Cerebellar Contributions to Motor and Cognitive Control in Multiple Sclerosis(✰✰✰)

Propulsive Force Modulation Drives Split-Belt Treadmill Adaptation in People with Multiple Sclerosis

Most people with multiple sclerosis (PwMS) experience significant gait asymmetries between their legs during walking, leading to an increased risk of falls. Split-belt treadmill training, where the speed of each limb is controlled independently, alters each leg's stepping pattern and can improve gait symmetry in PwMS. However, the biomechanical mechanisms of this adaptation in PwMS remain poorly understood. In this study, 32 PwMS underwent a 10 min split-belt treadmill adaptation paradigm with the more affected (MA) leg moving twice as fast as the less affected (LA) leg. The most noteworthy biomechanical adaptation observed was increased peak propulsion asymmetry between the limbs. A kinematic analysis revealed that peak dorsiflexion asymmetry and the onset of plantarflexion in the MA limb were the primary contributors to the observed increases in peak propulsion. In contrast, the joints in the LA limb underwent only immediate reactive adjustments without subsequent adaptation. These findings demonstrate that modulation during gait adaptation in PwMS occurs primarily via propulsive forces and joint motions that contribute to propulsive forces. Understanding these distinct biomechanical changes during adaptation enhances our grasp of the rehabilitative impact of split-belt treadmill training, providing insights for refining therapeutic interventions aimed at improving gait symmetry.

Cognitive impairment associated with cerebellar volume loss in spinocerebellar ataxia type 3

BACKGROUND

Many neuroscience and neurology studies have forced a reconsideration of the traditional motor-related scope of cerebellar function, which has now expanded to include various cognitive functions. Spinocerebellar ataxia type 3 (SCA3; the most common hereditary ataxia) is neuropathologically characterized by cerebellar atrophy and frequently presents with cognitive impairment.

OBJECTIVE

To characterize cognitive impairment in SCA3 and investigate the cerebellum-cognition associations.

METHODS

This prospective, cross-sectional cohort study recruited 126 SCA3 patients and 41 healthy control individuals (HCs). Participants underwent a brain 3D T1-weighted images as well as neuropsychological tests. Voxel-based morphometry (VBM) and region of interest (ROI) approaches were performed on the 3D T1-weighted images. CERES was used to automatically segment cerebellums. Patients were grouped into cognitively impaired (CI) and cognitively preserved (CP), and clinical and MRI parameters were compared. Multivariable regression models were fitted to examine associations between cerebellar microstructural alterations and cognitive domain impairments.

RESULTS

Compared to HCs, SCA3 patients showed cognitive domain impairments in information processing speed, verbal memory, executive function, and visuospatial perception. Between CI and CP subgroups, the CI subgroup was older and had lower education, as well as higher severity scores. VBM and ROI analyses revealed volume loss in cerebellar bilateral lobule VI, right lobule Crus I, and right lobule IV of the CI subgroup, and all these cerebellar lobules were associated with the above cognitive domain impairments.

CONCLUSIONS

Our findings demonstrate the multiple cognitive domain impairments in SCA3 patients and indicate the responsible cerebellar lobules for the impaired cognitive domain(s).

Scale development to evaluate differences between concern about falling and fear of falling: the concern and fear of falling evaluation

Purpose

Individuals with multiple sclerosis (MS) experience fear of falling (FOF), which is associated with negative health and quality-of-life consequences. Prior research has used FOF and concern about falling (CAF) interchangeably, but persons with MS report that CAF and FOF represent separate constructs that lie on a continuum. Unfortunately, no scale exists to understand the differences between CAF and FOF. Therefore, we developed a novel questionnaire, the Concern and Fear of Falling Evaluation (CAFFE), in which respondents rank their CAF and FOF on a continuum across various activities. This study aims to describe the scale development process and examine its psychometric properties.

Methods

In a single online survey, MS participants responded to demographic questionnaires, indicated whether they experience CAF and FOF, and completed the CAFFE. Psychometric evaluation of the CAFFE involved internal consistency, split-half cross validation, exploratory factor analysis (EFA), and confirmatory factor analysis (CFA).

Results

Out of 1,025 respondents, 64.6% reported CAF and 47.2% reported FOF. The EFA yielded a two-factor solution encompassing activities in open (factor 1) and closed environments (factor 2). The CFA replicated this two-factor solution and the CAFFE demonstrated excellent internal consistency (α = 0.98).

Conclusion

The 27-item CAFFE is a highly reliable and valid measure capturing the tipping point at which point CAF moves to FOF. Future research should seek to define the tipping point from the MS community, as CAF may be an adaptive mechanism, whereas FOF may be a maladaptive behavior.

