Brain and spinal cord MR in benign multiple sclerosis: a follow-up study

Grey-matter sodium concentration as an individual marker of multiple sclerosis severity

OBJECTIVE

Quantification of brain injury in patients with variable disability despite similar disease duration may be relevant to identify the mechanisms underlying disability in multiple sclerosis (MS). We aimed to compare grey-matter sodium abnormalities (GMSAs), a parameter reflecting neuronal and astrocyte dysfunction, in MS patients with benign multiple sclerosis (BMS) and non-benign multiple sclerosis (NBMS).

METHODS

We identified never-treated BMS patients in our local MS database of 1352 patients. A group with NBMS was identified with same disease duration. All participants underwent ²³Na magnetic resonance imaging (MRI). The existence of GMSA was detected by statistical analysis.

RESULTS

In total, 102 individuals were included (21 BMS, 25 NBMS and 56 controls). GMSA was detected in 10 BMS and 19 NBMS (11/16 relapsing-remitting multiple sclerosis (RRMS) and 8/9 secondary progressive multiple sclerosis (SPMS) patients) (p = 0.05). On logistic regression including the presence or absence of GMSA, thalamic volume, cortical grey-matter volume and T2-weighted lesion load, thalamic volume was independently associated with BMS status (odds ratio (OR) = 0.64 for each unit). Nonetheless, the absence of GMSA was independently associated when excluding patients with significant cognitive alteration (n = 7) from the BMS group (OR = 4.6).

CONCLUSION

Detection of GMSA in individuals and thalamic volume are promising to differentiate BMS from NBMS as compared with cortical or whole grey-matter atrophy and T2-weighted lesions.

Magnetic Resonance Image Analysis for Brain CAD Systems with Machine Learning

This chapter describes the image analysis for brain Computer-Aided Diagnosis (CAD) systems with machine learning techniques, which could assist radiologists in the detection of such brain diseases as asymptomatic unruptured aneurysms, Alzheimer’s Disease (AD), vascular dementia, and Multiple Sclerosis (MS) by magnetic resonance imaging. Image analysis in CAD systems consists of image enhancement, initial detection, and image feature extraction, including segmentation. In addition, the authors review the classification of true and false positives using machine learning techniques, as well as the evaluation methods and development cycle for CAD systems.

Cluster analysis of behavioural and event-related potentials during a contingent negative variation paradigm in remitting-relapsing and benign forms of multiple sclerosis

Background

Event-related potentials (ERPs) may be used as a highly sensitive way of detecting subtle degrees of cognitive dysfunction. On the other hand, impairment of cognitive skills is increasingly recognised as a hallmark of patients suffering from multiple sclerosis (MS). We sought to determine the psychophysiological pattern of information processing among MS patients with the relapsing-remitting form of the disease and low physical disability considered as two subtypes: 'typical relapsing-remitting' (RRMS) and 'benign MS' (BMS). Furthermore, we subjected our data to a cluster analysis to determine whether MS patients and healthy controls could be differentiated in terms of their psychophysiological profile.

Methods

We investigated MS patients with RRMS and BMS subtypes using event-related potentials (ERPs) acquired in the context of a Posner visual-spatial cueing paradigm. Specifically, our study aimed to assess ERP brain activity in response preparation (contingent negative variation -CNV) and stimuli processing in MS patients. Latency and amplitude of different ERP components (P1, eN1, N1, P2, N2, P3 and late negativity -LN) as well as behavioural responses (reaction time -RT; correct responses -CRs; and number of errors) were analyzed and then subjected to cluster analysis.

Results

Both MS groups showed delayed behavioural responses and enhanced latency for long-latency ERP components (P2, N2, P3) as well as relatively preserved ERP amplitude, but BMS patients obtained more important performance deficits (lower CRs and higher RTs) and abnormalities related to the latency (N1, P3) and amplitude of ERPs (eCNV, eN1, LN). However, RRMS patients also demonstrated abnormally high amplitudes related to the preparation performance period of CNV (cCNV) and post-processing phase (LN). Cluster analyses revealed that RRMS patients appear to make up a relatively homogeneous group with moderate deficits mainly related to ERP latencies, whereas BMS patients appear to make up a rather more heterogeneous group with more severe information processing and attentional deficits.

Conclusions

Our findings are suggestive of a slowing of information processing for MS patients that may be a consequence of demyelination and axonal degeneration, which also seems to occur in MS patients that show little or no progression in the physical severity of the disease over time.

Relationship between brain MRI lesion load and short-term disease evolution in non-disabling MS: a large-scale, multicentre study

BACKGROUND AND OBJECTIVES

We evaluated clinical and conventional MRI features of a large population of patients with non-disabling MS to identify potential markers of a benign disease course.

