Identifying and understanding cognitive profiles in multiple sclerosis: a role for visuospatial memory functioning

BACKGROUND

The heterogeneous nature of cognitive impairment in people with multiple sclerosis (PwMS) hampers understanding of the underlying mechanisms and developing patient-tailored interventions. We aim to identify and classify cognitive profiles in PwMS, comparing these to cognitive status (preserved versus impaired).

METHODS

We included 1213 PwMS (72% female, age 45.4 ± 10.7 years, 83% relapsing-remitting MS). Cognitive test scores were converted to Z-scores compared to healthy controls for the functions: attention, inhibition, information processing speed (IPS), verbal fluency and verbal/visuospatial memory. Concerning cognitive status, impaired cognition (CI) was defined as performing at Z ≤ - 1.5 SD on ≥ 2 functions. Cognitive profiles were constructed using latent profile analysis on all cognitive functions. Cognitive profiles or status was classified using gradient boosting decision trees, providing the importance of each feature (demographics, clinical, cognitive and psychological functioning) for the overall classification.

RESULTS

Six profiles were identified, showing variations in overall performance and specific deficits (attention, inhibition, IPS, verbal fluency, verbal memory and visuospatial memory). Across the profiles, IPS was the most impaired function (%CI most preserved profile, Profile 1 = 22.4%; %CI most impaired profile, Profile 6 = 76.6%). Cognitive impairment varied from 11.8% in Profile 1 to 95.3% in Profile 6. Of all cognitive functions, visuospatial memory was most important in classifying profiles and IPS the least (area under the curve (AUC) = 0.910). For cognitive status, IPS was the most important classifier (AUC = 0.997).

CONCLUSIONS

This study demonstrated that cognitive heterogeneity in MS reflects a continuum of cognitive severity, distinguishable by distinct cognitive profiles, primarily explained by variations in visuospatial memory functioning.

Isolated cognitive impairment in people with multiple sclerosis: frequency, MRI patterns and its development over time

OBJECTIVES

To study the frequency of isolated (i.e., single-domain) cognitive impairments, domain specific MRI correlates, and its longitudinal development in people with multiple sclerosis (PwMS).

METHODS

348 PwMS (mean age 48 ± 11 years, 67% female, 244RR/52SP/38PP) underwent neuropsychological testing (extended BRB-N) at baseline and at five-year follow-up. At baseline, structural MRI was acquired. Isolated cognitive impairment was defined as a Z-score of at least 1.5 SD below normative data in one domain only (processing speed, memory, executive functioning/working memory, and attention). Multi-domain cognitive impairment was defined as being affected in ≥ 2 domains, and cognitively preserved otherwise. For PwMS with isolated cognitive impairment, MRI correlates were explored using linear regression. Development of isolated cognitive impairment over time was evaluated based on reliable change index.

RESULTS

At baseline, 108 (31%) PwMS displayed isolated cognitive impairment, 148 (43%) PwMS displayed multi-domain cognitive impairment. Most PwMS with isolated cognitive impairment were impaired on executive functioning/working memory (EF/WM; N = 37), followed by processing speed (IPS; N = 25), memory (N = 23), and attention (N = 23). Isolated IPS impairment was explained by a model of cortical volume and fractional anisotropy (adj. R2 = 0.539, p < 0.001); memory by a model with cortical volume and hippocampal volume (adj. R2 = 0.493, p = 0.002); EF/WM and attention were not associated with any MRI measure. At follow-up, cognitive decline was present in 11/16 (69%) of PwMS with isolated IPS impairment at baseline. This percentage varied between 18 and 31% of PwMS with isolated cognitive impairment in domains other than IPS at baseline.

CONCLUSION

Isolated cognitive impairment is frequently present in PwMS and can serve as a proxy for further decline, particularly when it concerns processing speed. Cortical and deep grey matter atrophy seem to play a pivotal role in isolated cognitive impairment. Timely detection and patient-tailored intervention, predominantly for IPS, may help to postpone further cognitive decline.

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 ).

Cognitive phenotypes predict response to restorative cognitive rehabilitation in multiple sclerosis

BACKGROUND

Cognitive phenotyping may be useful for predicting rehabilitation response in multiple sclerosis.

OBJECTIVE

To evaluate the association between cognitive phenotype(s) and response to restorative cognitive rehabilitation (RRCR).

METHODS

In a post hoc retrospective analysis of the RRCR study including 51 multiple sclerosis patients, we evaluated both impairment within specific cognitive domains as well as overall global impairment severity to investigate their relationship to improvement following rehabilitation.

RESULTS

Greater improvement in executive function was predicted by impairment within this domain as well as by having fewer impaired cognitive domains overall. Similar results were observed for visuospatial memory.

CONCLUSIONS

Patients most likely to benefit from restorative cognitive rehabilitation may exhibit impairment within the domain of interest yet lower cognitive burden overall.

Relative aerobic load of walking in people with multiple sclerosis

OBJECTIVE

To examine the energy demand of walking relative to aerobic capacity in people with multiple sclerosis.

DESIGN

Cross-sectional cohort study.

PATIENTS

A total of 45 people with multiple sclerosis (32 females), median disease duration 15 years (interquartile range (IQR) 9; 20), median Expanded Disability Status Scale 4 (min-max range: 2.0; 6.0).

METHODS

Aerobic capacity, derived from a cardiopulmonary exercise test and gas exchange measurements, assessed during a 6-min overground walk test at comfortable speed, were analysed. The relative aerobic load of walking was determined as the energy demand of walking relative to oxygen uptake at peak and at the first ventilatory threshold. Healthy reference data were used for clinical inference.

RESULTS

People with multiple sclerosis walk at a mean relative aerobic load of 60.0% (standard deviation 12.8%) relative to peak aerobic capacity, and 89.1% (standard deviation 19.9%) relative to the first ventilatory threshold. Fourteen participants walked above the first ventilatory threshold (31%). Peak aerobic capacity was reduced in 45% of participants, and energy demands were increased in 52% of participants.

CONCLUSION

People with multiple sclerosis walk at a relative aerobic load close to their first ventilatory threshold. A high relative aerobic load can guide clinicians to improve aerobic capacity or reduce the energy demands of walking.

Longitudinal fibre-specific white matter damage predicts cognitive decline in multiple sclerosis

During the course of multiple sclerosis, many patients experience cognitive deficits which are not simply driven by lesion number or location. By considering the full complexity of white matter structure at macro- and microstructural levels, our understanding of cognitive impairment in multiple sclerosis may increase substantially. Accordingly, this study aimed to investigate specific patterns of white matter degeneration, the evolution over time, the manifestation across different stages of the disease and their role in cognitive impairment using a novel fixel-based approach. Neuropsychological test scores and MRI scans including 30-direction diffusion-weighted images were collected from 327 multiple sclerosis patients (mean age = 48.34 years, 221 female) and 95 healthy controls (mean age = 45.70 years, 55 female). Of those, 233 patients and 61 healthy controls had similar follow-up assessments 5 years after. Patients scoring 1.5 or 2 standard deviations below healthy controls on at least two out of seven cognitive domains (from the Brief Repeatable Battery of Neuropsychological Tests, BRB-N) were classified as mildly cognitively impaired or cognitively impaired, respectively, or otherwise cognitively preserved. Fixel-based analysis of diffusion data was used to calculate fibre-specific measures (fibre density, reflecting microstructural diffuse axonal damage; fibre cross-section, reflecting macrostructural tract atrophy) within atlas-based white matter tracts at each visit. At baseline, all fixel-based measures were significantly worse in multiple sclerosis compared with healthy controls (P < 0.05). For both fibre density and fibre cross-section, a similar pattern was observed, with secondary progressive multiple sclerosis patients having the most severe damage, followed by primary progressive and relapsing-remitting multiple sclerosis. Similarly, damage was least severe in cognitively preserved (n = 177), more severe in mildly cognitively impaired (n = 63) and worst in cognitively impaired (n = 87; P < 0.05). Microstructural damage was most pronounced in the cingulum, while macrostructural alterations were most pronounced in the corticospinal tract, cingulum and superior longitudinal fasciculus. Over time, white matter alterations worsened most severely in progressive multiple sclerosis (P < 0.05), with white matter atrophy progression mainly seen in the corticospinal tract and microstructural axonal damage worsening in cingulum and superior longitudinal fasciculus. Cognitive decline at follow-up could be predicted by baseline fixel-based measures (R2 = 0.45, P < 0.001). Fixel-based approaches are sensitive to white matter degeneration patterns in multiple sclerosis and can have strong predictive value for cognitive impairment. Longitudinal deterioration was most marked in progressive multiple sclerosis, indicating that degeneration in white matter remains important to characterize further in this phenotype.

