Brain activation patterns and cognitive processing speed in patients with pediatric-onset multiple sclerosis

The Economic and Humanistic Burden of Pediatric-Onset Multiple Sclerosis

Background: Multiple sclerosis (MS) is a chronic inflammatory autoimmune disease of the central nervous system. Pediatric-onset MS (POMS), defined as onset of MS before 18 years of age, is estimated to account for 2% to 5% of the MS population worldwide. Objectives: To conduct a literature review focused on the healthcare resource utilization and cost as well as quality-of-life (QOL) outcomes among patients with POMS. Methods: We conducted a systematic literature review of English-language studies published after September 2010 in MEDLINE and Embase to describe the global economic healthcare resource utilization and costs and humanistic (QOL) burden in patients with POMS. Results: We found 11 studies that reported on healthcare resource utilization, cost, or insurance coverage and 36 studies that reported on QOL outcomes in patients with POMS. Patients with POMS had higher rates of primary care visits (1.41 [1.29-1.54]), hospital visits (10.74 [8.95-12.90]), and admissions (rate ratio, 4.27 [2.92-6.25];OR, 15.2 [12.0-19.1]) compared with healthy controls. Mean per-patient costs in the United States were $5907 across all settings per year of follow-up between 2002 and 2012; mean costs per hospital stay were $38 543 (in 2015 USD) between 2004 and 2013. Three studies reported psychosocial scores between 71.59 and 79.7, and 8 studies reported physical health scores between 74.62 to 82.75 using the Pediatric Quality of Life Measurement Model (PedsQLTM). Twelve studies used the PedsQL™ Multidimensional Fatigue Scale. Mean scores on the self-reported general fatigue scale ranged from 63.15 to 78.5. Quality-of-life scores were lower than those of healthy controls. Discussion: Our review presents a uniquely broad and recent overview of the global economic and humanistic burden of patients with POMS. Additional research on healthcare resource utilization and cost would provide a more robust understanding of the economic burden in this population. Conclusions: Healthcare resource utilization and costs are high in this population, and patients report reduced QOL and significant fatigue compared with healthy children and adolescents.

Fronto-cerebellar connectivity mediating cognitive processing speed

Processing speed is an important construct in understanding cognition. This study was aimed to control task specificity for understanding the neural mechanisms underlying cognitive processing speed. Forty young adult subjects performed attention tasks of two modalities (auditory and visual) and two levels of task rules (compatible and incompatible). Block-design fMRI captured BOLD signals during the tasks. Thirteen regions of interest were defined with reference to publicly available activation maps for processing speed tasks. Cognitive speed was derived from task reaction times, which yielded six sets of connectivity measures. Mixed-effect LASSO regression revealed six significant paths suggestive of a cerebello-frontal network predicting the cognitive speed. Among them, three are long range (two fronto-cerebellar, one cerebello-frontal), and three are short range (fronto-frontal, cerebello-cerebellar, and cerebello-thalamic). The long-range connections are likely to relate to cognitive control, and the short-range connections relate to rule-based stimulus-response processes. The revealed neural network suggests that automaticity, acting on the task rules and interplaying with effortful top-down attentional control, accounts for cognitive speed.

Pediatric Multiple Sclerosis Severity Score in a large US cohort

OBJECTIVE

To characterize disease severity and distribution of disability in pediatric-onset multiple sclerosis (POMS) and to develop an optimized modeling scale for measuring disability, we performed a multicenter retrospective analysis of disability scores in 873 persons with POMS over time and compared this to previously published data in adults with multiple sclerosis (MS).

METHODS

This was a retrospective analysis of prospectively collected data collected from 12 centers of the US Network of Pediatric MS Centers. Patients were stratified by the number of years from first symptoms of MS to Expanded Disability Status Scale (EDSS) assessment and an MS severity score (Pediatric Multiple Sclerosis Severity Score [Ped-MSSS]) was calculated per criteria developed by Roxburgh et al. in 2005.

