Brain dysconnectivity relates to disability and cognitive impairment in multiple sclerosis

Longitudinal investigation of neuroimaging changes related to memory decline in multiple sclerosis: Testing a mechanistic model

BACKGROUND

Memory decline is common in multiple sclerosis (MS), although pathophysiological mechanisms are not fully understood.

OBJECTIVE

The objective was to investigate the relationship of changes in structural and functional neuroimaging markers to memory decline over 3-year follow-up.

METHODS

Participants with MS underwent cognitive evaluation and structural, diffusion, and functional 3T magnetic resonance imaging (MRI) scans at baseline and 3-year follow-up. Changes in neuroimaging metrics from baseline to follow-up were compared between memory stable and memory decline groups. Our hypothesis that structural and functional connectivity changes mediate the association of atrophy to memory decline was tested.

RESULTS

A total of 249 MS patients completed baseline visit; 169 (67.8%) returned at 3-year follow-up. Based on ⩾10% decline, memory decline was observed in 44.4% (n = 75). Those with memory decline showed marginally greater whole-brain volume loss over time compared with those with stable memory performance (p = 0.08). In those with memory decline, changes in white matter tract integrity were related to regional cortical thinning (p < 0.01). Exploratory mediation analysis revealed structural and functional connectivity to mediate the relationship of atrophy to verbal and visual memory decline.

CONCLUSION

Further work is needed to characterize complex interrelationships of atrophy and structural/functional connectivity changes to memory decline in MS.

Disrupted working memory event-related network dynamics in multiple sclerosis

In multiple sclerosis (MS), working memory (WM) impairment can occur soon after disease onset and significantly affects the patient's quality of life. Functional imaging research in MS aims to investigate the neurophysiological underpinnings of WM impairment. In this context, we utilize a data-driven technique, the time delay embedded-hidden Markov model, to extract spectrally defined functional networks in magnetoencephalographic (MEG) data acquired during a WM visual-verbal n-back task. Here, we show that the activation of two networks is altered in relapsing remitting-MS patients. First, the activation of an early theta prefrontal network linked to stimulus encoding and attentional control significantly decreases in MS compared to HC. This diminished activation correlates with reduced accuracy and higher reaction time, suggesting that impaired attention control impacts task performance in MS patients. Secondly, a frontoparietal network characterized by beta coupling is activated between 300 and 600 ms post-stimulus, resembling the event-related P300, a cognitive marker extensively explored in EEG studies. The activation of this network is amplified in patients treated with benzodiazepine, in line with the well-known benzodiazepine-induced beta enhancement. Altogether, the TDE-HMM technique extracts task-relevant functional networks showing disease-specific and treatment-related alterations, revealing potential new markers to assess and track WM impairment in MS.

Cognitive impairment in multiple sclerosis: from phenomenology to neurobiological mechanisms

Multiple sclerosis (MS) is an autoimmune-mediated disease of the central nervous system characterized by inflammation, demyelination and chronic progressive neurodegeneration. Among its broad and unpredictable range of clinical symptoms, cognitive impairment (CI) is a common and disabling feature greatly affecting the patients' quality of life. Its prevalence is 20% up to 88% with a wide variety depending on the phenotype of MS, with highest frequency and severity in primary progressive MS. Involving different cognitive domains, CI is often associated with depression and other neuropsychiatric symptoms, but usually not correlated with motor and other deficits, suggesting different pathophysiological mechanisms. While no specific neuropathological data for CI in MS are available, modern research has provided evidence that it arises from the disease-specific brain alterations. Multimodal neuroimaging, besides structural changes of cortical and deep subcortical gray and white matter, exhibited dysfunction of fronto-parietal, thalamo-hippocampal, default mode and cognition-related networks, disruption of inter-network connections and involvement of the γ-aminobutyric acid (GABA) system. This provided a conceptual framework to explain how aberrant pathophysiological processes, including oxidative stress, mitochondrial dysfunction, autoimmune reactions and disruption of essential signaling pathways predict/cause specific disorders of cognition. CI in MS is related to multi-regional patterns of cerebral disturbances, although its complex pathogenic mechanisms await further elucidation. This article, based on systematic analysis of PubMed, Google Scholar and Cochrane Library, reviews current epidemiological, clinical, neuroimaging and pathogenetic evidence that could aid early identification of CI in MS and inform about new therapeutic targets and strategies.

