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Motor unit discharge characteristics and walking performance of individuals with multiple sclerosis.

ABSTRACT: Walking performance of persons with multiple sclerosis (MS) is strongly influenced by the activation signals received by lower leg muscles. We examined the associations between force steadiness and motor unit discharge characteristics of lower leg muscles during submaximal isometric contractions with tests of walking performance and disability status in individuals who self-reported walking difficulties due to MS. We expected that worse walking performance would be associated with weaker plantar flexor muscles, worse force steadiness, and slower motor unit discharge times. Twenty-three individuals with relapsing-remitting MS (56?±?7 yr) participated in the study. Participants completed one to three evaluation sessions that involved two walking tests (25-ft walk and 6-min walk), a manual dexterity test (grooved pegboard), health-related questionnaires, and measurement of strength, force steadiness, and motor unit discharge characteristics of lower leg muscles. Multiple regression analyses were used to construct models to explain the variance in measures of walking performance. There were statistically significant differences (effect sizes: 0.21-0.60) between the three muscles in mean interspike interval (ISI) and ISI distributions during steady submaximal contractions with the plantar flexor and dorsiflexor muscles. The regression models explained 40% of the variance in 6-min walk distance and 47% of the variance in 25-ft walk time with two or three variables that included mean ISI for one of the plantar flexor muscles, dorsiflexor strength, and force steadiness. Walking speed and endurance in persons with relapsing-remitting MS were reduced in individuals with longer ISIs, weaker dorsiflexors, and worse plantar flexor force steadiness. NEW & NOTEWORTHY The walking endurance and gait speed of persons with relapsing-remitting multiple sclerosis (MS) were worse in individuals who had weaker dorsiflexor muscles and greater force fluctuations and longer times between action potentials discharged by motor units in plantar flexor muscles during steady isometric contractions. These findings indicate that the control of motor unit activity in lower leg muscles of individuals with MS is associated with their walking ability.

SUBMITTER: Almuklass AM

PROVIDER: S-EPMC5966731 | biostudies-literature | 2018 Apr

REPOSITORIES: biostudies-literature

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Motor unit discharge characteristics and walking performance of individuals with multiple sclerosis.

Almuklass Awad M AM Davis Leah L Hamilton Landon D LD Vieira Taian M TM Botter Alberto A Enoka Roger M RM

Journal of neurophysiology 20180103 4

Walking performance of persons with multiple sclerosis (MS) is strongly influenced by the activation signals received by lower leg muscles. We examined the associations between force steadiness and motor unit discharge characteristics of lower leg muscles during submaximal isometric contractions with tests of walking performance and disability status in individuals who self-reported walking difficulties due to MS. We expected that worse walking performance would be associated with weaker plantar ...[more]

PMID: 29357453

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Project description:BACKGROUND: Although there is substantial anecdotal evidence that clutter is common among people with multiple sclerosis (MS), the literature contains no reports of studies on the actual prevalence of the problem or its impact on functional performance in this population. Clutter promotes confusion and places individuals in potentially dangerous situations by increasing their risks of falling, losing medications, and misplacing important documents. In addition, it may negatively affect activities of daily living (ADLs). Many common MS symptoms such as decreased mobility, visual or cognitive changes, fatigue, and depression can exacerbate clutter accumulation, which in turn can have detrimental effects on physical, financial, emotional, cognitive, and social functioning. It is critical for MS clinicians to address clutter management in order to improve patients' overall functional independence and participation. METHODS: A clutter reduction protocol was developed and implemented at our institution for individuals with MS. Our group program addresses psychosocial issues preventing organization and offers practical strategies for clutter removal and management to improve performance in ADLs. A clutter questionnaire is administered to individuals before and after their participation in the group program. RESULTS: Anecdotal reports indicate that the intervention helped to reduce clutter, promote a more realistic attitude toward "possessions," and establish a sense of accomplishment in controlling one's environment. Participants also reported fewer falls, feeling less isolated, increased ease in finding their medications, and a general sense of cognitive clarity in accomplishing ADLs. Outcome assessments are now being developed to objectively measure these effects as well as the prevalence of clutter within the MS population. CONCLUSIONS: Clutter management is an important area for MS clinicians to address because it can significantly affect patients' functioning, safety, performance of ADLs, and quality of life.

Project description:ImportanceCognitive impairment is a debilitating symptom of multiple sclerosis (MS) that affects up to 70% of patients. An improved understanding of the underlying pathology of MS-related cognitive impairment would provide considerable benefit to patients and clinicians.ObjectiveTo determine whether there is an association between myelin damage in tissue that appears completely normal on standard clinical imaging, but can be detected by myelin water imaging (MWI), with cognitive performance in MS.Design, setting, and participantsIn this cross-sectional study, participants with MS and controls underwent cognitive testing and magnetic resonance imaging (MRI) from August 23, 2017, to February 20, 2019. Participants were recruited through the University of British Columbia Hospital MS clinic and via online recruitment advertisements on local health authority websites. Cognitive testing was performed in the MS clinic, and MRI was performed at the adjacent academic research neuroimaging center. Seventy-three participants with clinically definite MS fulfilling the 2017 revised McDonald criteria for diagnosis and 22 age-, sex-, and education-matched healthy volunteers without neurological disease were included in the study. Data analysis was performed from March to November 2019.ExposuresMWI was performed at 3 T with a 48-echo, 3-dimensional, gradient and spin-echo (GRASE) sequence. Cognitive testing was performed with assessments drawn from cognitive batteries validated for use in MS.Main outcomes and measuresThe association between myelin water measures, a measurement of the T2 relaxation signal from water in the myelin bilayers providing a specific marker for myelin, and cognitive test scores was assessed using Pearson correlation. Three white matter regions of interest-the cingulum, superior longitudinal fasciculus (SLF), and corpus callosum-were selected a priori according to their known involvement in MS-related cognitive impairment.ResultsFor the 95 total participants, the mean (SD) age was 49.33 (11.44) years. The mean (SD) age was 50.2 (10.7) years for the 73 participants with MS and 46.4 (13.5) for the 22 controls. Forty-eight participants with MS (66%) and 14 controls (64%) were women. The mean (SD) years of education were 14.7 (2.2) for patients and 15.8 (2.5) years for controls. In MS, significant associations were observed between myelin water measures and scores on the Symbol Digit Modalities Test (SLF, r = -0.490; 95% CI, -0.697 to -0.284; P < .001; corpus callosum, r = -0.471; 95% CI, -0.680 to -0.262; P < .001; and cingulum, r = -0.419; 95% CI, -0.634 to -0.205; P < .001), Selective Reminding Test (SLF, r = -0.444; 95% CI, -0.660 to -0.217; P < .001; corpus callosum, r = -0.411; 95% CI, -0.630 to -0.181; P = .001; and cingulum, r = -0.361; 95% CI, -0.602 to -0.130; P = .003), and Controlled Oral Word Association Test (SLF, r = -0.317; 95% CI, -0.549 to -0.078; P = .01; and cingulum, r = -0.335; 95% CI, -0.658 to -0.113; P = .006). No significant associations were found in controls.Conclusions and relevanceThis study used MWI to demonstrate that otherwise normal-appearing brain tissue is diffusely damaged in MS, and the findings suggest that myelin water measures are associated with cognitive performance. MWI offers an in vivo biomarker feasible for use in clinical trials investigating cognition, providing a means for monitoring changes in myelination and its association with symptom worsening or improvement.

Dataset Information

Motor unit discharge characteristics and walking performance of individuals with multiple sclerosis.

Publications

Motor unit discharge characteristics and walking performance of individuals with multiple sclerosis.

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