Correlation between fatigue and brain atrophy and lesion load in multiple sclerosis patients independent of disability

Structural MRI measures are associated with fatigue severity and persistence in a large, real-world cohort of people with multiple sclerosis

BACKGROUND

Results of research on radiological hallmarks of multiple sclerosis (MS) fatigue have been conflicting.

OBJECTIVE

To investigate the associations of lesion and brain compartment volumes with fatigue severity and persistence in people with multiple sclerosis (PwMS).

METHODS

The Multiple Sclerosis Partners Advancing Technology and Health Solutions (MS PATHS) network collects standardized data during routine care of PwMS from 10 healthcare institutions. Magnetic resonance imaging (MRI) predictors included baseline brain parenchymal (BPF) and gray matter fractions (GMF) and T2 lesion volume (T2LV). The Quality of Life in Neurological Disorders (Neuro-QOL) fatigue subscore was analyzed linearly and categorically using T-score cutpoints, with a period of elevated symptoms defined as T-score ⩾ mean + 0.5 SD over follow-up.

RESULTS

At baseline, of 4012 participants (average age: 45.6 ± 11.8 years; 73% female; 31% progressive MS), 2058 (51%) had no fatigue, 629 (16%) had mild fatigue, and 1325 (33%) had moderate-to-severe fatigue. One SD greater baseline BPF and GMF were associated with 0.83 (p < 0.001) and 0.38 (p = 0.02) lower values in the baseline Neuro-QOL fatigue T-score. A 1 SD lower log of total T2LV was associated with a 0.49 (p < 0.001) lower baseline fatigue T-score. Higher BPF and lower T2LV at baseline were associated with lower odds of subsequent periods of elevated fatigue.

CONCLUSION

Baseline lesion burden and lower generalized whole-brain volumes were associated with MS fatigue in cross-sectional and longitudinal analyses in a large, real-world cohort of PwMS.

Multiple sclerosis lesions that impair memory map to a connected memory circuit

BACKGROUND

Nearly 1 million Americans are living with multiple sclerosis (MS) and 30-50% will experience memory dysfunction. It remains unclear whether this memory dysfunction is due to overall white matter lesion burden or damage to specific neuroanatomical structures. Here we test if MS memory dysfunction is associated with white matter lesions to a specific brain circuit.

METHODS

We performed a cross-sectional analysis of standard structural images and verbal memory scores as assessed by immediate recall trials from 431 patients with MS (mean age 49.2 years, 71.9% female) enrolled at a large, academic referral center. White matter lesion locations from each patient were mapped using a validated algorithm. First, we tested for associations between memory dysfunction and total MS lesion volume. Second, we tested for associations between memory dysfunction and lesion intersection with an a priori memory circuit derived from stroke lesions. Third, we performed mediation analyses to determine which variable was most associated with memory dysfunction. Finally, we performed a data-driven analysis to derive de-novo brain circuits for MS memory dysfunction using both functional (n = 1000) and structural (n = 178) connectomes.

RESULTS

Both total lesion volume (r = 0.31, p < 0.001) and lesion damage to our a priori memory circuit (r = 0.34, p < 0.001) were associated with memory dysfunction. However, lesion damage to the memory circuit fully mediated the association of lesion volume with memory performance. Our data-driven analysis identified multiple connections associated with memory dysfunction, including peaks in the hippocampus (T = 6.05, family-wise error p = 0.000008), parahippocampus, fornix and cingulate. Finally, the overall topography of our data-driven MS memory circuit matched our a priori stroke-derived memory circuit.

CONCLUSIONS

Lesion locations associated with memory dysfunction in MS map onto a specific brain circuit centered on the hippocampus. Lesion damage to this circuit fully mediated associations between lesion volume and memory. A circuit-based approach to mapping MS symptoms based on lesions visible on standard structural imaging may prove useful for localization and prognosis of higher order deficits in MS.

EDSS and infratentorial white matter lesion volume are considered predictors of fatigue severity in RRMS

Fatigue is a common disabling symptom of relapsing remitting multiple sclerosis (RRMS). Many studies have linked grey matter atrophy to fatigue, but white matter lesion load (WM-LL) has received less attention. Here we assess the relation between fatigue and regional WM-LL volumetric measures. 63 patients with RRMS participated in this study; mean age was 31.9 ± 8.1 years. Each patient provided demographic details and was scored on the expanded disability status scale (EDSS) and fatigue severity scale (FSS). VolBrain, a fully automated, operator-independent tool was used to assess WM-LL and whole brain volume. The patients were classified into three groups: no fatigue (FSS < 4), low to moderate fatigue (FSS ≥ 4 ≤ 5) and high fatigue (FSS > 5). 33.3% of patients had no significant fatigue, 25.4% had mild-to-moderate fatigue, and 41.3% had significant fatigue. Age, disease duration, relapses, and EDSS were positively correlated to fatigue severity (P = 0.034, 0.002, 0.009 and 0.001 respectively). Whole brain volume, total and regional WM-LL (juxtacortical, periventricular, infratentorial) were also correlated with fatigue severity. Ordinal regression analysis for fatigue severity showed EDSS and infratentorial lesion volume were the best predictors. In conclusion, EDSS and infratentorial lesion volume (cerebellar and brainstem) are the best predictors of fatigue severity.

Monoaminergic network abnormalities: a marker for multiple sclerosis-related fatigue and depression

OBJECTIVE

To investigate monoaminergic network abnormalities in patients with multiple sclerosis (MS) according to their fatigue and depressive status through a positron emission tomography (PET)-based constrained independent component analysis (ICA) on resting state (RS) functional MRI (fMRI).

METHODS

In this prospective study, 213 patients with MS (mean age=40.6±12.5 years; 94/119 men/women; 153 relapsing-remitting; 60 progressive) and 62 healthy controls (HCs, mean age=39.0±10.4 years; 30/32 men/women) underwent neurological, fatigue, depression and RS fMRI assessment. Patterns of dopamine, norepinephrine-related and serotonin-related RS functional connectivity (FC) were derived by ICA, constrained to PET atlases for dopamine, norepinephrine and serotonin transporters, obtained in HCs' brain.

RESULTS

Compared with HCs, patients with MS showed abnormalities in all three explored monoaminergic networks, mostly with decreased RS FC within PET-guided monoaminergic networks in frontal regions and subcortical areas including the cerebellum and thalamus, and increased RS FC in temporo-parieto-occipital cortical areas, including bilateral precunei.MS-related fatigue was associated with decreased RS FC within the PET-guided dopamine network in the left thalamus and left cerebellum, and with increased RS FC within the PET-guided serotonin network in the left middle occipital gyrus. MS-related depression was associated with more distributed abnormalities involving the three explored monoaminergic networks, resulting in overall reduced RS FC in the frontal lobe, limbic areas and the precuneus.

CONCLUSIONS

Patients with MS present diffuse dysregulation in the monoaminergic networks. Specific alterations in these networks were associated with fatigue and depression, providing a pathological marker for these bothersome symptoms and putative targets for their treatment.

Making Visible the Invisible: Automatically Measured Global and Regional Brain Volume Is Associated with Cognitive Impairment and Fatigue in Multiple Sclerosis

In multiple sclerosis (MS), the transition from relapsing-remitting to the secondary-progressive phase is characterized by a progression independent of relapse activity (PIRA), resulting in physical disability accumulation and invisible symptoms, i.e., fatigue and cognitive impairment (CI). These symptoms are related to neurodegenerative processes and have been correlated with MRI measures of brain atrophy only at a group level; however, the application in clinical practice of atrophy-based measurements for single-patient evaluation is yet to be fully investigated. In the present study, we aimed to evaluate the association between brain atrophy, measured with easy-to-use automatic software, and the "invisible" MS symptoms of cognition and fatigue. A total of 69 MS patients were included in the study; cognitive impairment and fatigue (FSS) (in addition to neurological disability, EDSS) were assessed and correlated with brain volumes calculated using the automated software QyScore^® which is validated for single-patient use in the clinical setting. Results showed that the cognitive status was accurately reflected by measures of atrophy, with a sensitivity of up to 90%. CI patients showed a lower volume compared to cognitively normal patients in the whole brain (p = 0.017), gray matter (p = 0.042), insula (p = 0.035), cerebellum (p = 0.008), and limbic lobe (p = 0.049). FSS was associated with temporal lobe (r = -0.37, p = 0.013) and insular (r = -0.36, p = 0.019) volumes. The volumes of the same regions were also associated with EDSS. The global/regional atrophy results, assessed with automatic and easy-to-use software, correlated with cognitive and fatigue symptoms, thus supporting the clinical application in routine patient management.

