Plasticity of the motor system in multiple sclerosis

Predictive value of synaptic plasticity for functional decline in patients with multiple sclerosis

Background

Previous research suggested that quadripulse (QPS)-induced synaptic plasticity is associated with both cognitive and motor function in patients with multiple sclerosis (MS) and does not appear to be reduced compared to healthy controls (HCs).

Objective

This study aimed to explore the relationship between the degree of QPS-induced plasticity and clinically significant decline in motor and cognitive functions over time. We hypothesized that MS patients experiencing functional decline would exhibit lower levels of baseline plasticity compared to those without decline.

Methods

QPS-induced plasticity was evaluated in 80 MS patients (56 with relapsing-remitting MS and 24 with progressive MS), and 69 age-, sex-, and education-matched HCs. Cognitive and motor functions, as well as overall disability status were evaluated annually over a median follow-up period of 2 years. Clinically meaningful change thresholds were predefined for each outcome measure. Linear mixed-effects models, Cox proportional hazard models, logistic regression, and receiver-operating characteristic analysis were applied to analyse the relationship between baseline plasticity and clinical progression in the symbol digit modalities test, brief visuospatial memory test revised (BVMT-R), nine-hole peg test (NHPT), timed 25-foot walk test, and expanded disability status scale.

Results

Overall, the patient cohort showed no clinically relevant change in any functional outcome over time. Variability in performance was observed across time points in both patients and HCs. MS patients who experienced clinically relevant decline in manual dexterity and/or visuospatial learning and memory had significantly lower levels of synaptic plasticity at baseline compared to those without such decline (NHPT: β = -0.25, p = 0.02; BVMT-R: β = -0.50, p = 0.005). Receiver-operating characteristic analysis underscored the predictive utility of baseline synaptic plasticity in discerning between patients experiencing functional decline and those maintaining stability only for visuospatial learning and memory (area under the curve = 0.85).

Conclusion

Our study suggests that QPS-induced plasticity could be linked to clinically relevant functional decline in patients with MS. However, to solidify these findings, longer follow-up periods are warranted, especially in cohorts with higher prevalences of functional decline. Additionally, the variability in cognitive performance in both patients with MS and HCs underscores the importance of conducting further research on reliable change based on neuropsychological tests.

Physical Telerehabilitation interventions for Gait and balance in Multiple sclerosis: A Scoping review

BACKGROUND

Gait and balance impairments affects approximately a quarter of people with multiple sclerosis (pwMS) at onset and increases to almost half by five years. Physical rehabilitation has been recognised as the gold standard method to restore physical function in multiple sclerosis (MS). Emerging evidence in the literature is suggesting that a remote therapy rehabilitation platform (Telerehabilitation) is cost-effective, beneficial, and satisfying for patients and health care practitioners. The overarching aim of this review is to identify and summarise the evidence on the different types of telerehabilitation interventions available to manage gait and balance.

METHODS

This review followed a methodological framework for conducting scoping reviews. PubMed, Science Direct and Web of Science were searched in April 2023 for relevant published literature. The inclusion criteria were peer-reviewed journal articles written in English which included telerehabilitation interventions for pwMS. Search keywords included multiple sclerosis and telerehabilitation. A reviewer screened titles and abstracts and eligible articles were fully reviewed. The included studies were categorised based on the type of intervention.

RESULTS

Eight studies were included in this review. The participants (n = 355) had an average age of 48 years (SD = 9.9) with 50% who had relapsing remitting multiple sclerosis who were living with MS for 12 years on average. Study designs included randomised control trials (n = 3), pilot studies and feasibility studies (n = 4). Two types of interventions were identified: Exergaming (n = 5) and Web-Based Physical Therapy (n = 2) of which exergaming appeared to be optimal in improving gait and balance.

CONCLUSION

This scoping review identified and summarised the evidence on telerehabilitation interventions used for gait and balance in MS. The evidence is showing that telerehabilitation could be used as an alternative to conventional rehabilitation methods for improving gait and balance. More robust trials with larger sample sizes are needed to build on the current evidence to enable telerehabilitation to be integrated into care pathways in the future.

Changes in brain perfusion with training-related visuomotor improvement in MS

Multiple sclerosis (MS) is a chronic inflammatory disease of the central nervous system. A better understanding of the mechanisms supporting brain plasticity in MS would help to develop targeted interventions to promote recovery. A total of 29 MS patients and 19 healthy volunteers underwent clinical assessment and multi-modal MRI acquisition [fMRI during serial reaction time task (SRT), DWI, T1w structural scans and ASL of resting perfusion] at baseline and after 4-weeks of SRT training. Reduction of functional hyperactivation was observed in MS patients following the training, shown by the stronger reduction of the BOLD response during task execution compared to healthy volunteers. The functional reorganization was accompanied by a positive correlation between improvements in task accuracy and the change in resting perfusion after 4 weeks' training in right angular and supramarginal gyri in MS patients. No longitudinal changes in WM and GM measures and no correlation between task performance improvements and brain structure were observed in MS patients. Our results highlight a potential role for CBF as an early marker of plasticity, in terms of functional (cortical reorganization) and behavioral (performance improvement) changes in MS patients that may help to guide future interventions that exploit preserved plasticity mechanisms.