Don't be late! Postponing cognitive decline and preventing early unemployment in people with multiple sclerosis: a study protocol

BACKGROUND

Up to 65% of people with multiple sclerosis (PwMS) develop cognitive deficits, which hampers their ability to work, participating in day-to-day life and ultimately reducing quality of life (QoL). Early cognitive symptoms are often less tangible to PwMS and their direct environment and are noticed only when symptoms and work functioning problems become more advanced, i.e., when (brain) damage is already advanced. Treatment of symptoms at a late stage can lead to cognitive impairment and unemployment, highlighting the need for preventative interventions in PwMS.

AIMS

This study aims to evaluate the (cost-) effectiveness of two innovative preventative interventions, aimed at postponing cognitive decline and work functioning problems, compared to enhanced usual care in improving health-related QoL (HRQoL).

METHODS

Randomised controlled trial including 270 PwMS with mild cognitive impairment, who have paid employment ≥ 12 h per week and are able to participate in physical exercise (Expanded Disability Status Scale < 6.0). Participants are randomised across three study arms: 1) 'strengthening the brain' - a lifestyle intervention combining personal fitness, mental coaching, dietary advice, and cognitive training; 2) 'strengthening the mind' - a work-focused intervention combining the capability approach and the participatory approach in one-on-one coaching by trained work coaches who have MS themselves; 3) Control group-receiving general information about cognitive impairment in MS and receiving care as usual. Intervention duration is four months, with short-term and long-term follow-up measurements at 10 and 16 months, respectively. The primary outcome measure of the Don't be late! intervention study will be HRQoL as measured with the 36-item Short Form. Secondary outcomes include cognition, work related outcomes, physical functioning, structural and functional brain changes, psychological functioning, and societal costs. Semi-structured interviews and focus groups with stakeholders will be organised to qualitatively reflect on the process and outcome of the interventions.

DISCUSSION

This study seeks to prevent (further) cognitive decline and job loss due to MS by introducing tailor-made interventions at an early stage of cognitive symptoms, thereby maintaining or improving HRQoL. Qualitative analyses will be performed to allow successful implementation into clinical practice.

TRIAL REGISTRATION

Retrospectively registered at ClinicalTrials.gov with reference number NCT06068582 on 10 October 2023.

Don't be late! Timely identification of cognitive impairment in people with multiple sclerosis: a study protocol

BACKGROUND

Cognitive impairment occurs in up to 65% of people with multiple sclerosis (PwMS), negatively affecting daily functioning and health-related quality of life. In general, neuropsychological testing is not part of standard MS-care due to insufficient time and trained personnel. Consequently, a baseline assessment of cognitive functioning is often lacking, hampering early identification of cognitive decline and change within a person over time. To assess cognitive functioning in PwMS in a time-efficient manner, a BICAMS-based self-explanatory digital screening tool called the Multiple Screener©, has recently been developed. The aim of the current study is to validate the Multiple Screener© in a representative sample of PwMS in the Netherlands. Additionally, we aim to investigate how cognitive functioning is related to psychological factors, and both work and societal participation.

METHODS

In this cross-sectional multicentre study, 750 PwMS (aged 18-67 years) are included. To obtain a representative sample, PwMS are recruited via 12 hospitals across the Netherlands. They undergo assessment with the Minimal Assessment of Cognitive Functioning in MS (MACFIMS; reference-standard) and the Multiple Screener©. Sensitivity, specificity, and predictive values for identifying (mild) cognitive impairment are determined in a subset of 300 participants. In a second step, the identified cut-off values are tested in an independent subset of at least 150 PwMS. Moreover, test-retest reliability for the Multiple Screener© is determined in 30 PwMS. Information on psychological and work-related factors is assessed with questionnaires.

DISCUSSION

Validating the Multiple Screener© in PwMS and investigating cognition and its determinants will further facilitate early identification and adequate monitoring of cognitive decline in PwMS.

Multimodal MRI study on the relation between WM integrity and connected GM atrophy and its effect on disability in early multiple sclerosis

BACKGROUND

Multiple sclerosis (MS) is characterized by pathology in white matter (WM) and atrophy of grey matter (GM), but it remains unclear how these processes are related, or how they influence clinical progression.

OBJECTIVE

To study the spatial and temporal relationship between GM atrophy and damage in connected WM in relapsing-remitting (RR) MS in relation to clinical progression.

METHODS

Healthy control (HC) and early RRMS subjects visited our center twice with a 1-year interval for MRI and clinical examinations, including the Expanded Disability Status Scale (EDSS) and Multiple Sclerosis Functional Composite (MSFC) scores. RRMS subjects were categorized as MSFC decliners or non-decliners based on ΔMSFC over time. Ten deep (D)GM and 62 cortical (C) GM structures were segmented and probabilistic tractography was performed to identify the connected WM. WM integrity was determined per tract with, amongst others, fractional anisotropy (FA), mean diffusivity (MD), neurite density index (NDI), and myelin water fraction (MWF). Linear mixed models (LMMs) were used to investigate GM and WM differences between HC and RRMS, and between MSFC decliners and non-decliners. LMM was also used to test associations between baseline WM z-scores and changes in connected GM z-scores, and between baseline GM z-scores and changes in connected WM z-scores, in HC/RRMS subjects and in MSFC decliners/non-decliners.

RESULTS

We included 13 HCs and 31 RRMS subjects with an average disease duration of 3.5 years and a median EDSS of 3.0. Fifteen RRMS subjects showed declining MSFC scores over time, and they showed higher atrophy rates and greater WM integrity loss compared to non-decliners. Lower baseline WM integrity was associated with increased CGM atrophy over time in RRMS, but not in HC subjects. This effect was only seen in MSFC decliners, especially when an extended WM z-score was used, which included FA, MD, NDI and MWF. Baseline GM measures were not significantly related to WM integrity changes over time in any of the groups.

DISCUSSION

Lower baseline WM integrity was related to more cortical atrophy in RRMS subjects that showed clinical progression over a 1-year follow-up, while baseline GM did not affect WM integrity changes over time. WM damage, therefore, seems to drive atrophy more than conversely.

Neurobiological basis and risk factors of persistent fatigue and concentration problems after COVID-19: study protocol for a prospective case-control study (VeCosCO)

INTRODUCTION

The risk factors for persistent fatigue and cognitive complaints after infection with SARS-CoV-2 and the underlying pathophysiology are largely unknown. Both clinical factors and cognitive-behavioural factors have been suggested to play a role in the perpetuation of complaints. A neurobiological aetiology, such as neuroinflammation, could be the underlying pathophysiological mechanism for persisting complaints.To unravel factors associated with persisting complaints, VeCosCO will compare individuals with and without persistent fatigue and cognitive complaints >3 months after infection with SARS-CoV-2. The study consists of two work packages. The first work package aims to (1) investigate the relation between persisting complaints and neuropsychological functioning; (2) determine risk factors and at-risk phenotypes for the development of persistent fatigue and cognitive complaints, including the presence of postexertional malaise and (3) describe consequences of persistent complaints on quality of life, healthcare consumption and physical functioning. The second work package aims to (1) determine the presence of neuroinflammation with [¹⁸F]DPA-714 whole-body positron emission tomography (PET) scans in patients with persisting complaints and (2) explore the relationship between (neuro)inflammation and brain structure and functioning measured with MRI.

METHODS AND ANALYSIS

This is a prospective case-control study in participants with and without persistent fatigue and cognitive complaints, >3 months after laboratory-confirmed SARS-CoV-2 infection. Participants will be mainly included from existing COVID-19 cohorts in the Netherlands covering the full spectrum of COVID-19 acute disease severity. Primary outcomes are neuropsychological functioning, postexertional malaise, neuroinflammation measured using [¹⁸F]DPA-714 PET, and brain functioning and structure using (f)MRI.

ETHICS AND DISSEMINATION

Work package 1 (NL79575.018.21) and 2 (NL77033.029.21) were approved by the medical ethical review board of the Amsterdam University Medical Centers (The Netherlands). Informed consent is required prior to participation in the study. Results of this study will be submitted for publication in peer-reviewed journals and shared with the key population.

A multimodal marker for cognitive functioning in multiple sclerosis: the role of NfL, GFAP and conventional MRI in predicting cognitive functioning in a prospective clinical cohort

BACKGROUND

Cognitive impairment in people with MS (PwMS) has primarily been investigated using conventional imaging markers or fluid biomarkers of neurodegeneration separately. However, the single use of these markers do only partially explain the large heterogeneity found in PwMS.

OBJECTIVE

To investigate the use of multimodal (bio)markers: i.e., serum and cerebrospinal fluid (CSF) levels of neurofilament light chain (NfL) and glial fibrillary acidic protein (GFAP) and conventional imaging markers in predicting cognitive functioning in PwMS.

METHODS

Eighty-two PwMS (56 females, disease duration = 14 ± 9 years) underwent neuropsychological and neurological examination, structural magnetic resonance imaging, blood sampling and lumbar puncture. PwMS were classified as cognitively impaired (CI) if scoring ≥ 1.5SD below normative scores on ≥ 20% of test scores. Otherwise, PwMS were defined as cognitively preserved (CP). Association between fluid and imaging (bio)markers were investigated, as well as binary logistics regression to predict cognitive status. Finally, a multimodal marker was calculated using statistically important predictors of cognitive status.

