Correlation between brain MRI lesion volume and disability in patients with multiple sclerosis

The impact of multiple sclerosis relapses on worsening over the long term; insights in the treatment era

Relapses of multiple sclerosis (MS) are the clinical manifestations of inflammatory events involving eloquent anatomical structures within the central nervous system. Relapses are associated with worsening disability of MS patients in both early and later disease, even after progressive features are seen. The impact of relapses on the long-term course of the disease is now being realized as a generation of treated patients is now elderly. New MRI brain lesions can be viewed as a radiologic manifestation of acute inflammation and are associated with similar prognostic value. The complex relationship between clinical relapse activity and later slow progressive worsening remains incompletely understood, however, there is increasing biological plausibility for a causative association between relapse activity and lifelong disability.

TIMP-1 Promotes Oligodendrocyte Differentiation Through Receptor-Mediated Signaling

The extracellular protein tissue inhibitor of metalloproteinase (TIMP)-1 is both a matrix metalloproteinase (MMP) inhibitor and a trophic factor. Mice lacking TIMP-1 exhibit delayed central nervous system myelination during postnatal development and impaired remyelination following immune-mediated injury in adulthood. We have previously determined that the trophic action of TIMP-1 on oligodendrocyte progenitor cells (OPCs) to mature into oligodendrocytes is independent of its MMP inhibitory function. However, the mechanism by which TIMP-1 promotes OPC differentiation is not known. To address this gap in our understanding, herein, we report that TIMP-1 signals via a CD63/β1-integrin receptor complex to activate Akt (protein kinase B) to promote β-catenin signaling in OPCs. The regulation of β-catenin by TIMP-1 to promote OPC differentiation was counteracted, but not abrogated, by canonical signaling evoked by Wnt7a. These data provide a previously uncharacterized trophic action of TIMP-1 to regulate oligodendrocyte maturation via a CD63/β1-integrin/Akt pathway mechanism. These findings contribute to our emerging understanding on the role of TIMP-1 as a growth factor expressed to promote CNS myelination during development and induced in the adult to promote myelin repair.

Restriction spectrum imaging of white matter and its relation to neurological disability in multiple sclerosis

BACKGROUND

Restriction spectrum imaging (RSI) is a recently introduced magnetic resonance imaging diffusion technique. The utility of RSI in multiple sclerosis (MS) is unknown.

OBJECTIVE

To investigate the association between RSI-derived parameters and neurological disability in MS.

METHODS

Seventy-seven relapsing-remitting MS patients were scanned with RSI on a 3-T scanner. RSI-derived parameters: fast and slow apparent diffusion coefficient (sADC), fractional anisotropy, restricted fractional anisotropy, neurite density (ND), cellularity, extracellular water fraction, and free water fraction, were obtained in white matter lesions (WML) and normal appearing white matter (NAWM). Patients were divided into three groups according to their expanded disability status scale (EDSS): with minimal, low, and substantial disability (<2.5, 2.5-3, and >3, respectively). Group comparisons and correlation analyses were performed.

RESULTS

All tested RSI-derived parameters differed between WML and NAWM ( p < 0.001 for all pairwise comparisons). The sADC in WML showed largest difference across disability subgroups (analysis of variance (ANOVA): F = 5.1, η² = 0.12, p = 0.008). ND in NAWM showed strongest correlation with disability (ϱ = -0.39, p < 0.001).

CONCLUSION

The strongest correlation with EDSS of ND obtained in NAWM indicates that processes outside lesions are important for disability in MS. Our study suggests that RSI-derived parameters may help understand the "clinico-radiological paradox" and improve disease monitoring in MS.

Fully automated open-source lesion mapping of T2-FLAIR images with FSL correlates with clinical disability in MS

BACKGROUND

T2 Lesion Volume (T2LV) has been an important biomarker for multiple sclerosis (MS). Current methods available to quantify lesions from MR images generally require manual adjustments or multiple images with different contrasts. Further, implementations are often not easily or openly accessible.

OBJECTIVE

We created a fully unsupervised, single T2 FLAIR image T2LV quantification package based on the popular open-source imaging toolkit FSL.

METHODS

By scripting various processing tools in FSL, we developed an image processing pipeline that distinguishes normal brain tissue from CSF and lesions. We validated our method by hierarchical multiple regression (HMR) with a preliminary study to see if our T2LVs correlate with clinical disability measures in MS when controlled for other variables.