Toward reframing brain-social dynamics: current assumptions and future challenges

Evolutionary analyses suggest that the human social brain and sociality appeared together. The two fundamental tools that accelerated the concurrent emergence of the social brain and sociality include learning and plasticity. The prevailing core idea is that the primate brain and the cortex in particular became reorganised over the course of evolution to facilitate dynamic adaptation to ongoing changes in physical and social environments. Encouraged by computational or survival demands or even by instinctual drives for living in social groups, the brain eventually learned how to learn from social experience via its massive plastic capacity. A fundamental framework for modeling these orchestrated dynamic responses is that social plasticity relies upon neuroplasticity. In the present article, we first provide a glimpse into the concepts of plasticity, experience, with emphasis on social experience. We then acknowledge and integrate the current theoretical concepts to highlight five key intertwined assumptions within social neuroscience that underlie empirical approaches for explaining the brain-social dynamics. We suggest that this epistemological view provides key insights into the ontology of current conceptual frameworks driving future research to successfully deal with new challenges and possible caveats in favour of the formulation of novel assumptions. In the light of contemporary societal challenges, such as global pandemics, natural disasters, violent conflict, and other human tragedies, discovering the mechanisms of social brain plasticity will provide new approaches to support adaptive brain plasticity and social resilience.

Investigation of in-phase bilateral exercise effects on corticospinal plasticity in relapsing remitting multiple sclerosis: A registered report single-case concurrent multiple baseline design across five subjects

Relapsing-remitting Multiple Sclerosis is the most common demyelinating neurodegenerative disease and is characterized by periods of relapses and generation of various motor symptoms. These symptoms are associated with the corticospinal tract integrity, which is quantified by means of corticospinal plasticity which can be probed via transcranial magnetic stimulation and assessed with corticospinal excitability measures. Several factors, such as exercise and interlimb coordination, can influence corticospinal plasticity. Previous work in healthy and in chronic stroke survivors showed that the greatest improvement in corticospinal plasticity occurred during in-phase bilateral exercises of the upper limbs. During in-phase bilateral movement, both upper limbs are moving simultaneously, activating the same muscle groups and triggering the same brain region respectively. Altered corticospinal plasticity due to bilateral cortical lesions is common in MS, yet, the impact of these type of exercises in this cohort is unclear. The aim of this concurrent multiple baseline design study is to investigate the effects of in-phase bilateral exercises on corticospinal plasticity and on clinical measures using transcranial magnetic stimulation and standardized clinical assessment in five people with relapsing-remitting MS. The intervention protocol will last for 12 consecutive weeks (30-60 minutes /session x 3 sessions/week) and include in-phase bilateral movements of the upper limbs, adapted to different sports activities and to functional training. To define functional relation between the intervention and the results on corticospinal plasticity (central motor conduction time, resting motor threshold, motor evoked potential amplitude and latency) and on clinical measures (balance, gait, bilateral hand dexterity and strength, cognitive function), we will perform a visual analysis and if there is a potential sizeable effect, we will perform statistical analysis. A possible effect from our study, will introduce a proof-of-concept for this type of exercise that will be effective during disease progression. Trial registration: ClinicalTrials.gov NCT05367947.

Neurorehabilitation in Multiple Sclerosis-A Review of Present Approaches and Future Considerations

Multiple sclerosis is an increasingly prevalent disease, representing the leading cause of non-traumatic neurological disease in Europe and North America. The most common symptoms include gait deficits, balance and coordination impairments, fatigue, spasticity, dysphagia and an overactive bladder. Neurorehabilitation therapeutic approaches aim to alleviate symptoms and improve the quality of life through promoting positive immunological transformations and neuroplasticity. The purpose of this study is to evaluate the current treatments for the most debilitating symptoms in multiple sclerosis, identify areas for future improvement, and provide a reference guide for practitioners in the field. It analyzes the most cited procedures currently in use for the management of a number of symptoms affecting the majority of patients with multiple sclerosis, from different training routines to cognitive rehabilitation and therapies using physical agents, such as electrostimulation, hydrotherapy, cryotherapy and electromagnetic fields. Furthermore, it investigates the quality of evidence for the aforementioned therapies and the different tests applied in practice to assess their utility. Lastly, the study looks at potential future candidates for the treatment and evaluation of patients with multiple sclerosis and the supposed benefits they could bring in clinical settings.

