Enhancing postural stability and adaptability in multiple sclerosis

Impaired foot vibration sensitivity is related to altered plantar pressures during walking in people with multiple sclerosis

BACKGROUND

Balance and mobility impairment are two of the most common and debilitating symptoms among people with multiple sclerosis (MS). Somatosensory symptoms, including reduced plantar cutaneous sensation, have been identified in this cohort. Given the importance of the somatosensory system in gait, it is likely that impaired plantar sensation may play a role in the walking adaptations commonly observed in people with MS, including decreased stride length and increased stride width and dual support time, often described as a cautious gait strategy. Understanding the contributions of plantar sensation to these alterations may provide targets for interventions that seek to improve sensory feedback and normalize gait patterns. This cross-sectional study determined whether individuals with MS who demonstrate reduced sensitivity of the plantar surfaces also demonstrate altered plantar pressure distributions during walking compared to a control cohort.

METHODS

Twenty individuals with MS and twenty age- and sex-matched control participants walked barefoot at preferred and three matched speeds. Participants walked across a walkway with an embedded pressure plate used to quantify pressures within ten plantar zones. In addition, vibration perception thresholds were assessed at four sites on the plantar surface.

RESULTS

Individuals with MS demonstrated increased peak total plantar pressures compared to control participants, that increased with walking speed. For the MS group, plantar pressures were higher on the less sensitive foot, although pressures on both feet exceeded those of the control cohort. Positive correlations between vibration perception threshold and peak total pressure were evident, although generally stronger in the MS cohort.

CONCLUSION

A relationship between plantar vibration sensitivity and pressure could indicate that individuals with MS seek to increase plantar sensory feedback during walking. However, because proprioception may also be impaired, increased plantar pressure could result from inaccurate foot placement. Interventions targeting improved somatosensation may have the potential to normalize gait patterns and should be investigated.

Bridging the callosal gap in gait: corpus callosum white matter integrity's role in lower limb coordination

Bilateral coordination of the lower extremities is an essential component of mobility. The corpus callosum bridges the two hemispheres of the brain and is integral for the coordination of such complex movements. The aim of this project was to assess structural integrity of the transcallosal sensorimotor fiber tracts and identify their associations with gait coordination using novel methods of ecologically valid mobility assessments in persons with multiple sclerosis and age-/gender-matched neurotypical adults. Neurotypical adults (n = 29) and persons with multiple sclerosis (n = 27) underwent gait and diffusion tensor imaging assessments; the lower limb coordination via Phase Coordination Index, and radial diffusivity, an indirect marker of myelination, were applied as the primary outcome measures. Persons with multiple sclerosis possessed poorer transcallosal white matter microstructural integrity of sensorimotor fiber tracts compared to the neurotypical adults. Further, persons with multiple sclerosis demonstrated significantly poorer bilateral coordination of the lower limbs during over-ground walking in comparison to an age and gender-matched neurotypical cohort. Finally, bilateral coordination of the lower limbs was significantly associated with white matter microstructural integrity of the dorsal premotor and primary motor fiber bundles in persons with multiple sclerosis, but not in neurotypical adults. This analysis revealed that persons with multiple sclerosis exhibit poorer transcallosal microstructural integrity than neurotypical peers. Furthermore, these structural deficits were correlated to poorer consistency and accuracy of gait in those with multiple sclerosis. Together, these results, emphasize the importance of transcallosal communication for gait coordination in those with multiple sclerosis.

The Relationship Between Walking Speed and the Energetic Cost of Walking in Persons With Multiple Sclerosis and Healthy Controls: A Systematic Review

BACKGROUND

Persons with multiple sclerosis (pwMS) experience walking impairments, characterized by decreased walking speeds. In healthy subjects, the self-selected walking speed is the energetically most optimal. In pwMS, the energetically most optimal walking speed remains underexposed. Therefore, this review aimed to determine the relationship between walking speed and energetic cost of walking (Cw) in pwMS, compared with healthy subjects, thereby assessing the walking speed with the lowest energetic cost. As it is unclear whether the Cw in pwMS differs between overground and treadmill walking, as reported in healthy subjects, a second review aim was to compare both conditions.

METHOD

PubMed and Web of Science were systematically searched. Studies assessing pwMS, reporting walking speed (converted to meters per second), and reporting oxygen consumption were included. Study quality was assessed with a modified National Heart, Lung and Blood Institute checklist. The relationship between Cw and walking speed was calculated with a second-order polynomial function and compared between groups and conditions.

RESULTS

Twenty-nine studies were included (n = 1535 pwMS) of which 8 included healthy subjects (n = 179 healthy subjects). PwMS showed a similar energetically most optimal walking speed of 1.44 m/s with a Cw of 0.16, compared with 0.14 mL O₂/kg/m in healthy subjects. The most optimal walking speed in treadmill was 1.48 m/s, compared with 1.28 m/s in overground walking with a similar Cw.

CONCLUSION

Overall, the Cw is elevated in pwMS but with a similar energetically most optimal walking speed, compared with healthy subjects. Treadmill walking showed a similar most optimal Cw but a higher speed, compared with overground walking.