RESULTS

Pearson correlations between T2LV and Expanded Disability Status Scale (EDSS: r = 0.344, P = 0.013), Six-Minute Walk (6MW: r = -0.513, P = 0.000), Timed 25-Foot Walk (T25FW: r = -0.438, P = .000), and Symbol Digit Modalities Test (SDMT: r = -0.499, P = 0.000) were all significant. Partial correlations controlling for age were significant between T2LV and 6MW (r = -0.433, P = 0.002), T25FW (r = -0.392, P = 0.004), and SDMT (r = -0.450, P = 0.001). In HMR, T2LV explained significant additional variance in 6MW (R(2) change = 0.082, P = 0.020), after controlling for confounding variables such as age, white matter volume (WMV), and gray matter volume (GMV).

CONCLUSION

Our T2LV quantification software produces T2LVs from a single FLAIR image that correlate with physical disability in MS and is freely available as open-source software.

MRI evaluation of grey matter atrophy and disease course in multiple sclerosis: an overview of current knowledge

Multiple sclerosis (MS) is characterized by chronic inflammation of the central nervous system, and magnetic resonance imaging (MRI) is used as both a diagnostic tool and a parameter in the clinical evaluation. Multiple sclerosis was long regarded as a disease of the white matter (WM) in the brain, which can be visualized by the standard MRI used in daily practice. There is an increasing amount of evidence that grey matter (GM) pathology plays a role from the start of the MS disease and throughout the clinical course. Grey matter atrophy, both cortical and central, is present in the early course of MS and is also related above all to cognitive decline, but also to the development of physical disability as measured by EDSS. In this article, we give an overview of GM atrophy in MS evaluated by MRI and the relation to the clinical course in MS.

The generation and validation of white matter connectivity importance maps

Both the size and location of injury in the brain influences the type and severity of cognitive or sensorimotor dysfunction. However, even with advances in MR imaging and analysis, the correspondence between lesion location and clinical deficit remains poorly understood. Here, structural and diffusion images from 14 healthy subjects are used to create spatially unbiased white matter connectivity importance maps that quantify the amount of disruption to the overall brain network that would be incurred if that region were compromised. Some regions in the white matter that were identified as highly important by such maps have been implicated in strategic infarct dementia and linked to various attention tasks in previous studies. Validation of the maps is performed by investigating the correlations of the importance maps' predicted cognitive deficits in a group of 15 traumatic brain injury patients with their cognitive test scores measuring attention and memory. While no correlation was found between amount of white matter injury and cognitive test scores, significant correlations (r>0.68, p<0.006) were found when including location information contained in the importance maps. These tools could be used by physicians to improve surgical planning, diagnosis, and assessment of disease severity in a variety of pathologies like multiple sclerosis, trauma, and stroke.

Sympathetic skin responses in multiple sclerosis

OBJECTIVES

This study assessed the sympathetic skin responses (SSRs) and their correlation with brain lesion volumes in patients with multiple sclerosis (MS).

MATERIALS AND METHODS

The SSRs were measured in 27 patients with MS and 27 healthy controls. The volumes of the proton density-weighted MS lesions in the brain were measured using MRI.

RESULTS

The SSRs were abnormal in 52% of the patients with MS, but absent only in clinically severe MS. The total lesion volume in the whole brain correlated significantly with both the severity of MS expressed by the EDSS score (P < 0.001) and the decreased SSR amplitudes in the feet (P < 0.01). Focal lesion volumes in the temporal lobe (P < 0.01), in the pons (P < 0.01) and in the cerebellum (P < 0.01) were also separately associated with abnormal SSR reflexes.

CONCLUSIONS

Sudomotor regulation failure in MS is associated with certain focal MS lesions.

Incorporating domain knowledge into the fuzzy connectedness framework: application to brain lesion volume estimation in multiple sclerosis

A method for incorporating prior knowledge into the fuzzy connectedness image segmentation framework is presented. This prior knowledge is in the form of probabilistic feature distribution and feature size maps, in a standard anatomical space, and "intensity hints" selected by the user that allow for a skewed distribution of the feature intensity characteristics. The fuzzy affinity between pixels is modified to encapsulate this domain knowledge. The method was tested by using it to segment brain lesions in patients with multiple sclerosis, and the results compared to an established method for lesion outlining based on edge detection and contour following. With the fuzzy connections (FC) method, the user is required to identify each lesion with a mouse click, to provide a set of seed pixels. The algorithm then grows the features from the seeds to define the lesions as a set of objects with fuzzy connectedness above a preset threshold. The FC method gave improved interobserver reproducibility of lesion volumes, and the set of pixels determined to be lesion was more consistent compared to the contouring method. The operator interaction time required to evaluate one subject was reduced from an average of 111 min with contouring to 16 min with the FC method.

