Day-to-day variability of maximum walking distance in MS patients can mislead to relevant changes in the Expanded Disability Status Scale (EDSS): average walking speed is a more constant parameter

Ecological Momentary Assessment of Head Motion: Toward Normative Data of Head Stabilization

Head stabilization is fundamental for balance during locomotion but can be impaired in elderly or diseased populations. Previous studies have identified several parameters of head stability with possible diagnostic value in a laboratory setting. Recently, the ecological validity of measures obtained in such controlled contexts has been called into question. The aim of this study was to investigate the ecological validity of previously described parameters of head stabilization in a real-world setting. Ten healthy subjects participated in the study. Head and trunk movements of each subject were recorded with inertial measurement units (IMUs) for a period of at least 10 h. Periods of locomotion were extracted from the measurements and predominant frequencies, root mean squares (RMSs) and bout lengths were estimated. As parameters of head stabilization, attenuation coefficients (ACs), harmonic ratios (HRs), coherences, and phase differences were computed. Predominant frequencies were distributed tightly around 2 Hz and ACs, HRs, and coherences exhibited the highest values in this frequency range. All head stability parameters exhibited characteristics consistent with previous reports, although higher variances were observed. These results suggest that head stabilization is tuned to the 2 Hz fundamental frequency of locomotion and that previously described measures of head stability could generalize to a real-world setting. This is the first study to address the ecological validity of these measures, highlighting the potential use of head stability parameters as diagnostic tools or outcome measures for clinical trials. The low cost and ease of use of the IMU technology used in this study could additionally be of benefit for a clinical application.

Smart watch, smarter EDSS: Improving disability assessment in multiple sclerosis clinical practice

BACKGROUND

Patients' walking ability is critical for assessing the EDSS, the disability scale commonly used in MS clinical practice. Such assessment is usually based on patients' estimates or on the measures the neurologists observe during periodic visits.

OBJECTIVES AND METHODS

We evaluated the agreement between patients' and neurologists' estimates of maximum walking ability and patients' mean maximum walking ability measured in their daily life through a GPS smartwatch, and assessed limitations of the current methods.

RESULTS

Seventy-three patients with a median walking ability of 500m (IQR 400-800) were enrolled in the study. The agreement between patients' estimates and GPS measurements was modest (ICC 0.29, 95% CIs 0.06-0.49) and was influenced by course of the disease, patients' mood and inaccuracy at estimating long distances. A better reliability was found between neurologists' and GPS measures (ICC 0.68, 95% CIs 0.53-0.78), but the variability increased for longer distances and was influenced by patients' depressive symptoms, fatigue and course of the disease.

CONCLUSIONS

This study showed a poor agreement between patients' and neurologists' estimates of maximum walking ability and patients' mean maximum walking ability measured in their daily life through a GPS smartwatch, with many factors affecting patient's and neurologists' estimates of the EDSS. The use of remote measurement technologies may provide a better understanding of the impact of MS in a patient's life.

Symptom variability, affect and physical activity in ambulatory persons with multiple sclerosis: Understanding patterns and time-bound relationships

BACKGROUND

Individuals with multiple sclerosis (MS) experience a clinical course that is highly variable with daily fluctuations in symptoms significantly affecting functional ability and quality of life. Yet, understanding how MS symptoms co-vary and associate with physical and psychological health is unclear.

OBJECTIVE

The purpose of the study was to explore variability patterns and time-bound relationships across symptoms, affect, and physical activity in individuals with MS.

METHODS

The study employed a multivariate, replicated, single-subject repeated-measures (MRSRM) design and involved four individuals with MS. Mood, fatigue, pain, balance confidence, and losses of balance were measured daily over 28 days by self-report. Physical activity was also measured daily over this same time period via accelerometry. Dynamic factor analysis (DFA) was used to determine the dimensionality and lagged relationships across the variables.

RESULTS

Person-specific models revealed considerable time-dependent co-variation patterns as well as pattern variation across subjects. Results also offered insight into distinct variability structures at varying levels of disability.

CONCLUSION

Modeling person-level variability may be beneficial for addressing the heterogeneity of experiences in individuals with MS and for understanding temporal and dynamic interrelationships among perceived symptoms, affect, and health outcomes in this group.

Motor determinants of gait in 100 ambulatory patients with multiple sclerosis

A prospective analysis of gait and strength parameters was performed in 100 patients diagnosed with MS and pyramidal involvement admitted in a rehabilitation unit. The patients were divided into two groups based on their ability to walk in daily life (nonassisted or cane-assisted gait) and into four clinical subgroups depending on associated involvements such as sensory loss or cerebellar ataxia. Twenty healthy subjects were studied as a control group. Gait parameters were evaluated with a Locometre and muscle strength with an isokinetic dynamometer. The results showed that the average velocity and strength of the hamstring and quadriceps were strongly correlated and reduced in the MS group in comparison with the control, and in the cane-assisted group compared with the nonassisted group. Gait velocity tended to be more correlated to hamstring strength in the nonassisted group with a determination coefficient (r2) reaching a value of 0.44 in the sensory subgroup. These findings provide evidence that a correlation between strength reduction and gait impairment is obvious whatever the clinical form in patients with MS. This correlation is higher with hamstrings but may change depending on the disability level and the clinical form. This could be taken into account in the individual assessment of further rehabilitation programmes.