Individual differences in visual evoked potential latency are associated with variance in brain tissue volume in people with multiple sclerosis: An analysis of brain function-structure correlates

Visual evoked potentials (VEP) index visual pathway functioning, and are often used for clinical assessment and as outcome measures in people with multiple sclerosis (PwMS). VEPs may also reflect broader neural disturbances that extend beyond the visual system, but this possibility requires further investigation. In the present study, we examined the hypothesis that delayed latency of the P100 component of the VEP would be associated with broader structural changes in the brain in PwMS. We obtained VEP latency for a standard pattern-reversal checkerboard stimulus paradigm, in addition to Magnetic Resonance Imaging (MRI) measures of whole brain volume (WBV), gray matter volume (GMV), white matter volume (WMV), and T2-weighted fluid attenuated inversion recovery (FLAIR) white matter lesion volume (FLV). Correlation analyses indicated that prolonged VEP latency was significantly associated with lower WBV, GMV, and WMV, and greater FLV. VEP latency remained significantly associated with WBV, GMV, and WMV even after controlling for the variance associated with inter-ocular latency, age, time between VEP and MRI assessments, and other MRI variables. VEP latency delays were most pronounced in PwMS that exhibited low volume in both white and gray matter simultaneously. Furthermore, PwMS that had delayed VEP latency based on a clinically relevant cutoff (VEP latency ≥ 113 ms) in both eyes had lower WBV, GMV, and WMV and greater FLV in comparison to PwMS that had normal VEP latency in one or both eyes. The findings suggest that PwMS that have delayed latency in both eyes may be particularly at risk for exhibiting greater brain atrophy and lesion volume. These analyses also indicate that VEP latency may index combined gray matter and white matter disturbances, and therefore broader network connectivity and efficiency. VEP latency may therefore provide a surrogate marker of broader structural disturbances in the brain in MS.

Fatigue in Multiple Sclerosis Is Associated with Reduced Expression of Interleukin-10 and Worse Prospective Disease Activity

In multiple sclerosis (MS), fatigue is a frequent symptom that negatively affects quality of life. The pathogenesis of fatigue is multifactorial and inflammation may play a specific role. To explore the association between fatigue, central inflammation and disease course in MS in 106 relapsing-remitting (RR)-MS patients, clinical characteristics, including fatigue and mood, were explored at the time of diagnosis. NEDA (no evidence of disease activity)-3 status after one-year follow up was calculated. Cerebrospinal fluid (CSF) levels of a set of proinflammatory and anti-inflammatory molecules and peripheral blood markers of inflammation were also analyzed. MRI structural measures were explored in 35 patients. A significant negative correlation was found at diagnosis between fatigue measured with the Modified Fatigue Impact Scale (MFIS) and the CSF levels of interleukin (IL)-10. Conversely, no significant associations were found with peripheral markers of inflammation. Higher MFIS scores were associated with reduced probability to reach NEDA-3 status after 1-year follow up. Finally, T2 lesion load showed a positive correlation with MFIS scores and a negative correlation with CSF IL-10 levels at diagnosis. CSF inflammation, and particularly the reduced expression of the anti-inflammatory molecule IL-10, may exacerbate fatigue. Fatigue in MS may reflect subclinical CSF inflammation, predisposing to greater disease activity.

Symptom Interconnectivity in Multiple Sclerosis: A Narrative Review of Potential Underlying Biological Disease Processes

Introduction

Fatigue, cognitive impairment, depression, and pain are highly prevalent symptoms in multiple sclerosis (MS). These often co-occur and may be explained by a common etiology. By reviewing existing literature, we aimed to identify potential underlying biological processes implicated in the interconnectivity between these symptoms.

Methods

A literature search was conducted to identify articles reporting research into the biological mechanisms responsible for the manifestation of fatigue, cognitive impairment, depression, and pain in MS. PubMed was used to search for articles published from July 2011 to July 2021. We reviewed and assessed findings from the literature to identify biological processes common to the symptoms of interest.

Results

Of 693 articles identified from the search, 252 were selected following screening of titles and abstracts and assessing reference lists of review articles. Four biological processes linked with two or more of the symptoms of interest were frequently identified from the literature: (1) direct neuroanatomical changes to brain regions linked with symptoms of interest (e.g., thalamic injury associated with cognitive impairment, fatigue, and depression), (2) pro-inflammatory cytokines associated with so-called ‘sickness behavior,’ including manifestation of fatigue, transient cognitive impairment, depression, and pain, (3) dysregulation of monoaminergic pathways leading to depressive symptoms and fatigue, and (4) hyperactivity of the hypothalamic–pituitary-adrenal (HPA) axis as a result of pro-inflammatory cytokines promoting the release of brain noradrenaline, serotonin, and tryptophan, which is associated with symptoms of depression and cognitive impairment.

Conclusion

The co-occurrence of fatigue, cognitive impairment, depression, and pain in MS appears to be associated with a common set of etiological factors, namely neuroanatomical changes, pro-inflammatory cytokines, dysregulation of monoaminergic pathways, and a hyperactive HPA axis. This association of symptoms and biological processes has important implications for disease management strategies and, eventually, could help find a common therapeutic pathway that will impact both inflammation and neuroprotection.

Supplementary Information

The online version contains supplementary material available at 10.1007/s40120-022-00368-2.

Brain Structural and Functional Alterations in Multiple Sclerosis-Related Fatigue: A Systematic Review

Fatigue is one of the most disabling symptoms of multiple sclerosis (MS); it influences patients’ quality of life. The etiology of fatigue is complex, and its pathogenesis is still unclear and debated. The objective of this review was to describe potential brain structural and functional dysfunctions underlying fatigue symptoms in patients with MS. To reach this purpose, a systematic review was conducted of published studies comparing functional brain activation and structural brain in MS patients with and without fatigue. Electronic databases were searched until 24 February 2021. The structural and functional outcomes were extracted from eligible studies and tabulated. Fifty studies were included: 32 reported structural brain differences between patients with and without fatigue; 14 studies described functional alterations in patients with fatigue compared to patients without it; and four studies showed structural and functional brain alterations in patients. The results revealed structural and functional abnormalities that could correlate to the symptom of fatigue in patients with MS. Several studies reported the differences between patients with fatigue and patients without fatigue in terms of conventional magnetic resonance imaging (MRI) outcomes and brain atrophy, specifically in the thalamus. Functional studies showed abnormal activation in the thalamus and in some regions of the sensorimotor network in patients with fatigue compared to patients without it. Patients with fatigue present more structural and functional alterations compared to patients without fatigue. Specifically, abnormal activation and atrophy of the thalamus and some regions of the sensorimotor network seem linked to fatigue.

Subcortical volumes as early predictors of fatigue in multiple sclerosis

OBJECTIVE

Fatigue is a frequent and severe symptom in multiple sclerosis (MS), but its pathophysiological origin remains incompletely understood. We aimed to examine the predictive value of subcortical gray matter volumes for fatigue severity at disease onset and after four years by applying structural equation modeling (SEM).

METHODS

This multi-center cohort study included 601 treatment-naive MS patients after the first demyelinating event. All patients underwent a standardized 3T MRI protocol. A subgroup of 230 patients with available clinical follow-up data after four years was also analyzed. Associations of subcortical volumes (included into SEM) with MS-related fatigue were studied regarding their predictive value. In addition, subcortical regions that have a central role in the brain network (hubs) were determined through structural covariance network (SCN) analysis.

RESULTS

Predictive causal modeling identified volumes of the caudate (s [standardized path coefficient]=0.763, p=0.003 [left]; s=0.755, p=0.006 [right]), putamen (s=0.614, p=0.002 [left]; s=0.606, p=0.003 [right]) and pallidum (s=0.606, p=0.012 [left]; s=0.606, p=0.012 [right]) as prognostic factors for fatigue severity in the cross-sectional cohort. Moreover, the volume of the pons was additionally predictive for fatigue severity in the longitudinal cohort (s=0.605, p=0.013). In the SCN analysis, network hubs in patients with fatigue worsening were detected in the putamen (p=0.008 [left]; p=0.007 [right]) and pons (p=0.0001).

INTERPRETATION

We unveiled predictive associations of specific subcortical gray matter volumes with fatigue in an early and initially untreated MS cohort. The colocalization of these subcortical structures with network hubs suggests an early role of these brain regions in terms of fatigue evolution. This article is protected by copyright. All rights reserved.

