Cognitive impairment in multiple sclerosis

Neural substrates of alerting dysfunction in females with Multiple Sclerosis

MS is a disease characterised by demyelination of the central nervous system resulting in decreased quality of life, increased anxiety, depression, fatigue, and cognitive dysfunction. Attention is frequently impaired in MS. A previous study demonstrated impairment specifically in the attentional alerting domain. However, this study did not establish whether the impairment was in intrinsic or extrinsic alertness, and did not examine the neural substrates associated with the impairment. To examine the alerting deficit in MS and establish the associated neural substrates, 40 female patients with MS and 40 age and gender match controls completed an alertness-motor paradigm designed to test both intrinsic and extrinsic alertness during functional magnetic resonance imaging. We found the MS group had a significant deficit in extrinsic alertness, which was associated with a lack of dorsal prefrontal cortex (DPFC) activation. In addition, reduced gray matter volume in the dorsal prefrontal cortex, thalamus, and basal ganglia were observed. Both fMRI and VBM correlations were observed between fatigue severity scale (FSS) scores and the DPFC. The combined results of our functional and structural MRI data analysis demonstrate that attention deficits in females with MS are a result of the complex relationship between brain tissue loss having a significant impact on functional brain regions subserving executive control of cognitive functions. Understanding the underlying mechanisms of cognitive performance and how they relate to fatigue are crucial to developing novel treatments for the symptoms of MS.

Age and asymmetry of corticospinal excitability, but not cardiorespiratory fitness, predict cognitive impairments in multiple sclerosis

Background

Cognitive impairment is a disabling and underestimated consequence of multiple sclerosis (MS), with multiple determinants that are poorly understood.

Objectives

We explored predictors of MS-related processing speed impairment (PSI) and age-related mild cognitive impairment (MCI) and hypothesized that cardiorespiratory fitness and corticospinal excitability would predict these impairments.

Methods

We screened 73 adults with MS (53 females; median [range]: Age 48 [21-70] years, EDSS 2.0 [0.0-6.5]) for PSI and MCI using the Symbol Digit Modalities Test and Montréal Cognitive Assessment, respectively. We identified six persons with PSI (No PSI, n = 67) and 13 with MCI (No MCI, n = 60). We obtained clinical data from medical records and self-reports; used transcranial magnetic stimulation to test corticospinal excitability; and assessed cardiorespiratory fitness using a graded maximal exercise test. We used receiver operator characteristic (ROC) curves to discern predictors of PSI and MCI.

Results

Interhemispheric asymmetry of corticospinal excitability was specific for PSI, while age was both sensitive and specific for MCI. MS-related PSI was also associated with statin prescriptions, while age-related MCI was related to progressive MS and GABA agonist prescriptions. Cardiorespiratory fitness was associated with neither PSI nor MCI.

Discussion

Corticospinal excitability is a potential marker of neurodegeneration in MS-related PSI, independent of age-related effects on global cognitive function. Age is a key predictor of mild global cognitive impairment. Cardiorespiratory fitness did not predict cognitive impairments in this clinic-based sample of persons with MS.

The Usefulness of Optical Coherence Tomography in Disease Progression Monitoring in Younger Patients with Relapsing-Remitting Multiple Sclerosis: A Single-Centre Study

The purpose of the study was to assess the usefulness of optical coherence tomography (OCT) in the detection of the neurodegenerative process in younger patients with multiple sclerosis (MS). The study group consisted of 61 patients with a relapsing remitting course of MS (mean age 36.4 ± 6.7 years) divided into two groups: short (≤5 years) and long (>10 years) disease duration. OCT, P300 evoked potential, Montreal Cognitive Assessment, and performance subtests (Picture Completion and Digit Symbol) of the Wechsler Adult Intelligence Scale were performed in all patients. Mean values of most parameters assessed in OCT (pRNFL Total, pRNFL Inferior, pRNFL Superior, pRNFL Temporalis, mRNFL, GCIPL, mRNFL+GCIPL) were significantly lower in MS patients in comparison to controls. And in patients with longer disease duration in comparison to those with shorter. Most OCT parameters negatively correlated with the EDSS score (p < 0.05). No significant correlation was found between OCT results and both P300 latency and the results of psychometric tests. OCT, as a simple, non-invasive, quick, and inexpensive method, could be useful for monitoring the progression of disease in MS patients.

Development of a behavioural intervention for cognitive fatigability in multiple sclerosis: Protocol for a pilot and feasibility study

Background

Up to 90% of people with multiple sclerosis (PwMS) subjectively report fatigue as one of their worst symptoms. Fatigability is an objectively measured component of fatigue. Cognitive fatigability (CF) is a breakdown in task performance following sustained cognitive effort. There is a paucity of interventions targeting CF in MS. The prior success of behavioural interventions at improving subjective fatigue suggests that their adaptation may yield similar results for CF. Given the relationship between CF, sleep quality, and mood, a behavioural intervention targeting these factors, such as cognitive behavioural therapy (CBT), is warranted. Given the multidimensional nature of fatigue, a multifaceted approach targeting lifestyle factors and coping (e.g., fatigue management education supplemented by CBT for insomnia and exercise) might prove efficacious.

Aim

We describe a protocol for a pilot feasibility study to design and implement a multi-dimensional behavioural intervention to improve CF in PwMS.

Methods

Stage 1: development of a multi-dimensional group-based videoconference-delivered behavioural intervention based on a previously successful fatigue management program for PwMS. A facilitator manual will be drafted. Course material will focus on four themes: body (sleep and physical activity), mood (impact of depression and anxiety), mind (cognitive contributions), and context (pacing and communication). Stage 2: a needs assessment survey will be completed by 100 PwMS for input on what factors are important contributors to their CF. Modifications will be made to the course material and manual. Stage 3: the facilitator-delivered intervention will include 20 PwMS. After baseline assessment, participants will attend weekly 70-min videoconference group sessions for 8 weeks, including homework assignments. Follow-up assessment will re-evaluate outcomes. Stage 4: analysis and dissemination of results. The primary outcome is improvement in CF. Additional feasibility outcomes will determine if a randomized control trial (RCT) is pursued. Stage 5: refine the intervention based on outcomes and feedback from participants. Determining which aspects participants felt were most effective will help inform RCT design.

