Intra- and inter-rater reliability of motor unit number estimation and quantitative motor unit analysis in the upper trapezius.

OBJECTIVE: To collect normative data and assess the intra- and inter-rater reliability of decomposition-enhanced spike-triggered averaging (DE-STA) motor unit number estimation (MUNE) and quantitative MU analysis obtained using decomposition-based quantitative electromyography (DQEMG) in the upper trapezius (UT).
METHODS: In 10 control subjects, the experimental protocol was performed twice by the same examiner, and once by a second examiner.
RESULTS: Mean MUNE values were 339±121 (rater 1a), 320±131 (rater 1b), and 262±115 (rater 2) MUs. Intra- and inter-rater reliability was good for maximum CMAP (ICC=0.77 and 0.79, respectively) and moderate for MUNE (ICC=0.69 and 0.73, respectively), with poor inter-rater reliability for mean S-MUP (ICC=0.42). Significant differences between rater 1a and 2 were found for mean S-MUP (p=0.014) and MUNE (p=0.002), and moderate to good levels of reliability found for quantitative needle-detected MUP parameters.
CONCLUSIONS: Various components of the protocol may have contributed to mean S-MUP variability, and may require particular attention in a large, proximal muscle like the UT. SIGNIFICANCE: This study has established preliminary data using DQEMG in a novel muscle which may be relevant to study in patients with ALS.