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

Publication

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

Journal Paper/Review - Feb 21, 2019

Alix James J P, Nandedkar Sanjeev, Stålberg Erik, Barkhaus Paul E, Furtula Jasna, van Dijk Johannes P, Baldinger Reto, Costa João, Otto Marit, Sandberg Arne, Schrooten Maarten, Omer Taha, Moglia Cristina, Neuwirth Christoph, Gelder Lucy, Burkhardt Christian, Castro José, de Carvalho Mamede, Gawel Malgorzata, Goedee Stephan, Grosskreutz Julian, Lenglet Timothée, Weber Markus

Citation

Alix J, Nandedkar S, Stålberg E, Barkhaus P, Furtula J, van Dijk J, Baldinger R, Costa J, Otto M, Sandberg A, Schrooten M, Omer T, Moglia C, Neuwirth C, Gelder L, Burkhardt C, Castro J, de Carvalho M, Gawel M, Goedee S, Grosskreutz J, Lenglet T, Weber M. Assessment of the reliability of the motor unit size index (MUSIX) in single subject "round-robin" and multi-centre settings. Clin Neurophysiol 2019; 130:666-674.

Type

Journal Paper/Review (English)

Journal

Clin Neurophysiol 2019; 130

Publication Date

Feb 21, 2019

Issn Electronic

1872-8952

Pages

666-674

Brief description/objective

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.