METHODS

In seven MAGNIMS centres we retrospectively identified 182 patients with benign (B) MS (EDSS score ≤ 3.0, disease duration ≥ 15 years) and 187 patients with non-disabling relapsing-remitting MS (NDRRMS) (Expanded Disability Status Scale score ≤ 3.0, disease duration between 5 and 14 years), in whom clinical data were collected within two weeks from a brain T2-weighted scan. Brain T2 lesion volume (LV) was measured in all patients. In 146 BMS and 146 NDRRMS patients, clinical data were also available after a median follow up of 29 months (range: 7-104 months).

RESULTS

Mean LV was higher in BMS than in NDRRMS patients (p<0.001), but the mean ratio between LV and disease duration was higher in NDRRMS than in BMS patients (1.1 vs. 0.6 ml/year, p<0.001). In BMS patients, brain LV was correlated with EDSS score increase at follow up (r=0.18, p=0.03).

CONCLUSIONS

An overall low rate of brain LV increase during a long-lasting disease course might be a feature of BMS. In BMS patients, a high brain LV might be associated with worsening of locomotor disability at short-term follow up.

Structural and functional MRI correlates of Stroop control in benign MS

The objective of this study was to assess the functional and structural substrates of cognitive network changes in patients with benign multiple sclerosis (BMS), using an analysis of effective connectivity and MR tractography. Using a 3-Tesla scanner, we acquired dual-echo, diffusion tensor (DT) and functional MRI during the performance of the Stroop task from 15 BMS patients and 19 healthy controls. DT MRI tractography was used to calculate DT derived metrics from several white matter (WM) fiber bundles, thought to be involved in cognitive performance. DT MRI metrics from WM fiber bundles not directly related with cognitive performance were also derived. Effective connectivity analysis was performed using statistical parametric mapping. MS patients had significantly abnormal DT MRI metrics in all the structures analyzed. Compared with controls, MS patients had more significant activations of several areas of the cognitive network involved in Stroop performance, bilaterally. Compared with controls, BMS patients also had increased connectivity strengths between several cortical areas of the sensorimotor network and the right (R) inferior frontal gyrus and the R cerebellum, as well as decreased connectivity strengths with the anterior cingulate cortex. Coefficients of altered connectivity were moderately correlated with structural MRI metrics of tissue damage within intra- and inter-hemispheric cognitive-related WM fiber bundles, while no correlations were found with the remaining fiber bundles studied, suggesting that functional cortical changes in patients with BMS might represent an adaptive response driven by damage of specific WM structures.

The topographical distribution of tissue injury in benign MS: a 3T multiparametric MRI study

We compared the global and regional distribution of white matter (WM) and gray matter (GM) damage and T2-visible lesion between patients with benign (B) and relapsing remitting (RR) multiple sclerosis (MS). BMS and RRMS patients did not differ in terms of global volumes and diffusion tensor (DT) MRI metrics of the WM and GM. Compared to controls, BMS and RRMS patients had bilateral thalamic loss. Compared to controls, BMS and RRMS patients had lower WM fractional anisotropy (FA) in the corpus callosum (CC) and in several regions of temporal and occipital lobes. BMS also had a decreased WM FA in the parietal lobes. RRMS patients had also lower WM FA in several regions of the frontal lobes. Compared to BMS, RRMS patients had decreased WM FA in the frontal lobes, while the opposite comparison showed lower WM FA in the CC, the temporal lobes and the cuneus in BMS. Contrasted to controls, both MS groups showed several regions of increased MD in WM and GM, but no difference was found between MS sub-groups. T2-visible lesions were mainly located in the posterior regions of the brain in BMS patients, while they involved also regions in the frontal lobes, in RRMS patients. BMS and RRMS patients differ in terms of the topographical distribution of WM damage rather than in the overall extent of brain structural changes. The less prominent involvement of the frontal lobe WM and of the NAWM in general in BMS might be associated to their favorable clinical status.

Comparison of three different methods for measurement of cervical cord atrophy in multiple sclerosis

BACKGROUND AND PURPOSE

Evidence is mounting that spinal cord atrophy significantly correlates with disability in patients with multiple sclerosis (MS). The purpose of this work was to validate 3 different measures for the measurement of cervical cord atrophy on high-resolution MR imaging in patients with MS and in normal control subjects (NCs). We also wanted to evaluate the relationship between cervical cord atrophy and clinical disability in the presence of other conventional and nonconventional brain MR imaging metrics by using a unique additive variance regression model.