Neurostructural and Neurophysiological Correlates of Multiple Sclerosis Physical Fatigue: Systematic Review and Meta-Analysis of Cross-Sectional Studies

Fatigue is one of the most debilitating symptoms for people with multiple sclerosis (PwMS). By consolidating a diverse and conflicting evidence-base, this systematic review and meta-analysis aimed to gain new insights into the neurobiology of MS fatigue. MEDLINE, ProQuest, CINAHL, Web of Science databases and grey literature were searched using Medical Subject Headings. Eligible studies compared neuroimaging and neurophysiological data between people experiencing high (MS-HF) versus low (MS-LF) levels of perceived MS fatigue, as defined by validated fatigue questionnaire cut-points. Data were available from 66 studies, with 46 used for meta-analyses. Neuroimaging studies revealed lower volumetric measures in MS-HF versus MS-LF for whole brain (-22.74 ml; 95% CI: -37.72 to -7.76 ml; p = 0.003), grey matter (-18.81 ml; 95% CI: -29.60 to -8.03 ml; p < 0.001), putamen (-0.40 ml; 95% CI: -0.69 to -0.10 ml; p = 0.008) and acumbens (-0.09 ml; 95% CI: -0.15 to -0.03 ml; p = 0.003) and a higher volume of T1-weighted hypointense lesions (1.10 ml; 95% CI: 0.47 to 1.73 ml; p < 0.001). Neurophysiological data showed reduced lower-limb maximum voluntary force production (-19.23 N; 95% CI: -35.93 to -2.53 N; p = 0.02) and an attenuation of upper-limb (-5.77%; 95% CI:-8.61 to -2.93%; p < 0.0001) and lower-limb (-2.16%; 95% CI:-4.24 to -0.07%; p = 0.04) skeletal muscle voluntary activation, accompanied by more pronounced upper-limb fatigability (-5.61%; 95% CI: -9.57 to -1.65%; p = 0.006) in MS-HF versus MS-LF. Results suggest that MS fatigue is characterised by greater cortico-subcortical grey matter atrophy and neural lesions, accompanied by neurophysiological decrements, which include reduced strength and voluntary activation. Prospero registration Prospero registration number: CRD42016017934.

Identifying the Distinct Cognitive Phenotypes in Multiple Sclerosis

Importance

Cognitive impairment is a common and disabling feature of multiple sclerosis (MS), but a precise characterization of cognitive phenotypes in patients with MS is lacking.

Objectives

To identify cognitive phenotypes in a clinical cohort of patients with MS and to characterize their clinical and magnetic resonance imaging (MRI) features.

Design, Setting, and Participants

This multicenter cross-sectional study consecutively screened clinically stable patients with MS and healthy control individuals at 8 MS centers in Italy from January 1, 2010, to October 31, 2019. Patients with MS and healthy control individuals who were not using psychoactive drugs and had no history of other neurological or medical disorders, learning disability, severe head trauma, and alcohol or drug abuse were enrolled.

Main Outcomes and Measures

Participants underwent a neurological examination and a cognitive evaluation with the Rao Brief Repeatable Battery and Stroop Color and Word Test. A subgroup of participants also underwent a brain MRI examination. Latent profile analysis was used on cognitive test z scores to identify cognitive phenotypes. Linear regression and mixed-effects models were used to define clinical and MRI features of each phenotype.

Results

A total of 1212 patients with MS (mean [SD] age, 41.1 [11.1] years; 784 women [64.7%]) and 196 healthy control individuals (mean [SD] age, 40.4 [8.6] years; 130 women [66.3%]) were analyzed in this study. Five cognitive phenotypes were identified: preserved cognition (n = 235 patients [19.4%]), mild-verbal memory/semantic fluency (n = 362 patients [29.9%]), mild-multidomain (n = 236 patients [19.5%]), severe-executive/attention (n = 167 patients [13.8%]), and severe-multidomain (n = 212 patients [17.5%]) involvement. Patients with preserved cognition and mild-verbal memory/semantic fluency were younger (mean [SD] age, 36.5 [9.8] years and 38.2 [11.1] years) and had shorter disease duration (mean [SD] 8.0 [7.3] years and 8.3 [7.6] years) compared with patients with mild-multidomain (mean [SD] age, 42.6 [11.2] years; mean [SD] disease duration, 12.8 [9.6] years; P < .001), severe-executive/attention (mean [SD] age, 42.9 [11.7] years; mean [SD] disease duration, 12.2 [9.5] years; P < .001), and severe-multidomain (mean [SD] age, 44.0 [11.0] years; mean [SD] disease duration, 13.3 [10.2] years; P < .001) phenotypes. Severe cognitive phenotypes prevailed in patients with progressive MS. At MRI evaluation, compared with those with preserved cognition, patients with mild-verbal memory/semantic fluency exhibited decreased mean (SE) hippocampal volume (5.42 [0.68] mL vs 5.13 [0.68] mL; P = .04), patients with the mild-multidomain phenotype had decreased mean (SE) cortical gray matter volume (687.69 [35.40] mL vs 662.59 [35.48] mL; P = .02), patients with severe-executive/attention had higher mean (SE) T2-hyperintense lesion volume (51.33 [31.15] mL vs 99.69 [34.07] mL; P = .04), and patients with the severe-multidomain phenotype had extensive brain damage, with decreased volume in all the brain structures explored, except for nucleus pallidus, amygdala and caudate nucleus.

Conclusions and Relevance

This study found that by defining homogeneous and clinically meaningful phenotypes, the limitations of the traditional dichotomous classification in MS can be overcome. These phenotypes can represent a more meaningful measure of the cognitive status of patients with MS and can help define clinical disability, support clinicians in treatment choices, and tailor cognitive rehabilitation strategies.

Dynamic functional connectivity as a neural correlate of fatigue in multiple sclerosis

BACKGROUND

More than 80% of multiple sclerosis (MS) patients experience symptoms of fatigue. MS-related fatigue is only partly explained by structural (lesions and atrophy) and functional (brain activation and conventional static functional connectivity) brain properties.

OBJECTIVES

To investigate the relationship of dynamic functional connectivity (dFC) with fatigue in MS patients and to compare dFC with commonly used clinical and MRI parameters.

METHODS

In 35 relapsing-remitting MS patients (age: 42.83 years, female/male: 20/15, disease duration: 11 years) and 19 healthy controls (HCs) (age: 41.38 years, female/male: 11/8), fatigue was measured using the CIS-20r questionnaire at baseline and at 6-month follow-up. All subjects underwent structural and resting-state functional MRI at baseline. Global static functional connectivity (sFC) and dynamic functional connectivity (dFC) were calculated. dFC was assessed using a sliding-window approach by calculating the summed difference (diff) and coefficient of variation (cv) across windows. Moreover, regional connectivity between regions previously associated with fatigue in MS was estimated (i.e. basal ganglia and regions of the Default Mode Network (DMN): medial prefrontal, posterior cingulate and precuneal cortices). Hierarchical regression analyses were performed with forward selection to identify the most important correlates of fatigue at baseline. Results were not corrected for multiple testing due to the exploratory nature of the study.

RESULTS

Patients were more fatigued than HCs at baseline (p = 0.001) and follow-up (p = 0.002) and fatigue in patients was stable over time (p = 0.213). Patients had significantly higher baseline global dFC than HCs, but no difference in basal ganglia-DMN dFC. In the regression model for baseline fatigue in patients, basal ganglia-DMN dFC-cv (standardized β = -0.353) explained 12.5% additional variance on top of EDSS (p = 0.032). Post-hoc analysis revealed higher basal ganglia-DMN dFC-cv in non-fatigued patients compared to healthy controls (p = 0.013), whereas fatigued patients and healthy controls showed similar basal ganglia-DMN dFC.

CONCLUSIONS

Less dynamic connectivity between the basal ganglia and the cortex is associated with greater fatigue in MS patients, independent of disability status. Within patients, lower dynamics of these connections could relate to lower efficiency and increased fatigue. Increased dynamics in non-fatigued patients compared to healthy controls might represent a network organization that protects against fatigue or signal early network dysfunction.

