Segmented corpus callosum diffusivity correlates with the Expanded Disability Status Scale score in the early stages of relapsing-remitting multiple sclerosis

A cross-sectional multicentre study of multishell diffusion MRI in multiple sclerosis

BACKGROUND AND OBJECTIVES

White matter (WM) microstructural properties from advanced multishell diffusion MRI (dMRI) have been linked to clinical disability in multiple sclerosis (MS). This multicentre study used multishell dMRI to compute WM metrics and test for differences between people with MS (pwMS) and healthy controls (HCs).

METHODS

We included multishell dMRI data from 251 pwMS or clinically isolated syndrome (CIS) (mean age 40.7 years, 72.4 % women, 88.8 % relapsing remitting MS) at six MAGNIMS centres and 543 HCs. Eleven scalar metric maps were estimated from multishell dMRI sequences, based on diffusion tensor imaging (DTI) and restriction spectrum imaging (RSI). The maps were analysed using tract-based spatial statistics (TBSS). The diffusion output was submitted to paired sampled t-tests to test for case-control differences and linear regression models to test for associations with Expanded Disability Status Scale (EDSS) scores, while accounting for confounders. In a sub-sample from Oslo, we tested for correlations between EDSS and dMRI metrics within WM lesions.

RESULTS

Significant group differences were found in nine out of eleven dMRI metrics. Linear regression models revealed significant correlations between EDSS and fractional anisotropy (FA) fast (β=-4.54, p = 0.01) and apparent diffusion coefficient (ADC) fast (β=10.92, p = 8.7 × 10-3).

CONCLUSIONS

Diffusion MRI based on clinically feasible multishell sequences uncovers WM group differences between pwMS and HCs, but only a selection of the advanced multishell parameters were sensitive to disability, and no statistically significant correlations with disability remained after Bonferroni correction.

Cerebellar Contributions to Motor and Cognitive Control in Multiple Sclerosis✰✰✰

OBJECTIVE

To evaluate relationships between specific cerebellar regions and common clinical measures of motor and cognitive function in persons with multiple sclerosis (PwMS).

DESIGN

Cross-sectional.

SETTING

Laboratory.

PARTICIPANTS

Twenty-nine PwMS and 28 age- and sex-matched controls without multiple sclerosis (MS) (N=57).

INTERVENTIONS

Not applicable.

MAIN OUTCOME MEASURES

Both diffusion and lobule magnetic resonance imaging analyses and common clinical measures of motor and cognitive function were used to examine structure-function relationships in the cerebellum.

RESULTS

PwMS demonstrate significantly worse motor and cognitive function than controls, including weaker strength, slower walking, and poorer performance on the Symbol Digit Modalities Test, but demonstrate no differences in cerebellar volume. However, PwMS demonstrate significantly worse diffusivity (mean diffusivity: P=.0003; axial diffusivity: P=.0015; radial diffusivity: P=.0005; fractional anisotropy: P=.016) of the superior cerebellar peduncle, the primary output of the cerebellum. Increased volume of the motor lobules (I-V, VIII) was significantly related to better motor (P<.022) and cognitive (P=.046) performance, and increased volume of the cognitive lobules (VI-VII) was also related to better motor (P<.032) and cognitive (P=.008) performance, supporting the role of the cerebellum in both motor and cognitive functioning.

CONCLUSIONS

These data highlight the contributions of the cerebellum to both motor and cognitive function in PwMS. Using novel neuroimaging techniques to examine structure-function relationships in PwMS improves our understanding of individualized differences in this heterogeneous group and may provide an avenue for targeted, individualized rehabilitation aimed at improving cerebellar dysfunction in MS.

Using myelin water imaging to link underlying pathology to clinical function in multiple sclerosis: A scoping review

BACKGROUND

Multiple sclerosis (MS) symptoms and pathology are heterogenous and complex. Identifying links between MS-related pathology (i.e., myelin damage) and associated clinical symptoms is critical for developing targeted therapeutics. Conventional MRI, commonly used for MS diagnosis and disease monitoring, lacks specificity with functional performance. Myelin water imaging (MWI) demonstrates increased specificity to myelin and is viewed as the gold standard for imaging myelin content in vivo. Yet, there is a paucity of MWI studies in MS and only a limited number also examine clinical function. Thus, it remains unknown whether MWI corresponds to functional performance in MS. This scoping review aimed to examine relations between MWI and functional domains relevant to MS to inform and guide future research.