MATERIALS AND METHODS

We studied 66 MS patients (age, 41.2 +/- 12.4 years; disease duration, 11.8 +/- 10.7 years; Expanded Disability Status Scale, 3.1 +/- 2.1) and 19 NCs (age, 30.4 +/- 12.0 years). Disease course was relapsing-remitting (34), secondary-progressive (14), primary-progressive (7), and clinically isolated syndrome (11). The cervical cord absolute volume (CCAV) in cubic millimeters and 2 normalized cervical cord measures were calculated as follows: cervical cord fraction (CCF) = CCAV/thecal sac absolute volume, and cervical cord to intracranial volume (ICV) fraction (CCAV/ICV). Cervical and brain lesion volume measures, brain parenchyma fraction (BPF), and mean diffusivity were also calculated.

RESULTS

CCAV (P < .0001) and CCF (P = .007) showed the largest differences between NCs and MS patients and between different disease subtypes. In regression analysis predicting disability, CCAV was retained first (R(2) = 0.498; P < .0001) followed by BPF (R(2) = 0.08; P = .08). Only 8% of the variance in disability was explained by brain MR imaging measures when coadjusted for the amount of cervical cord atrophy.

CONCLUSIONS

3D CCAV measurement showed the largest differences between NCs and MS patients and between different disease subtypes. Cervical cord atrophy measurement provides valuable additional information related to disability that is not obtainable from brain MR imaging metrics.

Axonal protection achieved in a model of multiple sclerosis using lamotrigine

Axonal degeneration is a major cause of permanent disability in multiple sclerosis (MS). Recent observations from our and other laboratories suggest that sodium accumulation within compromised axons is a key, early step in the degenerative process, and hence that limiting axonal sodium influx may represent a mechanism for axonal protection in MS. Here we assess whether lamotrigine, a sodium channel-blocking agent, is effective in preventing axonal degeneration in an animal model of MS, namely chronic-relapsing experimental autoimmune encephalomyelitis (CR-EAE). When administered from 7 days post-inoculation, lamotrigine provided a small but significant reduction in the neurological deficit present at the termination of the experiments (averaged over three independent experiments; vehicle: 3.5+/-2.7; lamotrigine: 2.6+/-2.0, P<0.05) and preserved more functional axons in the spinal cord (measured as mean compound action potential area; vehicle: 31.7 microV.ms+/-23.0; lamotrigine: 42.9+/-27.4, P<0.05). Histological examination of the thoracic spinal cord (n=71) revealed that lamotrigine treatment also provided significant protection against axonal degeneration (percentage degeneration in dorsal column; vehicle: 33.5 %+/-38.5; lamotrigine: 10.4 %+/-12.5, P<0.01). The findings suggest that lamotrigine may provide a novel avenue for axonal protection in MS.

Axon loss is responsible for chronic neurological deficit following inflammatory demyelination in the rat

Axonal loss is now considered a consistent feature of MS pathology and evidence suggests that its accumulation may be the pathological correlate for the development of irreversible disability. In this study, we investigated the features of axonal loss in myelin autoimmunity and tested the hypothesis that loss of axons determines permanent neurological impairment in a model of inflammatory demyelination that closely mimics the pathology and course of MS. EAE was induced in DA rats by injection of recombinant mouse MOG with IFA. Animals that developed progressive EAE were killed at several time points after disease onset and animals that followed a chronic relapsing-remitting course of EAE were killed at approximately 4 months, exhibiting varying degrees of residual disability. Toluidine blue staining of semithin sections and immunohistochemistry for OX-42 were used to quantify demyelination, remyelination, inflammation and axonal loss in the spinal cord of MOG-EAE rats. In progressive EAE, the degree of axon loss, demyelination and inflammation all correlated significantly with clinical severity scores and a causative role for macrophages in the pathogenesis of axonal injury is suggested. However, in the chronic stage of relapsing-remitting EAE, in rats having suffered a variable number of relapses, only axonal loss correlated significantly with clinical severity scores. In addition, both axonal loss and clinical severity scores correlated with the number of relapses. These findings imply that secondary, or 'bystander', axonal loss is the main determinant of irreversible neurological disability in MOG-EAE and make the model a useful tool for the investigation of mechanisms of axonal loss and the evaluation of the benefits of neuroprotective therapies under conditions of antibody-mediated inflammatory demyelination.

Three-dimensional analysis of the geometry of individual multiple sclerosis lesions: detection of shape changes over time using spherical harmonics

PURPOSE

To suggest a quantitative method for assessing the temporal changes in the geometry of individual multiple sclerosis (MS) lesions in follow-up studies of MS patients.