Conclusion

The long-term goal is to ensure that PwMS have access to effective interventions in real-world settings to improve quality of life and enhance their ability to participate in cognitively demanding activities that they enjoy.

The Complex Interplay Between Trait Fatigue and Cognition in Multiple Sclerosis

Cognitive impairments are frequent in patients with Multiple Sclerosis (MS). Yet, the influence of MS-related symptoms on cognitive status is not clear. Studies investigating the impact of trait fatigue along with anxio-depressive symptoms on cognition are seldom, and even less considered fatigue as multidimensional. Moreover, these studies provided conflicting results.

Twenty-nine MS patients and 28 healthy controls, matched on age, gender and education underwent a full comprehensive neuropsychological assessment. Anxio-depressive and fatigue symptoms were assessed using the HAD scale and the MFIS, respectively. Six composite scores were derived from the neuropsychological assessment, reflecting the cognitive domains of working memory, verbal and visual learning, executive functions, attention and processing speed. Stepwise regression analyses were conducted in each group to investigate if trait cognitive and physical fatigue, depression and anxiety are relevant predictors of performance in each cognitive domain. In order to control for disease progression, patient’s EDSS score was also entered as predictor variable.

In the MS group, trait physical fatigue was the only significant predictor of working memory score. Cognitive fatigue was a predictor for executive functioning performance and for processing speed (as well as EDSS score for processing speed). In the healthy controls group, only an association between executive functioning and depression was observed.

Fatigue predicted cognition in MS patients only, beyond anxio-depressive symptoms and disease progression. Considering fatigue as a multidimensional symptom is paramount to better understand its association with cognition, as physical and cognitive fatigue are predictors of different cognitive processes.

Assessing Cognitive Function in Multiple Sclerosis With Digital Tools: Observational Study

BACKGROUND

Cognitive impairment (CI) is one of the most prevalent symptoms of multiple sclerosis (MS). However, it is difficult to include cognitive assessment as part of MS standard care since the comprehensive neuropsychological examinations are usually time-consuming and extensive.

OBJECTIVE

To improve access to CI assessment, we evaluated the feasibility and potential assessment sensitivity of a tablet-based cognitive battery in patients with MS.

METHODS

In total, 53 participants with MS (24 [45%] with CI and 29 [55%] without CI) and 24 non-MS participants were assessed with a tablet-based cognitive battery (Adaptive Cognitive Evaluation [ACE]) and standard cognitive measures, including the Symbol Digit Modalities Test (SDMT) and the Paced Auditory Serial Addition Test (PASAT). Associations between performance in ACE and the SDMT/PASAT were explored, with group comparisons to evaluate whether ACE modules can capture group-level differences.

RESULTS

Correlations between performance in ACE and the SDMT (R=-0.57, P<.001), as well as PASAT (R=-0.39, P=.01), were observed. Compared to non-MS and non-CI MS groups, the CI MS group showed a slower reaction time (CI MS vs non-MS: P<.001; CI MS vs non-CI MS: P=.004) and a higher attention cost (CI MS vs non-MS: P=.02; CI MS vs non-CI MS: P<.001).

CONCLUSIONS

These results provide preliminary evidence that ACE, a tablet-based cognitive assessment battery, provides modules that could potentially serve as a digital cognitive assessment for people with MS.

TRIAL REGISTRATION

ClinicalTrials.gov NCT03569618; https://clinicaltrials.gov/ct2/show/NCT03569618.

Neurocognitive impairment and social cognition in multiple sclerosis

PURPOSE/AIM OF THE STUDY

The impairment of neurocognitive functions occurs in all subtypes of multiple sclerosis, even from the earliest stages of the disease. Commonly reported manifestations of cognitive impairment include deficits in attention, conceptual reasoning, processing efficiency, information processing speed, memory (episodic and working), verbal fluency (language), and executive functions. Multiple sclerosis patients also suffer from social cognition impairment, which affects their social functioning. The objective of the current paper is to assess the effect of neurocognitive impairment and its potential correlation with social cognition performance and impairment in multiple sclerosis patients.

MATERIALS AND METHODS

An overview of the available-to-date literature on neurocognitive impairment and social cognition performance in multiple sclerosis patients by disease subtype was performed.

RESULTS

It is not clear if social cognition impairment occurs independently or secondarily to neurocognitive impairment. There are associations of variable strengths between neurocognitive and social cognition deficits and their neural basis is increasingly investigated.

CONCLUSIONS

The prompt detection of neurocognitive predictors of social cognition impairment that may be applicable to all multiple sclerosis subtypes and intervention are crucial to prevent further neural and social cognition decline in multiple sclerosis patients.

RISCOP-Cognitive profile in a Portuguese cohort of radiological isolated syndrome patients: A case-control study

INTRODUCTION

Radiologically isolated syndrome (RIS) refers to the incidental discovery of white matter lesions suggestive of MS, on brain MRI, in asymptomatic patients. Recent studies suggest similar features of cognitive impairment between RIS and MS patients. Also, lower levels of health-related quality of life (QOL) and fatigue are reported in such patients.

AIMS

characterize and compare the cognitive profile of a multicentric Portuguese cohort of RIS patients with a control group.

METHODS

multicentric comparative study of a cohort of adult patients with RIS, and age and gender-matched controls followed in the headache outpatient clinic with prior MRI not fulfilling criteria for RIS diagnosis. We conducted interviews with participants, collected clinical data and applied the BICAMS battery and self-reported questionnaires (HADS, MFIS, MSQOL-54).