Linking lesions in sensorimotor cortex to contralateral hand function in multiple sclerosis: a 7 T MRI study

Cortical lesions constitute a key manifestation of multiple sclerosis and contribute to clinical disability and cognitive impairment. Yet it is unknown whether local cortical lesions and cortical lesion subtypes contribute to domain-specific impairments attributable to the function of the lesioned cortex.

In this cross-sectional study, we assessed how cortical lesions in the primary sensorimotor hand area (SM1-HAND) relate to corticomotor physiology and sensorimotor function of the contralateral hand. 50 relapse-free patients with relapsing-remitting or secondary-progressive multiple sclerosis and 28 healthy age- and sex-matched participants underwent whole-brain 7 T MRI to map cortical lesions. Brain scans were also used to estimate normalized brain volume, pericentral cortical thickness, white matter lesion fraction of the corticospinal tract, infratentorial lesion volume and the cross-sectional area of the upper cervical spinal cord. We tested sensorimotor hand function and calculated a motor and sensory composite score for each hand. In 37 patients and 20 healthy controls, we measured maximal motor evoked potential (MEP) amplitude, resting motor threshold and corticomotor conduction time with transcranial magnetic stimulation (TMS) and the N20 latency from somatosensory evoked potentials (SSEPs).

Patients showed at least one cortical lesion in the SM1-HAND in 47 of 100 hemispheres. The presence of a lesion was associated with worse contralateral sensory (P = 0.014) and motor (P = 0.009) composite scores. TMS of a lesion-positive SM1-HAND revealed a decreased maximal MEP amplitude (P < 0.001) and delayed corticomotor conduction (P = 0.002) relative to a lesion-negative SM1-HAND. Stepwise mixed linear regressions showed that the presence of an SM1-HAND lesion, higher white-matter lesion fraction of the corticospinal tract, reduced spinal cord cross-sectional area and higher infratentorial lesion volume were associated with reduced contralateral motor hand function. Cortical lesions in SM1-HAND, spinal cord cross-sectional area and normalized brain volume were also associated with smaller maximal MEP amplitude and longer corticomotor conduction times. The effect of cortical lesions on sensory function was no longer significant when controlling for MRI-based covariates. Lastly, we found that intracortical and subpial lesions had the largest effect on reduced motor hand function, intracortical lesions on reduced MEP amplitude and leukocortical lesions on delayed corticomotor conduction.

Together, this comprehensive multi-level assessment of sensorimotor brain damage shows that the presence of a cortical lesion in SM1-HAND is associated with impaired corticomotor function of the hand, after accounting for damage at the subcortical level. The results also provide preliminary evidence that cortical lesion types may affect the various facets of corticomotor function differentially.

Prognostic Value of Serum Neurofilament Light Chain for Disease Activity and Worsening in Patients With Relapsing Multiple Sclerosis: Results From the Phase 3 ASCLEPIOS I and II Trials

Objective

This study aims to confirm the prognostic value of baseline serum neurofilament light chain (sNfL) for on-study disease activity and worsening in patients with relapsing MS (RMS).

Background

Previous post-hoc studies suggested that sNfL could be a prognostic biomarker in RMS. In the phase 3 ASCLEPIOS I/II trials in which ofatumumab demonstrated better efficacy outcomes than teriflunomide, treatment with ofatumumab also led to significantly reduced sNfL levels compared to teriflunomide treatment.

Design/Methods

In this study, we report protocol-planned analyses from the pooled ASCLEPIOS I/II trials (N=1882). Per protocol, patients were stratified by median baseline sNfL levels (9.3 pg/ml) into high (>median) and low (≤median) categories to prognosticate: annualized rate of new/enlarging T2 (neT2) lesions in year 1 and 2, annualized relapse rate, annual percentage change in whole brain (WB) and regional brain volume [thalamus, white matter (WM), cortical gray matter (cGM)], and disability outcomes. Similar analyses were performed for the recently diagnosed (within 3 years), treatment-naive patients (no prior disease-modifying therapy) subgroup.

Results

High versus low sNfL at baseline was prognostic of increased on-study T2 lesion formation at year 1 (relative increase: ofatumumab +158%; teriflunomide +69%, both p<0.001), which persisted in year 2 (+65%, p=0.124; +46%, p=0.003); of higher annual percentage change of WB volume (ofatumumab, −0.32% vs. −0.24%, p=0.044, and teriflunomide, −0.43% vs. −0.29%, p=0.002), thalamic volume (−0.56% vs. −0.31%, p=0.047 and −0.94% vs. −0.49%, p<0.001), and WM volume (−0.30% vs. −0.19%, p=0.083 and −0.38% vs. −0.18%, p=0.003) but not of cGM volume (−0.39% vs. −0.32%, p=0.337 and −0.49% vs. −0.46%, p=0.563). A single sNfL assessment at baseline was not prognostic for on-study relapses or disability worsening. Results were similar in the subgroup of recently diagnosed, treatment-naive patients.