METHODS

Seven databases were searched from their inception to September 1, 2021. Studies of adults with MS that included both brain MWI and either a measure of physical function, a measure of cognitive function, or a measure of disease severity were included. Thirteen studies (11 observational, 2 intervention) met the inclusion criteria.

RESULTS

The most commonly investigated MWI metric is the myelin water fraction (MWF). Persons with MS demonstrated markedly decreased MWF compared to healthy controls globally and across brain regions of interest (ROIs). Decreased MWF was associated with higher disability, worse motor and cognitive performance and decreased intervention response. Only five studies examined structure-function relationships in brain areas related to walking and cognitive function and only six studies extracted MWI metrics from explicit brain ROIs.

CONCLUSIONS

MWI is a neuroimaging technique with increased specificity to myelin and offers greater insight to MS-driven pathology and its clinical manifestations, including motor and cognitive dysfunction and rehabilitation response. This scoping review identified critical gaps in MWI research in MS to offer future perspectives including ROI-based studies, inclusion of multi-domain functional assessment and examining MWI to provide evidence of neuroplasticity following training.

Butterfly Tumor of the Corpus Callosum: Clinical Characteristics, Diagnosis, and Survival Analysis

Background:

The pathologies implicate the bilateral corpus callosum that builds the butterfly pattern on axial view. These tumors have seldom been investigated for both clinical manifestations and outcome.

Objective:

The objective of this study was to describe the clinical characteristics and outcomes of the butterfly tumor and to identify the predictive factors associated with survival outcome.

Methods:

A retrospective study of 50 butterfly tumor was conducted between 2003 and 2016. The clinical characteristics, imaging, and outcome were assessed for the purpose of descriptive analysis. Using the Kaplan–Meier method, the median overall survival of the butterfly tumor was determined. Furthermore, the Cox proportional hazard regression was the estimated hazard ratio for death.

Results:

Diffuse large B-cell lymphoma was common of butterfly lesions. The mortality rate was 78% and overall median survival time was 16.03 months (95% confidence interval: 14.0–19.8). Using Cox proportional hazards regression, the independent prognostic factors were Karnofsky Performance Status score ≤70, splenium involvement, and butterfly glioblastoma.

Conclusions:

The butterfly tumor is a poor prognostic disease compared with each histology subgroup. Further molecular investigation is preferable to explore genetic variations associated with these tumors.

Supplementary motor area connectivity and dual-task walking variability in multiple sclerosis

BACKGROUND

Despite the prevalence of dual-task (e.g., walking while talking) deficits in people with multiple sclerosis (MS), no neuroimaging studies to date have examined neuronal networks used for dual-task processing or specific brain areas related to dual-task performance in this population. A better understanding of the relationship among underlying brain areas and dual-task performance may improve targeted rehabilitation programs. The objective of this study was to examine relationships between neuroimaging measures and clinical measures of dual-task performance, and reported falls in persons with MS.

MATERIALS AND METHODS

All participants completed measures of dual-task performance, a fall history, and neuroimaging on a 3 T MRI scanner. Spearman correlations were used to examine relationships among dual-task performance, falls and neuroimaging measures.

RESULTS

Eighteen females with relapsing-remitting MS [mean age = 45.5 ± 8.2 SD; mean symptom duration = 12.3 ± 6.7 years; Expanded Disability Status Scale median 2.25 (range 1.5-4)] participated in this study. Structural imaging measures of supplementary motor area (SMA) interhemispheric connectivity were significantly related to dual-task walking variability.

CONCLUSIONS

The SMA interhemispheric tract may play a role in dual-task performance. Structural neuroimaging may be a useful adjunct to clinical measures to predict performance and provide information about recovery patterns in MS. Functional recovery can be challenging to objectively report in MS; diffusion tensor imaging could show microstructural improvements and suggest improved connectivity.

