Pathological study of spinal cord atrophy in multiple sclerosis suggests limited role of local lesions

Immunoexcitoxicity as the possible major pathophysiology behind multiple sclerosis and other autoimmune disorders

Autoimmune disorders are destructive processes considered to be an attack on "self " antigens by the immune system CD-+4 T-cells that are directed toward antigens, in the case of multiple sclerosis (MS), particularly myelin antigens. Yet, there is growing evidence that the major destructive events in MS, as well as other non-central nervous system (CNS) autoimmune disorders, are much more than an immune attack on the CNS initiated by a misdirected immune system that attacks a "self " antigen or antigens by a process called molecular mimicry. Extensive evidence suggests that inflammation, in turn, initiates excitotoxicity, which is responsible for the majority of pathological findings in all stages of the disease, especially a loss of oligodendroglia (source of myelin) and axon injury in MS. Excitotoxicity also is a better explanation for progressive MS, in which the immune attack has either slowed or is halted; yet, the destructive pathology continues to progress. It also explains the destructive lesions seen in gray matter, which is essentially devoid of inflammation. It has recently been shown that most of the damage to the oligodendrocytes, as well as axonal injury, is secondary to excitotoxicity. While there is a growing appreciation that excitotoxicity plays a major role, there has been little effort to link the immune changes to the excitotoxic process, recently named immunoexcitotoxicity, even though the role of excitotoxicity has been shown to occur in the inflammatory stage in the beginning and throughout the process of the disease, particularly the chronic progressive stage. It is also known that peripheral glutamate receptors exist throughout the body, thus making the process of immunoexcitotoxicity a possible integral part of all or most autoimmune disorders in which the immune system is intimately linked to enhancing the excitotoxic process. This is of special concern now that peripheral glutamate receptors have been isolated in many peripheral tissues and are known to be fully functional.

Hallmarks of spinal cord pathology in multiple sclerosis

A disparity exists between spinal cord and brain involvement in multiple sclerosis (MS), each independently contributing to disability. Underlying differences between brain and cord are not just anatomical in nature (volume, white/grey matter organization, vascularization), but also in barrier functions (differences in function and composition of the blood-spinal cord barrier compared to blood-brain barrier) and possibly in repair mechanisms. Also, immunological phenotypes seem to influence localization of inflammatory activity. Whereas the brain has gained a lot of attention in MS research, the spinal cord lags behind. Advanced imaging techniques and biomarkers are improving and providing us with tools to uncover the mechanisms of spinal cord pathology in MS. In the present review, we elaborate on the underlying anatomical and physiological factors driving differences between brain and cord involvement in MS and review current literature on pathophysiology of spinal cord involvement in MS and the observed differences to brain involvement.

Understanding the spectrum of non-motor symptoms in multiple sclerosis: insights from animal models

Multiple sclerosis is a chronic autoimmune disease of the central nervous system and is generally considered to be a non-traumatic, physically debilitating neurological disorder. In addition to experiencing motor disability, patients with multiple sclerosis also experience a variety of non-motor symptoms, including cognitive deficits, anxiety, depression, sensory impairments, and pain. However, the pathogenesis and treatment of such non-motor symptoms in multiple sclerosis are still under research. Preclinical studies for multiple sclerosis benefit from the use of disease-appropriate animal models, including experimental autoimmune encephalomyelitis. Prior to understanding the pathophysiology and developing treatments for non-motor symptoms, it is critical to characterize the animal model in terms of its ability to replicate certain non-motor features of multiple sclerosis. As such, no single animal model can mimic the entire spectrum of symptoms. This review focuses on the non-motor symptoms that have been investigated in animal models of multiple sclerosis as well as possible underlying mechanisms. Further, we highlighted gaps in the literature to explain the non-motor aspects of multiple sclerosis in experimental animal models, which will serve as the basis for future studies.