Conclusion

This study confirms that baseline sNfL levels are prognostic of future on-study lesion formation and whole brain and regional atrophy in all RMS patients, including recently diagnosed, treatment-naive patients.

The degree of cortical plasticity correlates with cognitive performance in patients with Multiple Sclerosis

BACKGROUND

Cortical reorganization and plasticity may compensate for structural damage in Multiple Sclerosis (MS). It is important to establish sensitive methods to measure these compensatory mechanisms, as they may be of prognostic value.

OBJECTIVE

To investigate the association between the degree of cortical plasticity and cognitive performance and to compare plasticity between MS patients and healthy controls (HCs).

METHODS

The amplitudes of the motor evoked potential (MEP) pre and post quadripulse stimulation (QPS) applied over the contralateral motor cortex served as measure of the degree of cortical plasticity in 63 patients with relapsing-remitting MS (RRMS) and 55 matched HCs. The main outcomes were the correlation coefficients between the difference of MEP amplitudes post and pre QPS and the Symbol Digit Modalities Test (SDMT) and Brief Visuospatial Memory Test-Revised (BVMT-R), and the QPS^xgroup interaction in a mixed model predicting the MEP amplitude.

RESULTS

SDMT and BVMT-R correlated significantly with QPS-induced cortical plasticity in RRMS patients. Plasticity was significantly reduced in patients with cognitive impairment compared to patients with preserved cognitive function and the degree of plasticity differentiated between both patient groups. Interestingly, the overall RRMS patient cohort did not show reduced plasticity compared to HCs.

CONCLUSIONS

We provide first evidence that QPS-induced plasticity may inform about the global synaptic plasticity in RRMS which correlates with cognitive performance as well as clinical disability. Larger longitudinal studies on patients with MS are needed to investigate the relevance and prognostic value of this measure for disease progression and recovery.

Motor Sequence Learning across Multiple Sessions Is Not Facilitated by Targeting Consolidation with Posttraining tDCS in Patients with Progressive Multiple Sclerosis

Compared to relapsing-remitting multiple sclerosis (MS), progressive MS is characterized by a lack of spontaneous recovery and a poor response to pharmaceutical immunomodulatory treatment. These patients may, therefore, particularly benefit from interventions that augment training-induced plasticity of the central nervous system. In this cross-sectional double-blind cross-over pilot study, effects of transcranial direct current stimulation (tDCS) on motor sequence learning were examined across four sessions on days 1, 3, 5, and 8 in 16 patients with progressive MS. Active or sham anodal tDCS of the primary motor cortex was applied immediately after each training session. Participants took part in two experiments separated by at least four weeks, which differed with respect to the type of posttraining tDCS (active or sham). While task performance across blocks of training and across sessions improved significantly in both the active and sham tDCS experiment, neither online nor offline motor learning was modulated by the type of tDCS. Accordingly, the primary endpoint (task performance on day 8) did not differ between stimulation conditions. In sum, patients with progressive MS are able to improve performance in an ecologically valid motor sequence learning task through training. However, even multisession posttraining tDCS fails to promote motor learning in progressive MS.

Impaired consolidation of visuomotor adaptation in patients with multiple sclerosis

BACKGROUND

Apart from inflammation and neurodegeneration, the individual clinical course of multiple sclerosis (MS) might be determined by differential adaptive capacities of the central nervous system. It has been postulated that the retention of adaptive training effects may be impaired in persons with MS (PwMS).

OBJECTIVE

To investigate motor adaptation and consolidation capacities of people with MS in a visual motor adaptation task (VAT).

METHODS

A total of 23 PwMS (Expanded Disability Status Scale (EDSS) score < 6) and 20 matched healthy controls were recruited. All participants completed three sessions of a VAT where a clockwise rotation angle of 30° was introduced as perturbation during the active learning part of the paradigm. The training session (T₀ ) was repeated after 24 h (T₁ ) and 72 h (T₂ ). Directional errors and parameters of adaptation and retention were evaluated.

RESULTS

PwMS showed similar adaptation and online learning abilities as controls. However, the retention ratio was significantly lower in patients compared to controls at T1 (p = 0.036) and T2 (p = 0.039). There was no significant correlation between the overall adaptation or retention ratio and the EDSS score, respectively.

CONCLUSION

Our findings indicate intact adaptation, but limited consolidation, in patients with mild-to-moderate MS. Future studies are needed to define the neurobiological substrates of this plasticity and the extent to which it can influence clinical outcomes.

Fatigue in multiple sclerosis: Does the functional or structural damage prevail?