The use of event-related potentials in the investigation of cognitive performance in people with Multiple Sclerosis: Systematic review

A biomarker of cognition in Multiple Sclerosis (MS) that is independent from the response of people with MS (PwMS) to test questions would provide a more holistic assessment of cognitive decline. One suggested method involves event-related potentials (ERPs). This systematic review tried to answer five questions about the use of ERPs in distinguishing PwMS from controls: which stimulus modality, which experimental paradigm, which electrodes, and which ERP components are most discriminatory, and whether amplitude or latency is a better measure. Our results show larger pooled effect sizes for visual stimuli than auditory stimuli, and larger pooled effect sizes for latency measurements than amplitude measurements. We observed great heterogeneity in methods and suggest that future research would benefit from more uniformity in methods and that results should be reported for the individual subtypes of PwMS. With more standardised methods, ERPs have the potential to be developed into a clinical tool in MS.

Thalamic atrophy and dysconnectivity are associated with cognitive impairment in a multi-center, clinical routine, real-word study of people with relapsing-remitting multiple sclerosis

BACKGROUND

Prior research has established a link between thalamic pathology and cognitive impairment (CI) in people with multiple sclerosis (pwMS). However, the translation of these findings to pwMS in everyday clinical settings has been insufficient.

OBJECTIVE

To assess which global and/or thalamic imaging biomarkers can be used to identify pwMS at risk for CI and cognitive worsening (CW) in a real-world setting.

METHODS

This was an international, multi-center (11 centers), longitudinal, retrospective, real-word study of people with relapsing-remitting MS (pwRRMS). Brain MRI exams acquired at baseline and follow-up were collected. Cognitive status was evaluated using the Symbol Digit Modalities Test (SDMT). Thalamic volume (TV) measurement was performed on T2-FLAIR, as well as on T1-WI, when available. Thalamic dysconnectivity, T2-lesion volume (T2-LV), and volumes of gray matter (GM), whole brain (WB) and lateral ventricles (LVV) were also assessed.

RESULTS

332 pwMS were followed for an average of 2.8 years. At baseline, T2-LV, LVV, TV and thalamic dysconnectivity on T2-FLAIR (p < 0.016), and WB, GM and TV volumes on T1-WI (p < 0.039) were significantly worse in 90 (27.1 %) CI vs. 242 (62.9 %) non-CI pwRRMS. Greater SDMT decline over the follow-up was associated with lower baseline TV on T2-FLAIR (standardized β = 0.203, p = 0.002) and greater thalamic dysconnectivity (standardized β = -0.14, p = 0.028) in a linear regression model.

CONCLUSIONS

PwRRMS with thalamic atrophy and worse thalamic dysconnectivity present more frequently with CI and experience greater CW over mid-term follow-up in a real-world setting.

Neurophysiological brain function predicts response to cognitive rehabilitation and mindfulness in multiple sclerosis: a randomized trial

BACKGROUND

Cognitive treatment response varies highly in people with multiple sclerosis (PwMS). Identification of mechanisms is essential for predicting response.

OBJECTIVES

This study aimed to investigate whether brain network function predicts response to cognitive rehabilitation therapy (CRT) and mindfulness-based cognitive therapy (MBCT).

METHODS

PwMS with cognitive complaints completed CRT, MBCT, or enhanced treatment as usual (ETAU) and performed three measurements (baseline, post-treatment, 6-month follow-up). Baseline magnetoencephalography (MEG) measures were used to predict treatment effects on cognitive complaints, personalized cognitive goals, and information processing speed (IPS) using mixed models (secondary analysis REMIND-MS study).

RESULTS

We included 105 PwMS (96 included in prediction analyses; 32 CRT, 31 MBCT, 33 ETAU), and 56 healthy controls with baseline MEG. MEG did not predict reductions in complaints. Higher connectivity predicted better goal achievement after MBCT (p = 0.010) and CRT (p = 0.018). Lower gamma power (p = 0.006) and higher connectivity (p = 0.020) predicted larger IPS benefits after MBCT. These MEG predictors indicated worse brain function compared to healthy controls (p < 0.05).

CONCLUSIONS

Brain network function predicted better cognitive goal achievement after MBCT and CRT, and IPS improvements after MBCT. PwMS with neuronal slowing and hyperconnectivity were most prone to show treatment response, making network function a promising tool for personalized treatment recommendations.

TRIAL REGISTRATION

The REMIND-MS study was prospectively registered in the Dutch Trial registry (NL6285; https://trialsearch.who.int/Trial2.aspx?TrialID=NTR6459 ).

Hub overload and failure as a final common pathway in neurological brain network disorders

Understanding the concept of network hubs and their role in brain disease is now rapidly becoming important for clinical neurology. Hub nodes in brain networks are areas highly connected to the rest of the brain, which handle a large part of all the network traffic. They also show high levels of neural activity and metabolism, which makes them vulnerable to many different types of pathology. The present review examines recent evidence for the prevalence and nature of hub involvement in a variety of neurological disorders, emphasizing common themes across different types of pathology. In focal epilepsy, pathological hubs may play a role in spreading of seizure activity, and removal of such hub nodes is associated with improved outcome. In stroke, damage to hubs is associated with impaired cognitive recovery. Breakdown of optimal brain network organization in multiple sclerosis is accompanied by cognitive dysfunction. In Alzheimer's disease, hyperactive hub nodes are directly associated with amyloid-beta and tau pathology. Early and reliable detection of hub pathology and disturbed connectivity in Alzheimer's disease with imaging and neurophysiological techniques opens up opportunities to detect patients with a network hyperexcitability profile, who could benefit from treatment with anti-epileptic drugs.