RESULTS

we evaluated 31 patients with RIS (median age 46 years, IQR [(Dusankova et al., 2012-52], 72% women) and 19 control individuals (median age 32 years, IQR [(O'Jile et al., 2005-48], 71% women). Prevalence of cognitive impairment did not differ between groups (16% of the RIS and 10% of the controls, p=0.579). We found no differences between groups on the BICAMS tests, although the results of the California Verbal Learning Test (CVLT-II) score presented a trend to significance, with a lower value on the RIS group (53.9 vs. 59.3, p=0.066). There were no significant differences regarding fatigue, QOL, anxiety/depression scores.

CONCLUSION

this is the first study on a Portuguese cohort of RIS patients assessing cognitive profile with BICAMS. A non-neglectable part of our cohort presented cognitive impairment. Our findings add to previous studies in suggesting that a more pronounced impairment of verbal memory and learning, evaluated by CVLT-II, may be present in RIS patients compared to controls. BICAMS should be assessed on future studies with larger cohorts.

Association between TNFA, IL10 and IL18 promoter gene variants and cognitive functions in patients with relapsing-remitting multiple sclerosis

OBJECTIVES

To investigate the relationship between TNFA-308G > A, IL10-1082A > G, IL18-607C > A, and cognitive functioning in relapsing-remitting multiple sclerosis (RRMS).

RESULTS

In the patients' group: AG genotype of TNFA-308G > A was associated with higher serum tumor necrosis factor-alpha (TNF-alpha) than GG genotype, and higher TNF-alpha levels correlated with poorer results on Symbol Digit Modalities Test; CC genotype of IL18-607C > A was related to lower score on Isaacs test, compared to AC variant; AA genotype of IL10-1082A > G was associated with abnormally low results on Paced Auditory Series Addition Test.

CONCLUSIONS

TNFA-308G > A, IL10-1082A > G and IL18-607C > A gene variants may be associated with impaired cognitive functions in RRMS patients.

Resting-state connectivity stratifies premanifest Huntington's disease by longitudinal cognitive decline rate

Patient stratification is critical for the sensitivity of clinical trials at early stages of neurodegenerative disorders. In Huntington’s disease (HD), genetic tests make cognitive, motor and brain imaging measurements possible before symptom manifestation (pre-HD). We evaluated pre-HD stratification models based on single visit resting-state functional MRI (rs-fMRI) data that assess observed longitudinal motor and cognitive change rates from the multisite Track-On HD cohort (74 pre-HD, 79 control participants). We computed longitudinal performance change on 10 tasks (including visits from the preceding TRACK-HD study when available), as well as functional connectivity density (FCD) maps in single rs-fMRI visits, which showed high test-retest reliability. We assigned pre-HD subjects to subgroups of fast, intermediate, and slow change along single tasks or combinations of them, correcting for expectations based on aging; and trained FCD-based classifiers to distinguish fast- from slow-progressing individuals. For robustness, models were validated across imaging sites. Stratification models distinguished fast- from slow-changing participants and provided continuous assessments of decline applicable to the whole pre-HD population, relying on previously-neglected white matter functional signals. These results suggest novel correlates of early deterioration and a robust stratification strategy where a single MRI measurement provides an estimate of multiple ongoing longitudinal changes.

Cognitive Fatigability Interventions in Neurological Conditions: A Systematic Review

INTRODUCTION

Although fatigue is a well-studied concept in neurological disease, cognitive fatigability (CF) is less understood. While most studies measure fatigue using subjective self-report, fewer have measured CF objectively. Given the negative impact of CF on quality-of-life, there is a need for targeted interventions. The objective of this review was to determine which procedural, behavioural and pharmacological treatments for objectively measured CF are available to people living with neurological conditions.

METHODS

In accordance with the PRISMA guidelines, systematic searches for randomized control trials (RCTs), case-controlled studies and case reports/series were conducted across the Ovid Medline, PsycInfo, EMBASE and Cochrane Library databases. English-language articles published between 1980 and February 2019 were considered for eligibility. Included were those that objectively measured CF in individuals with neurological disease/disorder/dysfunction between the ages of 18 and 65 years. Studies were reviewed using a modified Cochrane Data Extraction Template. Risk of bias was assessed using the Cochrane Risk of Bias tool. The review process was facilitated using Covidence software (www.covidence.org). Two authors reviewed articles independently, with a third resolving conflicts regarding article inclusion.

RESULTS

The search identified 450 records. After duplicates were removed and remaining titles/abstracts were screened for eligibility, 28 full-text articles were assessed, and two studies were included in the qualitative synthesis. Studies were a priori divided into those with pharmacological, procedural or behavioural interventions. Two studies met eligibility criteria; both of these included participants with multiple sclerosis. One study utilized a procedural intervention (i.e. transcranial direct current stimulation), while the other utilized a pharmacological intervention (i.e. fampridine-SR). Studies were evaluated for risk of bias, and evidence from both eligible studies was discussed.

CONCLUSION

Despite the positive results of the procedural intervention, the paucity of eligible studies and the nascent nature of the field suggests that more studies are required before firm conclusions can be drawn regarding the amenability of CF to treatment.

TRIAL REGISTRATION

The review was registered with PROSPERO (CRD42019118706).

Neurophysiological Assessment of Cognitive Dysfunction in Patients with Multiple Sclerosis

Cognitive impairment occurs in a high percentage in all forms of multiple sclerosis, regardless of physical disability. Slowing the speed of information processing is one of the most difficult and the most frequently mentioned, but impairment of memory, attention, executive functions are included also. Long latency event related potentials (ERP) are much more objective means of cognitive functioning evaluation. Different types of immunomodulatory therapies which are used for relapsing- remitting forms of multiple sclerosis may affect the results of ERP. ERP can evaluate subclinical changes and provide important information on the evolution of cognitive changes in patients with MS.

