James J P Alix1, Christoph Neuwirth2, Lucy Gelder3, Christian Burkhardt2, José Castro4, Mamede de Carvalho4, Malgorzata Gawel5, Stephan Goedee6, Julian Grosskreutz7, Timothée Lenglet8, Cristina Moglia9, Taha Omer10, Maarten Schrooten11, Sanjeev Nandedkar12, Erik Stalberg13, Paul E Barkhaus14, Jasna Furtula15, Johannes P van Dijk16, Reto Baldinger2, Joao Costa4, Marit Otto15, Arne Sandberg13, Markus Weber2. 1. Sheffield Institute for Translational Neuroscience, University of Sheffield, 385A Glossop Road, Sheffield S10 2HQ, UK. Electronic address: j.alix@sheffield.ac.uk. 2. Neuromuscular Diseases Unit/ALS Clinic, Kantonsspital, St. Gallen, Switzerland. 3. Statistical Services Unit, University of Sheffield, UK. 4. Department of Neurosciences, Hospital de Santa Maria, Instituto de Medicina Molecular, Faculty of Medicine, University of Lisbon, Portugal. 5. Department of Neurology, Medical University of Warsaw, Warsaw, Poland. 6. Brain Centre Rudolf Magnus, Department of Neurology and Neurosurgery, UMC Utrecht, Utrecht, The Netherlands. 7. Hans-Berger Department of Neurology, Jena University Hospital, Jena, Germany. 8. Département de Neurophysiologie, Groupe hospitalier Pitié-Salpêtrière, APHP, Paris, France. 9. ALS Centre of Torino, Department of Neuroscience "Rita Levi Montalcini", University of Torino, Torino, Italy. 10. Trinity College Biomedical Science Institute (TBSI) and Beaumont Hospital, Dublin, Ireland. 11. Department of Neurology, University Hospital Leuven, Leuven, Belgium. 12. Natus Medical, Inc., 15 Dartantra Drive, Hopewell Junction, NY 12533, USA. 13. Department of Neuroscience, Clinical Neurophysiology, Uppsala University, Sweden. 14. Milwaukee Veterans Administration Medical Center and Medical College of Wisconsin, Milwaukee, WI, USA. 15. Department of Clinical Neurophysiology, Aarhus University Hospital, Aarhus, Denmark. 16. Department of Orthodontics, University of Ulm, Ulm, Germany.
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.
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.
Authors: Steve Vucic; Matthew C Kiernan; Parvathi Menon; William Huynh; Austin Rynders; Karen S Ho; Robert Glanzman; Michael T Hotchkin Journal: BMJ Open Date: 2021-01-11 Impact factor: 2.692