Effect of Tai-chi on balance, mood, cognition, and quality of life in women with multiple sclerosis: A one-year prospective study

INTRODUCTION

One of the most debilitating problems encountered by people with multiple sclerosis (MS) is the loss of balance and coordination. Our study aimed to comprehensively evaluate the effectiveness of one year of Tai-chi exercise in patients with MS using both subjective and objective methods, including posturography.

METHODS

This was a single-group longitudinal one-year study performed from the 1st of January 2019 to the 1st of January 2020. The primary outcomes of interest were the Mini-Balance Evaluation Systems Test (Mini-BESTest) and static posturography measures as objective methods to detect subtle changes associated with postural control/balance impairment. Secondary outcomes were measures of depression, anxiety, cognitive performance, and quality of life. All objective and subjective parameters were assessed four times: at baseline, and after three, six and 12 months of regular Tai-chi training. The difference was calculated as a subtraction of baseline values from every timepoint value for each measurement. If the normality test was passed, parametric one-sample t-test was used, if failed, Wilcoxon signed ranks test was used to test the difference between the baseline and each timepoint. Alpha was set to 0.017 using Bonferroni correction for multiple comparisons.

RESULTS

Out of 25 patients with MS enrolled, 15 women with MS (mean age 44.27 years) were included for statistical analyses after completing the 12-month program. After 12 months, significant improvements were found in all objective balance and gait tests: Mini-BESTest (p<0.001), static posturography measures (total area of the centre of foot pressure - TA; p = 0.015), 25 Feet Walk Test (25FWT; p = 0.001), anxiety (Beck Anxiety Inventory - BAI; p = 0.005) and cognition tests (Paced Auditory Serial Addition Test - PASAT; p = 0.003). Measures of depression (Beck Depression Inventory - BDI; p = 0.071), cognition (Symbol Digit Modalities Test - SDMT; p = 0.079), and health-related quality of life (European Quality of Life 5-Dimensions Questionnaire - EQ-5D-5L; p = 0.095) showed a trend of improvement but were not significant, which could be the result of a small sample and increased bias due the type II error.

CONCLUSION

According to these preliminary results, this study indicates the possible beneficial effects of long-term Tai-chi training on patients with MS. Although these findings need to be confirmed by further studies with a larger sample of participants of both genders and require more rigorous randomized controlled trials (RCT) design, our findings support the recommendation of regular and long-term Tai-chi exercise in patients with MS.

CLINICALTRIALS

GOV IDENTIFIER (RETROSPECTIVELY REGISTERED)

NCT05474209.

The role of clinical neurophysiology in the definition and assessment of fatigue and fatigability

Though a common symptom, fatigue is difficult to define and investigate, occurs in a wide variety of neurological and systemic disorders, with differing pathological causes. It is also often accompanied by a psychological component. As a symptom of long-term COVID-19 it has gained more attention. In this review, we begin by differentiating fatigue, a perception, from fatigability, quantifiable through biomarkers. Central and peripheral nervous system and muscle disorders associated with these are summarised. We provide a comprehensive and objective framework to help identify potential causes of fatigue and fatigability in a given disease condition. It also considers the effectiveness of neurophysiological tests as objective biomarkers for its assessment. Among these, twitch interpolation, motor cortex stimulation, electroencephalography and magnetencephalography, and readiness potentials will be described for the assessment of central fatigability, and surface and needle electromyography (EMG), single fibre EMG and nerve conduction studies for the assessment of peripheral fatigability. The purpose of this review is to guide clinicians in how to approach fatigue, and fatigability, and to suggest that neurophysiological tests may allow an understanding of their origin and interactions. In this way, their differing types and origins, and hence their possible differing treatments, may also be defined more clearly.

Cortical thickness and cognition in older people with multiple sclerosis

BACKGROUND

The structural changes associated with cognitive performance in older people with multiple sclerosis (PwMS; age ≥ 50 years old) remain unknown.

OBJECTIVE

To determine the relationship between whole-brain (WBV), thalamus as the largest deep gray matter nuclei, and cortex-specific volume measurements with both cognitive impairment and numerical performance in older PwMS. The main hypothesis is that cognitive impairment (CI) in older PwMS is explained by cortical thinning in addition to global and thalamic neurodegenerative changes.