Oculomotor Fatigue and Neuropsychological Assessments mirror Multiple Sclerosis Fatigue

Fatigue is a major complaint in MS. Up to now no objective assessment tools have been established which hampers any treatment approach. Previous work has indicated an association of fatigue with cognitive measures of attention. Oculomotor tests have been established in healthy individuals as a read-out of fatigue, and to some extent in MS patients. Based on these observations we compared two groups of MS patients, one with fatigue (n=28) and one without fatigue (n=21) and a group of healthy subjects (n=15) with a standardised computerised measure of alertness and an oculomotor stress test. Patients with fatigue showed highly significant changes of their saccade dynamics as defined by the Main Sequence and Phase Plane plots: They showed slowing of saccades, the characteristical fatigue double peak, and an asymmetrical phase plane. Oculomotor tests differentiated significantly between fatigue and fatigabiliy in our MS patients. They also showed significantly worse performance in the alertness test as well as in the oculomotor task. Significantly slower reaction times were observed for tonic alertness in 2 series without a cue (p=.025 and p=.037) but not in phasic alertness with a cue (p=.24 and p=.34). Performance was influenced by disability as well as by affective state. We conclude, when controlling for disability and depression, saccadic stress tests and alertness tests could be used as an objective read-out for fatigability and fatigue in MS patients.

Motor fatigue is associated with asymmetric connectivity properties of the corticospinal tract in multiple sclerosis

Multiple Sclerosis (MS) is characterized by demyelination and neurodegeneration of the central nervous system and causes excessive fatigue in more than 80% of the patients. The pathophysiologic mechanisms causing fatigue are still largely unknown. In 46 right-handed patients with relapsing-remitting MS and 25 right-handed controls, we performed diffusion MRI and applied streamline based probabilistic tractography to derive unilateral anatomical connectivity maps for the white matter of the right and left hemispheres. The maps provide an indication how often a streamline has passed through a given voxel. Since tractography based anatomical connectivity mapping (ACM) is sensitive to disease-induced changes in anatomical connectivity, we used ACM to test whether motor fatigue is associated with altered ipsi-hemispherical anatomical connectivity in the major motor output pathway, the corticospinal tract (CST). Patients had higher mean ACM values in the CST than healthy controls. This indicated that a higher number of streamlines, starting from voxels in the same hemisphere, travelled through the CST and may reflect an accumulated disease-induced disintegration of CST. The motor subscale of the Fatigue Scale for Motor and Cognitive functions (FSMCMOTOR) was used to define sub-groups with (n = 29, FSMCMOTOR score ≥ 27) and without motor fatigue (n = 17, FSMSMOTOR score ≤ 26). Patients without fatigue only showed higher ACM values in right CST, while mean ACM values were unaltered in left CST. The higher the mean ACM values in the left relative to the right CST, the more patients reported motor fatigue. Left-right asymmetry in anatomical connectivity outside the CST did not scale with individual motor fatigue. Our results link lateralized changes of tractography-based microstructural properties in the CST with motor fatigue in relapsing-remitting MS.

Difference in fatigue and pain between neuromyelitis optica spectrum disorder and multiple sclerosis

Objective

To investigate the difference of fatigue and pain in patients with neuromyelitis optica spectrum disorder (NMOSD) and multiple sclerosis (MS).

Methods

Data from the Modified Fatigue Impact Scale (MFIS) and Pain Effects Scale (PES) were compared between 51 NMOSD and 85 MS patients. Each score was compared in each disease group with or without clinical abnormalities. Since almost no MS patients are without brain magnetic resonance imaging abnormalities, volumetry analysis by the Lesion Segmentation Tool and statistical parametric mapping 12 were added to obtain total lesion volume and intracranial volume in MS patients, and the correlations between total lesion volume/intracranial volume and each score were investigated.

Results

Compared to the MS group, the NMOSD group showed a higher PES score (median, 15.0 vs. 7.0, P = 0.045), no difference in MFIS, and an increased percentage of patients with extended spinal cord lesions (58.8% vs. 8.2%, P < 0.001). Moreover, NMOSD and MS patients with extended spinal cord lesions tended to demonstrate higher PES scores than those without. A positive correlation between MFIS and PES were found in patients with NMOSD and MS. On the other hand, MS patients showed a higher percentage of brain abnormalities (80.4% vs. 97.6%, P = 0.001) and a positive correlation between total lesion volume/intracranial volume and MFIS (Spearman’s ρ = 0.50, P = 0.033).

Conclusions

The origin of fatigue may be associated with spinal cord lesions causing pain in NMOSD patients, but with brain lesions in MS patients.

A novel classification of fatigue in multiple sclerosis based on longitudinal assessments

BACKGROUND

Magnetic resonance imaging (MRI) studies of multiple sclerosis-related fatigue had limited reproducibility. Temporal fatigue fluctuations have not been considered.

OBJECTIVE

To investigate whether a novel group allocation that reflects temporal dynamics of fatigue improves our ability to detect fatigue-associated structural brain abnormalities.

METHODS

Patient stratification based on biennial fatigue assessments: sustained fatigue (SF, n = 29, fatigued at the latest ⩾2 assessments), one time-point fatigue (1F, n = 15, fatigued at the latest, but non-fatigued at the penultimate assessment), reversible fatigue (RF, n = 31, non-fatigued at the latest assessment, but reported fatigue previously), and never fatigued (NF, n = 54). Brain parenchymal fraction (BPF) and T2 lesion volume (T2LV) were compared between these groups and were derived using a conventional, single time-point fatigued versus non-fatigued stratification.

RESULTS

The SF versus NF stratification yielded improved power. SF (p = 0.005) and RF (p = 0.043) showed significantly higher T2LV than NF. T2LV showed no significant differences in SF versus 1F, SF versus RF, or 1F versus RF. Fatigued versus non-fatigued patients showed significantly higher T2LV (p = 0.030). We found no significant differences in BPF between the groups.

CONCLUSION

Taking into account temporal fatigue dynamics increases the statistical power with respect to T2LV and may improve characterization of brain pathological correlates of MS-related fatigue.

History of fatigue in multiple sclerosis is associated with grey matter atrophy

Fatigue in multiple sclerosis (MS) has been associated with brain damage with low replicability. Temporal fatigue fluctuations have not been considered. We assessed whether sustained fatigue (SF) associates more strongly with grey matter (GM) changes than reversible fatigue (RF). Patients were stratified into three groups according to historical fatigue levels: SF (n = 30, i.e. patients who reported fatigue at the latest ≥2 assessments), RF (n = 31, i.e. patients not fatigued at the latest assessment, but reported fatigue previously), and never fatigued (NF, n = 37). Groups were compared for brain GM volume using cross-sectional voxel-based and volumetric analyses of 3T T1-weighted MRI. Confounding effects of depression and related medications were also investigated. SF and RF patients showed similar anatomical distribution of GM atrophy. While we robustly replicated the anatomical patterns of GM atrophy described in previous work, we also found an association between hippocampal atrophy and fatigue. Depression showed confounding effects in frontal, parietal, occipital, accumbal and thalamic regions. Assessed treatments showed confounding effects in frontal, parietal and striatal areas. Our results suggest that history of clinically-relevant fatigue in currently non-fatigued patients is associated with GM atrophy, potentially explaining inconsistent findings of previous studies that stratified patients using a single fatigue assessment.

Fatigue scores correlate with other self-assessment data, but not with clinical and biomarker parameters, in CIS and RRMS

BACKGROUND

Fatigue is common in multiple sclerosis and is associated with reduced quality of life. This study aimed to assess the correlation between fatigue scores and data from other self-assessment questionnaires, neuropsychological tests and neuroimaging, as well as data on neuroimmunological markers in cerebrospinal fluid (CSF) and serum/plasma, in clinically isolated syndrome (CIS) and relapsing remitting MS (RRMS).

METHODS

Modified fatigue impact scale (MFIS) scores were determined in 38 patients with newly diagnosed CIS or RRMS at baseline and after one year in a prospective longitudinal cohort study. Non-parametric correlation analyses were used to assess associations between MFIS scores and other self-assessment questionnaire data (Hospital Anxiety and Depression scale (HAD), Multiple Sclerosis Impact Scale 29 (MSIS-29) and Short Form 36 (SF-36)), as well as with neuropsychological test performances (e.g. Auditory Consonant Trigram Test (ACTT)), clinical parameters (e.g. disease duration and expanded disability status scale (EDSS)), magnetic resonance imaging (MRI) data (number of T2 lesions in brain MRI and total brain volume) and several neurodegenerative/neuroinflammatory markers in CSF and serum/plasma (IL-1β, IL-6, CXCL1, CXCL10, CXCL13, CCL-22 in plasma; neurofilament light chain (NFL) in serum; IL-6, CXCL1, CXCL10, CXCL13, CCL22, NFL and chitinase-3-like-1 (CHI3L1) in CSF. CSF and serum/plasma from 21 age- and sex-matched healthy controls were available for comparison.