RESULTS

Only higher NfL levels (in serum and CSF) correlated with worse processing speed (r = - 0.286, p = 0.012 and r = - 0.364, p = 0.007, respectively). sNfL added unique variance in the prediction of cognitive status on top of grey matter volume (NGMV), p = 0.002). A multimodal marker of NGMV and sNfL yielded most promising results in predicting cognitive status (sensitivity = 85%, specificity = 58%).

CONCLUSION

Fluid and imaging (bio)markers reflect different aspects of neurodegeneration and cannot be used interchangeably as markers for cognitive functioning in PwMS. The use of a multimodal marker, i.e., the combination of grey matter volume and sNfL, seems most promising for detecting cognitive deficits in MS.

Neurophysiological MEG markers of cognitive impairment and performance validity in multiple sclerosis

BACKGROUND

Suboptimal performance during neuropsychological testing frequently occurs in multiple sclerosis (MS), leading to unreliable cognitive outcomes. Neurophysiological alterations correlate with MS-related cognitive impairment, but studies have not yet considered performance validity.

OBJECTIVES

To investigate neurophysiological markers of cognitive impairment in MS, while explicitly addressing performance validity.

METHODS

Magnetoencephalography recordings, neuropsychological assessments, and performance validity testing were obtained from 90 MS outpatients with cognitive complaints. Spectral and resting-state functional connectivity (rsFC) properties were compared between cognitively impaired (CI), cognitively preserved (CP), and suboptimally performing (SUB) patients using regression models and permutation testing.

RESULTS

CI had higher power in low-frequency bands and lower power in high bands compared to CP, indicating neuronal slowing. CI also showed lower beta power compared to SUB. Overall power spectra visually differed between CI and CP, and SUB showed overlap with both groups. CI had lower rsFC than CP and SUB patients. CP and SUB patients showed no differences.

CONCLUSION

Neuronal slowing and altered rsFC can be considered cognitive markers in MS. Patients who performed suboptimally showed resemblance with patients with and without cognitive impairments, and although their overall neurophysiological profile was more similar to patients without impairments, it suggests heterogeneity regarding their pathophysiology.

Brain-derived neurotrophic factor, neurofilament light and glial fibrillary acidic protein do not change in response to aerobic training in people with MS-related fatigue - a secondary analysis of a randomized controlled trial

BACKGROUND

Neuroinflammation and neurodegeneration are pathological hallmarks of multiple sclerosis (MS). Brain-derived neurotrophic factor (BDNF), neurofilament light (NfL), and glial fibrillary acidic protein (GFAP) are blood-based biomarkers for neurogenesis, axonal damage and astrocyte reactivity, respectively. We hypothesize that exercise has a neuroprotective effect on MS reflected by normalization of BDNF, NfL and GFAP levels.

OBJECTIVES

To investigate the neuroprotective effect of aerobic training (AT) compared to a control intervention on blood-based biomarkers (i.e. BDNF, NfL, GFAP) in people with MS (pwMS).

METHODS

In the TREFAMS-AT (Treating Fatigue in Multiple Sclerosis - Aerobic Training) study, 89 pwMS were randomly allocated to either a 16-week AT intervention or a control intervention (3 visits to a MS nurse). In this secondary analysis, blood-based biomarker concentrations were measured in 55 patients using Simoa technology. Changes in pre- and post-intervention concentrations were compared and between-group differences were assessed using analysis of covariance (ANCOVA). Confounding effects of age, sex, MS-related disability assessed using the Expanded Disability Status Scale (EDSS), MS duration, use of disease-modifying medication, and Body Mass Index were considered.

RESULTS

Blood samples were available for 30 AT and 25 control group participants (mean age 45.6 years, 71% female, median disease duration 8 years, median EDSS score 2.5). Within-group changes in both study groups were small and non-significant, with the exception of BDNF in the control group (median (interquartile range) -2.1 (-4.7; 0)). No between-group differences were found for any biomarker: BDNF (β = 0.11, 95%CI (-3.78 to 4.00)), NfL (β = -0.04, 95%CI (-0.26 to 0.18)), and GFAP (β = -0.01, 95%CI (-0.16 to 0.15)), adjusted for confounders.

CONCLUSION

Aerobic exercise therapy did not result in statistically significant changes in the tested neuro-specific blood-based biomarkers in people with MS.

TRIAL REGISTRATION

this study is registered under number ISRCTN69520623 (https://www.isrctn.com/ISRCTN695206).

Cognitive performance in multiple sclerosis: what is the role of the gamma-aminobutyric acid system?

Cognitive impairment occurs in 40-65% of persons with multiple sclerosis and may be related to alterations in glutamatergic and GABAergic neurotransmission. Therefore, the aim of this study was to determine how glutamatergic and GABAergic changes relate to cognitive functioning in multiple sclerosis in vivo. Sixty persons with multiple sclerosis (mean age 45.5 ± 9.6 years, 48 females, 51 relapsing-remitting multiple sclerosis) and 22 age-matched healthy controls (45.6 ± 22.0 years, 17 females) underwent neuropsychological testing and MRI. Persons with multiple sclerosis were classified as cognitively impaired when scoring at least 1.5 standard deviations below normative scores on ≥30% of tests. Glutamate and GABA concentrations were determined in the right hippocampus and bilateral thalamus using magnetic resonance spectroscopy. GABA-receptor density was assessed using quantitative [¹¹C]flumazenil positron emission tomography in a subset of participants. Positron emission tomography outcome measures were the influx rate constant (a measure predominantly reflecting perfusion) and volume of distribution, which is a measure of GABA-receptor density. Twenty persons with multiple sclerosis (33%) fulfilled the criteria for cognitive impairment. No differences were observed in glutamate or GABA concentrations between persons with multiple sclerosis and healthy controls, or between cognitively preserved, impaired and healthy control groups. Twenty-two persons with multiple sclerosis (12 cognitively preserved and 10 impaired) and 10 healthy controls successfully underwent [¹¹C]flumazenil positron emission tomography. Persons with multiple sclerosis showed a lower influx rate constant in the thalamus, indicating lower perfusion. For the volume of distribution, persons with multiple sclerosis showed higher values than controls in deep grey matter, reflecting increased GABA-receptor density. When comparing cognitively impaired and preserved patients to controls, the preserved group showed a significantly higher volume of distribution in cortical and deep grey matter and hippocampus. Positive correlations were observed between both positron emission tomography measures and information processing speed in the multiple sclerosis group only. Whereas concentrations of glutamate and GABA did not differ between multiple sclerosis and control nor between cognitively impaired, preserved and control groups, increased GABA-receptor density was observed in preserved persons with multiple sclerosis that was not seen in cognitively impaired patients. In addition, GABA-receptor density correlated to cognition, in particular with information processing speed. This could indicate that GABA-receptor density is upregulated in the cognitively preserved phase of multiple sclerosis as a means to regulate neurotransmission and potentially preserve cognitive functioning.

Inhibitory synaptic loss drives network changes in multiple sclerosis: An ex vivo to in silico translational study

Background:

Synaptic and neuronal loss contribute to network dysfunction and disability in multiple sclerosis (MS). However, it is unknown whether excitatory or inhibitory synapses and neurons are more vulnerable and how their losses impact network functioning.

Objective:

To quantify excitatory and inhibitory synapses and neurons and to investigate how synaptic loss affects network functioning through computational modeling.

Methods:

Using immunofluorescent staining and confocal microscopy, densities of glutamatergic and GABAergic synapses and neurons were compared between post-mortem MS and non-neurological control cases. Then, a corticothalamic biophysical model was employed to study how MS-induced excitatory and inhibitory synaptic loss affect network functioning.

Results:

In layer VI of normal-appearing MS cortex, excitatory and inhibitory synaptic densities were significantly lower than controls (reductions up to 14.9%), but demyelinated cortex showed larger losses of inhibitory synapses (29%). In our computational model, reducing inhibitory synapses impacted the network most, leading to a disinhibitory increase in neuronal activity and connectivity.

Conclusion:

In MS, excitatory and inhibitory synaptic losses were observed, predominantly for inhibitory synapses in demyelinated cortex. Inhibitory synaptic loss affected network functioning most, leading to increased neuronal activity and connectivity. As network disinhibition relates to cognitive impairment, inhibitory synaptic loss seems particularly relevant in MS.

A randomized trial predicting response to cognitive rehabilitation in multiple sclerosis: Is there a window of opportunity?

Background:

Cognitive training elicits mild-to-moderate improvements in cognitive functioning in people with multiple sclerosis (PwMS), although response heterogeneity limits overall effectiveness.

Objective:

To identify patient characteristics associated with response and non-response to cognitive training.