METHODS

A total of 101 older PwMS underwent cognitive and neuroimaging assessment. Cognitive assessment included tests established as sensitive in MS samples (Minimal Assessment of Cognitive Function in MS; MACFIMS), as well as those tests often utilized in Alzheimer's dementia studies (Wechsler's Memory Scale, Boston Naming Test, Visual Motor Integration and language). Cognitive impairment (CI) was based on -1.5 standard deviations in at least 2 cognitive domains (executive function, learning and memory, spatial processing, processing speed and working memory and language) when compared to healthy controls. WBV and thalamic volume were calculated using SIENAX/FIRST and cortical thickness using FreeSurfer. Differences in cortical thickness between CI and cognitively preserved (CP) were determined using age, sex, education, depression and WBV-adjusted analysis of covariance (ANCOVA). The relationship between domain-specific cognitive performance and cortical thickness was analyzed by linear regression models adjusted for age, sex, education, depression, WBV and thalamic volume. Benjamini-Hochberg-adjusted p-values lower than 0.05 were considered significant.

RESULTS

The average age of the study population was 62.6 (5.9) years old. After adjustment, CI PwMS had significantly thinner left fusiform (p = 0.0003), left inferior (p = 0.0032), left transverse (p = 0.0013), and bilateral superior temporal gyri (p = 0.002 and p = 0.0011) when compared to CP PwMS. After adjusting for age, sex, education, depression WBV, and thalamic volume, CI status was additionally predicted by the thickness of the left fusiform (p = 0.001) and left cuneus gyri (p = 0.004). After the adjustment, SDMT scores were additionally associated with left fusiform gyrus (p < 0.001) whereas letter-based verbal fluency performance with left pars opercularis gyrus (p < 0.001).

CONCLUSION

In addition to global and thalamic neurodegenerative changes, the presence of CI in older PwMS is additionally explained by the thickness of multiple cortical regions.

Resting-state EEG and MEG biomarkers of pathological fatigue - A transdiagnostic systematic review

Fatigue is a highly prevalent and disabling symptom of many disorders and syndromes, resulting from different pathomechanisms. However, whether and how different mechanisms converge and result in similar symptomatology is only partially understood, and transdiagnostic biomarkers that could further the diagnosis and treatment of fatigue are lacking. We, therefore, performed a transdiagnostic systematic review (PROSPERO: CRD42022330113) of quantitative resting-state electroencephalography (EEG) and magnetoencephalography (MEG) studies in adult patients suffering from pathological fatigue in different disorders. Studies investigating fatigue in healthy participants were excluded. The risk of bias was assessed using a modified Newcastle-Ottawa Scale. Semi-quantitative data synthesis was conducted using modified albatross plots. After searching MEDLINE, Web of Science Core Collection, and EMBASE, 26 studies were included. Cross-sectional studies revealed increased brain activity at theta frequencies and decreased activity at alpha frequencies as potential diagnostic biomarkers. However, the risk of bias was high in many studies and domains. Together, this transdiagnostic systematic review synthesizes evidence on how resting-state M/EEG might serve as a diagnostic biomarker of pathological fatigue. Beyond, this review might help to guide future M/EEG studies on the development of fatigue biomarkers.

Cell therapy procedure using anti-inflammatory macrophage M2 can potentially reduce Clinical Score in animals with Experimental Autoimmune Encephalomyelitis: A preclinical systematic review and meta-analysis study