Motor equivalence and structure of variance: multi-muscle postural synergies in Parkinson's disease

We explored posture-stabilizing multi-muscle synergies with two methods of analysis of multi-element, abundant systems: (1) Analysis of inter-cycle variance; and (2) Analysis of motor equivalence, both quantified within the framework of the uncontrolled manifold (UCM) hypothesis. Data collected in two earlier studies of patients with Parkinson's disease (PD) were re-analyzed. One study compared synergies in the space of muscle modes (muscle groups with parallel scaling of activation) during tasks performed by early-stage PD patients and controls. The other study explored the effects of dopaminergic medication on multi-muscle-mode synergies. Inter-cycle variance and absolute magnitude of the center of pressure displacement across consecutive cycles were quantified during voluntary whole-body sway within the UCM and orthogonal to the UCM space. The patients showed smaller indices of variance within the UCM and motor equivalence compared to controls. The indices were also smaller in the off-drug compared to on-drug condition. There were strong across-subject correlations between the inter-cycle variance within/orthogonal to the UCM and motor equivalent/non-motor equivalent displacements. This study has shown that, at least for cyclical tasks, analysis of variance and analysis of motor equivalence lead to metrics of stability that correlate with each other and show similar effects of disease and medication. These results show, for the first time, intimate links between indices of variance and motor equivalence. They suggest that analysis of motor equivalence, which requires only a handful of trials, could be used broadly in the field of motor disorders to analyze problems with action stability.

Tai chi for health benefits in patients with multiple sclerosis: A systematic review

The aim of this systematic review was to evaluate the existing evidence on the effectiveness and safety of Tai chi, which is critical to provide guidelines for clinicians to improve symptomatic management in patients with multiple sclerosis (MS). After performing electronic and manual searches of many sources, ten relevant peer-reviewed studies that met the inclusion criteria were retrieved. The existing evidence supports the effectiveness of Tai chi on improving quality of life (QOL) and functional balance in MS patients. A small number of these studies also reported the positive effect of Tai chi on flexibility, leg strength, gait, and pain. The effect of Tai chi on fatigue is inconsistent across studies. Although the findings demonstrate beneficial effects on improving outcome measures, especially for functional balance and QOL improvements, a conclusive claim should be made carefully for reasons such as methodological flaws, small sample size, lack of specific-disease instruments, unclear description of Tai chi protocol, unreported safety of Tai chi, and insufficient follow-up as documented by the existing literature. Future research should recruit a larger number of participants and utilize the experimental design with a long-term follow-up to ascertain the benefits of Tai chi for MS patients.

Gait deficits in people with multiple sclerosis: A systematic review and meta-analysis

BACKGROUND

Multiple Sclerosis (MS) results in postural instability and gait abnormalities which are associated with accidental falls.

OBJECTIVE

This systematic review and meta-analysis aims to quantify the effect of MS on gait to inform the development of falls prevention interventions.

METHODS

A systematic literature search identified case-control studies investigating differences in gait variables between people with MS and healthy controls. Meta-analysis examined the effect of MS on gait under normal and fast paced conditions.

RESULTS

Forty-one studies of people with Expanded Disability Status Scale (EDSS) 1.8 to 4.5 were included, of which 32 contributed to meta-analysis. A large effect of MS was found on stride length (Standardised Mean Difference, SMD=1.27, 95% CI{0.93, 1.61}), velocity (SMD=1.12, 95% CI{0.85, 1.39}), double support duration (SMD=0.85, 95% CI{0.51, 1.2}), step length (SMD=1.15, 95% CI{0.75, 1.5})and swing phase duration (SMD=1.23, 95% CI{0.06, 2.41}). A moderate effect was found on step width and stride time with the smallest effect found on cadence (SMD=0.43, 95% CI{0.14, 0.72}). All effect sizes increased for variables investigated under a fast walking pace condition (for example the effect on cadence increased to SMD=1.15, 95% CI{0.42, 1.88}).

CONCLUSIONS

MS has a significant effect on gait even for those with relatively low EDSS. This effect is amplified when walking at faster speeds suggesting this condition may be more beneficial for assessment and treatment. No studies investigated the association between these deficits and falls. Further investigation relating to the predictive or protective nature of these deficits in relation to falls is warranted.

Multiscale entropy identifies differences in complexity in postural control in women with multiple sclerosis

Loss of postural center-of-pressure complexity (COP complexity) has been associated with reduced adaptability that accompanies disease and aging. The aim of this study was to identify if COP complexity is reduced: (1) in those with Multiple Sclerosis (MS) compared to controls; (2) when vision is limited compared to remaining intact; and (3) during more demanding postural conditions compared to quiet standing. Additionally, we explored the relationship between the COP complexity and disease severity, fatigue, cutaneous sensation and central motor drive. Twelve women with MS and 12 age-matched controls were tested under quiet standing and postural maximal lean conditions with normal and limited vision. The key dependent variable was the complexity index (CI) of the center of pressure. We observed a lower CI in the MS group compared to controls in both anterior-posterior (AP) and medio-lateral (ML) directions (p's<0.002), during the performance of maximal self-regulated leans (AP: p<0.001; ML: p=0.018), and under limited vision (AP: p=0.001; ML: p=0.006). No group-by-vision interaction (p>0.05) was observed, indicating that limiting vision did not impact COP complexity differently in the two groups. Decreased cutaneous sensitivity was associated with lower CI values in the AP direction among those with MS (r(2)=0.57); all other measures did not exhibit significant relationships. The findings reported here suggest that (1) MS is associated with diminished COP complexity under both normal and challenging postures, and (2) complexity is strongly correlated with cutaneous sensitivity, suggesting the unique contribution of impaired somatosensation on postural control deficits in persons with MS.