RESULTS

At both baseline and one-year follow-up, fatigue scores correlated significantly with HAD, MSIS-29 and SF-36 scores and ACTT performance (Spearman´s rho 0.45-0.78, all p ≤ 0.01) but not with the other neuropsychological test results, disease duration, EDSS ratings, number of T2 lesions, total brain volume or neurodegenerative/neuroinflammatory markers, including neurofilament light chain levels in CSF and serum. In group comparisons, MFIS scores were similar in patients fulfilling no evidence of disease activity-3 (NEDA-3) (n = 18) and patients not fulfilling NEDA-3 (n = 20) during one year of follow-up (p > 0.01).

CONCLUSIONS

In this cohort of patients with newly diagnosed CIS and RRMS, fatigue scores were associated with mood, disease impact on daily life and quality of life as well as with alterations of attentive functions. Study results indicate that subjective fatigue scores are not well reflected by some commonly used and objectively measurable disease parameters like EDSS, T2 lesions and NFL levels.

Brain anatomical correlates of fatigue in multiple sclerosis

Fatigue is one of the most debilitating symptoms in patients with multiple sclerosis (MS). Despite its clinical significance, the aetiology and pathophysiology of MS-related fatigue are not well understood. Current evidence and understanding of the neuroanatomical underpinnings of MS-related fatigue are reviewed in this article. The aims of this paper are to (1) review the findings of previous structural neuroimaging studies on MS-related fatigue and summarize consistent findings regarding brain circuitry associated with fatigue in MS, (2) contextualize these findings with the neurochemistry of the relevant circuits and (3) discuss future perspectives with regard to impact on fatigue management of MS patients and methodological challenges towards improved understanding of fatigue pathogenesis. The detailed understanding of the neuroanatomical underpinnings of fatigue might contribute to the identification of novel treatment targets and factors determining treatment resistance to drugs used in current clinical practice.

Pathophysiological and cognitive mechanisms of fatigue in multiple sclerosis

Fatigue is one of the most common symptoms in multiple sclerosis (MS), with a major impact on patients' quality of life. Currently, treatment proceeds by trial and error with limited success, probably due to the presence of multiple different underlying mechanisms. Recent neuroscientific advances offer the potential to develop tools for differentiating these mechanisms in individual patients and ultimately provide a principled basis for treatment selection. However, development of these tools for differential diagnosis will require guidance by pathophysiological and cognitive theories that propose mechanisms which can be assessed in individual patients. This article provides an overview of contemporary pathophysiological theories of fatigue in MS and discusses how the mechanisms they propose may become measurable with emerging technologies and thus lay a foundation for future personalised treatments.

Fatigue in multiple sclerosis: The role of thalamus

Fatigue is very common in multiple sclerosis (MS) and is often considered as its most disabling symptom. Over the last 20 years, an increasing number of studies have evaluated the pathogenetic bases of MS-related fatigue. Converging evidence from neurophysiology and neuroimaging research suggests that a dysfunction in a cortico-subcortical pathway, centered on thalamus, is involved in the pathogenesis of fatigue. However, type and significance of such dysfunction remain unknown, and some studies reported an increase in the activity and connectivity within the thalamic network, whereas others suggested its reduction. Hereby, we review the results of neuroimaging studies supporting the different hypotheses about the role of thalamic network in the pathophysiology of MS-related fatigue and discuss limitations and shortcomings of available data, highlighting the key challenges in the field and the directions for future research.

Characterizing Fatigue-Related White Matter Changes in MS: A Proton Magnetic Resonance Spectroscopy Study

Few cross-sectional studies have investigated the correlation between neurochemical changes and multiple sclerosis (MS) fatigue, but little is known on the fatigue-related white matter differences between time points. We aim to investigate the longitudinal neurometabolite profile of white matter in MS fatigue. Forty-eight relapsing remitting multiple sclerosis (RRMS) patients with an expanded disability status scale (EDSS) ≤ 4 underwent high field ¹H-multivoxel magnetic resonance spectroscopy (MRS) at baseline and year 1. Fatigue severity was evaluated by the fatigue severity scale (FSS). Patients were divided into low (LF, FSS ≤ 3), moderate (MF, FSS = 3.1–5), and high fatigue (HF, FSS ≥ 5.1) groups. In a two-way analysis of variance (ANOVA), we observed a decline in the ratio of the sum of N-acetylaspartate (NAA) and N-acetylaspartylglutamate (NAAG) to the sum of creatine (Cr) and phosphocreatine (PCr) in the right anterior quadrant (RAQ) and left anterior quadrant (LAQ) of the MRS grid in the HF group at baseline and year 1. This decline was significant when compared with the LF group (p = 0.018 and 0.020). In a one-way ANOVA, the fatigue group effect was significant and the ratio difference in the right posterior quadrant (RPQ) and left posterior quadrant (LPQ) of the HF group was also significant (p = 0.012 and 0.04). Neurochemical changes in the bilateral frontal white matter and possibly parietooccipital areas were noted in the HF group at two different time points. Our findings may shed some light on the pathology of MS fatigue.

Evaluation of MS related central fatigue using MR neuroimaging methods: Scoping review

BACKGROUND

Fatigue is a common and debilitating symptom in multiple sclerosis (MS). Over the past decade, a growing body of research has focussed on the pathophysiological mechanisms underlying central (cognitive and physical) fatigue in MS. The precise mechanisms causing fatigue in MS patients are complex and poorly understood, and may differ between patients. Advanced quantitative magnetic resonance imaging (MRI) techniques allow for objective assessment of disease pathology and have been used to characterise the pathophysiology of central fatigue in MS.

OBJECTIVE

To systematically review the existing literature of MRI-based studies assessing the pathophysiological mechanisms of MS-related central fatigue.

METHODS

A systematic literature search of four major databases (PubMed, Medline, Embase, Scopus and Google Scholar) was conducted to identify MRI-based studies of MS-related fatigue published in the past 20 years. Studies using the following MRI-based methods were included: structural (lesion load/atrophy), T1 relaxation time/magnetisation transfer ratio (MTR), diffusion tensor imaging (DTI), functional MRI (fMRI) and magnetic resonance spectroscopy (MRS).

RESULTS

A total of 92 studies were identified as meeting the search criteria and included for review. Structurally, regional gray/white matter atrophy, cortical thinning, decreased T1 relaxation times and reduced fractional anisotropy were associated with central fatigue in MS. Functionally, hyperactivity and reduced functional connectivity in several regional areas of frontal, parietal, occipital, temporal and cerebellum were suggested as causes of central fatigue. Biochemically, a reduction in N-acetyl aspartate/creatine and increased (glutamine+glutamate)/creatine ratios were correlated with fatigue severity in MS.

CONCLUSION

Several advanced quantitative MRI methods have been employed in the study of central fatigue in MS. Central fatigue in MS is associated with macro/microstructural and functional changes within specific brain regions (frontal, parietal, temporal and deep gray matter) and specific pathways/networks (cortico-cortical and cortico-subcortical). Alternations in the cortico-striatal-thalamocortical (CSTC) loop are correlated with the development of fatigue in MS patients.

Structural and cognitive correlates of fatigue in progressive multiple sclerosis

BACKGROUND

Fatigue in multiple sclerosis (MS) is a debilitating symptom and experienced by most patients. In recent studies investigating this phenomenon, the majority of patients had a relapsing-remitting disease course.

METHODS

Patients with progressive MS participating in one of three treatment trials during a period from 2010 to 2014 were included. Fatigue was assessed with the Fatigue Scale for Motor and Cognitive Functions (FSMC) and patients were further examined with a cognitive test battery, including Symbol Digit Modalities Test (SDMT), and 3 T MRI with subsequent quantitative analyses of 13 cortical regions of interest, deep grey matter and lesion volume.

RESULTS

Twenty-two patients were enrolled. The thickness of the pre-central gyrus correlated significantly with motor fatigue. We found only a non-significant trend towards a correlation between cognitive fatigue and the thickness of the pre-central gyrus, the parietal inferior supra-marginal gyrus and the opercular part of the inferior frontal gyrus. 36% of participants had impaired processing speed and 9% had normal function on all tests. The scores on the FSMC-cognitive scale were related to performance on SDMT.

CONCLUSION

In this exploratory study of patients with progressive MS, fatigue was related to processing speed. Motor fatigue was also related to the cortical thickness of the primary motor cortex and there was a trend towards a relationship between cognitive fatigue and the thickness of cortical areas involved in attentional processes. Additional studies are needed to further elucidate the relationship between regional cortical atrophy, cognitive functioning and the perception of fatigue.

