Cerebellar abnormalities contribute to disability including cognitive impairment in multiple sclerosis

Cerebellar contribution to motor and cognitive performance in multiple sclerosis: An MRI sub-regional volumetric analysis

OBJECTIVE

To investigate the role of cerebellar sub-regions on motor and cognitive performance in multiple sclerosis (MS) patients.

METHODS

Whole and sub-regional cerebellar volumes, brain volumes, T2 hyperintense lesion volumes (LV), and motor performance scores were obtained from 95 relapse-onset MS patients and 32 healthy controls (HC). MS patients also underwent an evaluation of working memory and processing speed functions. Cerebellar anterior and posterior lobes were segmented using the Spatially Unbiased Infratentorial Toolbox (SUIT) from Statistical Parametric Mapping (SPM12). Multivariate linear regression models assessed the relationship between magnetic resonance imaging (MRI) measures and motor/cognitive scores.

RESULTS

Compared to HC, only secondary progressive multiple sclerosis (SPMS) patients had lower cerebellar volumes (total and posterior cerebellum). In MS patients, lower anterior cerebellar volume and brain T2 LV predicted worse motor performance, whereas lower posterior cerebellar volume and brain T2 LV predicted poor cognitive performance. Global measures of brain volume and infratentorial T2 LV were not selected by the final multivariate models.

CONCLUSION

Cerebellar volumetric abnormalities are likely to play an important contribution to explain motor and cognitive performance in MS patients. Consistently with functional mapping studies, cerebellar posterior-inferior volume accounted for variance in cognitive measures, whereas anterior cerebellar volume accounted for variance in motor performance, supporting the assessment of cerebellar damage at sub-regional level.

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.

The role of the cerebellum in multiple sclerosis

In multiple sclerosis (MS), cerebellar signs and symptoms as well as cognitive dysfunction are frequent and contribute to clinical disability with only poor response to symptomatic treatment. The current consensus paper highlights the broad range of clinical signs and symptoms of MS patients, which relate to cerebellar dysfunction. There is considerable evidence of cerebellar involvement in MS based on clinical, histopathological as well as structural and functional magnetic resonance imaging (MRI) studies. The review of the recent literature, however, also demonstrates a high variability of results. These discrepancies are, at least partially, caused by the use of different techniques and substantial heterogeneity among the patient cohorts in terms of disease duration, number of patients, and progressive vs. relapsing disease courses. Moreover, the majority of studies were cross-sectional, providing little insight into the dynamics of cerebellar involvement in MS. Some links between the histopathological changes, the structural and functional abnormalities as captured by MRI, cerebellar dysfunction, and the clinical consequences are starting to emerge and warrant further study. A consensus is formed that this line of research will benefit from advances in neuroimaging techniques that allow to trace cerebellar involvement at higher resolution. Using a prospective study design, multimodal high-resolution cerebellar imaging is highly promising, particularly in patients who present with radiologically or clinically isolated syndromes or newly diagnosed MS.

The role of global and regional gray matter volume decrease in multiple sclerosis

Disability in multiple sclerosis (MS) patients is associated with white matter (WM) and gray matter (GM) pathology, and both processes contribute differently over the disease course. Total and regional GM volume loss can be imaged via voxel-based morphometry (VBM). Here, we retrospectively analyzed a group of 213 MS patients [163 relapsing remitting (RR) and 50 secondary progressive (SP)] using semi-automated white matter (WM) lesion mapping and voxel-based morphometry (VBM). Our aim was to assess the association of increasing disability with decreasing total and regional GM volume. As expected, total GM volume and WM lesion load were associated with patients disability, measured with the Expanded Disability Status Scale (EDSS). The more impaired the patients, the greater the statistical association to the total GM volume. Regional volume loss in the cerebellar gray matter was associated with increasing EDSS and WM lesion volume. Furthermore, SPMS patients had significantly more gray matter volume loss in the cerebellum and the hippocampus compared to RRMS patients. Our results confirm histopathological studies emphasizing the important role of the cerebellum and the hippocampus in MS patients' disability.