Fatigue in multiple sclerosis (MS) is a highly invalidating symptom, lacking efficacious drugs. This topical review aims at assessing the signs in the literature of functional versus structural damage prevalence at the origin of MS fatigue by focusing on papers that assessed the two counterparts in the same patients, paying attention that the fatigue levels do not correlate with clinical severity. We summarize and discuss evidence of increased levels of fatigue occurring together with the alterations of functional connectivity at multiple levels, in the absence of any relationship with lesion load and local atrophy of the involved structures. Specifically, neuronal communication mainly altered in the corticomuscular synchronizations, between hemispheric homologs and in the resting-state networks involved in emotion (cingulate cortex) and effort-reward balance (striatum and inferior parietal lobule). Finally, given the functional prevalence in neuronal network alterations at the origin of fatigue in MS, we highlight the relevance of developing treatments aiming at compensating the neuronal electric communication dysfunctions.

Altered sensorimotor representations after recovery from peripheral nerve damage in neuralgic amyotrophy

Neuralgic amyotrophy is a common peripheral nerve disorder caused by acute autoimmune inflammation of the brachial plexus. Subsequent weakness of the stabilizing shoulder muscles leads to compensatory strategies and abnormal motor control of the shoulder. Despite recovery of peripheral nerves and muscle strength over time, motor dysfunction often persists. Suboptimal motor recovery has been linked to maladaptive changes in the central motor system in several nervous system disorders. We therefore hypothesized that neuralgic amyotrophy patients with persistent motor dysfunction may have altered cerebral sensorimotor representations of the affected upper limb. To test this hypothesis, 21 neuralgic amyotrophy patients (mean age 45 ± 12 years, 5 female) with persistent lateralized symptoms in the right upper limb and 20 age- and sex-matched healthy controls, all right-handed, performed a hand laterality judgement task in a cross-sectional comparison. Previous evidence has shown that to solve this task, subjects rely on sensorimotor representations of their own upper limb, using a first-person imagery perspective without actual motor execution. This enabled us to investigate altered central sensorimotor representations while controlling for altered motor output and altered somatosensory afference. We found that neuralgic amyotrophy patients were specifically less accurate for laterality judgments of their affected right limb, as compared to healthy controls. There were no significant group differences in reaction times. Both groups used a first-person imagery perspective, as evidenced by changes in reaction times as a function of participants' own arm posture. We conclude that cerebral sensorimotor representations of the affected upper limb are altered in neuralgic amyotrophy patients. This suggests that maladaptive central neuroplasticity may occur in response to peripheral nerve damage, thereby contributing to motor dysfunction. Therapies focused on altering cerebral sensorimotor representations may help to treat peripheral nerve disorders such as neuralgic amyotrophy.

Two Sides to Every Story: Perspectives from Four Patients and a Healthcare Professional on Multiple Sclerosis Disease Progression

Abstract

Multiple sclerosis (MS) is a chronic progressive disease and many patients transition from an initial relapsing–remitting course to a secondary progressive pattern. Accurate classification of disease status is critical to ensure that patients are treated appropriately and kept informed of their prognosis. Consensus terms defining the different forms of MS are available but were developed primarily for healthcare professionals (HCPs) and may be of limited value to patients. This article provides direct insights from four patients with MS, at different points in their disease trajectory, regarding their understanding of, and attitudes toward, MS progression. We also examine the utility of the current classification systems from the perspectives of patients and HCPs. Responses collected during in-depth, structured interviews and questionnaires portrayed the difficulties patients face accepting their MS diagnosis and treatment, revealed how understanding of the term “disease progression” varies considerably, and highlighted the challenges surrounding the period of transition to secondary progressive MS (SPMS). The terms describing different MS types were considered confusing and can make patients feel “compartmentalized” or “labeled”. Patients also struggled to relate these terms to their reality of living with MS, were reluctant to discuss progression with their HCPs, and feared being diagnosed with SPMS owing to concerns about treatment access. These insights highlight the need to develop patient-friendly language to describe MS progression; it may also be preferable for HCPs to describe MS as a disease spectrum in discussions with their patients.

Funding

Novartis Pharmaceuticals Corporation.

Plain Language Summary

Plain language summary available for this article.

The Beneficial and Debilitating Effects of Environmental and Microbial Toxins, Drugs, Organic Solvents and Heavy Metals on the Onset and Progression of Multiple Sclerosis

Multiple sclerosis (MS), a chronic inflammatory disease of the central nervous system is common amongst young adults, leading to major personal and socioeconomic burdens. However, it is still considered complex and challenging to understand and treat, in spite of the efforts made to explain its etiopathology. Despite the discovery of many genetic and environmental factors that might be related to its etiology, no clear answer was found about the causes of the illness and neither about the detailed mechanism of these environmental triggers that make individuals susceptible to MS. In this review, we will attempt to explore the major contributors to MS autoimmunity including genetic, epigenetic and ecological factors with a particular focus on toxins, chemicals or drugs that may trigger, modify or prevent MS disease.