ABBREVIATIONS

FSMC: Motor and Cognitive Functions; MS: Multiple Sclerosis; SDMT: Symbol Digit Modalities Test; MRI: Magnetic Resonance Imaging; RRMS: Relapsing-Remitting Disease Course; EDSS: Kurtzke Expanded Disability Status Scale; FLAIR: Fluid Attenuated Inversion Recovery; NAWM: Normal-Appearing White Matter; CGM: Cortical Grey Matter; CTh: Cortical Thickness; ROIs: Regions of Interest; Raven: Raven Progressive Matrices; TM A: Trail Making A; TM B: Trail Making B; Rey: Rey Complex Figure; Similarities: WAIS III Similarities; Stroop: Stroop Colour Naming Test; BDI: Becks Depression Inventory II.

Fatigue at enrollment predicts EDSS worsening in the New York State Multiple Sclerosis Consortium

Background:

Fatigue is one of the most common and distressing symptoms among persons with multiple sclerosis (pwMS).

Objective:

The aim of this study is to evaluate fatigue as a predictor for disease worsening among pwMS.

Methods:

In this retrospective cohort study of New York State MS Consortium (NYSMSC) registry, MS patients reporting moderate-to-severe fatigue at study enrollment ( n = 2714) were frequency matched to less-fatigued subjects ( n = 2714) on age, baseline Kurtzke Expanded Disability Status Scale (EDSS), disease duration, and MS phenotype. Change from baseline patient-reported outcomes (PROs), as measured by LIFEware™, categorized participants into two groups: those with stable/improved outcomes and those who worsened. In a subgroup of patients with longitudinal data ( n = 1951), sustained EDSS worsening was analyzed using Cox proportional hazards modeling to explore the effect of fatigue.

Results:

The median survival time from study enrollment to sustained EDSS worsening was 8.7 years (CI: 7.2–10.1). Participants who reported fatigue at baseline were more likely to experience sustained EDSS worsening during follow-up (HR: 1.4, 95% CI: 1.2–1.7). Patients who were fatigued at baseline were also more likely to report worsening psychosocial limitations (all ps ⩽ 0.01).

Conclusion:

In addition to being a common symptom of MS, severe fatigue was a significant predictor for EDSS worsening in the NYSMSC.

The neural basis of fatigue in multiple sclerosis: A multimodal MRI approach

Background

Fatigue is a frequent disabling symptom in multiple sclerosis (MS), but its pathophysiology remains incompletely understood. This study aimed to explore the underlying neural basis of fatigue in patients with MS.

Methods

We enrolled 60 consecutive patients with MS and 60 healthy controls (HC) matched on age, sex, and education. Fatigue was assessed using the Portuguese version of the Modified Fatigue Impact Scale (MFIS). All participants underwent 3T brain MRI (conventional and diffusion tensor imaging [DTI] sequences). White matter (WM) focal lesions were identified and T1/T2 lesion volumes were computed. Tract-based spatial statistics were applied for voxel-wise analysis of DTI metrics fractional anisotropy and mean diffusivity (MD) on normal-appearing WM (NAWM). Using Freesurfer software, total and regional volumes of cortical and subcortical gray matter (GM) were calculated.

Results

Compared to HC, patients with MS scored significantly higher on MFIS (33.8 ± 19.7 vs 16.5 ± 15.1, p < 0.001). MFIS scores were not significantly correlated with T1/T2 lesion volumes, total GM volume, or any regional volume of cortical and subcortical GM. Significant correlations were found between global scores of MFIS and MD increase of the NAWM skeleton, including corona radiata, internal capsule, external capsule, corticospinal tract, cingulum, corpus callosum, fornix, superior longitudinal fasciculus, superior fronto-occipital fasciculus, sagittal stratum, posterior thalamic radiation, cerebral peduncle, and uncinate fasciculus.

Conclusions

In this study, fatigue was associated with widespread NAWM damage but not with lesion load or GM atrophy. Functional disconnection, caused by diffuse microstructural WM damage, might be the main neural basis of fatigue in MS.

Neural correlates of effort-dependent and effort-independent cognitive fatigue components in patients with multiple sclerosis

Background:

Among patients with multiple sclerosis (MS), fatigue is the most commonly reported symptom. It can be subdivided into an effort-dependent (fatigability) and an effort-independent component (trait-fatigue).

Objective:

The objective was to disentangle activity changes associated with effort-independent “trait-fatigue” from those associated with effort-dependent fatigability in MS patients.

Methods:

This study employed behavioral measures and functional magnetic imaging to investigate neural changes in MS patients associated with fatigue. A total of 40 MS patients and 22 age-matched healthy controls performed in a fatigue-inducing N-back task. Effort-independent fatigue was assessed using the Fatigue Scale of Motor and Cognition (FSMC) questionnaire.

Results:

Effort-independent fatigue was observed to be reflected by activity increases in fronto-striatal-subcortical networks primarily involved in the maintenance of homeostatic processes and in motor and cognitive control. Effort-dependent fatigue (fatigability) leads to activity decreases in attention-related cortical and subcortical networks.

Conclusion:

These results indicate that effort-independent (fatigue) and effort-dependent fatigue (fatigability) in MS patients have functionally related but fundamentally different neural correlates. Fatigue in MS as a general phenomenon is reflected by complex interactions of activity increases in control networks (effort-independent component) and activity reductions in executive networks (effort-dependent component) of brain areas.

No structural cerebral MRI changes related to fatigue in patients with primary Sjögren's syndrome

Objective

Whether or not chronic fatigue is reflected in structural changes in the brain is a matter of debate. Primary SS (pSS) is characterized by dryness of the mouth and eyes, migrating muscle and joint pain and prominent fatigue. We aimed to investigate whether the severity of fatigue in pSS was associated with cerebral MRI findings.

Methods

Fatigue was measured with the fatigue visual analog scale in 65 patients with pSS. Global grey matter (GM) and white matter volumes were estimated from magnetic resonance T1 images, and associations between fatigue and brain volumes were assessed in regression models. Voxel-based morphometric analyses of GM were performed to investigate possible associations between fatigue and GM volume changes in particular brain regions.

Results

The fatigue scores in the patient group were spread across a wide range. Global volume analyses showed no significant effect of GM volumes and white matter volumes on fatigue. Voxel-wise analyses of GM did not identify any particular brain region associated with fatigue.

Conclusion

Fatigue is a dominant phenomenon in pSS patients but is not reflected in structural abnormalities in the brain as visualized by conventional MRI. Our findings support the hypothesis of fatigue as a physiological phenomenon that does not lead to vascular changes or neuronal or glial death or damage.

Fatigue in multiple sclerosis: The contribution of resting-state functional connectivity reorganization

OBJECTIVES

To investigate resting-state functional connectivity (RS-FC) of the default-mode network (DMN) and of sensorimotor network (SMN) network in relapsing remitting (RR) multiple sclerosis (MS) patients with fatigue (F) and without fatigue(NF).

METHODS

In all, 59 RRMS patients and 29 healthy controls (HC) underwent magnetic resonance imaging (MRI) protocol including resting-state fMRI (RS-fMRI). Functional connectivity of the DMN and SMN was evaluated by independent component analysis (ICA). A linear regression analysis was performed to explore whether fatigue was mainly driven by changes observed in the DMN or in the SMN. Regional gray matter atrophy was assessed by voxel-based morphometry (VBM).

RESULTS

Compared to HC, F-MS patients showed a stronger RS-FC in the posterior cingulate cortex (PCC) and a reduced RS-FC in the anterior cingulated cortex (ACC) of the DMN. F-MS patients, compared to NF-MS patients, revealed (1) an increased RS-FC in the PCC and a reduced RS-FC in the ACC of the DMN and (2) an increased RS-FC in the primary motor cortex and in the supplementary motor cortex of the SMN. The regression analysis suggested that fatigue is mainly driven by RS-FC changes of the DMN.

CONCLUSIONS

Fatigue in RRMS is mainly associated to a functional rearrangement of non-motor RS networks.