Relation of Posterior Cerebellar Volume to Cognition in MS

Investigators from the Montreal Neurological Institute, York University, Universities of Toronto and McGill, Canada, and University of Pennsylvania, studied the relationship between cerebellar pathology and cognitive function in adolescent and pediatric-onset multiple sclerosis (MS).

Can hand dexterity predict the disability status of patients with multiple sclerosis?

BACKGROUND

Multiple Sclerosis (MS) is the most common disabling neurological disease. Hand dysfunction is one of the main complaints of patients with MS. The present study aimed to compare hand dexterity of MS patients with low Expanded Disability Status Scale (EDSS) scores and healthy adults. It also sought to identify the predictors of disability status of patients with MS based on their manual dexterity and demographic characteristics.

METHODS

In this cross-sectional study, 60 (16 male/44 female) patients with MS and 60 (19 male/41 female) healthy people, who matched in terms of age and sex, were recruited. Their hand dexterity was evaluated by the Purdue Pegboard Test. The disability status of the MS group was determined by the Expanded Disability Status Scale. The data were analyzed using SPSS15.

RESULTS

The hand dexterity in MS group even with low EDSS score (1.5 ± 1.07) was weaker than control group. Moreover, the dexterity of dominant hand and alternating two hands coordination subtests of the PPT was a good discriminator between two groups (p<0.001). The results of linear regression analysis suggested dominant hand dexterity and disease duration as predictors of disability status that predict 60.5 per cent of the variation in EDSS scores in patients with MS (p<0.001).

CONCLUSION

Reduced dominant hand dexterity in patients with MS is a disabling factor. Further research is recommended to determine if early hand rehabilitation can reduce the severity of disability in Patients with MS.

Contribution of the cerebellum to cognitive performance in children and adolescents with multiple sclerosis

Background:

Posterior fossa lesions are common in pediatric-onset multiple sclerosis (MS), which is of concern, given the known role of the cerebellum in cognition.

Objectives:

To investigate the relationship between cerebellar pathology and cognitive function in youth with pediatric-onset MS.

Methods:

Twenty-eight pediatric-onset relapsing–remitting MS patients (21 girls; mean age 16.2 years; mean disease duration 4.3 years, median Expanded Disability Status Scale 1.25) were compared to 33 age- and sex-matched healthy controls. Participants underwent structural magnetic resonance imaging (MRI) and neuropsychological evaluation to assess intelligence, attention, processing speed, language, visuo-motor integration, and fine-motor dexterity. Associations between cognitive outcomes and cerebellar volume independent of cerebral volume were examined.

Results:

Cognitive and motor performance of the MS group was reduced relative to controls (all p<0.003). While cerebellar volumes did not differ between groups, cerebellar posterior lobe volume and infratentorial lesion volume accounted for extra variance on measures of information processing ( R2=0.43; p=0.02) and vocabulary ( R2=0.56; p=0.04) in patients (controlling for cerebral volume and sex), but not in controls.

Conclusion:

Smaller cerebellar posterior lobe volume, a known region for cognitive processing, and increased lesion burden in the posterior fossa adversely impact cognitive function, an important functional consequence of MS onset during childhood.

The neurocognitive profile of the cerebellum in multiple sclerosis

In recent years, a high number of studies have demonstrated that neuropsychological functions are altered in multiple sclerosis (MS) patients with cerebellar lesions, mainly including attention, working memory and verbal fluency. Since the present literature is often elusive on this topic, we aim to provide a comprehensive report about the real impact of cerebellar damages (evaluated as volume, lesions or connectivity measures) on cognitive functions. In particular in this review, we report and discuss recent works from 2009 to 2015, which have demonstrated the key role of the cerebellum in cognitive impairment of MS patients.

