Motor Imagery of Walking in People Living with and without Multiple Sclerosis: A Cross-Sectional Comparison of Mental Chronometry.

Motor imagery represents the ability to simulate anticipated movements mentally prior to their actual execution and has been proposed as a tool to assess both individuals' perception of task difficulty as well as their perception of their own abilities. People with multiple sclerosis (pwMS) often present with motor and cognitive dysfunction, which may negatively affect motor imagery. In this cross-sectional study, we explored differences in motor imagery of walking performance between pwMS (n = 20, age = 57.1 (SD = 8.6) years, 55% female) and age- and sex-matched healthy controls (n = 20, age = 58.1 (SD = 7.0) years, 60% female). Participants underwent mental chronometry assessments, a subset of motor imagery, which evaluated the difference between imagined and actual walking times across four walking tasks of increasing difficulty (i.e., large/narrow-width walkway with/without obstacles). Raw and absolute mental chronometry (A-MC) measures were recorded in single- (ST) and dual-task (DT) conditions. In ST conditions, pwMS had higher A-MC scores across all walking conditions (p ≤ 0.031, η2 ≥ 0.119), indicating lower motor imagery ability compared to healthy controls. During DT, all participants tended to underestimate their walking ability (3.38 ± 6.72 to 5.63 ± 9.17 s). However, after physical practice, pwMS were less able to adjust their imagined walking performance compared to healthy controls. In pwMS, A-MC scores were correlated with measures of balance confidence (ρ = -0.629, p < 0.01) and the self-reported expanded disability status scale (ρ = 0.747, p < 0.01). While the current study revealed that pwMS have lower motor imagery of walking performance compared to healthy individuals, further work is necessary to examine how the disassociation between mental chronometry and actual performance relates to quality of life and well-being.

Influence of the environment on cognitive-motor interaction during walking in people living with and without multiple sclerosis.

BACKGROUND: Motor and cognitive impairments are highly prevalent in people with multiple sclerosis (pwMS). The current theoretical frameworks of cognitive-motor interaction (CMI) suggest that the environment can influence both motor and cognitive performance during walking. However, the relationship between increasing environmental demands and CMI in pwMS remains to be elucidated. RESEARCH QUESTION: What is the impact of increased environmental demands on CMI during walking in people living with and without MS? METHODS: Twenty pwMS and 20 age-matched healthy adults (HA) participated in this cross-sectional study. Participants (age = 57.6 ± 7.8 years) performed four walks (baseline walking (BW), obstacle walking (OW), narrow walking (NW), and narrow with obstacles (NO)) in single-task and dual-task (serial-7 subtraction test) conditions. The dual-task costs (DTC) of gait (% change in walking time) and cognition (% change in correctly verbalized utterances) were calculated to quantify CMI. Secondary outcomes included physiological profile assessment (PPA), measures of cognition and falls efficacy scale international (FES-I). RESULTS: Mixed-factor ANOVAs revealed no main effect of task (F = 1.71, p = 0.196) and group (F = 0.71, p = 0.406) on DTC of gait, while there were significant main effects of both task (F = 23.75, p < 0.001) and group (F = 6.53, p = 0.015) on DTC of cognition. Simple main effects revealed that pwMS had a significantly higher DTC of cognition during BW (+37.6 %, p=0.013), NW (+34.2 %, p=0.014) and NO (+49 %, p=0.016) compared to HA. Additionally, DTC of cognition increased during the more environmentally demanding conditions compared to BW (range: +28.4 % to +54.2 %, all p-values<0.01) in both pwMS and HA. Only DTCs of cognition were significantly correlated with PPA and FES-I. SIGNIFICANCE: The study findings suggest that CMI may be influenced by the individual/environment at levels above those described by the more mechanistic theories of attention.

Use of a Short Version of the Activities-specific Balance Confidence Scale in Multiple Sclerosis.