Methods:

Eighty-two PwMS were randomized into a 7-week attention training (n = 58, age = 48.4 ± 10.2 years) or a waiting-list control group (n = 24, age = 48.5 ± 9.4 years). Structural and functional magnetic resonance imaging (MRI) was obtained at baseline and post-intervention. Twenty-one healthy controls (HCs, age = 50.27 ± 10.15 years) were included at baseline. Responders were defined with a reliable change index of 1.64 on at least 2/6 cognitive domains. General linear models and logistic regression were applied.

Results:

Responders (n = 36) and non-responders (n = 22) did not differ on demographics, clinical variables and baseline cognition and structural MRI. However, non-responders exhibited a higher baseline functional connectivity (FC) between the default-mode network (DMN) and the ventral attention network (VAN), compared with responders (p = 0.018) and HCs (p = 0.001). Conversely, responders exhibited no significant baseline differences in FC compared with HCs. Response to cognitive training was predicted by lower DMN-VAN FC (p = 0.004) and DMN-frontoparietal FC (p = 0.029) (Nagelkerke R² = 0.25).

Conclusion:

An intact pre-intervention FC is associated with cognitive training responsivity in pwMS, suggesting a window of opportunity for successful cognitive interventions.

Assessment of data consistency through cascades of independently recurrent inference machines for fast and robust accelerated MRI reconstruction

Objective. Machine Learning methods can learn how to reconstruct magnetic resonance images (MRI) and thereby accelerate acquisition, which is of paramount importance to the clinical workflow. Physics-informed networks incorporate the forward model of accelerated MRI reconstruction in the learning process. With increasing network complexity, robustness is not ensured when reconstructing data unseen during training. We aim to embed data consistency (DC) in deep networks while balancing the degree of network complexity. While doing so, we will assess whether either explicit or implicit enforcement of DC in varying network architectures is preferred to optimize performance. Approach. We propose a scheme called Cascades of Independently Recurrent Inference Machines (CIRIM) to assess DC through unrolled optimization. Herein we assess DC both implicitly by gradient descent and explicitly by a designed term. Extensive comparison of the CIRIM to compressed sensing as well as other Machine Learning methods is performed: the End-to-End Variational Network (E2EVN), CascadeNet, KIKINet, LPDNet, RIM, IRIM, and UNet. Models were trained and evaluated on T1-weighted and FLAIR contrast brain data, and T2-weighted knee data. Both 1D and 2D undersampling patterns were evaluated. Robustness was tested by reconstructing 7.5× prospectively undersampled 3D FLAIR MRI data of multiple sclerosis (MS) patients with white matter lesions. Main results. The CIRIM performed best when implicitly enforcing DC, while the E2EVN required an explicit DC formulation. Through its cascades, the CIRIM was able to score higher on structural similarity and PSNR compared to other methods, in particular under heterogeneous imaging conditions. In reconstructing MS patient data, prospectively acquired with a sampling pattern unseen during model training, the CIRIM maintained lesion contrast while efficiently denoising the images. Significance. The CIRIM showed highly promising generalization capabilities maintaining a very fair trade-off between reconstructed image quality and fast reconstruction times, which is crucial in the clinical workflow.

miR-150-5p and let-7b-5p in Blood Myeloid Extracellular Vesicles Track Cognitive Symptoms in Patients with Multiple Sclerosis

Cognitive deficits strongly affect the quality of life of patients with multiple sclerosis (MS). However, no cognitive MS biomarkers are currently available. Extracellular vesicles (EVs) contain markers of parental cells and are able to pass from the brain into blood, representing a source of disease biomarkers. The aim of this study was to investigate whether small non-coding microRNAs (miRNAs) targeting synaptic genes and packaged in plasma EVs may reflect cognitive deficits in MS patients. Total EVs were precipitated by Exoquick from the plasma of twenty-six cognitively preserved (CP) and twenty-three cognitively impaired (CI) MS patients belonging to two independent cohorts. Myeloid EVs were extracted by affinity capture from total EVs using Isolectin B4 (IB4). Fourteen miRNAs targeting synaptic genes were selected and measured by RT-PCR in both total and myeloid EVs. Myeloid EVs from CI patients expressed higher levels of miR-150-5p and lower levels of let-7b-5p compared to CP patients. Stratification for progressive MS (PMS) and relapsing-remitting MS (RRMS) and correlation with clinical parameters suggested that these alterations might be attributable to cognitive deficits rather than disease progression. This study identifies miR-150-5p and let-7b-5p packaged in blood myeloid EVs as possible biomarkers for cognitive deficits in MS.

A more unstable resting-state functional network in cognitively declining multiple sclerosis

Cognitive impairment is common in people with multiple sclerosis and strongly affects their daily functioning. Reports have linked disturbed cognitive functioning in multiple sclerosis to changes in the organization of the functional network. In a healthy brain, communication between brain regions and which network a region belongs to is continuously and dynamically adapted to enable adequate cognitive function. However, this dynamic network adaptation has not been investigated in multiple sclerosis, and longitudinal network data remain particularly rare. Therefore, the aim of this study was to longitudinally identify patterns of dynamic network reconfigurations that are related to the worsening of cognitive decline in multiple sclerosis. Resting-state functional MRI and cognitive scores (expanded Brief Repeatable Battery of Neuropsychological tests) were acquired in 230 patients with multiple sclerosis and 59 matched healthy controls, at baseline (mean disease duration: 15 years) and at 5-year follow-up. A sliding-window approach was used for functional MRI analyses, where brain regions were dynamically assigned to one of seven literature-based subnetworks. Dynamic reconfigurations of subnetworks were characterized using measures of promiscuity (number of subnetworks switched to), flexibility (number of switches), cohesion (mutual switches) and disjointedness (independent switches). Cross-sectional differences between cognitive groups and longitudinal changes were assessed, as well as relations with structural damage and performance on specific cognitive domains. At baseline, 23% of patients were cognitively impaired (≥2/7 domains Z < −2) and 18% were mildly impaired (≥2/7 domains Z < −1.5). Longitudinally, 28% of patients declined over time (0.25 yearly change on ≥2/7 domains based on reliable change index). Cognitively impaired patients displayed more dynamic network reconfigurations across the whole brain compared with cognitively preserved patients and controls, i.e. showing higher promiscuity (P = 0.047), flexibility (P = 0.008) and cohesion (P = 0.008). Over time, cognitively declining patients showed a further increase in cohesion (P = 0.004), which was not seen in stable patients (P = 0.544). More cohesion was related to more severe structural damage (average r = 0.166, P = 0.015) and worse verbal memory (r = −0.156, P = 0.022), information processing speed (r = −0.202, P = 0.003) and working memory (r = −0.163, P = 0.017). Cognitively impaired multiple sclerosis patients exhibited a more unstable network reconfiguration compared to preserved patients, i.e. brain regions switched between subnetworks more often, which was related to structural damage. This shift to more unstable network reconfigurations was also demonstrated longitudinally in patients that showed cognitive decline only. These results indicate the potential relevance of a progressive destabilization of network topology for understanding cognitive decline in multiple sclerosis.

Feasibility of cognitive rehabilitation in patients with advanced multiple sclerosis: A pilot study

Background

The feasibility of cognitive rehabilitation is rarely investigated in patients with advanced multiple sclerosis.

Methods

Eighteen patients with advanced multiple sclerosis (median EDSS = 7.5) were randomized into restorative or compensatory cognitive rehabilitation. Feasibility was determined by adherence rate, completion rate, patient satisfaction, self-reported fatigue, training difficulty, and training duration.

Results

Adherence rates and completion rates were over 70%, and patients were highly satisfied in both groups. Energy levels decreased minimally during the sessions (pre = 6.9 vs post = 6.4). Training difficulty (4.6) and duration (5.7) were close to ideal (scale 1-10, 5 = ideal).

Conclusions

Cognitive rehabilitation, with minor adjustments, appears feasible in patients with advanced multiple sclerosis.

Functional network dynamics and decreased conscientiousness in multiple sclerosis

BACKGROUND

Conscientiousness is a personality trait that declines in people with multiple sclerosis (PwMS) and its decline predicts worse clinical outcomes. This study aims to investigate the neural underpinnings of lower Conscientiousness in PwMS by examining MRI anomalies in functional network dynamics.

METHODS

70 PwMS and 50 healthy controls underwent personality assessment and resting-state MRI. Associations with dynamic functional network properties (i.e., eigenvector centrality) were evaluated, using a dynamic sliding-window approach.

RESULTS

In PwMS, lower Conscientiousness was associated with increased variability of centrality in the left insula (t_max = 4.21) and right inferior parietal lobule (t_max = 3.79); a relationship also observed in regressions accounting for handedness, disease duration, disability, and tract disruption in relevant structural networks (ΔR² = 0.071, p = 0.003; ΔR² = 0.094, p = 0.004). Centrality dynamics of the observed regions were not associated with Neuroticism (R² < 0.001, p = 0.956; R² < 0.001, p = 0.945). As well, higher Conscientiousness was associated with greater variability in connectivity for the left insula with the default-mode network (F = 3.92, p = 0.023) and limbic network (F = 5.66, p = 0.005).