Evidence for early, non-lesional cerebellar damage in patients with multiple sclerosis: DTI measures correlate with disability, atrophy, and disease duration

BACKGROUND

Common symptoms of multiple sclerosis (MS) such as gait ataxia, poor coordination of the hands, and intention tremor are usually the result of dysfunctionality in the cerebellum. Magnetic resonance imaging (MRI) has frequently failed to detect cerebellar damage in the form of inflammatory lesions in patients presenting with symptoms of cerebellar dysfunction.

OBJECTIVE

To detect microstructural cerebellar tissue alterations in early MS patients with a "normal appearing" cerebellum using diffusion tensor imaging (DTI).

METHODS

A total of 68 patients with relapsing-remitting MS (RRMS) and without cerebellar lesions and 26 age-matched healthy controls were admitted to high-resolution MRI and DTI to assess microstructure and volume of the cerebellar white matter (CBWM).

RESULTS

We found cerebellar fractional anisotropy (FA) and CBWM volume reductions in the group of 68 patients. Interestingly, a subgroup of these patients that was derived by including only patients with early and mild MS (N=23, median age 30 years, median Expanded Disability Status Scale =1.5, median duration 28 months) showed already cerebellar FA but no CBWM volume reductions. FA reductions were correlated with disability, atrophy, and disease duration.

CONCLUSION

"Normal appearing" cerebellar white matter can be damaged in a very early stage of RRMS. DTI seems to be a sensitive tool for detecting this hidden cerebellar damage.

Investigating the phenomenon of "cognitive-motor interference" in multiple sclerosis by means of dual-task posturography

BACKGROUND

Two simultaneously performed tasks may compete for common brain network resources in patients with multiple sclerosis (MS), suggesting the occurrence of a cognitive-motor interference. While this phenomenon has been well described for walking and gait, data on static balance are scarce.

METHODS

In this cross-sectional study, 92 patients and 46 sex/age-matched healthy controls (HCs) were tested by means of static posturography under eyes opened (single-task condition) and while performing the Stroop word-colour task (dual-task condition), to estimate the dual-task cost (DTC) of standing balance. The patient group also underwent the Expanded Disability Status Scale, 25-foot walking test, 12-item MS walking scale, Modified Fatigue Impact Scale, and Symbol Digit Modalities Test.

RESULTS

Patients had larger postural sway under both single-task and dual-task conditions (p<0.001), as well as greater DTC of standing balance (p=0.021) than HCs. Although secondary progressive (SP) patients had larger sway in both conditions than relapsing-remitting (RR) patients (p<0.05), these latter ones exhibited a greater DTC of postural balance (p=0.045). Deficits in sustained attention and information processing speed, as assessed by the SDMT, were also independently associated with the magnitude of DTC of standing balance (p=0.005).

CONCLUSIONS

The phenomenon of cognitive-motor interference might be unmasked by a dual-task posturography and was associated with impaired sustained attention and information processing speed, especially in RR patients. The smaller DTC of standing balance observed in SP patients may be due to the ceiling effect of postural sway, or alternatively to the lack of postural reserve which constrained the more disabled patients to prioritize the balance over the cognitive task.

Rostrocaudal thickness on sagittal diffusion-weighted imaging as a predictor of motor deficits in an acute isolated pontine infarction

BACKGROUND

The relationship between infarct dimensions and neurologic severity in patients with acute pontine infarctions remains unclear. This study aimed to clarify the morphometric predictive value of magnetic resonance imaging for motor deficits in pontine infarction.

METHODS

Nineteen patients with an acute pontine infarction (12 males and 7 females, 70.6 ± 13.5 years [mean age ± SD]) had ventrodorsal length and rostrocaudal thickness and width retrospectively measured as parameters of infarct size on axial and sagittal diffusion-weighted imaging (DWI). Each patient's functional score (FS) based on Brunnstrom scale (upper limb, hand, and lower limb) was assessed. The functional score of bulbar symptoms was coded as follows: 2, none; 1, dysarthria or dysphasia; and 0, both. The mean FS was compared with each infarct size parameter and the patients' clinical features.