Imaging correlates of axonal swelling in chronic multiple sclerosis brains

OBJECTIVE

T2-weighted magnetic resonance imaging is a sensitive tool for monitoring progression of multiple sclerosis, but it does not provide information on the severity of the underlying tissue damage. Measurement of T1 hypointensities and magnetization transfer ratio (MTR) can potentially distinguish lesions with more severe tissue damage. The objective of this study was to use image-guided pathology to determine histological differences between lesions that are abnormal only on T2-weighted images versus lesions that are abnormal on T2-weighted, T1-weighted, and MTR images.

METHODS

A total of 110 regions were selected from postmortem magnetic resonance images of 10 multiple sclerosis patients. Regions were classified into three magnetic resonance imaging-defined categories: normal-appearing white matter; abnormal on T2-weighted image only (T2-only); and abnormal on T2-weighted, T1-weighted, and MTR images (T2T1MTR). Myelin status, lesion activity, astrocytosis, serum protein distribution, axonal area, and axonal loss were evaluated histopathologically.

RESULTS

Comparisons between groups showed that T2T1MTR regions were more likely to be demyelinated (83% compared with 55% of T2-only regions) and more likely to be chronic inactive lesions (68% compared with 0% of demyelinated T2-only regions). There was no difference between T2-only and T2T1MTR regions in axonal area, but there was a significant difference in axonal count, indicating that axons in the T2T1MTR regions were enlarged relative to those in T2-only regions.

INTERPRETATION

Axonal swelling and axonal loss were major pathological features that distinguish T2T1MTR regions from T2-only regions.

Significance of T2 lesions in multiple sclerosis: A 13-year longitudinal study

OBJECTIVE

To evaluate the relation between T2 lesions and disease severity in relapsing-remitting multiple sclerosis (MS).

METHODS

This article describes a 13-year longitudinal study in 30 patients.

RESULTS

Patients were 36.3 +/- 6.0 years old, had MS for 6.1 +/- 5.8 years, Expanded Disability Status Scale was 2.2 +/- 0.8, and brain parenchymal fraction (BPF) was 0.825 +/- 0.015 at study entry. At last visit, Expanded Disability Status Scale was 4.4 +/- 1.95, Multiple Sclerosis Functional Composite was -0.34 +/- 1.7, and BPF was 0.774 +/- 0.037. Baseline T2 lesion volume correlated with the BPF of the last visit (r = -0.66; p < 0.0001), magnetization transfer ratio (MTR) in normal-appearing brain tissue (r = -0.52; p = 0.004), and lesion MTR (r = -0.76; p < 0.0001). Change in T2 lesion volume in the first 2 years correlated with BPF of the last visit (r = -0.40; p = 0.03), normal-appearing brain tissue MTR (r = -0.44; p = 0.015), lesion MTR (r = -0.46; p = 0.018), Multiple Sclerosis Functional Composite scores (r = -0.50; p = 0.005), and Paced Auditory Serial Addition Task scores (r = -0.52; p = 0.003). Age was a significant covariate for clinical but not magnetic resonance imaging outcomes.

INTERPRETATION

T2 lesions in relapsing-remitting MS correlate strongly with brain tissue loss and brain tissue integrity 13 years later, and with clinical disease severity, though age significantly impacts the clinical correlation. The results provide direct evidence for the disability threshold hypothesis in MS and support monitoring T2 lesions in relapsing-remitting MS.

Volumetric quantitation by MRI in primary progressive multiple sclerosis: volumes of plaques and atrophy correlated with neurological disability

In primary progressive multiple sclerosis (PPMS) abnormalities in brain magnetic resonance imaging (MRI) differ from abnormalities in other subtypes of multiple sclerosis (MS). It was investigated whether the extent of brain and spinal cord MRI abnormalities is reflected in the neurological disability in PPMS. Focal and diffuse changes and atrophy in central nervous system (CNS) in patients with PPMS (n = 28) and healthy controls (n = 20) were assessed by semi-automatic MRI segmentation and volumetric analysis. The measurements were related to neurological disability as expressed by the expanded disability status scale (EDSS), the regional functional scoring system (RFSS), the arm index and the ambulation index. Plaques in T1- and/or T2-weighted images were seen in all brains, while spinal plaques were detected in 23 of 28 patients (82%). The total volumes of brain and spinal cord were significantly smaller in patients than in controls (P = 0.001 and 0.000, respectively). The volumes of T1 or T2 lesions in the brain correlated to the ambulation index (r = 0.51, P = 0.005 and r = 0.53, P = 0.004, respectively). No correlations were detected between MRI measurements and total EDSS score, but relative brain atrophy correlated inversely with the total RFSS scores, poor arm index and higher cerebral disturbances (r = -0.53, P = 0.004; r = -0.53, P = 0.004; and r = -0.52, P = 0.005, respectively). Although the number of spinal T2 lesions correlated with sensory disturbances (r = 0.60, P = 0.001), no correlations were found between EDSS subscores and spinal cord atrophy. These findings show that marked atrophy of brain and spinal cord detected by volumetric quantitation correlates with neurological disability. This observation indicates the importance of neurodegenerative events in PPMS.

