Translational and Clinical Research Institute, Newcastle University, Newcastle upon Tyne, UK.
NIHR Newcastle Biomedical Research Centre, Newcastle upon Tyne Hospitals NHS Foundation Trust, Faculty of Medical Sciences, Newcastle University, Newcastle upon Tyne, UK.
J Cachexia Sarcopenia Muscle. 2021 Feb;12(1):17-29. doi: 10.1002/jcsm.12655. Epub 2020 Dec 22.
Sarcopenia is a progressive and generalized disease, more common in older adults, which manifests as a loss of muscle strength and mass. The pathophysiology of sarcopenia is still poorly understood with many mechanisms suggested. Age associated changes to the neuromuscular architecture, including motor units and their constituent muscle fibres, represent one such mechanism. Electromyography can be used to distinguish between different myopathies and produce counts of motor units. Evidence from electromyography studies suggests that with age, there is a loss of motor units, increases to the sizes of remaining units, and changes to their activity patterns. However, electromyography is invasive, can be uncomfortable, does not reveal the exact spatial position of motor units within muscle and is difficult to perform in deep muscles. We present a novel diffusion-weighted magnetic resonance imaging technique called 'motor unit magnetic resonance imaging (MUMRI)'. MUMRI aims to improve our understanding of the changes to the neuromuscular system associated with ageing, sarcopenia and other neuromuscular diseases. To date, we have demonstrated that MUMRI can be used to detect statistically significant differences in fasciculation rate of motor units between (n = 4) patients with amyotrophic lateral sclerosis (mean age ± SD: 53 ± 15) and a group of (n = 4) healthy controls (38 ± 7). Patients had significantly higher rates of fasciculation compared with healthy controls (mean = 99.1/min, range = 25.7-161.0 in patients vs. 7.7/min, range = 4.3-9.7 in controls; P < 0.05. MUMRI has detected differences in size, shape, and distribution of single human motor units between (n = 5) young healthy volunteers (29 ± 2.2) and (n = 5) healthy older volunteers (65.6 ± 14.8). The maximum size of motor unit territories in the older group was 12.4 ± 3.3 mm and 9.7 ± 2.7 mm in the young group; P < 0.05. MUMRI is an entirely non-invasive tool, which can be used to detect physiological and pathological changes to motor units in neuromuscular diseases. MUMRI also has the potential to be used as an intermediate outcome measure in sarcopenia trials.
肌肉减少症是一种进行性和全身性疾病，多见于老年人，表现为肌肉力量和质量的丧失。肌肉减少症的病理生理学机制尚不清楚，有许多机制被提出。与年龄相关的神经肌肉结构变化，包括运动单位及其组成的肌纤维，就是其中之一。肌电图可用于区分不同的肌病，并对运动单位进行计数。肌电图研究的证据表明，随着年龄的增长，运动单位丧失，剩余单位的大小增加，其活动模式发生变化。然而，肌电图具有侵入性，可能会引起不适，无法揭示运动单位在肌肉内的确切空间位置，并且难以在深部肌肉中进行。我们提出了一种新的弥散加权磁共振成像技术，称为“运动单位磁共振成像（MUMRI）”。MUMRI 旨在提高我们对与衰老、肌肉减少症和其他神经肌肉疾病相关的神经肌肉系统变化的理解。迄今为止，我们已经证明，MUMRI 可用于检测（n=4）肌萎缩侧索硬化症患者（平均年龄±标准差：53±15）和（n=4）健康对照组（38±7）之间运动单位纤维颤动率的统计学显著差异。与健康对照组相比，患者的纤维颤动率明显更高（平均值=99.1/min，范围=25.7-161.0 在患者中，范围=4.3-9.7 在对照组中；P<0.05）。MUMRI 已检测到（n=5）年轻健康志愿者（29±2.2）和（n=5）健康老年志愿者（65.6±14.8）之间单个人类运动单位的大小、形状和分布的差异。老年组运动单位区域的最大尺寸为 12.4±3.3mm，年轻组为 9.7±2.7mm；P<0.05。MUMRI 是一种完全非侵入性的工具，可用于检测神经肌肉疾病中运动单位的生理和病理变化。MUMRI 还有可能作为肌肉减少症试验的中间结果测量指标。