Machine Learning EEG to Predict Cognitive Functioning and Processing Speed Over a 2-Year Period in Multiple Sclerosis Patients and Controls

Event-related potentials (ERPs) show promise to be objective indicators of cognitive functioning. The aim of the study was to examine if ERPs recorded during an oddball task would predict cognitive functioning and information processing speed in Multiple Sclerosis (MS) patients and controls at the individual level. Seventy-eight participants (35 MS patients, 43 healthy age-matched controls) completed visual and auditory 2- and 3-stimulus oddball tasks with 128-channel EEG, and a neuropsychological battery, at baseline (month 0) and at Months 13 and 26. ERPs from 0 to 700 ms and across the whole scalp were transformed into 1728 individual spatio-temporal datapoints per participant. A machine learning method that included penalized linear regression used the entire spatio-temporal ERP to predict composite scores of both cognitive functioning and processing speed at baseline (month 0), and months 13 and 26. The results showed ERPs during the visual oddball tasks could predict cognitive functioning and information processing speed at baseline and a year later in a sample of MS patients and healthy controls. In contrast, ERPs during auditory tasks were not predictive of cognitive performance. These objective neurophysiological indicators of cognitive functioning and processing speed, and machine learning methods that can interrogate high-dimensional data, show promise in outcome prediction.

Neuropsychological Assessment in Multiple Sclerosis

Abstract. Neuropsychological deficits in multiple sclerosis (MS) are common. Over the past decades, many different procedures have been employed in diagnosing these deficits. Even though certain aspects of cognitive performance such as information processing speed and working memory may be affected more frequently than other cognitive functions, no specific deficit profile has been established in MS. This article provides an overview of the neuropsychological diagnostic procedures in MS and allows the reader to reach an informed decision on the applicability of specific procedures and the availability of study data in the context of MS. Additionally, it makes recommendations on the compilation of both screening procedures and extensive test batteries.

Cognitive Impairment in Multiple Sclerosis

Multiple sclerosis (MS) is a socially significant immune-mediated disease, characterized by demyelination, axonal transection and oligodendropathy in the central nervous system. Inflammatory demyelination and neurodegeneration lead to brain atrophy and cognitive deficit in up to 75% of the patients. Cognitive dysfunctions impact significantly patients’ quality of life, independently from the course and phase of the disease.

The relationship between pathological brain findings and cognitive impairment is a subject of intensive research.

Summarizing recent data about prevalence, clinical specificity and treatment of cognitive disorders in MS, this review aims to motivate the necessity of early diagnosis and complex therapeutic approach to these disturbances in order to reduce the social burden of the disease.

Structural correlates for fatigue in early relapsing remitting multiple sclerosis

OBJECTIVES

Fatigue is a common symptom in multiple sclerosis (MS) patients, even early in the disease, but the pathophysiology remains unclear. We aimed to determine morphologic and microstructural correlates and neuropsychological parameters of cognitive fatigue in early relapsing-remitting MS patients.

METHODS

Seventy-nine early relapsing-remitting MS patients (38 with fatigue and 41 without), none of whom suffered from depression, underwent neuropsychological testing. Magnetic resonance imaging was performed using anatomical and diffusion tensor imaging sequences on all patients and 40 controls. Voxel-based morphologic analysis and tract-based spatial statistics were performed.

RESULTS

Only patients with cognitive fatigue, but not those without, exhibited alterations in the thalamic region, showing reduced thalamic fractional anisotropy and increased mean diffusivity values. No differences in lesion volume and lesion distribution were observed between patient groups. In cognitive tests, no significant differences were found between the two groups in the number of patients with pathologic scores; however, subjective cognitive impairment differed.

CONCLUSION

Morphological alterations and distinct microstructural changes (mainly in the thalamus) but not typical MS lesions were found to be related to cognitive fatigue in early MS. We suggest that compensatory processes adapting to these changes could initially facilitate normal cognitive performance, but also result in a feeling of fatigue.

KEY POINTS

• Morphological alterations and microstructural changes are related to fatigue in multiple sclerosis • Thalamic alterations in particular were related to fatigue in early MS • Fatigued patients exhibited subjective but not measurable cognitive impairment • Compensatory processes help preserve or maintain cognitive performance but also contribute to fatigue.

Oligodendrocyte gap junction loss and disconnection from reactive astrocytes in multiple sclerosis gray matter

Gap junctions are essential for glial cell function and have been increasingly implicated in multiple sclerosis (MS). Because increasing cortical abnormalities correlate with disease progression and cognitive dysfunction, we examined the expression of oligodendrocytic connexin32 (Cx32) and Cx47 and their astrocytic partners Cx30 and Cx43 in cortical lesions and normal-appearing gray matter (NAGM) in MS patients. Postmortem brain tissue samples from 9 MS cases were compared with 10 controls using real-time polymerase chain reaction, immunoblot, and immunohistochemical analyses. Connexin32 and Cx47 gap junction formation in oligodendrocytes was reduced within lesions, whereas Cx32 loss also extended to NAGM. In contrast, astrocytic Cx30 expression was increased within cortical lesions, whereas Cx43 was elevated in both lesions and NAGM. Diffuse microglial activation and marked astrogliotic changes accompanied these connexin abnormalities. Increased expression of Cx43 correlated with inflammatory load (r = 0.828, p = 0.042), whereas Cx32 expression correlated with longer disease duration and, therefore, milder course (r = 0.825, p = 0.043). Thus, there is a loss of intramyelin and intercellular oligodendrocyte gap junctions in MS gray matter lesions and NAGM, whereas interastrocytic gap junctions are increased, reflecting astrogliosis. These changes correlate with inflammation and disease duration and suggest that disconnection of oligodendrocytes from reactive astrocytes may play a role in failed remyelination and disease progression.