RESULTS

In total, 873 patients were evaluated. In our cohort, 52%, 19.4%, and 1.5% of all patients at any time point reached an EDSS of 2.0, 3.0, and 6.0. Comparison of our Ped-MSSS scores and previously published adult Multiple Sclerosis Severity Scores (MSSS) showed slower progression of Ped-MSSS with increasing gaps between higher EDSS score and years after diagnosis. Decile scores in our POMS cohort for EDSS of 2.0, 3.0, and 6.0 were 8.00/9.46/9.94, 7.86/9.39/9.91, and 7.32/9.01/9.86 at 2, 5, and 10 years, respectively. Notable predictors of disease progression in both EDSS and Ped-MSSS models were ever having a motor relapse and EDSS at year 1. Symbol Digit Modalities Test (SDMT) scores were inversely correlated with duration of disease activity and cerebral functional score.

CONCLUSIONS

Persons with POMS exhibit lower EDSS scores compared to persons with adult-onset MS. Use of a Ped-MSSS model may provide an alternative to EDSS scoring in clinical assessment of disease severity and disability accrual.

Cognitive processing speed in pediatric-onset multiple sclerosis: Baseline characteristics of impairment and prediction of decline

BACKGROUND

Cognitive impairment occurs in approximately one-third of pediatric-onset multiple sclerosis (POMS) patients. The Symbol Digit Modalities Test (SDMT), a widely used cognitive screen in adults, has yet to be incorporated early into the standard care of POMS.

OBJECTIVE

To screen for cognitive impairment early in the course of POMS and analyze predictive factors.

METHODS

Of the 955 POMS or clinically isolated syndrome (CIS) patients prospectively assessed from March 2014 to July 2018, 500 POMS and 116 CIS patients met inclusion criteria (disease onset before the age of 18, one or more SDMTs, and 8 years or older at the time of testing). Those with relapse were analyzed separately from those who were relapse-free.

RESULTS

At initial assessment, the mean (interquartile range (IQR)) age at symptom onset was 13.5 years (12.0, 15.9) and the mean (±SD) disease duration was 3.0 ± 2.9 years. Impaired processing speed occurred in 23.4% of POMS and in 16.4% of CIS. On serial testing (n = 383, mean follow-up: 1.8 years), 14.1% had clinically meaningful decline predicted by older age of multiple sclerosis (MS) onset and male gender. Disease relapse or steroid use led to transient worsening on the SDMT.

CONCLUSION

Early in the disease, some POMS and CIS patients are at risk for cognitive impairment and subsequent decline.

Computerized neuropsychological assessment devices in multiple sclerosis: A systematic review

Background:

The proliferation of computerized neuropsychological assessment devices (CNADs) for screening and monitoring cognitive impairment is increasing exponentially. Previous reviews of computerized tests for multiple sclerosis (MS) were primarily qualitative and did not rigorously compare CNADs on psychometric properties.

Objective:

We aimed to systematically review the literature on the use of CNADs in MS and identify test batteries and single tests with good evidence for reliability and validity.

Method:

A search of four major online databases was conducted for publications related to computerized testing and MS. Test–retest reliability and validity coefficients and effect sizes were recorded for each CNAD test, along with administration characteristics.

Results:

We identified 11 batteries and 33 individual tests from 120 peer-reviewed articles meeting the inclusion criteria. CNADs with the strongest psychometric support include the CogState Brief Battery, Cognitive Drug Research Battery, NeuroTrax, CNS-Vital Signs, and computer-based administrations of the Symbol Digit Modalities Test.

Conclusion:

We identified several CNADs that are valid to screen for MS-related cognitive impairment, or to supplement full, conventional neuropsychological assessment. The necessity of testing with a technician, and in a controlled clinic/laboratory environment, remains uncertain.

Long-term Cognitive Outcomes in Patients With Pediatric-Onset vs Adult-Onset Multiple Sclerosis

Importance

Cognitive impairment in multiple sclerosis (MS) can lead to reduced quality of life, social functioning, and employment. Few studies have investigated cognitive outcomes among patients with pediatric-onset MS (POMS) over the long term.

Objective

To compare long-term information-processing efficiency between patients with POMS and adult-onset MS (AOMS).

Design, Setting, and Participants

This population-based longitudinal cohort study accessed the Swedish MS Registry (SMSreg), which collates information from all 64 neurology clinics in Sweden. Registered cases with definite MS in the SMSreg with an onset before April 15, 2018, and at least 2 Symbol Digit Modalities Test (SDMT) scores recorded were included. Only persons aged 18 to 55 years and with duration of disease of less than 30 years at the time of SDMT administration were included, to ensure comparable ranges between patients with POMS and AOMS. Of 8247 persons with an SDMT recorded in the SMSreg, 5704 met inclusion criteria, 300 (5.3%) of whom had POMS. Data were collected from April 1, 2006, through April 15, 2018 and analyzed from April through August 2018.