BACKGROUND: Multiple sclerosis (MS) is a neurologic disease that results in balance and mobility impairments that are associated with elevated fall risk. One common patient-reported outcome measure of balance is the 16-item Activities-specific Balance Confidence (ABC) scale. The ABC scale is valid and reliable in assessing balance confidence in people with MS. However, a shorter, six-question version of the ABC scale, the ABC-6 scale, has been proposed to save time in a clinical setting. Thus, we assessed the convergent validity and internal consistency reliability of the ABC-6 scale in people with MS. METHODS: A total of 221 participants were included in this secondary analysis to compare the ABC-6 scale with the ABC scale. Convergent validity and internal consistency reliability were applied to participants based on fall history and physiological fall risk. RESULTS: Statistical analysis indicated a main effect of group of the ABC and ABC-6 scales (P < .001). Both scales showed good to very good internal consistency (Cronbach α range, 0.832-0.975) and good reliability (intraclass correlation coefficient score range, 0.888-0.941). Furthermore, both versions had moderate convergent validity. Sensitivity ranged from 30% to 97%, and specificity ranged from 64% to 100% across groups tested. CONCLUSIONS: The ABC and ABC-6 scales demonstrated good internal consistency reliability and moderate convergent validity in predicting balance confidence in people with MS. However, poor sensitivity of both versions in distinguishing between MS groups at risk for falls may call into question the usefulness of this self-report measure.

The attentional cost of movement in multiple sclerosis.

Individuals living with multiple sclerosis frequently have impairments in mobility. These impairments are more pronounced when they engage in a cognitively demanding mobility tasks (i.e., walking and talking, obstacle clearance, etc). Based in part on the attentional capacity model of movement, these impairments are suggested to result from greater attentional demands. Yet, this model has not been directly tested in neurological populations. The objective of the study was to determine whether individuals with multiple sclerosis have greater attentional cost of movement across a range of tasks. This study tested probe reaction times of 20 individuals with multiple sclerosis and 26 healthy controls in five different movement tasks. The tasks were specifically chosen to challenge the perceptual-motor system based on variations in static and dynamic balance requirements. Participants were asked to verbally respond as quickly as possible to randomly presented audio probes during motor performance. Task order was randomized, and average probe reaction time was calculated for each task. The results showed tasks requiring dynamic stability had greater probe reaction times in both healthy controls and individuals with multiple sclerosis. Furthermore, individuals with multiple sclerosis had longer probe reaction times across all tasks compared to healthy controls. Yet, there was no relationship between probe reaction times and performance during a complex walking scenario. The results indicate the attentional capacity model may be inadequate to explain cognitive-motor interaction in people with multiple sclerosis. Future studies should address the theoretical framework of cognitive-motor interaction, which may influence the design of interventions aimed at improving performance in individuals with MS.

Smartphone technology can measure postural stability and discriminate fall risk in older adults.

BACKGROUND: Falls are the leading cause of injury related death in older adults. Impaired postural stability is a predictor of falls but is seldom objectively assessed in clinical or home settings. Embedded accelerometers within smartphones offer potential to objectively measure postural stability. The purpose of this study was to determine if a smartphone embedded accelerometer can measure static postural stability and distinguish older adults at high levels of fall risk. METHODS: Thirty older adults (age: 65.9 ± 8.8) underwent seven balance tests while standing on a force plate and holding a smartphone against their chest in a standardized order. Participants also completed the Physiological Profile Assessment to assess their fall risk. Center of pressure (COP) parameters from the force plate including velocity in the anterioposterior (AP) and mediolateral (ML) directions and 95% confidence ellipse were derived. Maximum acceleration and root mean square (RMS) in ML, AP and vertical axes were derived from the smartphone. Spearman rank-order correlations between force plate and smartphone measures were conducted, and receiver operating characteristic (ROC) and the area under the curves (AUC) were constructed to distinguish between low and high fall risk. RESULTS: There were moderate to strong significant correlations between measures derived from the force plate and measures derived from the smartphone during challenging balance conditions (ρ = 0.42-0.81; p < 0.01-0.05). The AUC for ROC plots were significant for all COP measures during challenging balance conditions (p < 0.01-0.05). The AUC for ROC plots were significant for RMS vertical and AP during challenging balance conditions (p = 0.01-0.04). SIGNIFICANCE: This study provides evidence that a smartphone is a valid measure of postural stability and capable of distinguishing fall risk stratification in older adults. There is potential for smartphones to offer objective, fall risk assessments for older adults.

