Assessment of the reliability of the motor unit size index (MUSIX) in single subject "round-robin" and multi-centre settings. Issue 5 (May 2019)

• Record Type: Journal Article
• Authors: Alix, James J.P.; Neuwirth, Christoph; Gelder, Lucy; Burkhardt, Christian; Castro, José; de Carvalho, Mamede; Gawel, Malgorzata; Goedee, Stephan; Grosskreutz, Julian; Lenglet, Timothée; Moglia, Cristina; Omer, Taha; Schrooten, Maarten; Nandedkar, Sanjeev; Stalberg, Erik; Barkhaus, Paul E.; Furtula, Jasna; van Dijk, Johannes P.; Baldinger, Reto; Costa, Joao; Otto, Marit; Sandberg, Arne; Weber, Markus
• Is Part Of: Clinical neurophysiology. Volume 130:Issue 5(2019:May)
• Page Start: 666
• Page End: 674
• Publication Date: 2019-05
• Subjects: Motor unit number index -- Motor unit size index -- Motor unit -- Motor neuron -- Amyotrophic lateral sclerosis -- Electrophysiology; ADM abductor digiti minimi -- AH abductor hallucis -- ALS amyotrophic lateral sclerosis -- APB abductor pollicis brevis -- CMAP compound muscle action potential -- COV coefficient of variation -- EDB extensor digitorum brevis -- BB biceps brachii -- EMG electromyography -- LOA limits of agreement -- MOVER method of variance recovery for ratios -- MUNIX motor unit number index -- MUSIX motor unit size index -- SD standard deviation -- SIP surface interference pattern -- TA tibialis anterior; Neurophysiology -- Periodicals; Electroencephalography -- Periodicals; Electromyography -- Periodicals; Neurology -- Periodicals; 612.8
• DOI: 10.1016/j.clinph.2019.01.020
• Languages: English
• ISSNs: 1388-2457

Abstract

Highlights: Motor unit size index (MUSIX) is a rapid, non-invasive means of assessing reinnervation. Using healthy volunteers reliable data were provided by both experienced and non-experienced raters. Results across single subject and multi-centre settings demonstrate high reliability/reproducibility. Abstract: Objective: The motor unit size index (MUSIX) is incorporated into the motor unit number index (MUNIX). Our objective was to assess the intra-/inter-rater reliability of MUSIX in healthy volunteers across single subject "round robin" and multi-centre settings. Methods: Data were obtained from (i) a round-robin assessment in which 12 raters (6 with prior experience and 6 without) assessed six muscles (abductor pollicis brevis, abductor digiti minimi, biceps brachii, tibialis anterior, extensor digitorum brevis and abductor hallucis) and (ii) a multi-centre study with 6 centres studying the same muscles in 66 healthy volunteers. Intra/inter-rater data were provided by 5 centres, 1 centre provided only intra-rater data. Intra/inter-rater variability was assessed using the coefficient of variation (COV), Bland-Altman plots, bias and 95% limits of agreement. Results: In the round-robin assessment intra-rater COVs for MUSIX ranged from 7.8% to 28.4%. Inter-rater variability was between 7.8% and 16.2%. Prior experience did not impact on MUSIX values. In the multi-centre study MUSIX was more consistent than the MUNIX. Abductor hallucis was the least reliable muscle. Conclusions: The MUSIX is a reliable neurophysiological biomarker of reinnervation. Significance: MUSIX could provide insights into the pathophysiology of a range of neuromuscular disorders, providing a quantitative biomarker of reinnervation.