How changes in brain activity and connectivity are associated with motor performance in people with MS

People with multiple sclerosis (MS) exhibit pronounced changes in brain structure, activity, and connectivity. While considerable work has begun to elucidate how these neural changes contribute to behavior, the heterogeneity of symptoms and diagnoses makes interpretation of findings and application to clinical practice challenging. In particular, whether MS related changes in brain activity or brain connectivity protect against or contribute to worsening motor symptoms is unclear. With the recent emergence of neuromodulatory techniques that can alter neural activity in specific brain regions, it is critical to establish whether localized brain activation patterns are contributing to (i.e. maladaptive) or protecting against (i.e. adaptive) progression of motor symptoms. In this manuscript, we consolidate recent findings regarding changes in supraspinal structure and activity in people with MS and how these changes may contribute to motor performance. Furthermore, we discuss a hypothesis suggesting that increased neural activity during movement may be either adaptive or maladaptive depending on where in the brain this increase is observed. Specifically, we outline preliminary evidence suggesting sensorimotor cortex activity in the ipsilateral cortices may be maladaptive in people with MS. We also discuss future work that could supply data to support or refute this hypothesis, thus improving our understanding of this important topic.

Tissue microstructure features derived from anomalous diffusion measurements in magnetic resonance imaging

OBJECTIVES

Tissue microstructure features, namely axon radius and volume fraction, provide important information on the function of white matter pathways. These parameters vary on the scale much smaller than imaging voxels (microscale) yet influence the magnetic resonance imaging diffusion signal at the image voxel scale (macroscale) in an anomalous manner. Researchers have already mapped anomalous diffusion parameters from magnetic resonance imaging data, but macroscopic variations have not been related to microscale influences. With the aid of a tissue model, we aimed to connect anomalous diffusion parameters to axon radius and volume fraction using diffusion-weighted magnetic resonance imaging measurements.

EXPERIMENTAL DESIGN

An ex vivo human brain experiment was performed to directly validate axon radius and volume fraction measurements in the human brain. These findings were validated using electron microscopy. Additionally, we performed an in vivo study on nine healthy participants to map axon radius and volume fraction along different regions of the corpus callosum projecting into various cortical areas identified using tractography.

PRINCIPAL OBSERVATIONS

We found a clear relationship between anomalous diffusion parameters and axon radius and volume fraction. We were also able to map accurately the trend in axon radius along the corpus callosum, and in vivo findings resembled the low-high-low-high behaviour in axon radius demonstrated previously.

CONCLUSIONS

Axon radius and volume fraction measurements can potentially be used in brain connectivity studies and to understand the implications of white matter structure in brain diseases and disorders. Hum Brain Mapp 38:1068-1081, 2017. © 2016 Wiley Periodicals, Inc.

The relationship between regional microstructural abnormalities of the corpus callosum and physical and cognitive disability in relapsing-remitting multiple sclerosis

Significant corpus callosum (CC) involvement has been found in relapsing–remitting multiple sclerosis (RRMS), even if conventional magnetic resonance imaging measures have shown poor correlation with clinical disability measures. In this work, we tested the potential of multimodal imaging of the entire CC to explain physical and cognitive disability in 47 patients with RRMS. Values of thickness, fractional anisotropy (FA) and mean diffusivity (MD) were extracted from 50 regions of interest (ROIs) sampled along the bundle. The relationships between clinical, neuropsychological and imaging variables were assessed by using Spearman's correlation. Multiple linear regression analysis was employed in order to identify the relative importance of imaging metrics in modeling different clinical variables. Regional fiber composition of the CC differentially explained the response variables (Expanded Disability Status Scale [EDSS], cognitive impairment). Increases in EDSS were explained by reductions in CC thickness and MD. Cognitive impairment was mainly explained by FA reductions in the genu and splenium. Regional CC imaging properties differentially explained disability within RRMS patients revealing strong, distinct patterns of correlation with clinical and cognitive status of patients affected by this specific clinical phenotype.

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We assess corpus callosum damage in relapsing–remitting multiple sclerosis.

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We used no a priori subdivisions to model the bundle in a continuous fashion.

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Imaging–clinical relationship was explored by correlation and regression analyses.

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Damage of large, heavily myelinated axons was mainly linked to physical disability.

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Damage of small-diameter axons was mainly linked to cognitive impairment.