Dual task training in persons with Multiple Sclerosis: a feasability randomized controlled trial.

OBJECTIVE: To determine the feasibility of dual task training in persons with Multiple Sclerosis. DESIGN: Randomized, single-blinded controlled trial. SETTING: University research laboratory. PARTICIPANTS: A total of 234 individuals inquired about the investigation. After screening, 20 individuals with multiple sclerosis who self-reported problems with multitasking and were ambulatory volunteered for the investigation. 14 participants completed the post-assessment following the 12-week intervention. INTERVENTION: Participants were randomly assigned to either single task training program which focused on balance and walking function ( n=6) or dual task training program that incorporated cognitive tasks in balance and walking training ( n=8). MEASURES: Before and after the 12-week interventions participants underwent assessments of walking; dual task walking; balance (Berg Balance Scale and balance confidence) and cognition as indexed by the Brief International Cognitive Assessment for MS. RESULTS: There was an 8.5% recruitment rate, a 70% retention rate, and a 100% adherence rate. There was a trend for dual task gait speed to improve in the dual task training group following the intervention (Pre: task 1: 109.8±39, task 2: 104.2±34.1; Post: task 1:127.6±40.1, task 2: 122.8±37.4; P=0.14; η2 = 0.24). There was also a trend for the dual task training group (28.1) to have greater performance than the control group (24.7) on visuospatial memory ( P=0.10; η2= 0.23). There were no changes in cognitive performance during walking trials. CONCLUSIONS: The study procedures were found to be feasible and improvements should be made in recruitment efforts going forward. Further examination of dual task training programs in individuals with multiple sclerosis is warranted.

Intervention modalities for targeting cognitive-motor interference in individuals with neurodegenerative disease: a systematic review.

INTRODUCTION: Individuals with neurodegenerative disease (NDD) commonly have elevated cognitive-motor interference, change in either cognitive or motor performance (or both) when tasks are performed simultaneously, compared to healthy controls. Given that cognitive-motor interference is related to reduced community ambulation and elevated fall risk, it is a target of rehabilitation interventions. Areas covered: This review details the collective findings of previous dual task interventions in individuals with NDD. A total of 21 investigations focusing on 4 different neurodegenerative diseases and one NDD precursor (Parkinson's disease, multiple sclerosis, Alzheimer's disease (AD), dementia other than AD, and mild cognitive impairment) consisting of 721 participants were reviewed. Expert commentary: Preliminary evidence from interventions targeting cognitive-motor interference, both directly and indirectly, show promising results for improving CMI in individuals with neurodegenerative diseases. Methodological limitations, common to pilot investigations preclude firm conclusions. Well-designed randomized control trials targeting cognitive motor interference are warranted.

Three-Month Test-Retest Reliability of Center of Pressure Motion During Standing Balance in Individuals with Multiple Sclerosis.