CONCLUSION

Lower Conscientiousness in PwMS was associated with increased variability in network centrality, most prominently for the left insula and right inferior parietal cortex. This effect, specific to Conscientiousness and significant after accounting for disability and structural network damage, could indicate that overall stable network centrality is lost in patients with low Conscientiousness, especially for the insula and right parietal cortex. The positive relationship between Conscientiousness and variability of connectivity between left insula and default-mode network potentially affirms that dynamics between the salience and default-mode networks is related to the regulation of behavior.

Longitudinal Network Changes and Conversion to Cognitive Impairment in Multiple Sclerosis

OBJECTIVE

To characterize functional network changes related to conversion to cognitive impairment in a large sample of patients with multiple sclerosis (MS) over a period of 5 years.

METHODS

Two hundred twenty-seven patients with MS and 59 healthy controls of the Amsterdam MS cohort underwent neuropsychological testing and resting-state fMRI at 2 time points (time interval 4.9 ± 0.9 years). At both baseline and follow-up, patients were categorized as cognitively preserved (CP; n = 123), mildly impaired (MCI; z < -1.5 on ≥2 cognitive tests, n = 32), or impaired (CI; z < -2 on ≥2 tests, n = 72), and longitudinal conversion between groups was determined. Network function was quantified with eigenvector centrality, a measure of regional network importance, which was computed for individual resting-state networks at both time points.

RESULTS

Over time, 18.9% of patients converted to a worse phenotype; 22 of 123 patients who were CP (17.9%) converted from CP to MCI, 10 of 123 from CP to CI (8.1%), and 12 of 32 patients with MCI converted to CI (37.5%). At baseline, default-mode network (DMN) centrality was higher in CI individuals compared to controls (p = 0.05). Longitudinally, ventral attention network (VAN) importance increased in CP, driven by stable CP and CP-to-MCI converters (p < 0.05).

CONCLUSIONS

Of all patients, 19% worsened in their cognitive status over 5 years. Conversion from intact cognition to impairment is related to an initial disturbed functioning of the VAN, then shifting toward DMN dysfunction in CI. Because the VAN normally relays information to the DMN, these results could indicate that in MS normal processes crucial for maintaining overall network stability are progressively disrupted as patients clinically progress.

Cognitive functioning in everyday life: The development of a questionnaire on instrumental activities of daily living in multiple sclerosis

Neuropsychological test scores in people with MS (PwMS) do not fully reflect cognitive functioning in daily life. Therefore, we developed a questionnaire based on instrumental activities of daily living (IADL), using the Amsterdam IADL-Q^© for Alzheimer’s disease as starting point. Forty-eight items were evaluated on relevance and clarity by (inter)national experts (n = 30), PwMS (n = 61) and proxies (n = 30). Consequently, four items were omitted, two items were merged and seven items were added. Fifty items were included in the IADL questionnaire specific to cognitive functioning in MS (the MS-IADL-Q). Future studies are warranted to assess the psychometric properties of the MS-IADL-Q.

Artificial double inversion recovery images for (juxta)cortical lesion visualization in multiple sclerosis

Background:

Cortical lesions are highly inconspicuous on magnetic resonance imaging (MRI). Double inversion recovery (DIR) has a higher sensitivity than conventional clinical sequences (i.e. T1, T2, FLAIR) but is difficult to acquire, leading to overseen cortical lesions in clinical care and clinical trials.

Objective:

To evaluate the usability of artificially generated DIR (aDIR) images for cortical lesion detection compared to conventionally acquired DIR (cDIR).

Methods:

The dataset consisted of 3D-T1 and 2D-proton density (PD) T2 images of 73 patients (49RR, 20SP, 4PP) at 1.5 T. Using a 4:1 train:test-ratio, a fully convolutional neural network was trained to predict 3D-aDIR from 3D-T1 and 2D-PD/T2 images. Randomized blind scoring of the test set was used to determine detection reliability, precision and recall.

Results:

A total of 626 vs 696 cortical lesions were detected on 15 aDIR vs cDIR images (intraclass correlation coefficient (ICC) = 0.92). Compared to cDIR, precision and recall were 0.84 ± 0.06 and 0.76 ± 0.09, respectively. The frontal and temporal lobes showed the largest differences in discernibility.

Conclusion:

Cortical lesions can be detected with good reliability on artificial DIR. The technique has potential to broaden the availability of DIR in clinical care and provides the opportunity of ex post facto implementation of cortical lesions imaging in existing clinical trial data.

Functional connectivity in multiple sclerosis modelled as connectome stability: A 5-year follow-up study

Background:

Brain functional connectivity (FC) in multiple sclerosis (MS) is abnormal compared to healthy controls (HCs). More longitudinal studies in MS are needed to evaluate whether FC stability is clinically relevant.

Objective:

To compare functional magnetic resonance imaging (fMRI)-based FC between MS and HC, and to determine the relationship between longitudinal FC changes and structural brain damage, cognitive performance and physical disability.

Methods:

T1-weighted MPRAGE and resting-state fMRI (1.5T) were acquired from 70 relapsing-remitting MS patients and 94 matched HC at baseline (mean months since diagnosis 14.0 ± 11) and from 60 MS patients after 5 years. Independent component analysis and network modelling were used to measure longitudinal FC stability and cross-sectional comparisons with HC. Linear mixed models, adjusted for age and sex, were used to calculate correlations.

Results:

At baseline, patients with MS showed FC abnormalities both within networks and in single connections compared to HC. Longitudinal analyses revealed functional stability and no significant relationships with clinical disability, cognitive performance, lesion or brain volume.

Conclusion:

FC abnormalities occur already at the first decade of MS, yet we found no relevant clinical correlations for these network deviations. Future large-scale longitudinal fMRI studies across a range of MS subtypes and outcomes are required.

Performance validity in outpatients with multiple sclerosis and cognitive complaints

BACKGROUND

Suboptimal performance during neuropsychological assessment renders cognitive test results invalid. However, suboptimal performance has rarely been investigated in multiple sclerosis (MS).

OBJECTIVES

To investigate potential underlying mechanisms of suboptimal performance in MS.

METHODS

Performance validity testing, neuropsychological assessments, neuroimaging, and questionnaires were analyzed in 99 MS outpatients with cognitive complaints. Based on performance validity testing patients were classified as valid or invalid performers, and based on neuropsychological test results as cognitively impaired or preserved. Group comparisons and correlational analyses were performed on demographics, patient-reported, and disease-related outcomes.

RESULTS

Twenty percent displayed invalid performance. Invalid and valid performers did not differ regarding demographic, patient-reported, and disease-related outcomes. Disease severity of invalid and valid performers with cognitive impairment was comparable, but worse than cognitively preserved valid performers. Lower performance validity scores related to lower cognitive functioning, lower education, being male, and higher disability levels (p < 0.05).

CONCLUSION

Suboptimal performance frequently occurs in patients with MS and cognitive complaints. In both clinical practice and in cognitive research, suboptimal performance should be considered in the interpretation of cognitive outcomes. Identification of factors that differentiate between suboptimal and optimal performers with cognitive impairment needs further exploration.

Reliability, construct and concurrent validity of a smartphone-based cognition test in multiple sclerosis

Background:

Early detection and monitoring of cognitive dysfunction in multiple sclerosis (MS) may be enabled with smartphone-adapted tests that allow frequent measurements in the everyday environment.

Objectives:

The aim of this study was to determine the reliability, construct and concurrent validity of a smartphone-adapted Symbol Digit Modalities Test (sSDMT).

Methods:

During a 28-day follow-up, 102 patients with MS and 24 healthy controls (HC) used the MS sherpa^® app to perform the sSDMT every 3 days on their own smartphone. Patients performed the Brief International Cognitive Assessment for MS at baseline. Test–retest reliability (intraclass correlation coefficients, ICC), construct validity (group analyses between cognitively impaired (CI), cognitively preserved (CP) and HC for differences) and concurrent validity (correlation coefficients) were assessed.

Results:

Patients with MS and HC completed an average of 23.2 (SD = 10.0) and 18.3 (SD = 10.2) sSDMT, respectively. sSDMT demonstrated high test–retest reliability (ICCs > 0.8) with a smallest detectable change of 7 points. sSDMT scores were different between CI patients, CP patients and HC (all ps < 0.05). sSDMT correlated modestly with the clinical SDMT (highest r = 0.690), verbal (highest r= 0.516) and visuospatial memory (highest r= 0.599).

Conclusion:

Self-administered smartphone-adapted SDMT scores were reliable and different between patients who were CI, CP and HC and demonstrated concurrent validity in assessing information processing speed.