Ecological validity of walking capacity tests in multiple sclerosis

Background

Ecological validity implicates in how far clinical assessments refer to real life. Short clinical gait tests up to ten meters and 2- or 6-Minutes Walking Tests (2MWT/6MWT) are used as performance-based outcomes in Multiple Sclerosis (MS) studies and considered as moderately associated with real life mobility.

Objective

To investigate the ecological validity of 10 Meter Walking Test (10mWT), 2MWT and 6MWT.

Methods

Persons with MS performed 10mWT, 6MWT including 2MWT and 7 recorded days by accelerometry. Ecological validity was assumed if walking tests represented a typical walking sequence in real-life and correlations with accelerometry parameters were strong.

Results

In this cohort (n=28, medians: age=45, EDSS=3.2, disease duration=9 years), uninterrupted walking of 2 or 6 minutes occurred not frequent in real life (2.61 and 0.35 sequences/day). 10mWT correlated only with slow walking speed quantiles in real life. 2MWT and 6MWT correlated moderately with most real life walking parameters.

Conclusion

Clinical gait tests over a few meters have a poor ecological validity while validity is moderate for 2MWT and 6MWT. Mobile accelerometry offers the opportunity to control and improve the ecological validity of MS mobility outcomes.

A passive exoskeleton can push your life up: application on multiple sclerosis patients

In the present study, we report the benefits of a passive and fully articulated exoskeleton on multiple sclerosis patients by means of behavioral and electrophysiological measures, paying particular attention to the prefrontal cortex activity. Multiple sclerosis is a neurological condition characterized by lesions of the myelin sheaths that encapsulate the neurons of the brain, spine and optic nerve, and it causes transient or progressive symptoms and impairments in gait and posture. Up to 50% of multiple sclerosis patients require walking aids and 10% are wheelchair-bound 15 years following the initial diagnosis. We tested the ability of a new orthosis, the “Human Body Posturizer”, designed to improve the structural and functional symmetry of the body through proprioception, in multiple sclerosis patients. We observed that a single Human Body Posturizer application improved mobility, ambulation and response accuracy, in all of the tested patients. Most importantly, we associated these clinical observations and behavioral effects to changes in brain activity, particularly in the prefrontal cortex.

Association between walking speed and age in healthy, free-living individuals using mobile accelerometry--a cross-sectional study

CONTEXT

Walking speed is a fundamental parameter of human motion and is increasingly considered as an important indicator of individuals' health status.

OBJECTIVE

To evaluate the relationship of gait parameters, and demographic and physical characteristics in healthy men and women.

DESIGN, SETTING, AND PARTICIPANTS

Recruitment of a subsample (n = 358) of male and female blood donors taking part in the Cambridge CardioResource study. Collection of demographic data, measurement of physical characteristics (height, weight and blood pressure) and assessment of 7-day, free-living activity parameters using accelerometry and a novel algorithm to measure walking speed. Participants were a median (interquartile range[IQR]) age of 49 (16) years; 45% women; and had a median (IQR) BMI of 26 (5.4).

MAIN OUTCOME MEASURE

Walking speed.

RESULTS

In this study, the hypothesis that walking speed declines with age was generated using an initial 'open' dataset. This was subsequently validated in a separate 'closed' dataset that showed a decrease of walking speed of -0.0037 m/s per year. This is equivalent to a difference of 1.2 minutes, when walking a distance of 1 km aged 20 compared to 60 years. Associations between walking speed and other participant characteristics (i.e. gender, BMI and blood pressure) were non-significant. BMI was negatively correlated with the number of walking and running steps and longest non-stop distance.

CONCLUSION

This is the first study using accelerometry which shows an association between walking speed and age in free-living, healthy individuals. Absolute values of gait speed are comparable to published normal ranges in clinical settings. This study highlights the potential use of mobile accelerometry to assess gait parameters which may be indicative of future health outcomes in healthy individuals.

