The numbers and physiological characteristics of motor units in health and disease.

摘要

It is the objective of this thesis to further validate, develop and assess the applicability of decomposition-based quantitative electromyography (DQEMG) in providing electrophysiological data pertaining to the physiological characteristics and numbers of motor units (MUs) in both health and disease. Methodological considerations associated with the use of DQEMG were addressed in the initial studies of this thesis, culminating in the application of the technique in a population of patients with amyotrophic lateral sclerosis (ALS) in the final study.;The effect of varying force levels on DQEMG analysis, including MUNEs, was examined (experiment 2). Increasing the level of force from 10-50% of maximal voluntary contraction resulted in increased MUP size and decreased MUNEs, suggesting the need to control for force during studies using DQEMG.;Determining the within-subject reliability of DQEMG is important in establishing the usefulness of these measures in longitudinal studies (experiment 3). Results of the study were highly reliable, and 95% confidence intervals calculated based on the test retest data identify the range of MUNE variability expected using DQEMG, allowing values falling outside this range to be identified as independent of the variability inherent to the technique.;The relationship between force and the surface EMG signal was examined in control subjects and patients with neuromuscular disease (experiment 4). The results show a strong linear relationship, supporting the use of the surface EMG signal as a proxy for force during studies using DQEMG, increasing the clinical utility of the technique.;The ability to sample surface-detected motor unit potentials (MUPs) and derive motor unit number estimates (MUNEs) was demonstrated (experiment 1). Considering methodological differences, the values obtained using DQEMG were similar to previous reports, with the current methods displaying improvements over earlier techniques. Lastly, DQEMG analysis was highly reliable, supporting its clinical utility.;Lastly, DQEMG was used to obtain quantitative electrophysiological data, including MUNEs, from a group of patients with ALS (experiment 5). The results suggest that the data obtained using DQEMG are representative of the pathophysiological changes in the MU pool of ALS patients, supporting its use in studies documenting the natural history and progression of the disease.;Keywords: electromyography, amyotrophic lateral sclerosis, motor unit number estimate, motor unit, quantitative electromyography, isometric force, first dorsal interosseous, biceps-brachii.