Balance Changes in Patients With Relapsing-Remitting Multiple Sclerosis: A Pilot Study Comparing the Dynamics of the Relapse and Remitting Phases

Aims: To compare balance changes over time during the relapse phase of relapsing-remitting multiple sclerosis (RRMS) with balance control during the remitting phase.

Methods: Balance control during stance and gait tasks of 24 remitting-phase patients (mean age 43.7 ± 10.5, 15 women, mean EDSS at baseline 2.45 ± 1.01) was examined every 3 months over 9 months and compared to that of nine relapsing patients (age 42.0 ± 12.7, all women, mean EDSS at relapse onset 3.11 ± 0.96) examined at relapse onset and 3 months later. Balance was also compared to that of 40 healthy controls (HCs) (age 39.7 ± 12.6, 25 women). Balance control was measured as lower-trunk sway angles with body-worn gyroscopes. Expanded Disability Status Scale scores (EDSS) were used to monitor, clinically, disease progression.

Results: Remitting-phase patients showed more unstable stance balance control than HCs (p < 0.04) with no worsening over the observation period of 9 months. Gait balance control was normal (p > 0.06). Relapsing patients had stance balance control significantly worse at onset compared to remitting-phase patients and HCs (p < 0.04). Gait tasks showed a significant decrease of gait speed and trunk sway in relapsing patients (p = 0.018) compatible with having increased gait instability at normal speeds. Improvement to levels of remitting patients generally took longer than 3 months. Balance and EDSS scores were correlated for remitting but not for relapse patients.

Conclusions: Balance in remitting RRMS patients does not change significantly over 9 months and correlated well with EDSS scores. Our results indicate that balance control is a useful measure to assess recovery after a relapse, particularly in patients with unchanged EDSS scores. Based on our results, balance could be considered as additional measurement to assess recovery after a relapse, particularly in patients with unchanged EDSS.

Interplay Between Age and Neuroinflammation in Multiple Sclerosis: Effects on Motor and Cognitive Functions

Aging is one of the main risk factors for the development of many neurodegenerative diseases. Emerging evidence has acknowledged neuroinflammation as potential trigger of the functional changes occurring during normal and pathological aging. Two main determinants have been recognized to cogently contribute to neuroinflammation in the aging brain, i.e., the systemic chronic low-grade inflammation and the decline in the regulation of adaptive and innate immune systems (immunosenescence, ISC). The persistence of the inflammatory status in the brain in turn may cause synaptopathy and synaptic plasticity impairments that underlie both motor and cognitive dysfunctions. Interestingly, such inflammation-dependent synaptic dysfunctions have been recently involved in the pathophysiology of multiple sclerosis (MS). MS is an autoimmune neurodegenerative disease, typically affecting young adults that cause an early and progressive deterioration of both cognitive and motor functions. Of note, recent controlled studies have clearly shown that age at onset modifies prognosis and exerts a significant effect on presenting phenotype, suggesting that aging is a significant factor associated to the clinical course of MS. Moreover, some lines of evidence point to the different impact of age on motor disability and cognitive deficits, being the former most affected than the latter. The precise contribution of aging-related factors to MS neurological disability and the underlying molecular and cellular mechanisms are still unclear. In the present review article, we first emphasize the importance of the neuroinflammatory dependent mechanisms, such as synaptopathy and synaptic plasticity impairments, suggesting their potential exacerbation or acceleration with advancing age in the MS disease. Lastly, we provide an overview of clinical and experimental studies highlighting the different impact of age on motor disability and cognitive decline in MS, raising challenging questions on the putative age-related mechanisms involved.

Therapies for mobility disability in persons with multiple sclerosis

INTRODUCTION

Mobility disability is one of the most widespread and impactful consequences of multiple sclerosis (MS). Disease modifying drugs (DMDs) may delay the progression of disability over time; however, there is minimal evidence supporting the efficacy of DMDs for reversing mobility disability or restoring ambulatory function in persons with MS. Areas covered: This review outlines symptomatic pharmacologic and non-pharmacologic therapeutic approaches that target mobility disability with the goal of restoring and improving walking function. First, the efficacy of dalfampridine, currently the only Food and Drug Administration approved symptomatic pharmacologic agent that improves walking in persons with MS is described. Next, a review of the efficacy of non-pharmacologic therapies for improving walking, including exercise training, physical therapy, and gait training is given. Last, guidance on future research on mobility in MS is provided by emphasizing the importance of combinatory treatment approaches that include multiple intervention modalities, as the best treatment plan likely involves a comprehensive, multidisciplinary approach. Expert commentary: There has been an increased effort to develop symptom-specific treatments in MS that directly target mobility disability; however, more research is needed to determine the efficacy of these rehabilitative strategies alone and together for improving walking in persons with MS.

