Measurement of motor evoked potential resting threshold and amplitude of proximal and distal arm muscles in healthy adults: a reliability study

Abstract

Purpose: Reliability of motor evoked potential threshold and amplitude measurement of upper limb muscles is important when detecting changes in cortical excitability. The objective of this study was to investigate intra-rater, test-retest reliability and minimal detectable change of resting motor threshold and amplitude of a proximal and distal upper limb muscles, anterior deltoid and distal extensor digitorum communis, in healthy adults.
Method: To measure MEP responses, transcranial magnetic stimulation was interfaced with electromyography and neuronavigation equipment. Two measurements were conducted on day one and a third measurement three days later. Reliability was analysed using intraclass correlation coefficients.
Results: Twenty participants completed the study. Excellent intra-rater (ICC=0.91[extensor digitorum], 0.94[anterior deltoid]) and good to excellent test-retest reliability (ICC=0.69[anterior deltoid], 0.84[extensor digitorum]) was found for resting motor threshold. Minimal detectable change for resting motor threshold was found at 10.95% [extensor digitorum] and 16.35% [anterior deltoid] between first and third measurements. Motor evoked potential amplitude of EDC had fair to good inta-rater (ICC=0.50) and test-retest reliability (ICC=0.65).
Conclusions: Our results suggest that resting motor threshold is a reliable neurophysiological measure even for proximal shoulder muscles. Future research should further explore the reliability of motor evoked potential amplitude before integration into neurological rehabilitation.

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Identifiers

ORCID for Ann-Marie Hughes: orcid.org/0000-0002-3958-8206

ORCID for Jane Burridge: orcid.org/0000-0003-3497-6725

ORCID for Martin Warner: orcid.org/0000-0002-1483-0561

ORCID for Simon Brown: orcid.org/0000-0001-9646-3285

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