MRI assessment of cervical spinal cord cross-sectional area in patients with multiple sclerosis

Objectives

Spinal cord abnormalities including cervical cord atrophy are common in multiple sclerosis (MS). This study aimed to assess the cervical spinal cord cross-sectional area (CSA) using magnetic resonance imaging (MRI) in MS patients.

Materials and Methods

Sixty participants were enrolled in this study (16 male and 44 female), 30 patients with MS, diagnosed according to the revised McDonald criteria, and 30 apparently healthy individuals as the control group. CSA of the spinal cord was measured on axial T2-weighted images of the cervical MRI studies from C2 to C7 vertebral levels.

Results

There was a significant difference between MS patients and the control group in mean CSA at a different level. The mean CSA at C2, in MS cases, was significantly lower than controls (67.7 ± 9.4 mm2 vs. 81.3 ± 4.6 mm2). Similarly, the mean CSA at C7 (64.4 ± 9.9 mm2) and average C2-7 (68 ± 9.1 mm2) of MS cases were significantly lower than the control. There was a strong inverse correlation between mean cervical cord CSA and duration of the disease and disability score. The reduction in cervical cord CSA was more prominent in patients with secondary progressive MS. There was no significant difference regarding age, gender, type of treatment, or the number of cervical cord lesions.

Conclusion

The mean CSA was significantly lower in patients with MS than in the control group and was lesser in progressive types. Patients with a longer duration of MS and a high disability score tend to have smaller CSA.

Feasibility of diffusion kurtosis imaging in evaluating cervical spinal cord injury in multiple sclerosis

This research aimed to assess gray matter (GM), white matter (WM), lesions of multiple sclerosis (MS) and the therapeutic effect using diffusion kurtosis imaging (DKI). From January 2018 to October 2019, 78 subjects (48 of MS and 30 of health) perform routine MR scan and DKI of cervical spinal cord. The MS patients were divided into 2 groups according to the presence or absence of T2 hyperintensity. DKI-metrics were measured in the lesions, normal-appearing GM and WM. Significant differences were detected in DKI metrics between MS and healthy (P < .05) and between patients with cervical spinal cord T2-hyperintense and without T2-hyperintense (P < .001). Compared to healthy, GM-mean kurtosis (MK), GM-radial kurtosis, and WM-fractional anisotropy, WM-axial diffusion were statistically reduced in patients without T2-hyperintense (P < .05). Significant differences were observed in DKI metrics between patients with T2-hyperintense after therapy (P < .05), as well as GM-MK and WM-fractional anisotropy, WM-axial diffusion in patients without T2-hyperintense (P < .05); Expanded Disability Status Scale was correlated with MK values, as well as Expanded Disability Status Scale scores and MK values after therapy. Our results indicate that DKI-metrics can detect and quantitatively evaluate the changes in cervical spinal cord micropathological structure.

Magnetic Resonance Imaging in Primary Progressive Multiple Sclerosis Patients : Review

The recently developed effective treatment of primary progressive multiple sclerosis (PPMS) requires the accurate diagnosis of patients with this type of disease. Currently, the diagnosis of PPMS is based on the 2017 McDonald criteria, although the contribution of magnetic resonance imaging (MRI) to this process is fundamental. PPMS, one of the clinical types of MS, represents 10%-15% of all MS patients. Compared to relapsing-remitting MS (RRMS), PPMS differs in terms of pathology, clinical presentation and MRI features. Regarding conventional MRI, focal lesions on T2-weighted images and acute inflammatory lesions with contrast enhancement are less common in PPMS than in RRMS. On the other hand, MRI features of chronic inflammation, such as slowly evolving/expanding lesions (SELs) and leptomeningeal enhancement (LME), and brain and spinal cord atrophy are more common MRI characteristics in PPMS than RRMS. Nonconventional MRI also shows differences in subtle white and grey matter damage between PPMS and other clinical types of disease. In this review, we present separate diagnostic criteria, conventional and nonconventional MRI specificity for PPMS, which may support and simplify the diagnosis of this type of MS in daily clinical practice.

