Assessment of the reliability of the motor unit size index (MUSIX) in single subject “round-robin” and multi-centre settings

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  • James J.P. Alix, University of Sheffield, Sheffield
  • ,
  • Christoph Neuwirth, Neuromuscular Diseases Unit/ALS Clinic
  • ,
  • Lucy Gelder, University of Sheffield, Sheffield
  • ,
  • Christian Burkhardt, Neuromuscular Diseases Unit/ALS Clinic
  • ,
  • José Castro, University of Lisbon
  • ,
  • Mamede de Carvalho, University of Lisbon
  • ,
  • Malgorzata Gawel, Medical University of Warsaw
  • ,
  • Stephan Goedee, University Medical Center Utrecht, Utrecht
  • ,
  • Julian Grosskreutz, Jena University Hospital
  • ,
  • Timothée Lenglet, AP-HP Assistance Publique - Hopitaux de Paris
  • ,
  • Cristina Moglia, University of Torino
  • ,
  • Taha Omer, Trinity College, Dublin, Beaumont Hospital, Dublin
  • ,
  • Maarten Schrooten, University Hospital, Leuven, Belgium
  • ,
  • Sanjeev Nandedkar, Natus Medical Inc
  • ,
  • Erik Stalberg, Uppsala universitet
  • ,
  • Paul E. Barkhaus, Milwaukee Veterans Administration Medical Center and Medical College of Wisconsin
  • ,
  • Jasna Furtula
  • ,
  • Johannes P. van Dijk, Universitat Ulm
  • ,
  • Reto Baldinger, Neuromuscular Diseases Unit/ALS Clinic
  • ,
  • Joao Costa, University of Lisboa
  • ,
  • Marit Otto
  • Arne Sandberg, Uppsala universitet
  • ,
  • Markus Weber, Neuromuscular Diseases Unit/ALS Clinic

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.

Original languageEnglish
JournalClinical Neurophysiology
Volume130
Issue5
Pages (from-to)666-674
Number of pages9
ISSN1388-2457
DOIs
Publication statusPublished - May 2019

    Research areas

  • Amyotrophic lateral sclerosis, Electrophysiology, Motor neuron, Motor unit, Motor unit number index, Motor unit size index

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