Macrophage M2 (MP2)-based cell therapy is a novel medicinal treatment for animals with Experimental Autoimmune Encephalomyelitis (EAE) as an experimental model of multiple sclerosis (MS). This systematic review and meta-analysis study was designed to assess the overall therapeutic effects of MP2 cell therapy on Clinical Score and motor impairment in EAE-induced animals. All experiments on MP2 cell therapy in animals with EAE were gathered (by October 2, 2022) from English (PubMed, Scopus, WoS, Science Direct, and ISC) and Persian (MagIran and SID) databases. The searching strategy was designed using "Experimental Autoimmune Encephalomyelitis," "Multiple Sclerosis," and "Macrophage M2" keywords. Following primary and secondary screenings, eligible papers were selected based on the PRISMA 2020 guideline, and the study quality was assessed using the Animal Research: Reporting of In Vivo Experiments (ARRIVE) checklist. The difference in means of Clinical Score (score 0-5) as the effect size (ES) was analyzed based on the random effect model (CMA software, v.2). Subgrouping (EAE phases of Onset, Peak, and Recovery) was applied, and I² index was used to assess the heterogeneity index. Publication bias and sensitivity indices were also evaluated. P < 0.05 was considered significant, and the confidence interval (CI) was determined 95%. Among 22 gathered papers, medium to high quality studies were selected for meta-analysis. Difference in means, P value, and I² for Onset, Peak, and Recovery phases were 0.082 (CI95%: -0.323-0.159, P value: 0.504, I² : 67.961%), -0.606 (CI95%: -1.518 to -0.305, P value: 0.192, I² : 96.070%), and -1.103 (CI95%: -1.390 to -0.816, P value: 0.000, I² : 30.880%), respectively and Overall Effect was found -0.509 (CI95%: -0.689 to -0.328, P value < 0.001). Also, P value (two-tailed) indices for publication bias were 0.366 and 0.583 for Egger's regression intercept and Begg rank correlation, respectively. The P value for sensitivity was detected 0.003. Cell therapy procedure using MP2 can potentially alleviate the Clinical Scores Index and correct the motor defects in Recovery phase of EAE animals. In healthy mice, the brain and myelin surrounding neurons are in a healthy and physiological state (1). To evaluate MS in humans, it is necessary to model this type of disease in animals using EAE procedure through subcutaneous injection of CFA, MOG_35-55 , MT, and Pert. Thus, inflammation and autoimmunity occur, which finally lead to myelin destruction and motor symptoms (2). By aspiration of progenitor cells available in bone marrow, the MP2 can be isolated and cultured. By activation of these types of cells, a rich collection of MP2 can be prepared for the cell-therapy process (3). After injection through the tail vein or intra-peritoneal procedure, these cells can be located in CNS through crossing from the BBB. They begin their anti-inflammatory activities and help repair the damaged myelin (4). Eventually, the clinical symptoms can be modified considerably, and the animal motor function improves (5). CFA, complete Freund's adjuvant; MOG_35-55 , myelin oligodendrocyte glycoprotein; MT, Mycobacterium tuberculosis; Pert, pertussis; EAE, Experimental Autoimmune Encephalomyelitis; BM, bone marrow; MP2, macrophage M2; and BBB, blood brain barrier.

Molecular biomarkers and cognitive impairment in multiple sclerosis: State of the field, limitations, and future direction - A systematic review and meta-analysis

OBJECTIVE

Multiple sclerosis (MS) is associated with cognitive impairment (CI) such as slowed information processing speed (IPS). Currently, no immunocellular or molecular markers have been established in cerebrospinal fluid and serum analysis as surrogate biomarkers with diagnostic or predictive value for the development of CI. This systematic review and meta-analysis aims to sum up the evidence regarding currently discussed markers for CI in MS.

METHODS

A literature search was conducted on molecular biomarkers of CI in MS, such as neurofilament light chain, chitinases, and vitamin D.

RESULTS

5543 publications were screened, of which 77 entered the systematic review. 13 studies were included in the meta-analysis. Neurofilament light chain (CSF: r_p = -0.294, p = 0.003; serum: r_p = -0.137, p = 0.001) and serum levels of vitamin D (r_p = 0.190, p = 0.014) were associated with IPS outcomes.

CONCLUSIONS

Neurofilament light chain and vitamin D are promising biomarkers to track impairments in IPS in MS. Further longitudinal research is needed to establish the use of molecular biomarkers to monitor cognitive decline.

Topological reorganization of brain network might contribute to the resilience of cognitive functioning in mildly disabled relapsing remitting multiple sclerosis

Multiple sclerosis (MS) is an inflammatory and demyelinating disease which leads to impairment in several functional systems including cognition. Alteration of brain networks is linked to disability and its progression. However, results are mostly cross-sectional and yet contradictory as putative adaptive and maladaptive mechanisms were found. Here, we aimed to explore longitudinal reorganization of brain networks over 2-years by combining diffusion tensor imaging (DTI), resting-state functional MRI (fMRI), magnetoencephalography (MEG), and a comprehensive neuropsychological-battery. In 37 relapsing-remitting MS (RRMS) and 39 healthy-controls, cognition remained stable over-time. We reconstructed network models based on the three modalities and analyzed connectivity in relation to the hierarchical topology and functional subnetworks. Network models were compared across modalities and in their association with cognition using linear-mixed-effect-regression models. Loss of hub connectivity and global reduction was observed on a structural level over-years (p < .010), which was similar for functional MEG-networks but not for fMRI-networks. Structural hub connectivity increased in controls (p = .044), suggesting a physiological mechanism of healthy aging. Despite a general loss in structural connectivity in RRMS, hub connectivity was preserved (p = .002) over-time in default-mode-network (DMN). MEG-networks were similar to DTI and weakly correlated with fMRI in MS (p < .050). Lower structural (β between .23-.33) and both lower (β between .40-.59) and higher functional connectivity (β = -.54) in DMN was associated with poorer performance in attention and memory in RRMS (p < .001). MEG-networks involved no association with cognition. Here, cognitive stability despite ongoing neurodegeneration might indicate a resilience mechanism of DMN hubs mimicking a physiological reorganization observed in healthy aging.