Relaxometry and brain myelin quantification with synthetic MRI in MS subtypes and their associations with spinal cord atrophy

Immune-mediated demyelination and neurodegeneration are pathophysiological hallmarks of Multiple Sclerosis (MS) and main drivers of disease related disability. The principal method for evaluating qualitatively demyelinating events in the clinical context is contrast-weighted magnetic resonance imaging (MRI). Moreover, advanced MRI sequences provide reliable quantification of brain myelin offering new opportunities to study tissue pathology in vivo. Towards neurodegenerative aspects of the disease, spinal cord atrophy - besides brain atrophy - is a powerful and validated predictor of disease progression. The etiology of spinal cord volume loss is still a matter of research, as it remains unclear whether the impact of local lesion pathology or the interaction with supra- and infratentorial axonal degeneration and demyelination of the long descending and ascending fiber tracts are the determining factors. Quantitative synthetic MR using a multiecho acquisition of saturation recovery pulse sequence provides fast automatic brain tissue and myelin volumetry based on R1 and R2 relaxation rates and proton density quantification, making it a promising modality for application in the clinical routine. In this cross sectional study a total of 91 MS patients and 31 control subjects were included to investigate group differences of global and regional measures of brain myelin and relaxation rates, in different MS subtypes, using QRAPMASTER sequence and SyMRI postprocessing software. Furthermore, we examined associations between these quantitative brain parameters and spinal cord atrophy to draw conclusions about possible pathophysiological relationships. Intracranial myelin volume fraction of the global brain exhibited statistically significant differences between control subjects (10.4%) and MS patients (RRMS 9.4%, PMS 8.1%). In a LASSO regression analysis with total brain lesion load, intracranial myelin volume fraction and brain parenchymal fraction, the intracranial myelin volume fraction was the variable with the highest impact on spinal cord atrophy (standardized coefficient 4.52). Regional supratentorial MRI metrics showed altered average myelin volume fraction, R1, R2 and proton density in MS patients compared to controls most pronounced in PMS. Interestingly, quantitative MRI parameters in supratentorial regions showed strong associations with upper cord atrophy, suggesting an important role of brain diffuse demyelination on spinal cord pathology possibly in the context of global disease activity. R1, R2 or proton density of the thalamus, cerebellum and brainstem correlated with upper cervical cord atrophy, probably reflecting the direct functional connection between these brain structures and the spinal cord as well as the effects of retrograde and anterograde axonal degeneration. By using Synthetic MR-derived myelin volume fraction, we were able to effectively detect significant differences of myelination in relapsing and progressive MS subtypes. Total intracranial brain myelin volume fraction seemed to predict spinal cord volume loss better than brain atrophy or total lesion load. Furthermore, demyelination in highly myelinated supratentorial regions, as an indicator of diffuse disease activity, as well as alterations of relaxation parameters in adjacent infratentorial and midbrain areas were strongly associated with upper cervical cord atrophy.

NFL during acute spinal cord lesions in MS: a hurdle for the detection of inflammatory activity

INTRODUCTION

Levels of neuro-filament light chain (NFL) correlate with clinical and radiological activity in multiple sclerosis (MS) and have been used as a surrogate biomarker of axonal destruction related to inflammatory activity. The main objective of this work is to explore the specific contribution of acute inflammation within the spinal cord to the elevation of NFL levels.

PATIENTS AND METHODS

MS patients with a baseline study of NFL at diagnosis of the disease and a brain and spinal cord MRI scan were selected. Patients were classified according to the presence, number and location of gadolinium enhancing lesion (GEL) and the relationship between NFL levels and both brain and spinal cord GEL were explored.

RESULTS

Seventy-seven patients were selected. NFL levels were significantly higher in patients with only one GEL restricted to the brain than those without GEL (1702 pg/ml vs 722.7 pg/mL, p = 0.03) and correlated with number. However, no differences were seen among patients with GEL limited to the spinal cord and those without GEL (735.2 pg/ml vs 722.7 pg/mL).

