Feasibility and reliability of MScanFit motor unit number estimation in peroneus longus muscle

Abstract

Introduction/Aims Motor unit number estimation (MUNE) methods may be valuable to detect motor involvement earlier than compound muscle action potential (CMAP) amplitude. The most recent MUNE method, MScanFit, has been shown to have advantages compared with previously described methods. However, MScanFit has only been applied in a few lower extremity muscles. In this study we examined the feasibility and reliability of MScanFit in peroneus longus muscle. Methods Twenty healthy controls (16 males and 4 females; mean age, 36.05 ± 2.58 years) were examined twice within a 1‐ to 2‐week interval. Fibular nerve was stimulated at the knee and CMAP scans were recorded from peroneus longus muscle. From this, MScanFit MUNE and size parameters were calculated, as was the CMAP amplitude. The reliability was examined using coefficient of variation (CV) and intraclass correlation coefficient (ICC). MUNE was correlated with CMAP amplitude using linear regression analysis. Results The CV between sessions was higher for CMAP amplitude (11.63 ± 1.88%) than MScanFit MUNE (3.13 ± 0.78%). Among the size parameters, mean unit amplitude (μV) showed the lowest CV (11.46 ± 1.77%). Using ICC, CMAP amplitude exhibited good reliability (0.787), whereas that of MScanFit MUNE was excellent (0.902). Reliability was good for all size parameters. There was no significant correlation between MScanFit MUNE and CMAP amplitude (R = 0.25, P > .05). Discussion MScanFit MUNE is feasible in the peroneus longus muscle, with high test‐retest reliability in healthy subjects. Studies in patients are needed to examine the sensitivity of this muscle in disease.

Estimation of the number of motor units in the human extensor digitorum brevis using MScanFit

“…MUNE and CMAP maximum were not correlated, despite the near 3-fold range of values in both (Fig 3C). Others reported a similar lack of correlation between these measures when data were analyzed using MScanFit-2 [11,22], although significant correlations were reported…”

“…The minimum unit size was set to the greater of the CMAP amplitude/300, and 1/5th of the mean unit size. MUNE values have been found to be less dependent on CMAP maximum using MScanFit-2 compared to the original MScanFit-1 options [11,22]. First, a flat section of the pre and post-scan periods, where signal fluctuation was minimal, was set manually.…”

“…A mathematical model is applied to characterize numbers, thresholds, and SMUP amplitudes of all units underlying the CMAP scan or "MScan". MScanFit MUNE has been found to be reproducible and sensitive at detecting motor unit loss in different muscles [7][8][9][10][11][12][13]. However, no one has used it to examine motor unit number in the EDB, although other methods have been employed.…”

Feasibility and tolerability of multimodal peripheral electrophysiological techniques in a cohort of patients with spinal muscular atrophy

“…In SMA proximal muscles are most severely affected, so analysis in distal muscles and nerves might underestimate true disease-related effects. ( Kiernan et al, 2020 , Song et al, 2022 , Tankisi et al, 2022 , Wadman et al, 2012 ).…”

MScanFit motor unit number estimation of abductor pollicis brevis: Findings from different experimental parameters

“…Although this study examined pulse duration of 0.1 ms and 0.2 ms, standardized longer pulse duration might be necessary for such nerves. For example, a pulse duration of 0.5 or 1 ms was used for CMAP scan examination of tibialis anterior and peroneus longus muscles innervated by peroneal nerve ( Kristensen et al, 2020 ; Sørensen et al, 2022 ; Tankisi et al, 2022 ). Given that there was no significant difference in MUNE between protocols of 500 and 1,000 steps at the same pulse width, the protocol of 500 steps is preferred because it requires less time to record and is thus more tolerable for the subject.…”