Functional MRI activation in white matter during the Symbol Digit Modalities Test

Background: Recent evidence shows that functional magnetic resonance imaging (fMRI) can detect activation in white matter (WM). Such advances have important implications for understanding WM dysfunction. A key step in linking neuroimaging advances to the evaluation of clinical disorders is to examine whether WM activation can be detected at the individual level during clinical tests associated with WM function. We used an adapted Symbol Digit Modalities Test (SDMT) in a 4T fMRI study of healthy adults.

Results: Results from 17 healthy individuals revealed WM activation in 88% of participants (15/17). The activation was in either the corpus callosum (anterior and/or posterior) or internal capsule (left and/or right).

Conclusions: The findings link advances in fMRI to an established clinical test of WM function. Future work should focus on evaluating patients with WM dysfunction.

Intra-individual variability in information processing speed reflects white matter microstructure in multiple sclerosis

Slowed information processing speed is commonly reported in persons with multiple sclerosis (MS), and is typically investigated using clinical neuropsychological tests, which provide sensitive indices of mean-level information processing speed. However, recent studies have demonstrated that within-person variability or intra-individual variability (IIV) in information processing speed may be a more sensitive indicator of neurologic status than mean-level performance on clinical tests. We evaluated the neural basis of increased IIV in mildly affected relapsing–remitting MS patients by characterizing the relation between IIV (controlling for mean-level performance) and white matter integrity using diffusion tensor imaging (DTI). Twenty women with relapsing–remitting MS and 20 matched control participants completed the Computerized Test of Information Processing (CTIP), from which both mean response time and IIV were calculated. Other clinical measures of information processing speed were also collected. Relations between IIV on the CTIP and DTI metrics of white matter microstructure were evaluated using tract-based spatial statistics. We observed slower and more variable responses on the CTIP in MS patients relative to controls. Significant relations between white matter microstructure and IIV were observed for MS patients. Increased IIV was associated with reduced integrity in more white matter tracts than was slowed information processing speed as measured by either mean CTIP response time or other neuropsychological test scores. Thus, despite the common use of mean-level performance as an index of cognitive dysfunction in MS, IIV may be more sensitive to the overall burden of white matter disease at the microstructural level. Furthermore, our study highlights the potential value of considering within-person fluctuations, in addition to mean-level performance, for uncovering brain–behavior relationships in neurologic disorders with widespread white matter pathology.

•

Intra-individual variability (IIV) predicts neurologic status in multiple sclerosis (MS).

•

Diffusion tensor imaging (DTI) was used to study the neural correlates of IIV in MS.

•

IIV was significantly related to DTI metrics in many white matter regions.

•

Compared to mean response speed, IIV may be more sensitive to disease burden in MS.

•

Evaluating IIV may be important for characterizing brain–behavior relationships.

Cognitive change and neuroimaging following immunoablative therapy and hematopoietic stem cell transplantation in multiple sclerosis: A pilot study

BACKGROUND

Individuals with MS undergoing immunoablative therapy and hematopoietic stem cell transplantation (HSCT) show substantial decrease in brain volume over 2.4 months, presumably from chemotoxic effects, although other mechanisms have also been postulated.

OBJECTIVE

We examined whether volume loss was accompanied by a concomitant decrease in cognition. White and gray matter volumes, and the effect of stem cell dosage were considered.

METHODS

Seven individuals with rapidly progressing MS and poor prognosis underwent high dose immunosuppression and autologous HSCT. Neuropsychological testing and MRI scans were performed at baseline, 2 and 24 months post-procedure.

RESULTS

Cognitive impairment was noted at all times in most participants. Median decline of 1.39% in total brain volume was noted 2 months post-HSCT. By 24 months a further decline of 1.65% was noted. At 2 months significant decline was observed for areas of executive functioning. At 24 months almost no significant declines were noted. No significant correlations were found between cognitive decline and change in imaging variables or stem cell dosage.

CONCLUSIONS

Cognition changed in the early period following treatment but with little apparent relationship to volume changes. With temporal distance from the HSCT procedure, cognition returned to baseline levels. With the caution of a very small sample, preliminary results suggest that immunoablation and HSCT may have no lasting deleterious effects on cognition.

Impaired information-processing speed and working memory in leukoencephalopathy with brainstem and spinal cord involvement and elevated lactate (LBSL) and DARS2 mutations: a report of three adult patients

Leukoencephalopathy with brainstem and spinal cord involvement and elevated lactate (LBSL) is clinically characterized by progressive pyramidal and cerebellar dysfunction, dorsal column dysfunction and sometimes with axonal neuropathy. Magnetic resonance imaging of brain and the spinal cord reveals characteristic findings. LBSL is caused by mutations in the DARS2 gene that encodes the mitochondrial aspartyl-tRNA synthetase. The presentation and clinical course of LBSL is not uniform, and there is lack of longitudinal data on these patients. In addition, the existing data on the prevalence and characteristics of cognitive abnormalities in patients with LBSL are scarce and somewhat conflicting. Here we report long-term data of neurological and cognitive functioning in three non-related adult patients with LBSL. Cognitive impairment seems to be common among patients with LBSL and DARS2 mutations. The cognitive profile in LBSL shares similarities with that reported in multiple sclerosis, as information-processing speed and working memory are especially affected. In addition, our results and the previously reported carrier frequencies of common pathogenic DARS2 mutations suggest that LBSL may be underdiagnosed in the population.

