department at Medical College of Wisconsin

MESH terms used to index this publication - Major topics in bold

Action Potentials
Adult
Artifacts
Electromyography
Female
Humans
Male
Middle Aged
Motor Neurons
Muscle, Skeletal
Needles
Young Adult