CONCLUSION

Our study reaffirms the value of NFL levels in monitoring asymptomatic inflammatory activity in the brain measured by GEL. However, NFL concentration is not as useful when only inflammatory activity occurs in the spinal cord.

Multiple sclerosis lesions and atrophy in the spinal cord: Distribution across vertebral levels and correlation with disability

BACKGROUND

The vast majority of magnetic resonance imaging (MRI) studies on multiple sclerosis (MS) covered the spinal cord (SC), if at all, incompletely.

OBJECTIVE

To assess SC involvement in MS, as detectable by whole SC MRI, with regard to distribution across vertebral levels and relation to clinical phenotypes and disability.

METHODS

We investigated SC MRI with sagittal and axial coverage. Analyzed were brain and SC MRI scans of 17 healthy controls (HC) and of 370 patients with either clinically isolated syndrome (CIS, 27), relapsing remitting MS (RRMS, 303) or progressive MS (PMS, 40). Across vertebral levels, cross-sectional areas were semiautomatically segmented, and lesions manually delineated.

RESULTS

The frequency of SC lesions was highest at the level C3-4. The volume of SC lesions increased from CIS to RRMS, and from RRMS to PMS whereas lesion distribution across SC levels did not differ. SC atrophy was demonstrated in RRMS and, to a higher degree, in PMS; apart from an accentuation at the level C3-4, it was evenly distributed across SC levels. SC lesions and atrophy volume were not correlated with each other and were independently associated with disability.

CONCLUSION

SC lesions and atrophy already exist at the stage of RRMS in the whole SC with an accentuation in the cervical enlargement; SC lesions and atrophy are more pronounced in the stage of PMS. Both contribute to the clinical picture but are largely independent.

Upper cervical cord atrophy is independent of cervical cord lesion volume in early multiple sclerosis: A two-year longitudinal study

BACKGROUND

Upper cervical cord atrophy and lesions have been shown to be associated with disease and disability progression already in early relapsing-remitting multiple sclerosis (RRMS). However, their longitudinal relationship remains unclear.

OBJECTIVE

To investigate the cross-sectional and longitudinal relation between focal T2 cervical cord lesion volume (CCLV) and regional and global mean upper cervical cord area (UCCA), and their relations with disability.

METHODS

Over a two-year interval, subjects with RRMS (n = 36) and healthy controls (HC, n = 16) underwent annual clinical and MRI examinations. UCCA and CCLV were obtained from C1 through C4 level. Linear mixed model analysis was performed to investigate the relation between UCCA, CCLV, and disability over time.

RESULTS

UCCA at baseline was significantly lower in RRMS subjects compared to HCs (p = 0.003), but did not decrease faster over time (p ≥ 0.144). UCCA and CCLV were independent of each other at any of the time points or cervical levels, and over time. Lower baseline UCCA, but not CCLV, was related to worsening of both upper and lower extremities function over time.

CONCLUSION

UCCA and CCLV are independent from each other, both cross-sectionally and longitudinally, in early MS. Lower UCCA, but not CCLV, was related to increasing disability over time.

Improved Assessment of Longitudinal Spinal Cord Atrophy in Multiple Sclerosis Using a Registration-Based Approach: Relevance for Clinical Studies

BACKGROUND

Reliable measurements of cervical cord atrophy progression may be useful for monitoring neurodegeneration in multiple sclerosis (MS).

PURPOSE

To compare a new, registration-based (Reg) method with two existing methods (active surface [AS] and propagation segmentation [PropSeg]) to measure cord atrophy changes over time in MS.

STUDY TYPE

Retrospective.

SUBJECTS

Cohort I: Eight healthy controls (HC) and 28 MS patients enrolled at a single institution, and cohort II: 25 HC and 63 MS patients enrolled at three European sites.