3-D surface reconstruction of multiple sclerosis lesions using spherical harmonics

A new approach to approximate the 3-D shape of multiple sclerosis (MS) lesions and to calculate their volumes is presented. The suggested method utilizes sets of MS lesion contours taken from segmented MR images and approximates their 3-D surfaces by spherical harmonics. This method was applied to obtain 3-D reconstructions of in vivo and simulated MS lesions and to calculate their volumes. The results show good geometrical approximations of the original MS lesions' 3-D shapes and good consistency in volume estimation independent of the size of the lesions. The average volume estimation error was smaller than the commonly used technique of slice stacking (15.5 +/- 13.4% and 13.1 +/- 10.1% vs. 25.0 +/- 17.0%). The method presented here offers a tool for analyzing the geometrical characteristics of MS lesions in 3-D as well as their volumes. The geometrical information may potentially serve as an additional clinical index for monitoring the disease.

Correlations of brain MRI parameters to disability in multiple sclerosis

OBJECTIVES

The objective was to correlate magnetic resonance imaging (MRI) T2-weighted lesion load and measures of white matter atrophy in the brain to disability in a population-based sample of patients with multiple sclerosis (MS).

MATERIAL AND METHODS

A well defined cohort of patients was drawn at random from the general MS population by using the Danish Multiple Sclerosis Registry. A semi-automated local thresholding technique was used to quantify T2-weighted lesions on MRI; whereas manual tracing was applied to measure the corpus callosum brain ratio (CCR) and the ventricle brain ratio (VBR).

RESULTS

A sample of 86 patients with a mean age of 43.3 years (SD 4.3), mean disease duration of 13.6 years (SD 4.4) and a median Expanded Disability Status Score (EDSS) of 6.0 was identified. The correlation between total lesion area of the brain (TLA) and disability (EDSS) for the whole sample was moderate (Spearman rank correlation coefficient r=0.48, P<0.001). Also correlations of CCR and VBR to disability (r=0.32-0.46) were significant.

CONCLUSIONS

Correlations of TLA and disability in this study were rather strong. Hence, T2-weighted MRI lesion load in the brain still plays an important role as a surrogate marker of disease and as a secondary outcome measure in phase III treatment trials.

Serial magnetic resonance imaging in multiple sclerosis: correlation with attacks, disability, and disease stage

Serial MRI and clinical testing was performed on 45 well-defined untreated multiple sclerosis patients in different categories of disease (relapsing-remitting, progressive, stable). Up to 24 MRIs were scheduled over a 1-year period for each patient. Clinical evaluation was performed monthly and at times of attacks using the Expanded Disability Status Scale (EDSS) and the Ambulation Index (AI). MRI scans were performed both with and without gadolinium enhancement. MRI lesion volume was determined by computerized analysis and gadolinium-enhancing lesions were counted by radiologists. We observed an increase in lesion volume over 1 year in all patient groups except those classified clinically as stable. In relapsing-remitting patients there were correlations between increases in the number of gadolinium enhancing lesions and increases in EDSS and the occurrence of attacks. In chronic progressive patients, increases in lesion volume were correlated with both increases in EDSS and AI. These results demonstrate a linkage between MRI and clinical disease that depends both on the stage of MS and the MRI measures used and support the use of MRI as a surrogate marker of clinical disability in the study of multiple sclerosis.

Inflammatory central nervous system demyelination: correlation of magnetic resonance imaging findings with lesion pathology

Magnetic resonance imaging (MRI) is widely used to evaluate and monitor disease activity in inflammatory demyelinating central nervous system (CNS) diseases such as multiple sclerosis. The present study aimed at correlating MRI findings with histological parameters in 6 cases of biopsy-proven inflammatory demyelination of the CNS. The earliest stages of demyelinating activity manifested as almost isointense lesions with a massive gadolinium-DTPA (Gd-DTPA) enhancement in T1-weighted scans. In T2-weighted scans, early active lesions formed a border of decreased intensity compared with the lesion center and the perifocal edema. The morphological correlate of this pattern in our patients was activated macrophages in the zone of myelin destruction at the plaque border. Late active lesions were hypointense in T1 and hyperintense in T2 scans. Inactive demyelinated and remyelinating lesions were hyperintense in T2 scans and enhanced inhomogenously after Gd-DTPA application. T1 scans revealed major differences in the degree of hypointensity that correlated with the extent of axonal damage, extracellular edema, and the degree of demyelination or remyelination.