Radial diffusivity reflects general decline rather than specific cognitive deterioration in multiple sclerosis

Advanced structural brain imaging techniques, such as diffusion tensor imaging (DTI), have been used to study the relationship between DTI-parameters and cognitive scores in multiple sclerosis (MS). In this study, we assessed cognitive function in 61 individuals with MS and a control group of 35 healthy individuals with the Symbol Digit Modalities Test, the California Verbal Learning Test-II, the Brief Visuospatial Memory Test-Revised, the Controlled Oral Word Association Test, and Stroop-test. We also acquired diffusion-weighted images (b = 1000; 32 directions), which were processed to obtain the following DTI scalars: fractional anisotropy, mean, axial, and radial diffusivity. The relation between DTI scalars and cognitive parameters was assessed through permutations. Although fractional anisotropy and axial diffusivity did not correlate with any of the cognitive tests, mean and radial diffusivity were negatively correlated with all of these tests. However, this effect was not specific to any specific white matter tract or cognitive test and demonstrated a general effect with only low to moderate individual voxel-based correlations of <0.6. Similarly, lesion and white matter volume show a general effect with medium to high voxel-based correlations of 0.5-0.8. In conclusion, radial diffusivity is strongly related to cognitive impairment in MS. However, the strong associations of radial diffusivity with both cognition and whole brain lesion volume suggest that it is a surrogate marker for general decline in MS, rather than a marker for specific cognitive functions.

Multistage classification identifies altered cortical phase- and amplitude-coupling in Multiple Sclerosis

Distinguishing groups of subjects or experimental conditions in a high-dimensional feature space is a common goal in modern neuroimaging studies. Successful classification depends on the selection of relevant features as not every neuronal signal component or parameter is informative about the research question at hand. Here, we developed a novel unsupervised multistage analysis approach that combines dimensionality reduction, bootstrap aggregating and multivariate classification to select relevant neuronal features. We tested the approach by identifying changes of brain-wide electrophysiological coupling in Multiple Sclerosis. Multiple Sclerosis is a demyelinating disease of the central nervous system that can result in cognitive decline and physical disability. However, related changes in large-scale brain interactions remain poorly understood and corresponding non-invasive biomarkers are sparse. We thus compared brain-wide phase- and amplitude-coupling of frequency specific neuronal activity in relapsing-remitting Multiple Sclerosis patients (n = 17) and healthy controls (n = 17) using magnetoencephalography. Changes in this dataset included both, increased and decreased phase- and amplitude-coupling in wide-spread, bilateral neuronal networks across a broad range of frequencies. These changes allowed to successfully classify patients and controls with an accuracy of 84%. Furthermore, classification confidence predicted behavioral scores of disease severity. In sum, our results unravel systematic changes of large-scale phase- and amplitude coupling in Multiple Sclerosis. Furthermore, our results establish a new analysis approach to efficiently contrast high-dimensional neuroimaging data between experimental groups or conditions.

Summary metrics of memory subnetwork functional connectivity alterations in multiple sclerosis

BACKGROUND

Memory dysfunction is common in multiple sclerosis (MS); mechanistic understanding of its causes is lacking. Large-scale network resting-state functional connectivity (RSFC) is sensitive to memory dysfunction.

OBJECTIVE

We derived and tested summary metrics of memory network RSFC.

METHODS

Cognitive data and 3T magnetic resonance imaging (MRI) scans were collected from 235 MS patients and 35 healthy controls (HCs). Index scores were calculated as RSFC within (anteriority index, AntI) and between (integration index, IntI) dorsomedial anterior temporal and medial temporal memory subnetworks. Group differences in index expression were evaluated. Associations between index scores and memory/non-memory cognition were evaluated; relationships between T2 lesion volume (T2LV) and index scores were assessed.

RESULTS

Index scores were related to memory and T2LV in MS patients, who showed marginally elevated AntI relative to HC (p = 0.06); no group differences were found for IntI. Better memory was associated with higher AntI (β = 0.15, p = 0.018) and IntI (β = 0.16, p = 0.014). No associations were found for non-memory cognition. Higher T2LV was associated with higher AntI and IntI; exploratory mediation analysis revealed significant inconsistent mediation, that is, higher index scores partially suppressed the negative association between T2LV and memory.

CONCLUSION

Summary, within-subject metrics permit replication and circumvent challenges of traditional (incommensurate) RSFC variables to advance development of mechanistic models of memory dysfunction in MS.