FIELD STRENGTH/SEQUENCE

3D T1-weighted gradient echo sequence, acquired at 1.5 T (cohort I) and 3.0 T (cohort II).

ASSESSMENT

Percentage cord area changes (PCACs) between baseline and follow-up (cohort I: 2.34 years [interquartile range = 2.00-2.55 years], cohort II: 1.05 years [interquartile range = 1.01-1.18 years]) were evaluated for all subjects using Reg, AS, and PropSeg. Reg included an accurate registration of baseline and follow-up straightened cord images, followed by AS-based optimized cord segmentation. A subset of studies was analyzed twice by two observers.

STATISTICAL TESTS

Linear regression models were used to estimate annualized PCAC, and effect sizes expressed as the ratio between the estimated differences and HC error term (P < 0.05). Reproducibility was assessed by linear mixed-effect models. Annualized PCACs were used for sample size calculations (significance: α = 0.05, power: 1 - β = 0.80).

RESULTS

Annualized PCACs and related standard errors (SEs) were lower with Reg than with other methods: PCAC in MS patients at 1.5 T was -1.12% (SE = 0.22) with Reg, -1.32% (SE = 0.30) with AS, and -1.40% (SE = 0.33) with PropSeg, while at 3.0 T PCAC was -0.83% (SE = 0.25) with Reg, -0.92% (SE = 0.32) with AS, and -1.18 (SE = 0.53) with PropSeg. This was reflected in larger effect sizes and lower sample sizes. Intra- and inter-observer agreement range was 0.72-0.91 with AS, and it was >0.96 with Reg.

DATA CONCLUSION

The results support the use of the registration method to measure cervical cord atrophy progression in future MS clinical studies.

LEVEL OF EVIDENCE

3 TECHNICAL EFFICACY STAGE: 2.

Cervical and thoracic cord atrophy in multiple sclerosis phenotypes: Quantification and correlation with clinical disability

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Spinal cord atrophy is prevalent across multiple sclerosis phenotypes.

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It correlates with disability, especially in relapsing-remitting patients.

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This correlation can be demonstrated both cross-sectionally and longitudinally.

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Cervical atrophy is highly associated with disability and disease progression.

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Thoracic atrophy contributes to improved correlation and radiological subgrouping.

Objective

We sought to characterize spinal cord atrophy along the entire spinal cord in the major multiple sclerosis (MS) phenotypes, and evaluate its correlation with clinical disability.

Methods

Axial T₁-weighted images were automatically reformatted at each point along the cord. Spinal cord cross‐sectional area (SCCSA) were calculated from C1-T10 vertebral body levels and profile plots were compared across phenotypes. Average values from C2-3, C4-5, and T4-9 regions were compared across phenotypes and correlated with clinical scores, and then categorized as atrophic/normal based on z-scores derived from controls, to compare clinical scores between subgroups. In a subset of relapsing-remitting cases with longitudinal scans these regions were compared to change in clinical scores.

Results

The cross-sectional study consisted of 149 adults diagnosed with relapsing-remitting MS (RRMS), 49 with secondary-progressive MS (SPMS), 58 with primary-progressive MS (PPMS) and 48 controls. The longitudinal study included 78 RRMS cases. Compared to controls, all MS groups had smaller average regions except RRMS in T4-9 region. In all MS groups, SCCSA from all regions, particularly the cervical cord, correlated with most clinical measures. In the RRMS cohort, 22% of cases had at least one atrophic region, whereas in progressive MS the rate was almost 70%. Longitudinal analysis showed correlation between clinical disability and cervical cord thinning.

Conclusions

Spinal cord atrophy was prevalent across MS phenotypes, with regional measures from the RRMS cohort and the progressive cohort, including SPMS and PPMS, being correlated with disability. Longitudinal changes in the spinal cord were documented in RRMS cases, making it a potential marker for disease progression. While cervical SCCSA correlated with most disability and progression measures, inclusion of thoracic measurements improved this correlation and allowed for better subgrouping of spinal cord phenotypes. Cord atrophy is an important and easily obtainable imaging marker of clinical and sub-clinical progression in all MS phenotypes, and such measures can play a key role in patient selection for clinical trials.