Mind the gap: from neurons to networks to outcomes in multiple sclerosis

MRI studies have provided valuable insights into the structure and function of neural networks, particularly in health and in classical neurodegenerative conditions such as Alzheimer disease. However, such work is also highly relevant in other diseases of the CNS, including multiple sclerosis (MS). In this Review, we consider the effects of MS pathology on brain networks, as assessed using MRI, and how these changes to brain networks translate into clinical impairments. We also discuss how this knowledge can inform the targeting of MS treatments and the potential future directions for research in this area. Studying MS is challenging as its pathology involves neurodegenerative and focal inflammatory elements, both of which could disrupt neural networks. The disruption of white matter tracts in MS is reflected in changes in network efficiency, an increasingly random grey matter network topology, relative cortical disconnection, and both increases and decreases in connectivity centred around hubs such as the thalamus and the default mode network. The results of initial longitudinal studies suggest that these changes evolve rather than simply increase over time and are linked with clinical features. Studies have also identified a potential role for treatments that functionally modify neural networks as opposed to altering their structure.

Manual and automated tissue segmentation confirm the impact of thalamus atrophy on cognition in multiple sclerosis: A multicenter study

BACKGROUND AND RATIONALE

Thalamus atrophy has been linked to cognitive decline in multiple sclerosis (MS) using various segmentation methods. We investigated the consistency of the association between thalamus volume and cognition in MS for two common automated segmentation approaches, as well as fully manual outlining.

METHODS

Standardized neuropsychological assessment and 3-Tesla 3D-T1-weighted brain MRI were collected (multi-center) from 57 MS patients and 17 healthy controls. Thalamus segmentations were generated manually and using five automated methods. Agreement between the algorithms and manual outlines was assessed with Bland-Altman plots; linear regression assessed the presence of proportional bias. The effect of segmentation method on the separation of cognitively impaired (CI) and preserved (CP) patients was investigated through Generalized Estimating Equations; associations with cognitive measures were investigated using linear mixed models, for each method and vendor.

RESULTS

In smaller thalami, automated methods systematically overestimated volumes compared to manual segmentations [ρ=(-0.42)-(-0.76); p-values < 0.001). All methods significantly distinguished CI from CP MS patients, except manual outlines of the left thalamus (p = 0.23). Poorer global neuropsychological test performance was significantly associated with smaller thalamus volumes bilaterally using all methods. Vendor significantly affected the findings.

CONCLUSION

Automated and manual thalamus segmentation consistently demonstrated an association between thalamus atrophy and cognitive impairment in MS. However, a proportional bias in smaller thalami and choice of MRI acquisition system might impact the effect size of these findings.

Neuroprotective effects of exercise in people with progressive multiple sclerosis (Exercise PRO-MS): study protocol of a phase II trial

Background

Neurodegeneration, rather than inflammation, plays a key role in the progressive phase of multiple sclerosis (MS). Current disease modifying treatment options for people with progressive MS (PMS) do not specifically target neurodegeneration. Preliminary evidence suggests that exercise therapy might have neuroprotective effects. However, neuroprotective effect studies of exercise interventions in PMS are scarce and the possible mode of action underlying neuroprotective effects of exercise are unknown and need to be elucidated. The main aim of this phase II trial is to assess whether progressive resistance training (PRT) and high intensity interval training (HIIT), can slow down neurodegeneration in people with PMS.

Methods

In a single-blinded phase II clinical trial with an extended baseline period, 60 people with PMS will be randomly assigned to PRT or HIIT. The participants should have had a relapse onset of MS with confirmed disease progression, however still ambulatory. The duration of the study is 48 weeks, consisting of 16 weeks baseline period (no intervention), 16 weeks intervention and 16 weeks follow-up. Patient-tailored training will be performed 3 times per week for one hour in groups, led by an experienced physiotherapist. The primary outcome measure is neurodegeneration, measured as whole brain atrophy on magnetic resonance imaging (MRI). Secondary outcome parameters will include other biomarkers associated with neurodegeneration (i.e. regional brain atrophy, lesion load, white matter integrity, resting state functional connectivity, blood biomarkers (brain derived neurotrophic factor (BDNF) and serum neurofilament light (sNFL)), patient functioning (physical and cognitive) and cardiovascular risk factors.

Discussion

Besides the primary outcome measures, this study will examine a large variety of biomarkers associated with neurodegeneration after an exercise intervention. Combining outcome parameters may help to elucidate the mode of action underlying neuroprotective effects of exercise.

Trial registration

This trial is prospectively registered at the Dutch Trial Registry (number NL8265, date 06-01-2020).

Introducing Multiple Screener: An unsupervised digital screening tool for cognitive deficits in MS

BACKGROUND

Cognitive deficits affect up to 70% of all patients with Multiple Sclerosis (MS) and have a significant impact on quality of life. Cognitive assessments need to be performed by a neuropsychologist and are often time-consuming, hampering timely identification and adequate monitoring of cognitive decline in MS.

OBJECTIVE

To develop a time-efficient, unsupervised, digital tool to screen for cognitive deficits in MS.

METHODS

A digital (adjusted) version of the Brief International Cognitive Assessment for MS, including the Symbol Digit Modalities Test (SDMT, information processing speed), the California Verbal Learning Test (CVLT-II, verbal memory) and the Spatial Recall Test (SPART, visuospatial memory) was developed: Multiple Screener (intellectual property of Sanofi Genzyme). Firstly, the clarity and feasibility of the tool was confirmed by 16 patients with MS (mean age 50.9 years (SD 9.4, range 37-68). Next, in 60 healthy controls (HCs, mean age 44.5 years (SD 14.0, range 18-67), intraclass correlation coefficients (ICC) were calculated to describe how strongly the digital version resembled the paper and pencil-based assessment. Finally, 236 HCs (mean age 42.8 years (SD 12.8, range 18-69) were included to obtain norm scores for each test.

RESULTS

ICCs between digital and paper and pencil-based assessment were excellent to good (SDMT (ICC 0.79, confidence interval (CI) 0.67-0.87); CVLT-II (ICC 0.77, CI 0.64-0.85); SPART (ICC 0.61, CI 0.42-0.75)). For each test, a regression-based correction for the effect of age was applied on the raw scores before converting them to norm Z-scores. Additionally, the SDMT scores needed correction for education and the CVLT-II for education and sex (subgroups were created).

CONCLUSIONS

Performance on an adjusted, digital version of the BICAMS correlates highly with the standard paper-and-pencil based test scores in HCs. Multiple Screener is an unsupervised, digital tool, with available norm scores, ultimately allowing for easy monitoring of cognitive decline in patients with MS.

Cortical atrophy accelerates as cognitive decline worsens in multiple sclerosis

Objective

To determine which pathologic process could be responsible for the acceleration of cognitive decline during the course of multiple sclerosis (MS), using longitudinal structural MRI, which was related to cognitive decline in relapsing-remitting MS (RRMS) and progressive MS (PMS).

Methods

A prospective cohort of 230 patients with MS (179 RRMS and 51 PMS) and 59 healthy controls was evaluated twice with 5-year (mean 4.9, SD 0.94) interval during which 22 patients with RRMS converted to PMS. Annual rates of cortical and deep gray matter atrophy as well as lesion volume increase were computed on longitudinal (3T) MRI data and correlated to the annual rate of cognitive decline as measured using an extensive cognitive evaluation at both time points.

Results

The deep gray matter atrophy rate did not differ between PMS and RRMS (−0.82%/year vs −0.71%/year, p = 0.11), while faster cortical atrophy was observed in PMS (−0.87%/year vs −0.48%/year, p < 0.01). Similarly, faster cognitive decline was observed in PMS compared to RRMS (p < 0.01). Annual cognitive decline was related to the rate of annual lesion volume increase in stable RRMS (r = −0.17, p = 0.03) to the rate of annual deep gray matter atrophy in converting RRMS (r = 0.50, p = 0.02) and annual cortical atrophy in PMS (r = 0.35, p = 0.01).

Conclusions

These results indicate that cortical atrophy and cognitive decline accelerate together during the course of MS. Substrates of cognitive decline shifted from worsening lesional pathology in stable RRMS to deep gray matter atrophy in converting RRMS and to accelerated cortical atrophy in PMS only.

A pilot study of the effects of running training on visuospatial memory in MS: A stronger functional embedding of the hippocampus in the default-mode network?

BACKGROUND/OBJECTIVE

Endurance exercise can improve memory function in persons with multiple sclerosis (pwMS), but the effects on hippocampal functioning are currently unknown. We investigated the effects of a running intervention on memory and hippocampal functional connectivity in pwMS.

METHODS/RESULTS

Memory and resting-state functional magnetic resonance imaging (fMRI) data were collected in a running intervention (n = 15) and waitlist group (n = 14). Visuospatial memory improvement was correlated to increased connectivity between the hippocampus and the default-mode network (DMN) in the intervention group only.

CONCLUSION

As a result of endurance exercise, improvements in visuospatial memory may be mediated by a stronger functional embedding of the hippocampus in the DMN.