Atypical resting-state functional brain connectivity in children with developmental coordination disorder

Children with developmental coordination disorder (DCD) present lower abilities to acquire and execute coordinated motor skills. DCD is frequently associated with visual perceptual (with or without motor component) impairments. This magnetoencephalography (MEG) study compares the brain resting-state functional connectivity (rsFC) and spectral power of children with and without DCD. 29 children with DCD and 28 typically developing (TD) peers underwent 2 × 5 min of resting-state MEG. Band-limited power envelope correlation and spectral power were compared between groups using a functional connectome of 59 nodes from eight resting-state networks. Correlation coefficients were calculated between fine and gross motor activity, visual perceptual and visuomotor abilities measures on the one hand, and brain rsFC and spectral power on the other hand. Nonparametric statistics were used. Significantly higher rsFC between nodes of the visual, attentional, frontoparietal, default-mode and cerebellar networks was observed in the alpha (maximum statistics, p = .0012) and the low beta (p = .0002) bands in children with DCD compared to TD peers. Lower visuomotor performance (copying figures) was associated with stronger interhemispheric rsFC within sensorimotor areas and power in the cerebellum (right lobule VIII). Children with DCD showed increased rsFC mainly in the dorsal extrastriate visual brain system and the cerebellum. However, this increase was not associated with their coordinated motor/visual perceptual abilities. This enhanced functional brain connectivity could thus reflect a characteristic brain trait of children with DCD compared to their TD peers. Moreover, an interhemispheric compensatory process might be at play to perform visuomotor task within the normative range.

Impaired saccadic eye movements in multiple sclerosis are related to altered functional connectivity of the oculomotor brain network

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Impaired eye movements in multiple sclerosis (MS) and functional connectivity (FC)

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Eye movements related to altered FC of the oculomotor brain network.

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Lower (beta band) and higher (theta/delta band) FC related to abnormal eye movements.

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Regional changes were more informative than whole-network measures.

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Eye movement parameters also related to disability and cognitive dysfunction.

Background

Impaired eye movements in multiple sclerosis (MS) are common and could represent a non-invasive and accurate measure of (dys)functioning of interconnected areas within the complex brain network. The aim of this study was to test whether altered saccadic eye movements are related to changes in functional connectivity (FC) in patients with MS.

Methods

Cross-sectional eye movement (pro-saccades and anti-saccades) and magnetoencephalography (MEG) data from the Amsterdam MS cohort were included from 176 MS patients and 33 healthy controls. FC was calculated between all regions of the Brainnetome atlas in six conventional frequency bands. Cognitive function and disability were evaluated by previously validated measures. The relationships between saccadic parameters and both FC and clinical scores in MS patients were analysed using multivariate linear regression models.

Results

In MS pro- and anti-saccades were abnormal compared to healthy controls A relationship of saccadic eye movements was found with FC of the oculomotor network, which was stronger for regional than global FC. In general, abnormal eye movements were related to higher delta and theta FC but lower beta FC. Strongest associations were found for pro-saccadic latency and FC of the precuneus (beta band β = -0.23, p = .006), peak velocity and FC of the parietal eye field (theta band β = -0.25, p = .005) and gain and FC of the inferior frontal eye field (theta band β = -0.25, p = .003). Pro-saccadic latency was also strongly associated with disability scores and cognitive dysfunction.

Conclusions

Impaired saccadic eye movements were related to functional connectivity of the oculomotor network and clinical performance in MS. This study also showed that, in addition to global network connectivity, studying regional changes in MEG studies could yield stronger correlations.

Age of onset modulates resting-state brain network dynamics in Friedreich Ataxia

This magnetoencephalography (MEG) study addresses (i) how Friedreich ataxia (FRDA) affects the sub‐second dynamics of resting‐state brain networks, (ii) the main determinants of their dynamic alterations, and (iii) how these alterations are linked with FRDA‐related changes in resting‐state functional brain connectivity (rsFC) over long timescales. For that purpose, 5 min of resting‐state MEG activity were recorded in 16 FRDA patients (mean age: 27 years, range: 12–51 years; 10 females) and matched healthy subjects. Transient brain network dynamics was assessed using hidden Markov modeling (HMM). Post hoc median‐split, nonparametric permutations and Spearman rank correlations were used for statistics. In FRDA patients, a positive correlation was found between the age of symptoms onset (ASO) and the temporal dynamics of two HMM states involving the posterior default mode network (DMN) and the temporo‐parietal junctions (TPJ). FRDA patients with an ASO <11 years presented altered temporal dynamics of those two HMM states compared with FRDA patients with an ASO > 11 years or healthy subjects. The temporal dynamics of the DMN state also correlated with minute‐long DMN rsFC. This study demonstrates that ASO is the main determinant of alterations in the sub‐second dynamics of posterior associative neocortices in FRDA patients and substantiates a direct link between sub‐second network activity and functional brain integration over long timescales.

The utility of Magnetoencephalography in multiple sclerosis - A systematic review

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We conducted a Systematic Review of studies, looking at 30 studies from 13 centres.