Microglial depletion exacerbates axonal damage and motor dysfunction in mice with cuprizone-induced demyelination

The cuprizone (CPZ)-induced demyelination model, an animal model of Multiple sclerosis (MS), is characterized by demyelination and motor dysfunction due to microglial-mediated neuroinflammation. To determine the contribution of microglia to motor function during CPZ-induced demyelination, the microglia of mice in the CPZ-model were depleted using PLX3397 (PLX), an orally bioavailable selective colony stimulating factor 1 receptor inhibitor. PLX treatment aggravated motor dysfunction as shown by the pole, beam walk, ladder walk, and rotarod tests. PLX treatment removed microglia from the superior cerebellar peduncle (SCP), but not from the corpus callosum (CC). Although PLX treatment did not affect the degree of demyelination in both of CC and SCP, the expression of axonal damage marker APP (amyloid precursor protein) was increased. Increased TNF-α, IL-1β, and iNOS expressions were observed in PLX-treated mice. These results suggest that microglial depletion exacerbates axonal damage and motor dysfunction in CPZ model mice. In this study, we found that microglia contribute to motor function and axon-protective effects in CPZ-induced demyelination.

Cognitive Contributors of Backward Walking in Persons with Multiple Sclerosis

Purpose

Individuals with multiple sclerosis (MS) are at an increased fall risk due to motor and cognitive dysfunction. Our past studies suggest that backward walking (BW) velocity predicts fall risk; however, specific cognitive domains associated with BW velocity remain understudied. The goal of this study was to determine the specific contributions of cognitive functioning to BW velocity in persons with MS. We hypothesized that better visuospatial memory, verbal immediate recall, and faster information processing speed would contribute to faster BW velocity, and deficits in these domains would partially account for disease severity-related impairment in BW velocity.

Methods

Participants completed demographic questionnaires, walking tests, and cognitive assessments. Applied structural equation modeling was used to test our hypothesized model of competing cognitive mediators. Within the model, disease severity was a predictor of BW via three intercorrelated cognitive mediators.

Results

Participants included 39 individuals with relapsing-remitting MS. Results indicated that 35.3% of the significant total effect of disease severity on BW was accounted for by specific cognitive deficits. Verbal immediate recall had the largest contribution, followed by visuospatial memory and information processing speed.

Conclusions

When examining the unique effects of cognitive domains on disease severity-related deficits in BW, a meaningful source of impairment related to visuospatial memory and verbal immediate recall was demonstrated. Considering the utility of BW velocity as a predictor of falls, these results highlight the importance of assessing cognition when evaluating fall risk in MS. Cognitive-based intervention studies investigating fall prevention may find BW as a more specific and sensitive predictor of fall risk than forward walking.

Tremor in Patients with Relapsing-Remitting Multiple Sclerosis: Clinical Characteristics and Impact on Quality of Life

Background

Little is known about the prevalence and clinical characteristics of tremors in patients with multiple sclerosis (MS), their associated clinical disability, and their impact on quality of life (QoL).

Objective

This study aimed to investigate the frequency and types of tremors in patients with relapsing remitting MS (RRMS) in remission, and their impact on patients' QoL.

Methods

A total of 250 patients with RRMS in remission were examined for tremors. All patients were assessed using the Expanded Disability Status Scale (EDSS). Patients with tremors underwent further assessment using the Fahn-Tolosa-Marin Tremor Rating Scale (FTMTRS), the Beck Depression Inventory (BDI), the Montreal Cognitive Assessment (MoCA) scale, and the Short Form 36 Health Survey Questionnaire (SF-36). Brain MRI was obtained for a subgroup of patients.

Results

Tremors were detected in 36 patients (14.4%) and were associated with significantly worse EDSS scores, BDI (P = 0.021), MoCA, most SF-36 domains, higher total and last year relapses (P < 0.001) and longer disease duration (P = 0.027). Patients with tremors showed higher lesion load (P = 0.007), more infratentorial (P ≤ 0.001), cerebellar and diencephalic lesions (P = 0.024), and cortical atrophy (P = 0.012). Total FTMTRS was significantly correlated to age, EDSS, and physical functioning. Dystonia was associated with tremors in 17 patients (6.8% of total RRMS patients and 47.2% of patients with tremors).

Conclusion

The current study confirms the common occurrence of tremors and their subtypes among patients with RRMS with mild disability and demonstrates their association with increased disability and impaired QoL.