Predicting cognitive decline in multiple sclerosis: a 5-year follow-up study

Cognitive decline is common in multiple sclerosis and strongly affects overall quality of life. Despite the identification of cross-sectional MRI correlates of cognitive impairment, predictors of future cognitive decline remain unclear. The objective of this study was to identify which MRI measures of structural damage, demographic and/or clinical measures at baseline best predict cognitive decline, during a 5-year follow-up period. A total of 234 patients with clinically definite multiple sclerosis and 60 healthy control subjects were examined twice, with a 5-year interval (mean = 4.9 years, standard deviation = 0.9). An extensive neuropsychological evaluation was performed at both time points and the reliable change index was computed to evaluate cognitive decline. Both whole-brain and regional MRI (3 T) measures were assessed at baseline, including white matter lesion volume, diffusion-based white matter integrity, cortical and deep grey matter volume. Logistic regression analyses were performed to determine which baseline measures best predicted cognitive decline in the entire sample as well as in early relapsing-remitting (symptom duration <10 years), late relapsing-remitting (symptom duration ≥10 years) and progressive phenotypes. At baseline, patients with multiple sclerosis had a mean disease duration of 14.8 (standard deviation = 8.4) years and 96/234 patients (41%) were classified as cognitively impaired. A total of 66/234 patients (28%) demonstrated cognitive decline during follow-up, with higher frequencies in progressive compared to relapsing-remitting patients: 18/33 secondary progressive patients (55%), 10/19 primary progressive patients (53%) and 38/182 relapsing-remitting patients (21%). A prediction model that included only whole-brain MRI measures (Nagelkerke R2 = 0.22, P < 0.001) showed cortical grey matter volume as the only significant MRI predictor of cognitive decline, while a prediction model that assessed regional MRI measures (Nagelkerke R2 = 0.35, P < 0.001) indicated integrity loss of the anterior thalamic radiation, lesions in the superior longitudinal fasciculus and temporal atrophy as significant MRI predictors for cognitive decline. Disease stage specific regressions showed that cognitive decline in early relapsing-remitting multiple sclerosis was predicted by white matter integrity damage, while cognitive decline in late relapsing-remitting and progressive multiple sclerosis was predicted by cortical atrophy. These results indicate that patients with more severe structural damage at baseline, and especially cortical atrophy, are more prone to suffer from cognitive decline. New studies now need to further elucidate the underlying mechanisms leading to cortical atrophy, evaluate the value of including cortical atrophy as a possible outcome marker in clinical trials as well as study its potential use in individual patient management.

[The invisible burden of cognitive problems in patients with multiple sclerosis]

Approximately 34-65% of patients with multiple sclerosis (MS) are confronted with cognitive problems sooner or later. These include problems with the speed of information processing, memory, attention and executive functioning. Cognitive problems in patients with MS are currently often not examined on a routine basis and therefore remain unrecognised, or are not recognised in time. This may have a negative impact on their work and lead to social problems. In this article, we talk about the importance of early recognition of cognitive problems in patients with MS. Routine questioning about cognitive problems and the use of a short screening test are first steps in the right direction.

Reduced dynamics of functional connectivity and cognitive impairment in multiple sclerosis

BACKGROUND

In multiple sclerosis (MS), abnormalities of brain network dynamics and their relevance for cognitive impairment have never been investigated.

OBJECTIVES

The aim of this study was to assess the dynamic resting state (RS) functional connectivity (FC) on 62 relapsing-remitting MS patients and 65 sex-matched healthy controls enrolled at 7 European sites.

METHODS

MS patients underwent clinical and cognitive evaluation. Between-group network FC differences were evaluated using a dynamic approach (based on sliding-window correlation analysis) and grouping correlation matrices into recurrent FC states.

RESULTS

Dynamic FC analysis revealed, in healthy controls and MS patients, three recurrent FC states: two characterized by strong intra- and inter-network connectivity and one characterized by weak inter-network connectivity (State 3). A total of 23 MS patients were cognitively impaired (CI). Compared to cognitively preserved (CP), CI-MS patients had reduced RS-FC between subcortical and default-mode networks in the low-connectivity State 3 and lower dwell time (i.e. time spent in a given state) in the high-connectivity State 2. CI-MS patients also exhibited a lower number and a less frequent switching between meta-states, as well as a smaller distance traveled through connectivity states.

CONCLUSION

Time-varying RS-FC was markedly less dynamic in CI- versus CP-MS patients, suggesting that slow inter-network connectivity contributes to cognitive dysfunction in MS.

Is impaired information processing speed a matter of structural or functional damage in MS?

Objective

Cognitive deficits, especially those of information processing speed (IPS), are common in multiple sclerosis (MS), however, the underlying neurobiological mechanisms remain poorly understood. In this study, we examined structural and functional brain changes separately, but also in an integrative manner, in relation to IPS performance.

Methods

IPS was measured using the symbol digit modalities test (SDMT) in 330 MS patients and 96 controls. Patients with IPS impairment (IPS-I, z-score < −1.5) were compared to patients with preserved IPS performance (IPS-P) on volumetric measures, white matter integrity loss (using diffusion tensor imaging) and the severity of functional connectivity changes (using resting-state fMRI). Significant predictors of IPS performance were used to create groups of mild or severe structural and/or functional damage to determine the relative effect of structural and/or functional changes on IPS.

Results

IPS-I patients, compared to IPS-P patients, showed lower deep gray matter volume and less WM integrity, but stronger increases in functional connectivity. Patients with predominantly structural damage had worse IPS (z-score = −1.49) than patients with predominantly functional changes (z-score = −0.84), although both structural and functional measures remained significant in a regression model. Patients with severe structural and functional changes had worst IPS (z-score = −1.95).

Conclusion

The level of structural damage explains IPS performance better than functional changes. After integrating functional and structural changes, however, we were able to detect more subtle and stepwise decline in IPS. In subgroups with a similar degree of structural damage, more severe functional changes resulted in worse IPS scores than those with only mild functional changes.

•

Impaired information processing in MS relates to structural and functional changes.

•

There is no one-to-one relation between structural and functional damage.

•

MS patients with severe structural and functional changes have the lowest IPS.

•

Structural changes affect information processing more than functional changes.

•

Functional changes seem to mediate the effect of structural damage on IPS.

The hippocampus in multiple sclerosis

Some of the clinical manifestations of multiple sclerosis, such as memory impairment and depression, are, at least partly, related to involvement of the hippocampus. Pathological studies have shown extensive demyelination, neuronal damage, and synaptic abnormalities in the hippocampus of patients with multiple sclerosis, and improvements in MRI technology have provided novel ways to assess hippocampal involvement in vivo. It is now accepted that clinical manifestations related to the hippocampus are due not only to focal hippocampal damage, but also to disconnection of the hippocampus from several brain networks. Evidence suggests anatomical and functional subspecialisation of the different hippocampal subfields, resulting in variability between regions in the extent to which damage and repair occur. The hippocampus also has important roles in plasticity and neurogenesis, both of which potentially contribute to functional preservation and restoration. These findings underline the importance of evaluation of the hippocampus not only to improve understanding of the clinical manifestations of multiple sclerosis, but also as a potential future target for treatment.

Altered nuclei-specific thalamic functional connectivity patterns in multiple sclerosis and their associations with fatigue and cognition

BACKGROUND

The thalamus, affected early in multiple sclerosis (MS), is a heterogeneous composition of functionally distinct nuclei and is associated with fatigue, cognition, and other outcomes. However, most previous functional imaging studies considered the thalamus only as a whole.

OBJECTIVE

To investigate MS-related abnormalities in nuclei-specific thalamic functional connectivity (FC) and their associations with fatigue and cognitive outcomes.

METHODS

Resting-state functional magnetic resonance imaging (fMRI) was analyzed in 64 MS patients and 26 healthy controls (HC). Whole-brain FC maps for four thalamic subregions seeds were computed for each subject. FC maps were compared between groups, and group by FC interaction effects were assessed for fatigue and cognitive measures.

RESULTS

MS patients had decreased FC between the left medial thalamic nuclei and left angular gyrus and reduced FC between the left posterior thalamic nuclei and left supramarginal gyrus, as well as decreased right medial thalamic nuclei connectivity with bilateral caudate/thalamus and left cerebellar areas (p < 0.05 corrected). MS patients had increased FC between the left anterior thalamic nuclei and anterior cingulate cortex bilaterally. There were significant relationships between connectivity alterations and fatigue and cognitive measures between groups (p < 0.05 corrected).

CONCLUSION

FC alteration is nuclei-specific and is differentially associated with fatigue and cognition.

The clinical value of the patient-reported multiple sclerosis neuropsychological screening questionnaire

Background:

Cognitive problems are difficult to identify in patients with multiple sclerosis (MS).

Objective:

To investigate the clinical applicability of the patient-reported MS Neuropsychological Screening Questionnaire (MSNQ-P).