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MS patients had reduced power in some induced responses (motor beta, visual gamma).

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Increased latency and reduced connectivity were seen for somatosensory evoked fields.

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There was an association between upper alpha connectivity and cognitive function.

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MEG shows promise, although work is too preliminary to recommend current clinical use.

Introduction

Magnetoencephalography (MEG), allows for a high degree temporal and spatial accuracy in recording cortical oscillatory activity and evoked fields. To date, no review has been undertaken to synthesise all MEG studies in Multiple Sclerosis (MS). We undertook a Systematic Review of the utility of MEG in MS.

Methods

We identified MEG studies carried out in MS using EMBASE, Medline, Cochrane, TRIP and Psychinfo databases. We included original research articles with a cohort of minimum of five multiple sclerosis patients and quantifying of at least one MEG parameter. We used a modified version of the JBI (mJBI) for case-control studies to assess for risk of bias.

Results

We identified 30 studies from 13 centres involving at least 433 MS patients and 347 controls. We found evidence that MEG shows perturbed activity (most commonly reduced power modulations), reduced connectivity and association with altered clinical function in Multiple Sclerosis. Specific replicated findings were decreased motor induced responses in the beta band, diminished increase of gamma power after visual stimulation, increased latency and reduced connectivity for somatosensory evoked fields. There was an association between upper alpha connectivity and cognitive measures in people with MS. Overall studies were of moderate quality (mean mJBI score 6.7).

Discussion

We find evidence for the utility of MEG in Multiple Sclerosis. Event-related designs are of particular value and show replicability between centres. At this stage, it is not clear whether these changes are specific to Multiple Sclerosis or are also observable in other diseases. Further studies should look to explore cognitive control in more depth using in-task designs and undertake longitudinal studies to determine whether these changes have prognostic value.

The application of principal component analysis to characterize gait and its association with falls in multiple sclerosis

People with multiple sclerosis (PwMS) demonstrate gait impairments that are related to falls. However, redundancy exists when reporting gait outcomes. This study aimed to develop an MS-specific model of gait and examine differences between fallers and non-fallers. 122 people with relapsing-remitting MS and 45 controls performed 3 timed up-and-go trials wearing inertial sensors. 21 gait parameters were entered into a principal component analysis (PCA). The PCA-derived gait domains were compared between MS fallers (MS-F) and MS non-fallers (MS-NF) and correlated to cognitive, clinical, and quality-of-life outcomes. Six distinct gait domains were identified: pace, rhythm, variability, asymmetry, anterior-posterior dynamic stability, and medial-lateral dynamic stability, explaining 79.15% of gait variance. PwMS exhibited a slower pace, larger variability, and increased medial-lateral trunk motion compared to controls (p < 0.05). The pace and asymmetry domains were significantly worse (i.e., slower and asymmetrical) in MS-F than MS-NF (p < 0.001 and p = 0.03, respectively). Fear of falling, cognitive performance, and functional mobility were associated with a slower gait (p < 0.05). This study identified a six-component, MS-specific gait model, demonstrating that PwMS, particularly fallers, exhibit deficits in pace and asymmetry. Findings may help reduce redundancy when reporting gait outcomes and inform interventions targeting specific gait domains.

Brain dysconnectivity relates to disability and cognitive impairment in multiple sclerosis

The pathophysiology of cognitive dysfunction in multiple sclerosis (MS) is still unclear. This magnetoencephalography (MEG) study investigates the impact of MS on brain resting-state functional connectivity (rsFC) and its relationship to disability and cognitive impairment. We investigated rsFC based on power envelope correlation within and between different frequency bands, in a large cohort of participants consisting of 99 MS patients and 47 healthy subjects. Correlations were investigated between rsFC and outcomes on disability, disease duration and 7 neuropsychological scores within each group, while stringently correcting for multiple comparisons and possible confounding factors. Specific dysconnections correlating with MS-induced physical disability and disease duration were found within the sensorimotor and language networks, respectively. Global network-level reductions in within- and cross-network rsFC were observed in the default-mode network. Healthy subjects and patients significantly differed in their scores on cognitive fatigue and verbal fluency. Healthy subjects and patients showed different correlation patterns between rsFC and cognitive fatigue or verbal fluency, both of which involved a shift in patients from the posterior default-mode network to the language network. Introducing electrophysiological rsFC in a regression model of verbal fluency and cognitive fatigue in MS patients significantly increased the explained variance compared to a regression limited to structural MRI markers (relative thalamic volume and lesion load). This MEG study demonstrates that MS induces distinct changes in the resting-state functional brain architecture that relate to disability, disease duration and specific cognitive functioning alterations. It highlights the potential value of electrophysiological intrinsic rsFC for monitoring the cognitive impairment in patients with MS.