Structural and Neuronal Integrity Measures of Fatigue Severity in Multiple Sclerosis

Fatigue is a common and disabling symptom in Multiple Sclerosis (MS). However, consistent neuroimaging correlates of its severity are not fully elucidated. In this article, we study the neuronal correlates of fatigue severity in MS. Forty-three Relapsing Remitting MS (RRMS) patients with MS-related fatigue (Fatigue Severity Scale (FSS) range: 1–7) and Expanded Disability Status Scale (EDSS) ≤ 4, were divided into high fatigue (HF, FSS ≥ 5.1) and low fatigue groups (LF, FSS ≤ 3). We measured T2 lesion load using a semi-automated technique. Cortical thickness, volume of sub-cortical nuclei, and brainstem structures were measured using Freesurfer. Cortical Diffusion Tensor Imaging (DTI) parameters were extracted using a cross modality technique. A correlation analysis was performed between FSS, volumetric, and DTI indices across all patients. HF patients showed significantly lower volume of thalamus, (p = 0.02), pallidum (p = 0.01), and superior cerebellar peduncle ((SCP), p = 0.002). The inverse correlation between the FSS score and the above volumes was significant in the total study population. In the right temporal cortex (RTC), the Radial Diffusivity ((RD), p = 0.01) and Fractional Anisotropy ((FA), p = 0.01) was significantly higher and lower, respectively, in the HF group. After Bonferroni correction, thalamic volume, FA-RTC, and RD-RTC remained statistically significant. Multivariate regression analysis identified FA-RTC as the best predictor of fatigue severity. Our data suggest an association between fatigue severity and volumetric changes of thalamus, pallidum, and SCP. Early neuronal injury in the RTC is implicated in the pathogenesis of MS-related fatigue.

Fatigue in multiple sclerosis: Associations with clinical, MRI and CSF parameters

BACKGROUND

Damage of different brain structures has been related to fatigue. Alternatively, functional alterations of central nervous system (CNS) cells by the inflammatory milieu within the CNS may be responsible for the development of fatigue.

AIM

To investigate the effect of structural brain damage and inflammatory cerebrospinal fluid (CSF) changes on fatigue in multiple sclerosis (MS).

METHODS

We determined the association of different clinical, CSF and magnetic resonance imaging (MRI) parameters with prevalence and severity of fatigue, as measured by the Fatigue Scale for Motor and Cognitive Functions in 68 early MS patients (discovery cohort). We validated our findings in two MS cohorts: the MRI validation cohort ( N = 233) for the clinical and MRI parameters, and the CSF validation cohort ( N = 81) for the clinical and CSF parameters.

RESULTS

Fatigue was associated with clinical disability. Fatigue did not correlate with any CSF parameter but correlated negatively with total and cortical grey matter volume. However, when controlling for Expanded Disability Status Scale (EDSS) in a multivariate model, these associations lost significance.

CONCLUSION

Disability and disease duration best explain fatigue severity but none of the tested MRI or CSF parameter was reliably associated with fatigue.

Potential pathophysiological pathways that can explain the positive effects of exercise on fatigue in multiple sclerosis: A scoping review

BACKGROUND

Fatigue is one of the most common and most disabling symptoms of multiple sclerosis (MS). It is a multidimensional and complex symptom with multifaceted origins, involving both central and peripheral fatigue mechanisms. Exercise has proven to be safe for people with MS, with cumulating evidence supporting significant reductions in fatigue. However, the potential pathophysiological pathways that can explain the positive effects of exercise on fatigue in MS remain elusive.

OBJECTIVES

The objectives were, in PwMS (1) to update the knowledge on the pathophysiology underlying primary and secondary fatigue, and (2) to discuss potential pathophysiological pathways that can explain the positive effects of exercise on MS fatigue.

METHODS

A comprehensive literature search of six databases (PubMed, Embase, Cochrane Library, PEDro, CINAHL and SPORTDiscus) was performed. To be included, the study had to 1) enroll participants with definite MS according to defined criteria, 2) assess explicit pathophysiological mechanisms related to MS fatigue, 3) be available in English, Danish or French, and 4) had undergone peer-review.

RESULTS

A total of 234 studies fulfilled the inclusion criteria. Primary MS fatigue mainly originated from a dysfunction of central nervous system neuronal circuits secondary to increased inflammation, reduced glucose metabolism, brain atrophy and diffuse demyelination and axonal lesions. Secondary MS fatigue was linked with sleep disturbances, depression, cognitive impairments, and deconditioning. Cardiovascular, immunologic, neuroendocrine, and neurotrophic changes associated with exercise may alleviate primary MS fatigue while exercise may improve secondary MS fatigue through symptomatic improvement of deconditioning, sleep disorders, and depression.

CONCLUSIONS

>30 primary and secondary pathophysiological fatigue pathways were identified underlining the multidimensionality and complexity of MS fatigue. Though the underlying key cellular and molecular cascades still have to be fully elucidated, exercise holds the potential to alleviate MS fatigue, through both primary and secondary fatigue pathways.

Pathophysiology, assessment and management of multiple sclerosis fatigue: an update

INTRODUCTION

Fatigue is one of the most common symptoms associated with multiple sclerosis, affecting almost 80% of patients with 55% of them reporting it as one of the worst symptoms experienced, often independently of the level of disability. Areas covered: We review the main pathophysiological hypothesis, fatigue assessment scales, and its management. Expert commentary: Fatigue pathophysiology is complex and is often influenced by other secondary but relevant factors (e.g. psychological disturbances, musculoskeletal problems, sleep disorders and medication side effects) which may vary over time. Both peripheral and central mechanisms are implicated. The large heterogeneity of the assessment scales, which were used in the therapeutic trials, is partially responsible for the uncertainty of their results. To date, the best therapeutic approach seems to be from a multidisciplinary management involving exercise, rehabilitation and education in conjunction with medication.

Fatigue and depression in multiple sclerosis: pharmacological and non-pharmacological interventions

Multiple sclerosis (MS) is a neuroinflammatory condition with a prominent progressive neurodegenerative facet that typically affects young- or middle-aged adults. Although physical disabilities have been in the foreground by being easier to assess, there is an increasing interest in mental disabilities and psychiatric co-morbidities, which have a disproportionally high impact on important outcome measures such as quality of life and occupational disability. In particular, cognitive impairment, depression and mental fatigue, which mutually interact with each other, seem to be of importance in this context. In recent decades, major efforts have been invested in developing more effective disease modulatory treatments. This has resulted in novel therapeutic options and awareness of the importance of early intervention. In comparison, good quality and adequately powered studies on symptomatic treatments of fatigue and psychiatric co-morbidities in MS are rare, and awareness of treatment options is much lower. We here review the existing evidence base for symptomatic treatment of fatigue and depression in MS patients. With regard to fatigue, off-label prescription of alertness improving drugs is common, in spite of all but absent evidence of efficacy. In contrast, a number of smaller studies suggest that physical exercise and fatigue management courses may have some clinical benefit. Very few studies have addressed the efficacy of antidepressants and non-pharmaceutical interventions specifically in MS patients. Therefore, treatment guidelines largely rely on data from non-MS populations. In the future, there is a strong motive to direct additional resources to the study of these important aspects of MS.

Evaluation of cognition and fatigue in multiple sclerosis: daily practice and future directions

The so-called hidden symptoms or soft signs of multiple sclerosis comprise cognitive dysfunction, fatigue, depression and anxiety. From a patient's perspective, these symptoms are rated as exerting much more negative impact on quality of life and daily functioning than their physical symptoms. Despite this knowledge, the symptoms remain disregarded by many neurologists in clinical practice. This missing awareness can be attributed to several reasons. First, the underlying pathophysiological mechanisms determining occurrence and severity of the different symptoms are still unclear. Second, there is uncertainty in how to reliably assess them. It is undeniable that assessment can be difficult as the hidden symptoms seldom appear isolated but more often highly interact. Third, if standardized, fast and cost-effective assessment to quantify and monitor the evolution of the hidden symptoms would be feasible, the question still remains how to treat these aspects. The present article will give an overview on symptom background and assessment strategies for clinical practice.

Design, rationale, and baseline characteristics of the randomized double-blind phase II clinical trial of ibudilast in progressive multiple sclerosis

BACKGROUND

Primary and secondary progressive multiple sclerosis (MS), collectively called progressive multiple sclerosis (PMS), is characterized by gradual progression of disability. The current anti-inflammatory treatments for MS have little or no efficacy in PMS in the absence of obvious active inflammation. Optimal biomarkers for phase II PMS trials is unknown. Ibudilast is an inhibitor of macrophage migration inhibitor factor and phosphodiesterases-4 and -10 and exhibits possible neuroprotective properties. The goals of SPRINT-MS study are to evaluate the safety and efficacy of ibudilast in PMS and to directly compare several imaging metrics for utility in PMS trials.

METHODS

SPRINT-MS is a randomized, placebo-controlled, phase II trial of ibudilast in patients with PMS. Eligible subjects were randomized 1:1 to receive either ibudilast (100mg/day) or placebo for 96weeks. Imaging is conducted every 24weeks for whole brain atrophy, magnetization transfer ratio, diffusion tensor imaging, cortical brain atrophy, and retinal nerve fiber layer thickness. Clinical outcomes include neurologic disability and patient reported quality of life. Safety assessments include laboratory testing, electrocardiography, and suicidality screening.