Exposures

Pediatric-onset MS (onset <18 years of age) vs AOMS (onset ≥18 years of age).

Main Outcomes and Measures

Information-processing efficiency measured every 6 or 12 months by the SDMT. Linear mixed-effects models were used to compare all available SDMT scores between patients with POMS and those with AOMS. Persons with cognitive impairment (ever vs never) were identified using regression-based norms and compared between POMS and AOMS groups using logistic regression.

Results

Of the 5704 participants, 4015 were female (70.4%), and 5569 had a relapsing-onset disease course (97.6%). Most participants were exposed to a disease-modifying therapy (DMT) during follow-up (98.8%). Median age at baseline for the POMS group was 25.6 years (interquartile range, 21.0-31.7 years) and for the AOMS group, 38.3 years (interquartile range, 31.4-45.2 years). A total of 46 429 unique SDMT scores were analyzed. After adjustment for sex, age, disease duration, disease course, total number of SDMTs completed, oral or visual SDMT form, and DMT exposure, the SDMT score for patients with POMS was significantly lower than that of patients with AOMS (β coefficient, -3.59 [95% CI, -5.56 to -1.54]). The SDMT score for patients with POMS declined faster than that of patients with AOMS (β coefficient, -0.30 [95% CI, -0.42 tp -0.17]). The odds of cognitive impairment were also significantly elevated in the POMS group (odds ratio, 1.44; 95% CI, 1.06-1.98).

Conclusions and Relevance

In adulthood, patients with POMS demonstrated a more rapid reduction in information-processing efficiency over time and were more likely to experience cognitive impairment than patients with AOMS, independent of age or disease duration. Further investigation is required to understand the mechanisms by which early MS onset influences cognitive outcomes.

Neural mechanisms of perceptual decision-making and their link to neuropsychiatric symptoms in multiple sclerosis

BACKGROUND

Decision-making (DM) capabilities are impaired in multiple sclerosis (MS). A variety of researchers hypothesized that this impairment is associated with reduced quality of life (QoL) and neuropsychiatric symptoms. Studies explicitly testing this hypothesis, however, are rare, provided inconclusive results, or evaluated only a limited selection of DM domains. Consequently, we conducted the first MS study on perceptual DM (e.g. deciding whether a car will fit into a parking lot based on a visual percept) to test this assumption.

METHODS

Specifically, we used an fMRI task that measured brain activity in 30 MS patients and 19 healthy controls (HCs) while the participants repeatedly decided whether objects referenced indirectly via their written object names would fit into a shoebox to investigate neural mechanisms of perceptual DM. The objects varied in size and thus decision difficulty. From these data, we determined voxel-wise brain activity parameters reflecting (i) decision difficulty and (ii) decision speed and related them to behavioral DM performance, QoL, mild to moderate depressive symptoms, and fatigue.

RESULTS

Patients showed reduced DM performance. Activity reflecting decision difficulty in the middle temporal gyrus was negatively related to DM performance across MS patients and HCs; activity reflecting decision speed in MS patients was associated with depressive symptoms and fatigue in areas of the dorsal visual stream.

CONCLUSION

The study shows that the perceptual DM capacity is reduced in MS. Moreover, the link between neural mechanisms of perceptual DM and neuropsychiatric symptoms suggests that an impairment in this domain is clinically relevant.

Cognitive Behavior Classification From Scalp EEG Signals

Electroencephalography (EEG) has become increasingly valuable outside of its traditional use in neurology. EEG is now used for neuropsychiatric diagnosis, neurological evaluation of traumatic brain injury, neurotherapy, gaming, neurofeedback, mindfulness, and cognitive enhancement training. The trend to increase the number of EEG electrodes, the development of novel analytical methods, and the availability of large data sets has created a data analysis challenge to find the "signal of interest" that conveys the most information about ongoing cognitive effort. Accordingly, we compare three common types of neural synchrony measures that are applied to EEG-power analysis, phase locking, and phase-amplitude coupling to assess which analytical measure provides the best separation between EEG signals that were recorded, while healthy subjects performed eight cognitive tasks-Hopkins Verbal Learning Test and its delayed version, Stroop Test, Symbol Digit Modality Test, Controlled Oral Word Association Test, Trail Marking Test, Digit Span Test, and Benton Visual Retention Test. We find that of the three analytical methods, phase-amplitude coupling, specifically theta (4-7 Hz)-high gamma (70-90 Hz) obtained from frontal and parietal EEG electrodes provides both the largest separation between the EEG during cognitive tasks and also the highest classification accuracy between pairs of tasks. We also find that phase-locking analysis provides the most distinct clustering of tasks based on their utilization of long-term memory. Finally, we show that phase-amplitude coupling is the least sensitive to contamination by intense jaw-clenching muscle artifact.