Neuroimaging Technology in Exercise Neurorehabilitation Research in Persons with MS: A Scoping Review

There is increasing interest in the application of neuroimaging technology in exercise neurorehabilitation research among persons with multiple sclerosis (MS). The inclusion and focus on neuroimaging outcomes in MS exercise training research is critical for establishing a biological basis for improvements in functioning and elevating exercise within the neurologist's clinical armamentarium alongside disease modifying therapies as an approach for treating the disease and its consequences. Indeed, the inclusion of selective neuroimaging approaches and sensor-based technology among physical activity, mobility, and balance outcomes in such MS research might further allow for detecting specific links between the brain and real-world behavior. This paper provided a scoping review on the application of neuroimaging in exercise training research among persons with MS based on searches conducted in PubMed, Web of Science, and Scopus. We identified 60 studies on neuroimaging-technology-based (primarily MRI, which involved a variety of sequences and approaches) correlates of functions, based on multiple sensor-based measures, which are typically targets for exercise training trials in MS. We further identified 12 randomized controlled trials of exercise training effects on neuroimaging outcomes in MS. Overall, there was a large degree of heterogeneity whereby we could not identify definitive conclusions regarding a consistent neuroimaging biomarker of MS-related dysfunction or singular sensor-based measure, or consistent neural adaptation for exercise training in MS. Nevertheless, the present review provides a first step for better linking correlational and randomized controlled trial research for the development of high-quality exercise training studies on the brain in persons with MS, and this is timely given the substantial interest in exercise as a potential disease-modifying and/or neuroplasticity-inducing behavior in this population.

Ataxias: Hereditary, Acquired, and Reversible Etiologies

A variety of etiologies can cause cerebellar dysfunction, leading to ataxia symptoms. Therefore, the accurate diagnosis of the cause for cerebellar ataxia can be challenging. A step-wise investigation will reveal underlying causes, including nutritional, toxin, immune-mediated, genetic, and degenerative disorders. Recent advances in genetics have identified new genes for both autosomal dominant and autosomal recessive ataxias, and new therapies are on the horizon for targeting specific biological pathways. New diagnostic criteria for degenerative ataxias have been proposed, specifically for multiple system atrophy, which will have a broad impact on the future clinical research in ataxia. In this article, we aim to provide a review focus on symptoms, laboratory testing, neuroimaging, and genetic testing for the diagnosis of cerebellar ataxia causes, with a special emphasis on recent advances. Strategies for the management of cerebellar ataxia is also discussed.

Associations between myelin water imaging and measures of fall risk and functional mobility in multiple sclerosis

BACKGROUND AND PURPOSE

Myelin water fraction (MWF) deficits as measured by myelin water imaging (MWI) have been related to worse motor function in persons with multiple sclerosis (PwMS). However, it is unknown if measures from MWI metrics in motor areas relate to fall risk measures in PwMS. The objective of this study was to examine the relationship between MWI measures in motor areas to performance on clinical measures of fall risk and disability in PwMS.

METHODS

Sixteen individuals with relapsing-remitting MS participated (1 male, 15 female; age 47.1 years [12.3]; Expanded Disability Status Scale 4.0 [range 0-6.5]) and completed measures of walking and fall risk (Timed 25 Foot Walk [T25FW] and Timed Up and Go). MWF and the geometric mean of the intra-/extracellular water T₂ (geomT_2IEW ) values reflecting myelin content and contribution of large-diameter axons/density, respectively, were assessed in three motor-related regions.

RESULTS

The geomT_2IEW of the corticospinal tract (r = -.599; p = .018) and superior cerebellar peduncles (r = -.613; p = .015) demonstrated significant inverse relationships with T25FW, suggesting that decreased geomT_2IEW was related to slower walking. Though not significant, MWF in the corticospinal tract and superior cerebellar peduncles also demonstrated fair relationships with the T25FW, suggesting that worse performance on the T25FW was associated with lower MWF values.

CONCLUSIONS

MWI of key motor regions was associated with walking performance in PwMS. Further MWI studies are needed to identify relationships between pathology and clinical function in PwMS to guide targeted rehabilitation therapies aimed at preventing falls.

Multisensory integration and white matter pathology: Contributions to cognitive dysfunction

The ability to simultaneously process and integrate multiple sensory stimuli is paramount to effective daily function and essential for normal cognition. Multisensory management depends critically on the interplay between bottom-up and top-down processing of sensory information, with white matter (WM) tracts acting as the conduit between cortical and subcortical gray matter (GM) regions. White matter tracts and GM structures operate in concert to manage both multisensory signals and cognition. Altered sensory processing leads to difficulties in reweighting and modulating multisensory input during various routine environmental challenges, and thus contributes to cognitive dysfunction. To examine the specific role of WM in altered sensory processing and cognitive dysfunction, this review focuses on two neurologic disorders with diffuse WM pathology, multiple sclerosis and mild traumatic brain injury, in which persistently altered sensory processing and cognitive impairment are common. In these disorders, cognitive dysfunction in association with altered sensory processing may develop initially from slowed signaling in WM tracts and, in some cases, GM pathology secondary to WM disruption, but also because of interference with cognitive function by the added burden of managing concurrent multimodal primary sensory signals. These insights promise to inform research in the neuroimaging, clinical assessment, and treatment of WM disorders, and the investigation of WM-behavior relationships.