A behavioral neuroenergetics theory of ADHD

Energetic insufficiency in neurons due to inadequate lactate supply is implicated in several neuropathologies, including attention-deficit/hyperactivity disorder (ADHD). By formalizing the mechanism and implications of such constraints on function, the behavioral Neuroenergetics Theory (NeT) predicts the results of many neuropsychological tasks involving individuals with ADHD and kindred dysfunctions, and entails many novel predictions. The associated diffusion model predicts that response times will follow a mixture of Wald distributions from the attentive state, and ex-Wald distributions after attentional lapses. It is inferred from the model that ADHD participants can bring only 75-85% of the neurocognitive energy to bear on tasks, and allocate only about 85% of the cognitive resources of comparison groups. Parameters derived from the model in specific tasks predict performance in other tasks, and in clinical conditions often associated with ADHD. The primary action of therapeutic stimulants is to increase norepinephrine in active regions of the brain. This activates glial adrenoceptors, increasing the release of lactate from astrocytes to fuel depleted neurons. The theory is aligned with other approaches and integrated with more general theories of ADHD. Therapeutic implications are explored.

Robust perfusion deficits in cognitively impaired patients with secondary-progressive multiple sclerosis

BACKGROUND AND PURPOSE

Cognitive impairment is a common, disabling symptom of MS. We investigated the impact of cerebral perfusion and brain and lesion volumetry on cognitive performance in 45 patients with SPMS by using MR imaging.

MATERIALS AND METHODS

Cognition was assessed by using a standard battery, the Minimal Assessment of Cognitive Function in Multiple Sclerosis. qCBF and qCBV maps were analyzed by using SPM and PLS. SPM was also used to conduct the GM, WM, and WML volumetric analyses.

RESULTS

Both SPM and PLS demonstrated significantly reduced qCBV in the superior medial frontal cortex of impaired patients. PLS also revealed significantly lower qCBV in the bilateral thalami and caudate nuclei of impaired patients and identified a pattern of significantly attenuated qCBF similar to that of qCBV. Performance on the Symbol Digit Modalities Test, which assesses information-processing speed, correlated most strongly overall with cerebral perfusion. Focal (ie, voxelwise) analyses of GM, WM, and WML volume revealed no significant differences between patients with and without cognitive impairment, though global GM volume was significantly decreased and global WML volume was significantly increased in impaired patients.

CONCLUSIONS

These results suggest that cognitively impaired patients with SPMS exhibit robust perfusion deficits in cortical and subcortical GM and impaired processing speed.

Only low frequency event-related EEG activity is compromised in multiple sclerosis: insights from an independent component clustering analysis

Cognitive impairment (CI), often examined with neuropsychological tests such as the Paced Auditory Serial Addition Test (PASAT), affects approximately 65% of multiple sclerosis (MS) patients. The P3b event-related potential (ERP), evoked when an infrequent target stimulus is presented, indexes cognitive function and is typically compared across subjects' scalp electroencephalography (EEG) data. However, the clustering of independent components (ICs) is superior to scalp-based EEG methods because it can accommodate the spatiotemporal overlap inherent in scalp EEG data. Event-related spectral perturbations (ERSPs; event-related mean power spectral changes) and inter-trial coherence (ITCs; event-related consistency of spectral phase) reveal a more comprehensive overview of EEG activity. Ninety-five subjects (56 MS patients, 39 controls) completed visual and auditory two-stimulus P3b event-related potential tasks and the PASAT. MS patients were also divided into CI and non-CI groups (n = 18 in each) based on PASAT scores. Data were recorded from 128-scalp EEG channels and 4 IC clusters in the visual, and 5 IC clusters in the auditory, modality were identified. In general, MS patients had significantly reduced ERSP theta power versus controls, and a similar pattern was observed for CI vs. non-CI MS patients. The ITC measures were also significantly different in the theta band for some clusters. The finding that MS patients had reduced P3b task-related theta power in both modalities is a reflection of compromised connectivity, likely due to demyelination, that may have disrupted early processes essential to P3b generation, such as orientating and signal detection. However, for posterior sources, MS patients had a greater decrease in alpha power, normally associated with enhanced cognitive function, which may reflect a compensatory mechanism in response to the compromised early cognitive processing.

Decreased frontal lobe gray matter perfusion in cognitively impaired patients with secondary-progressive multiple sclerosis detected by the bookend technique

BACKGROUND AND PURPOSE

There is increasing evidence implicating microvascular impairment in MS pathogenesis. Perfusion imaging offers a unique opportunity to investigate the functional impact of GM pathology. We sought to quantify differences in MR imaging-based bookend-derived cerebral perfusion between cognitively impaired and nonimpaired patients with SPMS.

MATERIALS AND METHODS

Patients were prospectively recruited and assessed using MR imaging and the standard cognitive battery called the Minimal Assessment of Cognitive Function in MS. Patients exhibiting impairment on ≥ 2 individual tests were classified as cognitively impaired. Healthy controls were prospectively recruited and assessed using MR imaging to validate bookend assumptions. Structural and perfusion scans were coregistered and partitioned into anatomic brain regions and tissue compartments. Clinical and radiologic characteristics were compared between patients with and without impairment to identify potential confounders. A Bonferroni adjusted P value threshold (P < .005) was used for lobar and sublobar level analyses to correct for multiple comparisons.

RESULTS

Thirty-seven patients with SPMS (age 56 ± 9 years; 23 women, 14 men) and 10 age- and sex-matched healthy controls were recruited. Bookend assumptions were found to be valid in MS. GM and WM qCBV were all globally reduced in impaired patients. After adjusting for potential confounders while examining sublobar level perfusion, only GM qCBV was significantly different between cognitive groups, and this hypoperfusion localized to the bilateral medial superior frontal regions and left inferior, middle, and superior frontal regions (P < .005) of impaired patients compared with nonimpaired patients. GM qCBV accounted for 22.5% of the model variance compared with a model including only confounders (P = .0007).

CONCLUSIONS

Bookend-derived GM qCBV was significantly reduced in cognitively impaired patients with SPMS in functionally relevant brain regions.