Enhanced Recruitment During Executive Control Processing in Cognitively Preserved Patients With Pediatric-Onset MS

OBJECTIVES

Youth and young adults with pediatric-onset multiple sclerosis (MS) are vulnerable to executive dysfunction; however, some patients do not demonstrate functional deficits despite showing abnormalities on structural magnetic resonance imaging (MRI). Cognitively intact adults with MS have shown enhanced activation patterns relative to healthy controls on working memory tasks. We aim to evaluate whether cognitively preserved pediatric-onset MS patients engage compensatory recruitment strategies to facilitate age-normative performance on a task of working memory.

METHODS

Twenty cognitively preserved patients (mean age=18.7±2.7 years; 15 female) and 20 age- and sex-matched controls (mean age=18.5±2.9 years; 15 female) underwent neuropsychological testing and 3.0 Tesla MRI, including structural and functional acquisitions. Patterns of activation during the Alphaspan task, a working memory paradigm with two levels of executive control demand, were examined via whole-brain and region of interest (ROI) analyses.

RESULTS

Across all participants, lower accuracy and greater activation of regions implicated in working memory were observed during the high demand condition. MS patients demonstrated 0.21 s longer response time than controls. ROI analyses revealed enhanced activation for pediatric-onset MS patients relative to controls in the right middle frontal, left paracingulate, right supramarginal, and left superior parietal gyri during the low executive demand condition, over and above differences in response time. MS patients also demonstrated heightened activation in the right supramarginal gyrus in the high executive demand condition.

CONCLUSIONS

Our findings suggest that pediatric-onset MS patients may engage compensatory recruitment strategies during working memory processing. (JINS, 2019, 25, 432-442).

Prefrontal-Temporal Pathway Mediates the Cross-Modal and Cognitive Reorganization in Sensorineural Hearing Loss With or Without Tinnitus: A Multimodal MRI Study

Objective: Hearing loss, one main risk factor of tinnitus and hyperacusis, is believed to involve significant central functional abnormalities. The recruitment of the auditory cortex in non-auditory sensory and higher-order cognitive processing has been demonstrated in the hearing-deprived brain. The dorsolateral prefrontal cortex (dlPFC), which has dense anatomical connections with the auditory pathway, is known to play a crucial role in multi-sensory integration, auditory regulation, and cognitive processing. This study aimed to verify the role of the dlPFC in the cross-modal reorganization and cognitive participation of the auditory cortex in long-term sensorineural hearing loss (SNHL) by combining functional and structural measurements.

Methods: Thirty five patients with long-term bilateral SNHL and 35 matched healthy controls underwent structural imaging, resting-state functional magnetic resonance imaging (rs-fMRI), diffusion tensor imaging (DTI), and neuropsychological assessments. Ten SNHL patients were with subjective tinnitus.

Results: No differences in gray matter volume, spontaneous neural activity, or diffusion characteristics in the dlPFC were found between the SNHL and control groups. The functional connectivity (FC) between the dlPFC and the auditory cortex and visual areas, such as the cuneus, fusiform, lingual cortex, and calcarine sulcus was increased in patients with SNHL. ANOVA and post hoc tests revealed similar FC alterations in the SNHL patients with and without tinnitus when compared with the normal hearing controls, and SNHL patients with and without tinnitus showed no difference in the dlPFC FC. The FC in the auditory cortex was associated with the symbol digit modality test (SDMT) scores in the SNHL patients, which reflect attentional function, processing speed, and visual working memory. Hearing-related FC with the dlPFC was found in the lingual cortex. A tract-based spatial statistics (TBSS) analysis revealed decreased fractional anisotropy (FA) values, mainly in the temporal inferior fronto-occipital fasciculus (IFOF), which showed remarkable negative correlations with the mean hearing thresholds in SNHL.