Upper limb robotics applied to neurorehabilitation: An overview of clinical practice

BACKGROUND

During the last two decades, extensive interaction between clinicians and engineers has led to the development of systems that stimulate neural plasticity to optimize motor recovery after neurological lesions. This has resulted in the expansion of the field of robotics for rehabilitation. Studies in patients with stroke-related upper-limb paresis have shown that robotic rehabilitation can improve motor capacity. However, few other applications have been evaluated (e.g. tremor, peripheral nerve injuries or other neurological diseases).

PURPOSE

This paper presents an overview of the current use of upper limb robotic systems for neurorehabilitation, and highlights the rationale behind their use for the assessment and treatment of common neurological disorders.

CONCLUSIONS

Rehabilitation robots are little integrated in clinical practice, except after stroke. Although few studies have been carried out to evaluate their effectiveness, evidence from the neurosciences and indications from pilot studies suggests that upper limb robotic rehabilitation can be applied safely in various other neurological conditions. Rehabilitation robots provide an intensity, quality and dose of treatment that exceeds therapist-mediated rehabilitation. Moreover, the use of force fields, multi-sensory environments, feedback etc. renders such rehabilitation engaging and motivating. Future studies should evaluate the effectiveness of rehabilitation robots in neurological pathologies other than stroke.

Altered motor plasticity in an acute relapse of multiple sclerosis

In relapsing-remitting MS (RRMS), the symptoms of a clinical relapse subside over time. Neuroplasticity is believed to play an important compensatory role. In this study, we assessed excitability-decreasing plasticity during an acute relapse of MS and 12 weeks afterwards. Motor plasticity was examined in 19 patients with clinically isolated syndrome or RRMS during a steroid-treated relapse (t1) and 12 weeks afterwards (t2) using paired-associative stimulation (PAS10). This method combines repetitive electric nerve stimulation with transcranial magnetic stimulation of the contralateral motor cortex to model long-term synaptic depression in the human cortex. Additionally, 19 age-matched healthy controls were assessed. Motor-evoked potentials of the abductor pollicis brevis muscle were recorded before and after intervention. Clinical disability was assessed by the multiple sclerosis functional composite and the subscore of the nine-hole peg test taken as a measure of hand function. The effect of PAS10 was significantly different between controls and patients; at t1, but not at t2, baseline-normalized postinterventional amplitudes were significantly higher in patients (106 [IQR 98-137] % post10-15 and 111 [IQR 88-133] % post20-25) compared to controls (92 [IQR 85-111] % and 90 [IQR 75-102] %). Additional exploratory analysis indicated a potentially excitability-enhancing effect of PAS10 in patients as opposed to controls. Significant clinical improvement between t1 and t2 was not correlated with PAS10 effects. Our results indicate an alteration of PAS10-induced synaptic plasticity during relapse, presumably reflecting a polarity shift due to metaplastic processes within the motor cortex. Further studies will need to elucidate the functional significance of such changes for the clinical course of MS.

Spinal cord atrophy in anterior-posterior direction reflects impairment in multiple sclerosis

OBJECTIVE

To investigate how atrophy is distributed over the cross section of the upper cervical spinal cord and how this relates to functional impairment in multiple sclerosis (MS).

METHODS

We analysed the structural brain MRI scans of 54 patients with relapsing-remitting MS (n=22), primary progressive MS (n=9), secondary progressive MS (n=23) and 23 age- and sex-matched healthy controls. We measured the cross-sectional area (CSA), left-right width (LRW) and anterior-posterior width (APW) of the spinal cord at the segmental level C2. We tested for a nonparametric linear relationship between these atrophy measures and clinical impairments as reflected by the Expanded Disability Status Scale (EDSS) and Multiple Sclerosis Impairment Scale (MSIS).

RESULTS

In patients with MS, CSA and APW but not LRW were reduced compared to healthy controls (P<.02) and showed significant correlations with EDSS, MSIS and specific MSIS subscores.

CONCLUSION

In patients with MS, atrophy of the upper cervical cord is most evident in the antero-posterior direction. As APW of the cervical cord can be readily derived from standard structural MRI of the brain, APW constitutes a clinically useful neuroimaging marker of disease-related neurodegeneration in MS.

Gait and balance deterioration over a 12-month period in multiple sclerosis patients with EDSS scores ≤ 3.0

BACKGROUND AND PURPOSE

It is not currently known whether gait and balance measures are responsive to deterioration of motor function in multiple sclerosis (MS) patients with low EDSS scores (≤3.0). The aim of this study was to quantify MS-related gait and balance deterioration over a 12-month period.

METHODS

Thirty-eight participants with MS (33 female, mean age: 41.1 ± 8.3 years), mean time since diagnosis 2.2 ± 4.1 years, EDSS score ≤3.0 and without clinical evidence of gait deterioration, were recruited. Participants performed walking trials and Functional and Lateral Reach Tests. Kinematics of the ankle and knee, and electromyography of the tibialis anterior and medial gastrocnemius muscles were also measured.