[Neuroprotection in the treatment of multiple sclerosis]

Atrophy, the wasting or shrinkage of tissue, of the nervous system is the main feature of neurodegeneration, i.e. the umbrella term for the progressive loss of structure or function of neurons. Loss of neurons due to cell death and axonal degeneration characterize neurodegenerative diseases such as Alzheimer's disease, Parkinson's disease or amyotrophic lateral sclerosis. In these illnesses, it still has to be elucidated to which extent inflammation is part of the pathology. Conversely, in chronic inflammation of the central nervous system (CNS), atrophy has previously also been described and neurodegeneration is discussed as a pathologic feature. The most frequent chronic inflammatory disease of the CNS is multiple sclerosis (MS), which leads to devastating relapsing-remitting symptoms and disability during the relapses, increasingly during the course of disease in patients. Meanwhile it became clear that axons already reveal pathology early in the disease and neurons are affected in the cortex and the spinal cord, albeit to a different extent. The broadening of understanding neurodegenerative aspects of MS pathology demands and creates new therapeutic strategies. Current medication used in MS treatment as well as medications about to be approved are primarily anti-inflammatory therapies. By modulating the immune system and thereby blocking key steps of the pathology, the immunomodulation therapies in MS have a slight impact on disability progression. There is, however, clinical and experimental data concerning the potential neuroprotective properties of novel therapies. Combining anti-inflammatory and direct neuroprotective or even neuroregenerative therapy strategies would be a step forward in the treatment of multiple sclerosis.

MRI predictors of cognitive outcome in early multiple sclerosis

OBJECTIVE

To determine MRI predictors for cognitive outcome in patients with early relapsing-remitting multiple sclerosis (MS).

METHODS

Forty-four patients recently diagnosed with clinically definite MS were followed up with clinical and cognitive evaluations at 1, 2, 5, and 7 years and underwent brain MRI including magnetization transfer (MT) imaging at baseline and 2 years. Cognitive evaluation was also performed in 56 matched healthy subjects at baseline. Cognitive testing included the Brief Repeatable Battery. Imaging parameters included lesion load, brain parenchymal fraction (BPF), ventricular fraction (VF), and mean MT ratio (MTR) of lesion and normal-appearing brain tissue (NABT) masks.

RESULTS

At baseline, patients presented deficits of memory, attention, and information processing speed (IPS). Over 2 years, all magnetic resonance parameters deteriorated significantly. Over 7 years, Expanded Disability Status Scale score deteriorated significantly. Fifty percent of patients deteriorated on memory cognitive domain and 22.7%of patients on IPS domain. Seven-year change of memory scores was significantly associated with baseline diffuse brain damage (NABT MTR). IPS z score change over 7 years was correlated with baseline global atrophy (BPF), baseline diffuse brain damage, and central brain atrophy (VF) change over 2 years.

CONCLUSION

The main predictors of cognitive changes over 7 years are baseline diffuse brain damage and progressive central brain atrophy over the 2 years after MS diagnosis.

Correlates of cognitive dysfunction in multiple sclerosis

Cognitive impairment is one of the most frequent symptoms in patients with multiple sclerosis (MS) but its underlying mechanisms are poorly understood. A number of pathogenetic correlates have previously been proposed including psychosocial factors (such as depression and fatigue), inflammation, neurodegeneration, and neuroendocrine dysregulation. However, these different systems have never been studied in parallel and their differential contributions to cognitive impairment in MS are unknown. We studied a well-characterized cohort of cognitively impaired (CI, n=25) and cognitively preserved (CP, n=25) MS patients based on a comprehensive neuropsychological testing battery, a test of hypothalamo-pituitary-adrenal axis functioning (dexamethasone-corticotropin-releasing hormone suppression test, Dex-CRH test) as well as peripheral blood and MRI markers of inflammatory activity. CI patients had significantly higher disability. In addition, CI patients showed higher levels of fatigue and depression. Fatigue was more closely associated with measures of attention while depression showed strongest correlations with memory tests. Furthermore, percentage of IFNγ-positive CD4+ and CD8+ T cells showed modest correlations with processing speed and working memory. MRI markers of inflammation or global atrophy were not associated with neuropsychological function. Compared to previous studies, the number of patients exhibiting HPA axis hyperactivity was very low and no correlations were found with neuropsychological function. We conclude that fatigue and depression are the main correlates of cognitive impairment, which show domain-specific associations with measures of attention and memory.

Assessment and rehabilitation of cognitive impairment in multiple sclerosis

Patients with multiple sclerosis (MS) have a substantial risk of cognitive dysfunction, even in the earliest stages of the disease, where there is minimum physical disability. Despite the high prevalence rates and the significant impact of cognitive dysfunction on quality of life in this population, cognitive functions are not routinely assessed due to the high cost and time consumption. This article provides an overview of the current state of knowledge related to cognition in MS and on the optimal approach to neuropsychological assessment of this population. It then focuses on the pharmacological and other treatment options available for MS patients with, or at risk for developing, cognitive impairment. The available immune-modulating agents may reduce the development of new lesions and therefore prevent or minimize the progression of cognitive decline. However, there is currently insufficient evidence concerning the efficiency of symptomatic treatment in MS. There is also currently no optimal non-pharmacological treatment strategy for cognitive decline in MS, as the studies published to date report heterogeneous results. Nevertheless, non-pharmacological treatments such as cognitive rehabilitation may benefit some MS patients. As cognition is increasingly recognized as a major feature of MS, its assessment and rehabilitation will become a greater priority.

Impaired information processing speed and attention allocation in multiple sclerosis patients versus controls: a high-density EEG study

BACKGROUND

The no-go P3a is a variant of the P300 event-related potential (ERP) that indexes speed of information processing and attention allocation. The aim of this study was to compare ERP findings with results from the paced auditory serial addition test (PASAT) and to quantify latency, amplitude and topographical differences in P3a ERP components between multiple sclerosis (MS) patients and controls.

