Motor Unit Discharge Variability Is Increased in Mild-To-Moderate Parkinson's Disease

Frontiers in Neurology

Christopher K. Thompson¹  Cindy Zadikoff²  Colum D. MacKinnon³  Laura Miller McPherson⁴  C.J. Heckman⁵  Jessica M. Wilson⁶ 

[1] Department of Health and Rehabilitation Sciences, Temple University, Philadelphia, PA, United States;Department of Neurology, Northwestern University, Chicago, IL, United States;Department of Neurology, University of Minnesota, Minneapolis, MN, United States;Department of Neurology, Washington University School of Medicine, St. Louis, MO, United States;Department of Physical Medicine and Rehabilitation, Northwestern University, Chicago, IL, United States;Department of Physical Therapy and Human Movement Sciences, Northwestern University, Chicago, IL, United States;Department of Physiology, Northwestern University, Chicago, IL, United States;Program in Physical Therapy, Washington University School of Medicine, St. Louis, MO, United States;

关键词: motor unit;    Parkinson's disease;    EMG;    biceps brachii;    triceps brachii;   

DOI  :  10.3389/fneur.2020.00477

来源: DOAJ

【 摘 要 】

Individuals with Parkinson's disease (PD) demonstrate deficits in muscle activation such as decreased amplitude and inappropriate bursting. There is evidence that some of these disturbances are more pronounced in extensor vs. flexor muscles. Surface EMG has been used widely to quantify muscle activation deficits in PD, but analysis of discharge of the underlying motor units may provide greater insight and be more sensitive to changes early in the disease. Of the few studies that have examined motor unit discharge in PD, the majority were conducted in the first dorsal interosseous, and no studies have measured motor units from extensor and flexor muscles within the same cohort. The objective of this study was to characterize the firing behavior of single motor units in the elbow flexor and extensor muscles during isometric contractions in people with mild-to-moderate PD. Ten individuals with PD (off-medication) and nine healthy controls were tested. Motor unit spike times were recorded via intramuscular EMG from the biceps and triceps brachii muscles during 30-s isometric contractions at 10% maximum voluntary elbow flexion and elbow extension torque, respectively. We selected variables of mean motor unit discharge rate, discharge variability, and torque variability to evaluate motor abnormalities in the PD group. The effects of group, muscle, and group-by-muscle on each variable were determined using separate linear mixed models. Discharge rate and torque variability were not different between groups, but discharge variability was significantly higher in the PD group for both muscles combined (p < 0.0001). We also evaluated the asymmetry in these motor variables between the triceps and biceps for each individual participant with PD to evaluate whether there was an association with disease severity. The difference in torque variability between elbow flexion and extension was significantly correlated with both the Hoehn and Yahr scale (rho = 0.71) and UPDRS (rho = 0.62). Our findings demonstrate that variability in motor output, rather than decreased discharge rates, may contribute to motor dysfunction in people with mild-to-moderate PD. Our findings provide insight into altered neural control of movement in PD and demonstrate the importance of measuring from multiple muscles within the same cohort.

【 授权许可】

Unknown