BACKGROUND: Balance impairment and an increased rate of falls are commonly reported in individuals with multiple sclerosis (MS). Force platform-generated center of pressure (COP) metrics have previously been recommended as an outcome measure to quantify balance deficits and distinguish between fallers and nonfallers in MS. Information is limited regarding the preservation of postural control in individuals with MS over extended time frames in the absence of an intervention. This report examines the test-retest reliability and magnitude of change of COP motion during standing balance over 3 months. METHODS: Twenty individuals with MS and a history of falling underwent testing on two occasions 3 months apart in the absence of an intervention. On both occasions, participants completed two 30-second trials of three conditions: eyes open, eyes closed, and eyes open with concurrent cognitive challenge (dual task). Measures of COP area, velocity, and temporal structure were calculated and included in the reliability analysis. RESULTS: The COP metrics displayed fair-to-excellent reliability over 3 months without an intervention. Reliability was maintained across the three commonly used balance conditions. CONCLUSIONS: These results offer insight into the reliability of COP measures over a 3-month period in MS and can inform the use of COP metrics for future study design (eg, sample size estimates) and balance outcome assessment during randomized controlled trials and fall-prevention studies in individuals with MS.

The Relationship Between Balance Confidence and Cognitive Motor Interference in Individuals With Multiple Sclerosis.

Gait and cognitive impairments are compounded when performed simultaneously in individuals with multiple sclerosis (MS), and this is termed cognitive-motor interference (CMI). The authors examined whether CMI is related to balance confidence in individuals with MS. They hypothesized that individuals with low balance confidence would exhibit greater CMI possibly indicating a behavioral modification during dual task conditions. Thirty-four individuals with MS completed Activity-specific Balance Confidence (ABC) scale and a cognitive assessment as well as single and dual task walking trials at a comfortable pace. CMI was calculated as the percent change in walking velocity and cognitive task performance from single- to dual-task conditions and termed dual-task cost (DTC). A correlation analysis was performed to determine the relationships between DTCs of gait and cognitive performance and ABC scores. The correlation analysis revealed no significant association between ABC and DTC of walking velocity (p > .05). A significant relationship between balance confidence and DTCs of cognition was observed. The observed relationships suggest individuals with MS tend to alter their cognitive performance rather than manipulating their gait when confronted with a dual task. Overall, the findings partially support a behavioral explanation of CMI in individuals with MS.

Gait termination in individuals with multiple sclerosis.

Despite the ubiquitous nature of gait impairment in multiple sclerosis (MS), there is limited information concerning the control of gait termination in individuals with MS. The purpose of this investigation was to examine planned gait termination in individuals with MS and healthy controls with and without cognitive distractors. Individuals with MS and age matched controls completed a series of gait termination tasks over a pressure sensitive walkway under non-distracting and cognitively distracting conditions. As expected the MS group had a lower velocity (89.9±33.3 cm/s) than controls (142.8±22.4 cm/s) and there was a significant reduction in velocity in both groups under the cognitive distracting conditions (MS: 73.9±30.7 cm/s; control: 120.0±25.9 cm/s). Although individuals with MS walked slower, there was no difference between groups in the rate a participant failed to stop at the target (i.e. failure rate). Overall failure rate had a 10-fold increase in the cognitively distracting condition across groups. Individuals with MS were more unstable during termination. Future research examining the neuromuscular mechanisms contributing to gait termination is warranted.

Cognitive-motor interference in multiple sclerosis: a systematic review of evidence, correlates, and consequences.

Individuals with multiple sclerosis (MS) regularly exhibit deficits in motor and cognitive function. Recent evidence suggests that these impairments are compounded when motor and cognitive task are performed simultaneously such as walking while talking. The changes incurred during simultaneous performance of motor and cognitive tasks are a result of cognitive-motor interference (CMI) and operationalized as dual task costs (DTC). Recently in MS, research has been conducted to understand and analyze the impact of CMI. The purpose of this paper was to review the current literature related to the evidence, correlates, and consequences of CMI in MS. Relevant literature was collected from the results of a PubMed search for terms including "Cognitive-motor interference" or "Cognitive-motor interaction" or "Dual task" and "multiple sclerosis." Overall, 20 papers were included for review which focused on CMI during balance and walking tasks. The finding that there is a lack of evidence pertaining to changes in the cognitive domain as well as to the specific consequences of CMI in MS was noted. Future work should aim to fill these gaps and ultimately investigate the usefulness of targeted interventions in reducing the deleterious effects of CMI in individuals with MS.