Methods:

Cut-off scores were determined to differentiate between cognitively impaired (n = 90), mildly cognitively impaired (n = 115), and cognitively preserved (n = 147) MS patients using receiver operating characteristic analyses.

Results:

We could not define specific and sensitive cut-off scores. Higher scores (≥27) did indicate cognitive impairment. Among patients with a higher education, lower scores (<12) indicated intact cognition.

Conclusion:

Certain scores can indicate intact or impaired cognitive function. Still, MSNQ-P scores should be interpreted with caution.

Information processing speed in multiple sclerosis: Relevance of default mode network dynamics

Objective

To explore the added value of dynamic functional connectivity (dFC) of the default mode network (DMN) during resting-state (RS), during an information processing speed (IPS) task, and the within-subject difference between these conditions, on top of conventional brain measures in explaining IPS in people with multiple sclerosis (pwMS).

Methods

In 29 pwMS and 18 healthy controls, IPS was assessed with the Letter Digit Substitution Test and Stroop Card I and combined into an IPS-composite score. White matter (WM), grey matter (GM) and lesion volume were measured using 3 T MRI. WM integrity was assessed with diffusion tensor imaging. During RS and task-state fMRI (i.e. symbol digit modalities task, IPS), stationary functional connectivity (sFC; average connectivity over the entire time series) and dFC (variation in connectivity using a sliding window approach) of the DMN was calculated, as well as the difference between both conditions (i.e. task-state minus RS; ΔsFC-DMN and ΔdFC-DMN). Regression analysis was performed to determine the most important predictors for IPS.

Results

Compared to controls, pwMS performed worse on IPS-composite (p = 0.022), had lower GM volume (p < 0.05) and WM integrity (p < 0.001), but no alterations in sFC and dFC at the group level. In pwMS, 52% of variance in IPS-composite could be predicted by cortical volume (β = 0.49, p = 0.01) and ΔdFC-DMN (β = 0.52, p < 0.01). After adding dFC of the DMN to the model, the explained variance in IPS increased with 26% (p < 0.01).

Conclusion

On top of conventional brain measures, dFC from RS to task-state explains additional variance in IPS. This highlights the potential importance of the DMN to adapt upon cognitive demands to maintain intact IPS in pwMS.

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Problems with information processing speed occur often in multiple sclerosis (MS)

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Dynamics in brain communication can reflect information transfer within the brain

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With fMRI, dynamic communication can be measured, which increases upon task demands

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This increase in dynamics explains information processing speed in MS

The importance of hippocampal dynamic connectivity in explaining memory function in multiple sclerosis

INTRODUCTION

Brain dynamics (i.e., variable strength of communication between areas), even at the scale of seconds, are thought to underlie complex human behavior, such as learning and memory. In multiple sclerosis (MS), memory problems occur often and have so far only been related to "stationary" brain measures (e.g., atrophy, lesions, activation and stationary (s) functional connectivity (FC) over an entire functional scanning session). However, dynamics in FC (dFC) between the hippocampus and the (neo)cortex may be another important neurobiological substrate of memory impairment in MS that has not yet been explored. Therefore, we investigated hippocampal dFC during a functional (f) magnetic resonance imaging (MRI) episodic memory task and its relationship with verbal and visuospatial memory performance outside the MR scanner.

METHODS

Thirty-eight MS patients and 29 healthy controls underwent neuropsychological tests to assess memory function. Imaging (1.5T) was obtained during performance of a memory task. We assessed hippocampal volume, functional activation, and sFC (i.e., FC of the hippocampus with the rest of the brain averaged over the entire scan, using an atlas-based approach). Dynamic FC of the hippocampus was calculated using a sliding window approach.

RESULTS

No group differences were found in hippocampal activation, sFC, and dFC. However, stepwise forward regression analyses in patients revealed that lower dFC of the left hippocampus (standardized β = -0.30; p = .021) could explain an additional 7% of variance (53% in total) in verbal memory, in addition to female sex and larger left hippocampal volume. For visuospatial memory, lower dFC of the right hippocampus (standardized β = -0.38; p = .013) could explain an additional 13% of variance (24% in total) in addition to higher sFC of the right hippocampus.

CONCLUSION

Low hippocampal dFC is an important indicator for maintained memory performance in MS, in addition to other hippocampal imaging measures. Hence, brain dynamics may offer new insights into the neurobiological mechanisms underlying memory (dys)function.

Fronto-limbic disconnection in patients with multiple sclerosis and depression

Background:

The biological mechanism of depression in multiple sclerosis (MS) is not well understood. Based on work in major depressive disorder, fronto-limbic disconnection might be important.

Objective:

To investigate structural and functional fronto-limbic changes in depressed MS (DMS) and non-depressed MS (nDMS) patients.

Methods:

In this retrospective study, 22 moderate-to-severe DMS patients (disease duration 8.2 ± 7.7 years), 21 nDMS patients (disease duration 15.3 ± 8.3 years), and 12 healthy controls underwent neuropsychological testing and magnetic resonance imaging (MRI; 1.5 T). Brain volumes (white matter (WM), gray matter, amygdala, hippocampus, thalamus), lesion load, fractional anisotropy (FA) of fronto-limbic tracts, and resting-state functional connectivity (FC) between limbic and frontal areas were measured and compared between groups. Regression analysis was performed to relate MRI measures to the severity of depression.

Results:

Compared to nDMS patients, DMS patients (shorter disease duration) had lower WM volume (p < 0.01), decreased FA of the uncinate fasciculus (p < 0.05), and lower FC between the amygdala and frontal regions (p < 0.05). Disease duration, FA of the uncinate fasciculus, and FC of the amygdala could explain 48% of variance in the severity of depression. No differences in cognition were found.

Conclusion:

DMS patients showed more pronounced (MS) damage, that is, structural and functional changes in temporo-frontal regions, compared to nDMS patients, suggestive of fronto-limbic disconnection.

Fronto-striatal network activation leads to less fatigue in multiple sclerosis

BACKGROUND

The fronto-striatal network has been implicated in both fatigue, a common multiple sclerosis (MS) symptom, and goal attainment, which has been shown to reduce fatigue in healthy individuals.

OBJECTIVES

To investigate whether stimulation of the fronto-striatal network through goal attainment (potential monetary gain) leads to fatigue reduction in MS and healthy control (HC) participants.

METHODS

In all, 14 healthy and 19 MS participants performed a gambling task during functional magnetic resonance imaging (fMRI). Participants were presented with an opportunity to receive monetary reward during the outcome condition of the task but not during the no outcome condition. Self-reported fatigue measures were obtained after each condition and outside of the scanner. Structural alterations were also examined.

RESULTS

A significant decrease in fatigue was observed after the outcome condition compared to the no outcome condition in both groups. Significantly greater activation was observed in the ventral striatum in association with the outcome condition compared to the no outcome condition in both groups. Ventromedial prefrontal cortex showed significantly greater activation during the no outcome condition compared to the outcome condition with greater difference between conditions in the HC group.

CONCLUSION

This is the first functional neuroimaging study showing that stimulation of the fronto-striatal network through goal attainment leads to decreased on-task fatigue in MS and healthy participants.

rTMS affects working memory performance, brain activation and functional connectivity in patients with multiple sclerosis

OBJECTIVE

To investigate the effects of high-frequency repetitive transcranial magnetic stimulation (rTMS) of the right dorsolateral prefrontal cortex (DLPFC) on working memory performance, while measuring task-related brain activation and task-related brain connectivity in patients with multiple sclerosis (MS).

METHODS

17 patients with MS and 11 healthy controls (HCs) underwent 3 experimental sessions (baseline, real-rTMS, sham-rTMS), all including an N-back task (3 task loads: N1, N2, N3; control condition: N0) inside the MR scanner. Prior to imaging, real-rTMS (10 Hz) was applied to the right DLPFC. The stimulation site was defined based on individually assessed N-back task activation at baseline and located using neuronavigation. Changes in whole brain functional activation and functional connectivity with the right DLPFC were calculated.

RESULTS

N-back task accuracy (N2 and N3) improved after real-rTMS (and not after sham-rTMS) compared with baseline (p=0.029 and p=0.015, respectively), only in patients. At baseline, patients with MS, compared with HCs, showed higher task-related frontal activation (left DLPFC, N2>N0), which disappeared after real-rTMS. Task-related (N1>N0) functional connectivity between the right DLPFC and the right caudate nucleus and bilateral (para)cingulate gyrus increased in patients after real-rTMS when compared with sham stimulation.

CONCLUSIONS

In patients with MS, N-back accuracy improved while frontal hyperactivation (seen at baseline relative to HCs) disappeared after real-rTMS. Together with the changes in functional connectivity after real-rTMS in patients, these findings may represent an rTMS-induced change in network efficiency in patients with MS, shifting patients' brain function towards the healthy situation. This implicates a potentially relevant role for rTMS in cognitive rehabilitation in MS.