Estimating motor unit numbers from a CMAP scan: Repeatability study on three muscles at 15 centres

Impact of reference electrode position on motor unit number estimation (MUNE) in the tibialis anterior muscle using MScanFit: test-retest reliability

“…Two cohorts of healthy control participants were recruited for this study through convenience sampling. The inclusion and exclusion criteria were adopted from the larger MScan Multicenter protocol (Sørensen et al, 2023). Potential participants underwent a pre-screening process to identify and exclude individuals meeting any of the following exclusion criteria: a history of prior injuries or diseases affecting the central nervous system, leg injuries resulting in numbness or weakness, previous chemotherapy treatments, a diagnosis of diabetes mellitus, self-reported alcohol consumption exceeding 14 units per week, other causes of polyneuropathy, documented history of nerve entrapment syndromes, cognitive impairment, or pregnancy.…”

“…The method was first introduced by McComas and colleagues in 1971, and subsequent years have seen the development of various alternative approaches (as comprehensively reviewed by Gooch et al, 2014; de Carvalho et al, 2018; Wright et al, 2023). Among these approaches is MScanFit MUNE, proposed by Bostock in 2016, which shares many similarities with standard nerve conduction studies and is currently undergoing evaluation in international multicenter studies to assess its measurement properties as a lower motor neuron biomarker for conditions like amyotrophic lateral sclerosis (ALS; Sørensen et al, 2022; Sørensen et al, 2023).…”

“…A recent study involving 15 participating centers from nine countries reported discrepancies in standard measures of compound muscle action potential (CMAP) amplitudes, despite all centers adhering to the same standard operating procedure (Sørensen et al, 2023). Our current study seeks to investigate whether these discrepancies could have been mitigated by utilizing an alternative (optimal) reference electrode position when examining the tibialis anterior muscle.…”

Effect of surface electrode recording area on compound muscle action potential scan processing for motor unit number estimation

“…Electrode recording area (the area of the recording surface of an electrode) is another major factor affecting CMAP, especially on its shape and amplitude due to the different filtering effects ( Wee and Ashley, 1990 ; Chang et al, 1993 ; Jonas et al, 1999 ; Barkhaus et al, 2006 ). The electrode recording area used for CMAP scan studies covered a wide range in literature from greater than 400 mm 2 ( Sørensen et al, 2022 , 2023 ) to around 100 mm 2 ( Li et al, 2018 ; Song et al, 2023 ). Furthermore, inconsistent electrode recording areas were reported when examining the same muscle ( Sleutjes et al, 2021 ).…”

“…Furthermore, inconsistent electrode recording areas were reported when examining the same muscle ( Sleutjes et al, 2021 ). For example, when performing CMAP scan recordings on the abductor pollicis brevis (APB) muscle, square electrodes with the size of 30 mm × 22 mm (with the recording area of 474 mm 2 ) and 30 mm × 24 mm (detailed recording area was not reported) were used in Araújo et al (2015) and Sørensen et al (2023) , respectively, while disk electrodes with the diameter of 10 mm (i.e., 79 mm 2 ) and 13 mm (i.e., 133 mm 2 ) were applied in Stikvoort García et al (2022) and Song et al (2023) , respectively. Note that 2-dimensional electrode arrays up to 128 channels have also been used for MUNE, where electrodes with diameters smaller than 2 mm are commonly used ( Sleutjes et al, 2016 ).…”