Conclusion: Higher functional coupling between the dlPFC and auditory and visual areas, accompanied by decreased FA along the IFOF connecting the frontal cortex and the occipito-temporal area, might mediate cross-modal plasticity via top-down regulation and facilitate the involvement of the auditory cortex in higher-order cognitive processing following long-term SNHL.

Cognitive Functioning in Patients with Pediatric-Onset Multiple Sclerosis, an Updated Review and Future Focus

Pediatric-onset multiple sclerosis (POMS) is relatively rare, but as technology and neuroimaging advance, an increasing number of cases are identified, and our understanding of how multiple sclerosis (MS) impacts the developing brain improves. There are consistent findings in the literature highlighting the impact of MS and other demyelinating diseases on cognitive functioning and cognitive development. We also have a better understanding of how POMS impacts psychosocial functioning and functional outcomes in daily living. This paper hopes to review findings associated with cognitive and psychosocial functioning in patients with POMS, as well as explore more recent advances in the field and how they relate to cognitive and psychosocial outcomes. We also discuss the ongoing need for future studies with a focus on better understanding deficits and disease correlates, but also preventative measures and potential rehabilitation.

Symbol Digit Modalities Test adaptation for Magnetic Resonance Imaging environment: A systematic review and meta-analysis

BACKGROUND

The Symbol Digit Modalities Test (SDMT) is widely used for cognitive evaluation of information processing speed (IPS), required in many cognitive operations. Despite being unspecific for different neurological disorders, it is sensitive to assess impaired performance related to stroke, Parkinson's disease, traumatic brain injury, and multiple sclerosis. However, in addition to evaluate the presence and severity of IPS impairment, it is of interest to determine the localization and integration of brain regions responsible for the functions assessed by the SDMT.

OBJECTIVE

To review the studies that adapted the SDMT to the magnetic resonance environment and obtain the brain areas associated with the performance of the task in healthy subjects with a meta-analysis.

METHODOLOGY

A systematic review was performed using ten studies published between 1990 and 2017, and selected from four databases. All studies included participants of both genders and age between 18 and 50 years, used Functional Magnetic Resonance Imaging (fMRI) and SDMT adaptation and reported brain regions associated with the task. Six of them also reported the region coordinates in a standard space, so they were included in a meta-analysis. Activation Likelihood Estimation algorithm, with significance for p < 0.05 corrected for multiple comparisons, was used to identify areas that are robustly related to the performance of the SDMT.

RESULTS

The areas predominantly reported in the studies of our meta-analysis were regions of the frontoparietal attentional network and occipital cortex, as well as cuneus, precuneus, and cerebellum. Individually all regions that survived the statistical threshold are consistent with what is expected after reviewing prospective studies.

CONCLUSIONS

The present study allowed the identification of brain areas activated during the performance of the SDMT in healthy subjects, and therefore it will help understanding the differences in brain activation by this task in clinical populations. Moreover, it may guide future studies of therapeutic strategies and interventions in those populations.

Neuropsychology of Multiple Sclerosis: Looking Back and Moving Forward

The neuropsychological aspects of multiple sclerosis (MS) have evolved over the past three decades. What was once thought to be a rare occurrence, cognitive dysfunction is now viewed as one of the most disabling symptoms of the disease, with devastating effects on patients' quality of life. This selective review will highlight major innovations and scientific discoveries in the areas of neuropathology, neuroimaging, diagnosis, and treatment that pertain to our understanding of the neuropsychological aspects of MS. Specifically, we focus on the recent discovery that MS produces pathogical lesions of gray matter (GM) that have consequences for cognitive functions. Methods for imaging these GM lesions in MS are discussed along with multimodal imaging studies that integrate structural and functional imaging methods to provide a better understanding of the relationship between cognitive test performance and functional reserve. Innovations in the screening and comprehensive assessment of cognitive disorders are presented along with recent research that examines cognitive dysfunction in pediatric MS. Results of innovative outcome studies in cognitive rehabilitation are discussed. Finally, we highlight trends for potential future innovations over the next decade. (JINS, 2017, 23, 832-842).

MRI substrates of sustained attention system and cognitive impairment in pediatric MS patients

Objective:

To explore the structural and functional integrity of the sustained attention system in patients with pediatric multiple sclerosis (MS) and its effect on cognitive impairment.