MATERIALS AND METHODS

Computer simulated and in vivo magnetic resonance (MR) imaged MS lesions were studied. Ten in vivo MS lesions were identified from sets of axial MR images acquired from a patient scanned consecutively for 24 times during a one-year period. Each of the lesions was segmented and its three-dimensional surface approximated using spherical harmonics (SH). From the obtained SH polynomial coefficients, indices of shape were defined, and analysis of the temporal changes in each lesion's geometry throughout the year was performed by determining the mean discrete total variation of the shape indices.

RESULTS

The results demonstrate that most of the studied lesions undergo notable geometrical changes with time. These changes are not necessarily associated with similar changes in size/volume. Furthermore, it was found that indices corresponding to changes in lesion shape could be 1.4 to 8.0 times higher than those corresponding to changes in the lesion size/volume.

CONCLUSION

Quantitative three-dimensional shape analysis can serve as a new tool for monitoring MS lesion activity and study patterns of MS lesion evolution over time.

Diffuse signal abnormalities in the spinal cord in multiple sclerosis: direct postmortem in situ magnetic resonance imaging correlated with in vitro high-resolution magnetic resonance imaging and histopathology

In this study, we compared direct postmortem in situ (whole-corpse) sagittal spinal cord magnetic resonance imaging (1.5T) of 7 multiple sclerosis cases with targeted high-resolution in vitro axial magnetic resonance imaging (4.7T) and histopathology. On sagittal in situ magnetic resonance imaging, 1 case had a normal spinal cord, 2 had only focal lesions, 3 had a combination of focal and diffuse abnormalities, and 1 had only diffuse abnormalities. All spinal cords showed abnormalities on high-resolution magnetic resonance imaging and histopathology, confirming the existence of diffuse cord changes as genuine multiple sclerosis-related abnormalities while highlighting the limited resolution of in vivo magnetic resonance imaging.

Adaptive functional changes in the cerebral cortex of patients with nondisabling multiple sclerosis correlate with the extent of brain structural damage

In multiple sclerosis, the mechanisms underlying the accumulation of disability are poorly understood. Recently, it has been suggested that adaptive cortical changes may limit the clinical impact of multiple sclerosis injury. In this study, functional magnetic resonance imaging and a general search method were used to assess patterns of brain activation associated with a simple motor task in 14 right-handed, nondisabled relapsing-remitting multiple sclerosis patients that were compared to those from 15 right-handed, sex- and age-matched healthy volunteers. Also investigated were the extent to which the functional magnetic resonance imaging changes correlated with T2 lesion volume and severity of multiple sclerosis pathology in lesions and normal-appearing brain tissue, measured using magnetisation transfer and diffusion tensor magnetic resonance imaging. Compared to controls, multiple sclerosis patients showed increased activation in the contralateral primary sensorimotor cortex, bilaterally in the supplementary motor area, bilaterally in the cingulate motor area, in the contralateral ascending bank of the sylvian fissure, and in the contralateral intraparietal sulcus. T2 lesion volume was correlated with relative activation in the ipsilateral supplementary motor area, and in the ipsilateral and contralateral cingulate motor area. Average lesion magnetisaiton transfer ratio and average lesion water diffusivity were correlated with relative activation in the contralateral sensorimotor cortex. Average lesion magnetisation transfer ratio was also correlated with relative activation in the ipsilateral cingulate motor area. Average water diffusivity and peak height of the normal-appearing brain tissue diffusivity histogram were both correlated with relative activation in the contralateral intraparietal sulcus. This study shows that cortical activation occurs over a rather distributed sensorimotor network in nondisabled relapsing-remitting multiple sclerosis patients. It also suggests that increased recruitment of this cortical network contributes to the limitation of the functional impact of white matter multiple sclerosis injury.

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.

Normal-appearing white matter changes in multiple sclerosis: the contribution of magnetic resonance techniques

Several magnetic resonance (MR) techniques have proved to be sensitive enough to detect the subtle pathological changes that post-mortem studies showed to occur in the normal-appearing white matter (NAWM) from patients with multiple sclerosis (MS). Although these abnormalities can be detected in other neurological conditions, they seem to be more frequent and diffuse in MS. However, the contribution of NAWM changes to the diagnosis is still unclear. Their nature is also unknown and perhaps differs in different phases and clinical manifestations of the disease. Nevertheless, the extent and severity of NAWM damage seems to be relevant in causing disability and influencing the clinical evolution in MS patients. This review will summarize the present knowledge about MR-detected NAWM changes in MS and their relevance to the diagnosis and the understanding of disease evolution.