CMAP Scan Examination of the First Dorsal Interosseous Muscle After Spinal Cord Injury

Abstract

The study assessed motor unit loss in muscles paralyzed by spinal cord injury (SCI) using a novel compound muscle action potential (CMAP) scan examination. The CMAP scan of the first dorsal interosseous (FDI) muscle was applied in tetraplegia (n=13) and neurologically intact (n=13) subjects. MScanFit was used for estimating motor unit numbers in each subject. The D50 value of the CMAP scan was also calculated. We observed a significant decrease in both CMAP amplitude and motor unit number estimation (MUNE) in paralyzed FDI muscles, as compared with neurologically intact muscles. Across all subjects, the CMAP (negative peak) amplitude was 8.01 ± 3.97 mV for the paralyzed muscles and 16.75 ± 3.55 mV for the neurologically intact muscles (p < 0.001). The CMAP scan resulted in a MUNE of 59 ± 37 for the paralyzed muscles, much lower than 108 ± 21 for the neurologically intact muscles (p < 0.001). No significant difference in D50 was observed between the two groups (p = 0.2). For the SCI subjects, there was no significant correlation between MUNE and CMAP amplitude, or any of the clinical assessments including pinch force, grip force, the Graded Redefined Assessment of Strength, Sensibility and Prehension (GRASSP) score, and SCI duration (p > 0.05). The findings provide an evidence of motor unit loss in the FDI muscles of individuals with tetraplegia, which may contribute to weakness and other hand function deterioration. The CMAP scan offers several practical benefits compared with the traditional MUNE techniques because it is noninvasive, automated and can be performed within several minutes.

Motor Unit Number Estimation of the Second Lumbrical Muscle in Human Hand

“…Among many MUNE methods, the MScanFit MUNE was used in this study, which is based on compound muscle action potential (CMAP) scan and a model simulation of the responses ( Bostock, 2016 ; Jacobsen et al, 2018 ). The MScanFit has been tested in both healthy control subjects and individuals with neuromuscular diseases, examining different muscles, including the first dorsal interosseous, abductor pollicis brevis, abductor digiti minimi, anterior tibial, abductor hallucis, and facial muscles ( Li et al, 2018 ; Sirin et al, 2019 ; Habeych et al, 2020 ; Higashihara et al, 2020 ; Kristensen et al, 2020 ; Witt et al, 2020 ; Zong et al, 2021 , among others). This study presents a novel application of MScanFit MUNE, and for the first time provides information about motor unit number in the lumbrical muscle, which is largely unexplored in previous literature.…”

Motor unit number of the first dorsal interosseous muscle estimated from CMAP scan with different pulse widths and steps

“…En paciente con lesión medular crónica se usó para determinar la perdida de unidades motoras funcionales como posible causa de la degeneración transináptica y planificar las intervenciones en rehabilitación (Witt et al, 2020), (Zong et al, 2021).…”

A single center report of MScanFit motor unit number estimation in five muscles of healthy subjects

“…In fact, we also performed MScanFit studies in a US center for both APB and FDI muscles. An unexpected finding was that the MScanFit MUNE performed in the US research center was smaller for both FDI and APB muscles, while the CMAP amplitude recorded at the US center was higher for both FDI and APB muscles (Zong et al, 2021 , 2022b ), although the same experimental protocols (stimulus pulse duration, steps, etc.) and MScanFit program parameter setting were used.…”