RESULTS

Three participants reported relapses with worsening EDSS scores and 4 non-relapsing participants had worse EDSS scores at 12 months. There were significant decreases in mean gait speed, stride length and balance scores, and a significant increase in double support. Marked changes in ankle kinematics, with decreased medial gastrocnemius activity were observed.

CONCLUSION

Gait and balance performance of non-disabled RRMS participants may progressively decline, even in the absence of both acute clinical relapse and change in clinical status measured by the EDSS.

Altered Functional Connectivity of Striatal Subregions in Patients with Multiple Sclerosis

Abnormal corticostriatal resting-state functional connectivity (rsFC) has been implicated in the neuropathology of multiple sclerosis. The striatum, a component of the basal ganglia, is involved in diverse functions including movement, cognition, emotion, and limbic information processing. However, the brain circuits of the striatal subregions contributing to the changes in rsFC in relapsing–remitting multiple sclerosis (RRMS) patients remain unknown. We used six subdivisions of the striatum in each hemisphere as seeds to investigate the rsFC of striatal subregions between RRMS patients and matched healthy controls (HCs). In addition, we also scanned a subcohort of RRMS patients after an average of 7 months to test the reliability of our findings. Compared to HCs, we found significantly increased dorsal caudal putamen (DCP) connectivity with the premotor area, dorsal lateral prefrontal cortex (DLPFC), insula, precuneus, and superior parietal lobule, and significantly increased connectivity between the superior ventral striatum and posterior cingulate cortex (PCC) in RRMS patients following both scans. Furthermore, we found significant associations between the Expanded Disability Status Scale and the rsFC of the left DCP with the DLPFC and parietal areas in RRMS patients. Our results suggest that the DCP may be a critical striatal subregion in the pathophysiology of RRMS.

Intrinsic functional plasticity of the sensorimotor network in relapsing-remitting multiple sclerosis: evidence from a centrality analysis

Background and Purpose

Advanced MRI studies have revealed regional alterations in the sensorimotor cortex of patients with relapsing-remitting multiple sclerosis (RRMS). However, the organizational features underlying the relapsing phase and the subsequent remitting phase have not been directly shown at the functional network or the connectome level. Therefore, this study aimed to characterize MS-related centrality disturbances of the sensorimotor network (SMN) and to assess network integrity and connectedness.

Methods

Thirty-four patients with clinically definite RRMS and well-matched healthy controls participated in the study. Twenty-three patients in the remitting phase underwent one resting-state functional MRI, and 11 patients in the relapsing-remitting phase underwent two different MRIs. We measured voxel-wise centrality metrics to determine direct (degree centrality, DC) and global (eigenvector centrality, EC) functional relationships across the entire SMN.

Results

In the relapsing phase, DC was significantly decreased in the bilateral primary motor and somatosensory cortex (M1/S1), left dorsal premotor (PMd), and operculum-integrated regions. However, DC was increased in the peripheral SMN areas. The decrease in DC in the bilateral M1/S1 was associated with the expanded disability status scale (EDSS) and total white matter lesion loads (TWMLLs), suggesting that this adaptive response is related to the extent of brain damage in the rapid-onset attack stage. During the remission process, these alterations in centrality were restored in the bilateral M1/S1 and peripheral SMN areas. In the remitting phase, DC was reduced in the premotor, supplementary motor, and operculum-integrated regions, reflecting an adaptive response due to brain atrophy. However, DC was enhanced in the right M1 and left parietal-integrated regions, indicating chronic reorganization. In both the relapsing and remitting phases, the changes in EC and DC were similar.

Conclusions

The alterations in centrality within the SMN indicate rapid plasticity and chronic reorganization with a biased impairment of specific functional areas in RRMS patients.

Functional and Structural Brain Plasticity Enhanced by Motor and Cognitive Rehabilitation in Multiple Sclerosis

Rehabilitation is recognized to be important in ameliorating motor and cognitive functions, reducing disease burden, and improving quality of life in patients with multiple sclerosis (MS). In this systematic review, we summarize the existing evidences that motor and cognitive rehabilitation may enhance functional and structural brain plasticity in patients with MS, as assessed by means of the most advanced neuroimaging techniques, including diffusion tensor imaging and task-related and resting-state functional magnetic resonance imaging (MRI). In most cases, the rehabilitation program was based on computer-assisted/video game exercises performed in either an outpatient or home setting. Despite their heterogeneity, all the included studies describe changes in white matter microarchitecture, in task-related activation, and/or in functional connectivity following both task-oriented and selective training. When explored, relevant correlation between improved function and MRI-detected brain changes was often found, supporting the hypothesis that training-induced brain plasticity is specifically linked to the trained domain. Small sample sizes, lack of randomization and/or an active control group, as well as missed relationship between MRI-detected changes and clinical performance, are the major drawbacks of the selected studies. Knowledge gaps in this field of research are also discussed to provide a framework for future investigations.