Implementing Motor Unit Number Index (MUNIX) in a large clinical trial: Real world experience from 27 centres

Christoph Neuwirth*, Nathalie Braun, Kristl G. Claeys, Robert Bucelli, Christina Fournier, Mark Bromberg, Susanne Petri, Stephan Goedee, Timothée Lenglet, Ron Leppanen, Antonio Canosa, Ira Goodman, Muhammad Al-Lozi, Takuya Ohkubo, Annemarie Hübers, Nazem Atassi, Agessandro Abrahao, Andreas Funke, Martin Appelfeller, Anke TümmlerEoin Finegan, Jonathan D. Glass, Suma Babu, Shafeeq S. Ladha, Olga Kwast-Rabben, Raul Juntas-Morales, Amina Coffey, Vinay Chaudhry, Tuan Vu, Chow Saephanh, Colleen Newhard, Marion Zakrzewski, Esther Rosier, Nancy Hamel, Divisha Raheja, Jesper Raaijman, Toby Ferguson, Markus Weber

*Corresponding author for this work

Research output: Contribution to journalArticleAcademicpeer-review

1 Citation (Scopus)


Objective: Motor Unit Number Index (MUNIX) is a quantitative neurophysiological method that reflects loss of motor neurons in Amyotrophic Lateral Sclerosis (ALS) in longitudinal studies. It has been utilized in one natural history ALS study and one drug trial (Biogen USA) after training and qualification of raters. Methods: Prior to testing patients, evaluators had to submit test-retest data of 4 healthy volunteers. Twenty-seven centres with 36 raters measured MUNIX in 4 sets of 6 different muscles twice. Coefficient of variation of all measurements had to be <20% to pass the qualification process. MUNIX COV of the first attempt, number of repeated measurements and muscle specific COV were evaluated. Results: COV varied considerably between raters. Mean COV of all raters at the first measurements was 12.9% ± 13.5 (median 8.7%). Need of repetitions ranged from 0 to 43 (mean 10.7 ± 9.1, median 8). Biceps and first dorsal interosseus muscles showed highest repetition rates. MUNIX variability correlated considerably with variability of compound muscle action potential. Conclusion: MUNIX revealed generally good reliability, but was rater dependent and ongoing support for raters was needed. Significance: MUNIX can be implemented in large clinical trials as an outcome measure after training and a qualification process.

Original languageEnglish
Pages (from-to)1756-1762
Number of pages7
JournalClinical Neurophysiology
Issue number8
Publication statusPublished - 1 Aug 2018


  • Implementation
  • Multicentre
  • Training
  • Variability


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