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Motor unit number index and compound muscle action potential amplitude

Bostock, H; Jacobsen, AB; Tankisi, H; (2019) Motor unit number index and compound muscle action potential amplitude. Clinical Neurophysiology , 130 (9) pp. 1734-1740. 10.1016/j.clinph.2019.05.031.

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Bostock_AAM_MUNIX and CMAP amplitude_R2 CLINPH-D-19-11920.pdf - Accepted version
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Abstract

OBJECTIVES: MUNIX (motor unit number index), derived from the compound muscle action potential (CMAP) and surface EMG interference pattern (SIP) has become popular as a substitute for motor unit number estimation (MUNE). This study was undertaken to determine why, in recent recordings from amyotrophic lateral sclerosis (ALS) patients and healthy controls, we found that MUNIX values resembled CMAP amplitudes more closely than MUNE values. // METHODS: The relationship between MUNIX and CMAP and SIP amplitudes was investigated by a theoretical analysis and by reanalysing the data from the previous study. // RESULTS: Theory indicates that when motor unit potentials overlap extensively, information about motor unit size and number is lost, and MUNIX depends only on CMAP area and power. Accordingly, MUNIX values were found to be sensitive to changes in CMAP amplitude but insensitive to changes in SIP amplitude. The reproducibility of MUNIX measurements in healthy controls was found to depend almost entirely on correlation with CMAP properties. // CONCLUSIONS: MUNIX gives misleading information about motor unit numbers in healthy controls, and provides little information about loss of motor units in ALS patients beyond that given by simple CMAP amplitude measurements. // SIGNIFICANCE: MUNIX should not be interpreted as a MUNE method.

Type: Article
Title: Motor unit number index and compound muscle action potential amplitude
DOI: 10.1016/j.clinph.2019.05.031
Publisher version: https://doi.org/10.1016/j.clinph.2019.05.031
Language: English
Additional information: This version is the author accepted manuscript. For information on re-use, please refer to the publisher’s terms and conditions.
Keywords: CMAP amplitude, Correlation, MUNE, Munix, Musix
UCL classification: UCL > Provost and Vice Provost Offices
UCL > Provost and Vice Provost Offices > School of Life and Medical Sciences
UCL > Provost and Vice Provost Offices > School of Life and Medical Sciences > Faculty of Brain Sciences
UCL > Provost and Vice Provost Offices > School of Life and Medical Sciences > Faculty of Brain Sciences > UCL Queen Square Institute of Neurology
UCL > Provost and Vice Provost Offices > School of Life and Medical Sciences > Faculty of Brain Sciences > UCL Queen Square Institute of Neurology > Department of Neuromuscular Diseases
URI: https://discovery.ucl.ac.uk/id/eprint/10080342
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