PATIENTS AND METHODS

Seventy-four subjects (20 relapsing remitting (RRMS) patients, 20 secondary progressive (SPMS) patients and 34 controls) completed a three-stimulus oddball paradigm (target, standard, and non-target). Subjects participated in separate visual and auditory tasks while data were recorded from 134 EEG channels. Latency differences were tested using an ANCOVA. Topographical differences were tested using statistical parametric mapping.

RESULTS

Visual P3a amplitude correlated with PASAT score in all MS patients over frontal and parietal areas. There were significant differences in latency, amplitude, and topography between MS patients and controls in the visual condition. RRMS and SPMS patients differed in visual P3a latency and amplitude at frontal and parietal scalp regions. In the auditory condition, there were latency differences between MS patients and controls only over the parietal region.

CONCLUSION

The present results demonstrate that information processing speed and attention allocation are impaired in MS.

T1 cortical hypointensities and their association with cognitive disability in multiple sclerosis

Background: Neocortical lesions (NLs) largely contribute to the pathology of multiple sclerosis (MS), although their relevance in patients’ disability remains unknown.

Objective: To assess the incidence of T1 hypointense NLs by 3.0-Tesla magnetic resonance imaging (MRI) in patients with MS and examine neocortical lesion association with cognitive impairment.

Methods: In this case-control study, 21 MS patients and 21 age-, sex- and years of education-matched healthy volunteers underwent: (i) a neuropsychological examination rating cognitive impairment (Minimal Assessment of Cognitive Function in MS); (ii) a 3.0-Tesla MRI inclusive of an isotropic 1.0 mm3 three-dimensional inversion prepared spoiled gradient-recalled-echo (3D-IRSPGR) image and T1- and T2-weighted images. Hypointensities on 3D-IRSPGR lying in the cortex, either entirely or partially were counted and association between NLs and cognitive impairment investigated.

Results: A total of 95 NLs were observed in 14 (66.7%) patients. NL+ patients performed poorer (p = 0.020) than NLpatients only on the delayed recall component of the California Verbal Learning Test. This difference lost statistical significance when a correction for white matter lesion volume was employed.

Conclusions: Although T 1 hypointense NLs may be present in a relatively high proportion of multiple sclerosis patients, the impact that they have in cognitive impairment is not independent from white matter disease.

Cognitive function in radiologically isolated syndrome

Background: Radiologically isolated syndrome (RIS) is characterized by patients with asymptomatic T2 hypersignals detected by brain MRI fulfilling dissemination in space criteria and is suggestive of subclinical multiple sclerosis (MS). In previous studies, it was demonstrated that visual evoked potential and cerebrospinal fluid help to identify pejorative markers in converting to MS.

Objective: To date the cognitive function has never been investigated in a cohort of RIS. The objective of this study was to investigate cognitive function in a cohort of 26 RIS patients.

Methods: We prospectively assessed the BCcogSEP (a French adaptation of the Brief Repeatable Battery (BRB) including eight cognitive tests) of 26 patients with RIS, compared with 26 MS patients and 26 healthy subjects matched for age, sex and level of education.

Results: When comparing the three groups, the cognitive performance was significantly lower in the RIS and MS groups compared with healthy subjects for the Paced Auditory Serial Addition Test (PASAT) 3 seconds ( p = 0.002), phonemic fluencies ( p = 0.02), the code of the WAIS ( p = 0.05), the direct ( p = 0.002) or indirect ( p = 0.007) digit span test, the cross-taping test ( p = 0.019) and Go—No-Go ( p = 0.001). When we compared RIS and MS, the cognitive performance was significantly lower in MS patients for the direct span number ( p = 0.003) and cross-tapping test ( p = 0.05). We did not find significant differences between the three groups for the other tests. We did not find a correlation between clinical, biological and MRI results and cognitive dysfunctions.

Conclusions: This study confirms the recently developed concept of RIS patients who present similar features to MS patients. Further studies are necessary to confirm these initial results and to correlate cognitive disorders with MRI surrogate markers.

Inflammation induced neurological handicap processes in multiple sclerosis: new insights from preclinical studies

Multiple sclerosis (MS) is described as originating from incompletely explained neuroinflammatory processes, dysfunction of neuronal repair mechanisms and chronicity of inflammation events. Blood-borne immune cell infiltration and microglia activation are causing both neuronal destruction and myelin loss, which are responsible for progressive motor deficiencies, organic and cognitive dysfunctions. MRI as a non-invasive imaging method offers various ways to visualise de- and remyelination, neuronal loss, leukocyte infiltration, blood-brain barrier modification and new sensors are emerging to detect inflammatory lesions at an early stage. We describe studies performed on experimental autoimmune encephalomyelitis (EAE) animal models of MS that shed new light on mechanisms of functional impairments to understand the neurological handicap in MS. We focus on examples of neuroinflammation-mediated inhibition of CNS repair involving adult neurogenesis in the sub-ventricular zone and hippocampus and such experimentally observed inhibitions could reflect deficient plasticity and activation of compensatory mechanisms in MS. In parallel with cognitive decline, organic deficits such as bladder dysfunction are described in most of MS patients. Neuropharmacological interventions, electrical stimulation of nerves, MRI and histopathology follow-up studies helped in understanding the operating events to remodel the neurological networks and to compensate the inflammatory lesions both in spinal cord and in cortical regions. At the molecular level, the local production of reactive products is a well-described phenomenon: oxidative species disturb cellular physiology and generate new molecular epitopes that could further promote immune reactions. The translational research from EAE animal models to MS patient cohorts helps in understanding the mechanisms of the neurological handicap and in development of new therapeutic concepts in MS.