Preliminary investigation of gait initiation and falls in multiple sclerosis.

OBJECTIVE: To examine the relationship between gait initiation, fall history, and physiological fall risk in individuals with multiple sclerosis (MS) during both cognitive distracting and nondistracting conditions. DESIGN: Single time point cross-sectional analysis. SETTING: University research laboratory. PARTICIPANTS: Ambulatory individuals (N=20) with MS ranging in age from 28 to 76 years. INTERVENTION: Not applicable. MAIN OUTCOME MEASURES: Gait initiation time was quantified as the time to toe-off of the first step after an auditory cue. Gait initiation was performed with and without a concurrent cognitive challenge of reciting alternating letters of the alphabet. Additionally, participants underwent a test of fall risk using the Physiological Profile Assessment (PPA) and provided a self-report of the number of falls in the previous 3 months. RESULTS: Gait initiation times ranged from .67 to 1.12 seconds during the single-task condition and .73 to 1.84 seconds during the cognitive challenge condition. PPA scores ranged from -.80 to 3.87. Participants reported a median of 0.0 falls (interquartile range, 0.0-2.75) in the previous 3 months. There was a significant correlation between PPA score and gait initiation times only in the cognitive distraction condition (ρ=.50). There was also a correlation between cognitive distraction gait initiation times and fall history (ρ=.60). CONCLUSIONS: The observations provide preliminary evidence that gait initiation during cognitive challenge may represent a target for fall prevention strategies in MS.

Stride-Time Variability and Fall Risk in Persons with Multiple Sclerosis.

Gait variability is associated with falls in clinical populations. However, gait variability's link to falls in persons with Multiple Sclerosis (PwMS) is not well established. This investigation examined the relationship between stride-time variability, fall risk, and physiological fall risk factors in PwMS. 17 PwMS (62.8 ± 7.4 years) and 17 age-matched controls (62.8 ± 5.9 years) performed the 6-minute walk test. Stride-time was assessed with accelerometers attached to the participants' shanks. Stride-time variability was measured by interstride coefficient of variation (CV) of stride-time. The participant's fall risk was measured by the short form physiological profile assessment (PPA). A Spearman correlation analysis was used to determine the relationship between variables. Increased fall risk was strongly associated with increased stride-time CV in both PwMS (ρ = 0.71, p < 0.01) and the controls (ρ = 0.67, p < 0.01). Fall risk was not correlated with average stride-time (p > 0.05). In PwMS, stride-time CV was related to postural sway (ρ = 0.74, p < 0.01) while in the control group, it was related to proprioception (ρ = 0.61, p < 0.01) and postural sway (ρ = 0.78, p < 0.01). Current observations suggest that gait variability is maybe more sensitive marker of fall risk than average gait parameters in PwMS. It was also noted that postural sway may be potentially targeted to modify gait variability in PwMS.

Fall risk and incidence reduction in high risk individuals with multiple sclerosis: a pilot randomized control trial.

OBJECTIVE: To determine the feasibility of three fall prevention programs delivered over 12 weeks among individuals with multiple sclerosis: (A) a home-based exercise program targeting physiological risk factors; (B) an educational program targeting behavioral risk factors; and (C) a combined exercise-and-education program targeting both factors. DESIGN: Randomized controlled trial. SETTING: Home-based training with assessments at research laboratory. PARTICIPANTS: A total of 103 individuals inquired about the investigation. After screening, 37 individuals with multiple sclerosis who had fallen in the last year and ranged in age from 45-75 years volunteered for the investigation. A total of 34 participants completed postassessment following the 12-week intervention. INTERVENTION: Participants were randomly assigned into one of four conditions: (1) wait-list control (n = 9); (2) home-based exercise (n = 11); (3) education (n = 9); or (4) a combined exercise and education (n = 8) group. MEASURES: Before and after the 12-week interventions, participants underwent a fall risk assessment as determined by the physiological profile assessment and provided information on their fall prevention behaviors as indexed by the Falls Prevention Strategy Survey. Participants completed falls diaries during the three-months postintervention. RESULTS: A total of 34 participants completed postintervention testing. Procedures and processes were found to be feasible. Overall, fall risk scores were lower in the exercise groups (1.15 SD 1.31) compared with the non-exercise groups (2.04 SD 1.04) following the intervention (p < 0.01). There was no group difference in fall prevention behaviors (p > 0.05). CONCLUSIONS: Further examination of home-based exercise/education programs for reducing falls in individuals with multiple sclerosis is warranted. A total of 108 participants would be needed in a larger randomized controlled trial.ClinicalTrials.org #NCT01956227.