Methods:

We enrolled 57 patients with pediatric MS and 14 age- and sex-matched healthy controls (HCs). Patients with >3 abnormal tests at neuropsychological evaluation were classified as cognitively impaired (CI). Sustained attention system activity was studied with fMRI during the Conners Continuous Performance Test (CCPT). Structural integrity of attention network connections was quantified with diffusion tensor (DT) MRI.

Results:

Within-group analysis showed similar patterns of recruitment of the attention network in HCs and patients with pediatric MS. Diffuse network DT MRI structural abnormalities were found in patients with MS. During CCPT, with increasing task demand, patients with pediatric MS showed increased activation of the left thalamus, anterior insula, and anterior cingulate cortex (ACC) and decreased recruitment of the right precuneus compared to HCs. Thirteen patients (23%) were classified as CI. Compared to cognitively preserved patients, CI patients with pediatric MS had decreased recruitment of several areas located mainly in parietal and occipital lobes and cerebellum and increased deactivation of the ACC, combined with more severe structural damage of white matter tracts connecting these regions.

Conclusions:

Our results suggest that the age-expected level of sustained attention system functional competence is achieved in patients with pediatric MS. Inefficient regulation of the functional interaction between different areas of this system, due to abnormal white matter integrity, may result in global cognitive impairment in these patients.

7T MRI Visualization of Cortical Lesions in Adolescents and Young Adults with Pediatric-Onset Multiple Sclerosis

BACKGROUND

Cortical pathology in multiple sclerosis (MS) has been associated with prolonged and progressive disease. 7T magnetic resonance imaging (MRI) provides enhanced visualization of cortical lesions (CLs). Hence, we conducted a pilot study to explore whether CLs occur early in MS, as evidenced by pediatric-onset patients.

METHODS

A total of 8 pediatric-onset MS patients were imaged using 7T MRI. CLs were annotated on T1-weighted magnetization-prepared rapid acquisition of gradient echoes images as leukocortical (LC), intracortical, or subpial. Total CLs, age at onset, age at scan, disease duration, total relapses, and Expanded Disability Status Scale (EDSS) score were recorded.

RESULTS

A median of 120 (range: 48-144) CLs was identified in 8 MS patients (3 female, all with relapsing remitting MS, mean age at scan 21 years ± 3.5 SD, mean age of disease onset 15 years ± 2.3 SD, mean disease duration 5.3 years ± 3.4 SD, median EDSS 2.0). Nearly all the lesions identified were LC.

CONCLUSIONS

Many CLs are detectable using 7T MRI in patients with pediatric-onset MS despite relatively brief disease duration, absence of progressive disease, and very limited physical disability-supporting early cortical involvement in MS.

The influence of posterior visual pathway damage on visual information processing speed in multiple sclerosis

Background:

The injury of visual pathway and abnormalities of visual processing speed (VPS) are frequent in MS, but their association remains unexplored.

Objective:

To evaluate the impact of posterior visual pathway structural and functional integrity on VPS of MS patients.

Methods:

Cross-sectional study of 30 MS patients and 28 controls, evaluating the association of a VPS tests composite (Salthouse Perceptual Comparison test, Trail Making Test A and Symbol Digit Modalities Test) with 3T MRI visual cortex thickness, optic radiations (OR) diffusion tensor imaging indexes, and medial visual component (MVC) functional connectivity (FC) (MVC-MVC FC (iFC) and MVC-brain FC (eFC)) by linear regression, removing the effect of premorbid IQ, fatigue, and depression.

Results:

V2 atrophy, lower OR fractional anisotropy (FA) and MVC FC significantly influenced VPS in MS (at none or lesser extent in controls), even after removing the effect of Expanded Disability Status Scale and previous optic neuritis (V2 ( r2 = 0.210): β = +0.366, p = 0.046; OR FA ( r2 = 0.243): β = +0.378, p = 0.034; MVC iFC, for example, left cuneus ( r2 = 0.450): β = −0.613, p < 0.001; MVC eFC, for example, right precuneus-postcentral gyrus ( r2 = 0.368): β = −0.466, p = 0.002).

Conclusion:

Posterior visual pathway integrity, structural (V2 thickness and OR FA) and functional (MVC FC), may explain respectively up to 24% and 45% of VPS variability in MS.