Development and validation of a new method to measure walking speed in free-living environments using the actibelt® platform

Walking speed is a fundamental indicator for human well-being. In a clinical setting, walking speed is typically measured by means of walking tests using different protocols. However, walking speed obtained in this way is unlikely to be representative of the conditions in a free-living environment. Recently, mobile accelerometry has opened up the possibility to extract walking speed from long-time observations in free-living individuals, but the validity of these measurements needs to be determined. In this investigation, we have developed algorithms for walking speed prediction based on 3D accelerometry data (actibelt®) and created a framework using a standardized data set with gold standard annotations to facilitate the validation and comparison of these algorithms. For this purpose 17 healthy subjects operated a newly developed mobile gold standard while walking/running on an indoor track. Subsequently, the validity of 12 candidate algorithms for walking speed prediction ranging from well-known simple approaches like combining step length with frequency to more sophisticated algorithms such as linear and non-linear models was assessed using statistical measures. As a result, a novel algorithm employing support vector regression was found to perform best with a concordance correlation coefficient of 0.93 (95%CI 0.92–0.94) and a coverage probability CP1 of 0.46 (95%CI 0.12–0.70) for a deviation of 0.1 m/s (CP2 0.78, CP3 0.94) when compared to the mobile gold standard while walking indoors. A smaller outdoor experiment confirmed those results with even better coverage probability. We conclude that walking speed thus obtained has the potential to help establish walking speed in free-living environments as a patient-oriented outcome measure.

Predicting habitual walking performance in multiple sclerosis: relevance of capacity and self-report measures

The objective was to establish the extent to which physical functioning capacity and self-report measures are able to predict the habitual walking performance in ambulatory persons with multiple sclerosis. Fifty persons with multiple sclerosis (Expanded Disability Status Scale, EDSS, 1.5-6.5) were tested on leg muscle strength as well as walking and balance capacity, and completed self-report indices on perceived physical functioning. Habitual walking performance, that is, the real amount of steps that is performed in the customary living environment, was registered by means of an ambulant accelerometer-based monitor during seven consecutive days. Mild (EDSS 1.5-4.0, n = 29) and moderate (EDSS 4.5-6.5, n = 21) multiple sclerosis subgroups were additionally distinguished as predictor variables and values were hypothesized to differ depending on multiple sclerosis severity and concomitant ambulatory function. Multiple regression analyses yielded a single most significant predictor for each (sub)group with other variables making no independent contribution to the variation in habitual walking performance. For the total study sample, this was the 6-Minute Walking Test (R(2) = 0.458, p < 0.01). In the mild multiple sclerosis subgroup, the 6-Minute Walking Test was again most predictive, yet to a modest degree (R(2) = 0. 187, p = 0.02). In the moderate multiple sclerosis subgroup, the 2-Minute Walking Test explained over half of the variance (R(2) = 0.532, p < 0.01). Habitual walking performance is best reflected by longer walking capacity tests. The extent to which it can be predicted based on clinical testing is larger in a multiple sclerosis patient sample with more severe walking disability. Ambulatory monitoring, however, includes aspects of community ambulation not captured in the clinic, and must be considered as an additional outcome for evaluating interventions in multiple sclerosis.

Gait variability in people with multiple sclerosis

Patients with multiple sclerosis (MS) present with varying symptoms that can differ between and within individuals. As new interventions and drug treatments become available to MS patients, it is essential to understand the relationship between fatigue and the variability of functional mobility measures in order to define a meaningful change due to treatment within the MS population. The purpose of this study was to examine the within-day and between-day changes in gait variability for subjects with MS in fresh and fatigued conditions. Walking gait parameters were measured from 20 subjects diagnosed with MS and eight healthy control subjects. Standard deviations of hip, knee and ankle kinematic and kinetic variables were quantified as the measure of variability and analysed with a two-way (group by condition) ANOVA. Results indicated MS subjects had significantly greater hip (P <0.020), knee (P <0.011) and ankle (P <0.034) joint angle variability than control subjects, but variability was not different between conditions. Kinetic variability was not different between groups or conditions. MS subjects in this study walked more slowly than the healthy controls and they also reported more fatigue. Research examining treatment effects within the MS population should account for increased levels of kinematic gait variability.

Repeat intrathecal triamcinolone acetonide application is beneficial in progressive MS patients

Available immunomodulatory and conventional steroid treatment regimens provide a limited symptomatic benefit for patients with progressive multiple sclerosis (MS). We performed an open trial on the short-term efficacy of repeated intrathecal application of the sustained release steroid triamcinolone acetonide (TCA) in 27 progressive MS patients. Six TCA administrations, performed every third day, reduced the Expanded Disability Status Scale (EDSS) score [initial: 5.4+/-1.3, 3-7.5 (mean+/-SD, range); end: 4.9+/-1.1; 2.5-6.5; P<0.001] and significantly increased the walking distance and speed in particular after the fourth TCA injection. Concomitantly serially determined cerebrospinal fluid (CSF) markers of cell injury, neuron-specific enolase, total tau-protein, S-100, and beta-amyloid did not significantly change within the interval of TCA treatment. No serious side effects appeared. We conclude that repeat intrathecal injection of 40 mg TCA provides a substantial benefit in progressive MS patients with predominant spinal symptoms and does not alter CSF markers of neuronal cell injury.