RESULTS

A total of 331 subjects were enrolled, of which 255 were randomized onto active study treatment. Randomized subjects were 53.7% female and mean age 55.7 (SD 7.3) years. The last subject is projected to complete the study in May 2017.

CONCLUSION

SPRINT-MS is designed to evaluate the safety and efficacy of ibudilast as a treatment for PMS while simultaneously validating five different imaging biomarkers as outcome metrics for use in future phase II proof-of-concept PMS trials.

Fatigue in Multiple Sclerosis: Misconceptions and Future Research Directions

Fatigue is one of the most disabling side effects in people with multiple sclerosis. While this fact is well known, there has been a remarkable lack of progress in determining the pathophysiological mechanisms behind fatigue and the establishment of effective treatments. The main barrier has been the lack of a unified definition of fatigue that can be objectively tested with validated experimental models. In this “perspective article” we propose the use of the following model and definition of fatigue: the decrease in physical and/or mental performance that results from changes in central, psychological, and/or peripheral factors. These changes depend on the task being performed, the environmental conditions it is performed in, and the physical and mental capacity of the individual. Our definition and model of fatigue outlines specific causes of fatigue and how it affects task performance. We also outline the strengths and weaknesses of commonly used measures of fatigue and suggest, based on our model and definition, new research strategies, which should include multiple measures. These studies should be mechanistic with validated experimental models to determine changes in central, psychological, and/or peripheral factors that explain fatigue. The proposed new research strategies may lead to the identification of the origins of MS related fatigue and the development of new, more effective treatments.

Dilated perivascular spaces and fatigue: is there a link? Magnetic resonance retrospective 3Tesla study

INTRODUCTION

Fatigue (F) is a common, inexplicable, and disabling symptom in multiple sclerosis (MS) patients. The purpose of this study was to evaluate a possible correlation between fatigue and morpho-volumetric features and site of dilated perivascular spaces (dPS), visible on 3T magnetic resonance (MR) in fatigued multiple sclerosis patients (FMS).

METHODS

We studied 82 relapsing remitting (RR) FMS patients and 43 HC, matched for age, sex, and education. F was assessed by the Fatigue Severity Scale (FSS). To evaluate a possible correlation between degree of F and characteristics of dPS, patients were divided in two groups: more (mFMS) (FSS ≥ 5; n = 30) and less fatigued (lFMS) (FSS ≥ 4; n = 52), compared to a matched healthy control (HC) subject group. The MR study was performed with 3T scanner by SpinEcho T1, Fast-SpinEcho DP-T2, FLAIR, and 3D FSPGR T1 sequences. dPS volumes were measured with Medical Image Processing Analysis and Visualization (MIPAV); Global Cerebral Atrophy (GCA), expressed as Brain Parenchymal Fraction (BPF), was assessed by FSL SIENAX.

RESULTS

The t test showed significantly increased dPS number (p = 0.021) in FMS patients (mFMS p = 0.0024 and lFMS p = 0.033) compared to HC. Pearson correlation revealed a significant correlation between dPS number and FSS (r = 0.208 p = 0.051). Furthermore, the chi-squared test confirms the intragroup (HC, mFMS, lFMS) differences about dPS location (p = 0.01) and size (p = 0.0001).

CONCLUSION

Our study confirms that PS in MS patients presents with different volumetric and site characteristics as compared to HC; moreover, F severity significantly correlates with dPS number, site, and size.

Central fatigue in multiple sclerosis: a review of the literature

CONCEPT

Fatigue is a major concern for patients with multiple sclerosis (MS). A clear definition of MS-related fatigue is a prerequisite for appropriate instruments for fatigue assessment. In turn, accurate assessment of fatigue in MS will enhance exploration of plausible mechanisms underlying this common and distressing symptom. Content/Objectives: To provide an integrative review of the current literature on theoretical models used to study fatigue in MS, instruments used to assess fatigue and other factors that impact fatigue during the various phases of MS.

DATA SOURCES

PUBMED, OVID, Ovid Health Star, Ovid MEDINE, CINAHL, Health and Psychosocial Instruments (HaPI), and PsycINFO. Seventeen articles fit the inclusion criteria and were included in the review.

RESULTS

Definitions of MS-related fatigue are reviewed. Several studies found a link with neurotransmitter dysfunction, circadian rhythm, and the timing of fatigue. Central fatigue in MS is associated with neurotransmitters disruptions as well as circadian rhythm disorders, but the evidence is not strong. Perceptions of fatigue or fatigability may arise as either a primary or secondary manifestation of disease. Based on findings from the literature review, a theoretical model of fatigue in MS is proposed.

CONCLUSION

Future research on MS-related fatigue may consider a longitudinal design with a carefully selected self-report instrument to advance understanding of the underlying pathological mechanisms.

Brain atrophy in multiple sclerosis: therapeutic, cognitive and clinical impact

ABSTRACT Multiple sclerosis (MS) was always considered as a white matter inflammatory disease. Today, there is an important body of evidence that supports the hypothesis that gray matter involvement and the neurodegenerative mechanism are at least partially independent from inflammation. Gray matter atrophy develops faster than white matter atrophy, and predominates in the initial stages of the disease. The neurodegenerative mechanism creates permanent damage and correlates with physical and cognitive disability. In this review we describe the current available evidence regarding brain atrophy and its consequence in MS patients.

Fatigue in Multiple Sclerosis: Assessing Pontine Involvement Using Proton MR Spectroscopic Imaging

Background/Objective

The underlying mechanism of fatigue in multiple sclerosis (MS) remains poorly understood. Our study investigates the involvement of the ascending reticular activating system (ARAS), originating in the pontine brainstem, in MS patients with symptoms of fatigue.

Methods

Female relapsing-remitting MS patients (n = 17) and controls (n = 15) underwent a magnetic resonance spectroscopic imaging protocol at 1.5T. Fatigue was assessed in every subject using the Fatigue Severity Scale (FSS). Using an FSS cut-off of 36, patients were categorized into a low (n = 9, 22 ± 10) or high (n = 10, 52 ± 6) fatigue group. The brain metabolites N-acetylaspartate (NAA) and total creatine (tCr) were measured from sixteen 5x5x10 mm³ spectroscopic imaging voxels in the rostral pons.

Results

MS patients with high fatigue had lower NAA/tCr concentration in the tegmental pons compared to control subjects. By using NAA and Cr values in the cerebellum for comparison, these NAA/tCr changes in the pons were driven by higher tCr concentration, and that these changes were focused in the WM regions.

Discussion/Conclusion

Since there were no changes in NAA concentration, the increase in tCr may be suggestive of gliosis, or an imbalanced equilibrium of the creatine and phosphocreatine ratio in the pons of relapsing-remitting MS patients with fatigue.

Fatigue in multiple sclerosis: The contribution of occult white matter damage

BACKGROUND

A functional cortico-subcortical disconnection has been recognized in fatigued multiple sclerosis (MS) patients. Normal appearing white matter (NAWM) damage might contribute to the abovementioned disconnectivity.

OBJECTIVES

To assess the relationship between fatigue and microstructural NAWM damage in relapsing-remitting (RR) MS.

METHODS

Sixty RRMS patients and 29 healthy controls (HC) underwent a magnetic resonance imaging (MRI) protocol including diffusion tensor imaging (DTI). Patients with a mean Fatigue Severity Scale (FSS) score ⩾ 4 were considered fatigued (fatigued MS (F-MS)). Tract-based spatial statistics were applied for voxel-wise analysis of DTI indices. A correlation analysis was performed between FSS score and DTI indices in the entire MS group.

RESULTS

Thirty MS patients were F-MS. Compared to HC, F-MS patients showed a more extensive NAWM damage than not fatigued MS (NF-MS) patients, with additional damage in the following tracts: frontal and occipital juxtacortical fibers, external capsule, uncinate fasciculus, forceps minor, superior longitudinal fasciculus, cingulum, and pons. No differences were found between F-MS and NF-MS patients. Fatigue severity correlated to DTI abnormalities of corona radiata, cingulum, corpus callosum, forceps minor, superior longitudinal fasciculus, inferior fronto-occipital fasciculus, thalamus and anterior thalamic radiation, cerebral peduncle, and midbrain.

CONCLUSIONS

Fatigue is associated to a widespread microstructural NAWM damage, particularly in associative tracts connected to frontal lobes.