Correlates of dual task cost of standing balance in individuals with multiple sclerosis.

Cognitive and balance dysfunction are common symptoms in individuals with multiple sclerosis (MS). Although traditionally seen as separate impairments, performing a concurrent cognitive task while maintaining an upright posture results in individuals with MS increasing their postural sway (i.e. dual task cost (DTC) of balance). However, the factors relating to this phenomenon are not clear. This investigation examined the demographic, clinical and cognitive correlates of DTC of balance in individuals with MS. Sixty-two persons with MS completed both quiet standing and dual task balance trials on a force platform. Additionally, they provided demographic information and performed clinical tests of balance, spasticity, fall risk and cognitive processing speed. Dual task cost was calculated as the percentage change in sway area from the baseline to dual task force platform conditions. Overall, there were no significant correlations between DTC of balance and any of the outcome measures in the entire sample. In contrast, postural sway in the baseline and dual task condition were found to correlate with disability, fall risk, balance performance, fatigue, cognitive processing speed and age. Secondary analysis revealed different correlates of DTC of balance in those with low versus high baseline sway. The results suggest that the change in standing balance with the simultaneous performance of cognitive task may only be informative in individuals with minimal balance dysfunction.

Effects of walking direction and cognitive challenges on gait in persons with multiple sclerosis.

Declines in walking performance are commonly seen when undergoing a concurrent cognitive task in persons with multiple sclerosis (MS). The purpose of this study was to determine the effect of walking direction and simultaneous cognitive task on the spatiotemporal gait parameters in persons with MS compared to healthy controls. Ten persons with MS (Median EDSS, 3.0) and ten healthy controls took part in this pilot study. Participants performed 4 walking trials at their self-selected comfortable pace. These trials included forward walking, forward walking with a cognitive task, backward walking, and backward walking with a cognitive task. Walking performance was indexed with measures of velocity, cadence, and stride length for each testing condition. The MS group walked slower with significantly reduced stride length compared to the control group. The novel observation of this investigation was that walking differences between persons with MS and healthy controls were greater during backward walking, and this effect was further highlighted during backward walking with added cognitive test. This raises the possibility that backward walking tests could be an effective way to examine walking difficulties in individuals with MS with relatively minimal walking impairment.

Dual task cost of walking is related to fall risk in persons with multiple sclerosis.

Persons with multiple sclerosis (MS) commonly have walking and cognitive impairments. While walking with a simultaneous cognitive task, persons with MS experience a greater decline in walking performance than healthy controls. This change in performance is termed dual task cost or dual task interference and has been associated with fall risk in older adults. We examined whether dual task cost during walking was related to fall risk in persons with MS. Thirty-three ambulatory persons with MS performed walking tasks with and without a concurrent cognitive task (dual task condition) as well as underwent a fall risk assessment. Dual task cost was operationalized as the percent change in velocity from normal walking conditions to dual task walking conditions. Fall risk was quantified using the Physiological Profile Assessment. A Spearman correlation analysis revealed a significant positive correlation between dual task cost of walking velocity and fall risk as well as dual task cost of stride length and fall risk. Overall, the findings indicate that dual task cost is associated with fall risk and may be an important target for falls prevention strategies.