RESULTS

Rostrocaudal thickness on sagittal DWI was the parameter most closely correlated with FS (Spearman rank correlation coefficient (rs) = -.474, P = .040). However, there is apparently no association between FS and infarct size with correction for age. FS was most severe in patients with an atherothrombotic infarction; it was mildest in patients with a lacunar infarction (value of K [Kruskal-Wallis] = 9.0, P = .015).

CONCLUSIONS

The branch orifices of the pontine paramedian arteries could be narrowed by atheromatous plaques within the basilar artery. These atheromatous lesions involving multiple branching paramedian arteries probably cause rostrocaudally thick infarctions. A pontine infarction extending rostrocaudally along the corticospinal tract may cause severe motor impairments.

Multicontrast connectometry: a new tool to assess cerebellum alterations in early relapsing-remitting multiple sclerosis

BACKGROUND

Cerebellar pathology occurs in late multiple sclerosis (MS) but little is known about cerebellar changes during early disease stages. In this study, we propose a new multicontrast "connectometry" approach to assess the structural and functional integrity of cerebellar networks and connectivity in early MS.

METHODS

We used diffusion spectrum and resting-state functional MRI (rs-fMRI) to establish the structural and functional cerebellar connectomes in 28 early relapsing-remitting MS patients and 16 healthy controls (HC). We performed multicontrast "connectometry" by quantifying multiple MRI parameters along the structural tracts (generalized fractional anisotropy-GFA, T1/T2 relaxation times and magnetization transfer ratio) and functional connectivity measures. Subsequently, we assessed multivariate differences in local connections and network properties between MS and HC subjects; finally, we correlated detected alterations with lesion load, disease duration, and clinical scores.

RESULTS

In MS patients, a subset of structural connections showed quantitative MRI changes suggesting loss of axonal microstructure and integrity (increased T1 and decreased GFA, P < 0.05). These alterations highly correlated with motor, memory and attention in patients, but were independent of cerebellar lesion load and disease duration. Neither network organization nor rs-fMRI abnormalities were observed at this early stage.

CONCLUSION

Multicontrast cerebellar connectometry revealed subtle cerebellar alterations in MS patients, which were independent of conventional disease markers and highly correlated with patient function. Future work should assess the prognostic value of the observed damage.

The Symbol Digit Modalities Test as sentinel test for cognitive impairment in multiple sclerosis

BACKGROUND AND PURPOSE

Cognitive impairment (CI) is found in about half of the multiple sclerosis (MS) population and is an important contributor to employment status and social functioning. CI is encountered in all disease stages and correlates only moderately with disease duration or Expanded Disability Status Scale scores. Most present neuropsychological test batteries are time-demanding and expensive. The Symbol Digit Modalities Test (SDMT) has been suggested as a screening tool for CI in MS. In this paper, we aim to assess the performance of the SDMT in predicting the outcome of an extensive battery.

METHODS

Neuropsychological test results from 359 patients were assessed in a multidisciplinary MS center (National MS Center Melsbroek, Belgium). Using receiver operating characteristic curves, the performance of the SDMT in predicting the general cognitive outcome of the extensive Neuropsychological Screening Battery for MS (NSBMS) could be assessed. The performance of the SDMT was assessed for different levels of CI and compared with other cognitive tests. Finally, useful covariates were included in a logistic regression model.

RESULTS

At a specificity of 0.60 a high sensitivity (0.91) was obtained indicating the potential of the SDMT as a sentinel test for CI in MS. The SDMT outperformed the individual tests included in the NSBMS, used as benchmark. As the logistic regression model did not result in a relevant improvement, it is concluded that most clinical variables influence both the SDMT and the NSBMS in a similar way. Excluding patients with possible practice effects, an optimal cutoff of 40 was found for the SDMT.

CONCLUSION

As the SDMT is an easy, low-cost and fast test, this result may help to detect CI in everyday clinical practice.