Classification of multiple sclerosis based on patterns of CNS regional atrophy covariance

There is evidence that multiple sclerosis (MS) pathology leads to distinct patterns of volume loss over time (VLOT) in different central nervous system (CNS) structures. We aimed to use such patterns to identify patient subgroups. MS patients of all classical disease phenotypes underwent annual clinical, blood, and MRI examinations over 6 years. Spinal, striatal, pallidal, thalamic, cortical, white matter, and T2‐weighted lesion volumes as well as serum neurofilament light chain (sNfL) were quantified. CNS VLOT patterns were identified using principal component analysis and patients were classified using hierarchical cluster analysis. 225 MS patients were classified into four distinct Groups A, B, C, and D including 14, 59, 141, and 11 patients, respectively). These groups did not differ in baseline demographics, disease duration, disease phenotype distribution, and lesion‐load expansion. Interestingly, Group A showed pronounced spinothalamic VLOT, Group B marked pallidal VLOT, Group C small between‐structure VLOT differences, and Group D myelocortical volume increase and pronounced white matter VLOT. Neurologic deficits were more severe and progressed faster in Group A that also had higher mean sNfL levels than all other groups. Group B experienced more frequent relapses than Group C. In conclusion, there are distinct patterns of VLOT across the CNS in MS patients, which do not overlap with clinical MS subtypes and are independent of disease duration and lesion‐load but are partially associated to sNfL levels, relapse rates, and clinical worsening. Our findings support the need for a more biologic classification of MS subtypes including volumetric and body‐fluid markers.

Neuroinflammation in the normal-appearing white matter (NAWM) of the multiple sclerosis brain causes abnormalities at the nodes of Ranvier

Changes to the structure of nodes of Ranvier in the normal-appearing white matter (NAWM) of multiple sclerosis (MS) brains are associated with chronic inflammation. We show that the paranodal domains in MS NAWM are longer on average than control, with Kv1.2 channels dislocated into the paranode. These pathological features are reproduced in a model of chronic meningeal inflammation generated by the injection of lentiviral vectors for the lymphotoxin-α (LTα) and interferon-γ (IFNγ) genes. We show that tumour necrosis factor (TNF), IFNγ, and glutamate can provoke paranodal elongation in cerebellar slice cultures, which could be reversed by an N-methyl-D-aspartate (NMDA) receptor blocker. When these changes were inserted into a computational model to simulate axonal conduction, a rapid decrease in velocity was observed, reaching conduction failure in small diameter axons. We suggest that glial cells activated by pro-inflammatory cytokines can produce high levels of glutamate, which triggers paranodal pathology, contributing to axonal damage and conduction deficits.

Current thinking on the mechanisms by which multiple sclerosis gives rise to cumulative neurological disability revolves largely around focal lesions of inflammation and demyelination. However, some of the debilitating symptoms, such as severe fatigue, might be better explained by a more diffuse pathology. This study shows that paranodes in the white matter become abnormal as a result of neuroinflammation, which may be the result of the action of cytokines that cause glia to release glutamate.

B cell rich meningeal inflammation associates with increased spinal cord pathology in multiple sclerosis

Increased inflammation in the cerebral meninges is associated with extensive subpial cortical grey matter pathology in the forebrain and a more severe disease course in a substantial proportion of secondary progressive multiple sclerosis (SPMS) cases. It is not known whether this relationship extends to spinal cord pathology. We assessed the contribution of meningeal and parenchymal immune infiltrates to spinal cord pathology in SPMS cases characterized in the presence (F+) or absence (F-) of lymphoid-like structures in the forebrain meninges. Transverse cryosections of cervical, thoracic and lumbar cord of 22 SPMS and five control cases were analyzed for CD20+ B cells, CD4+ and CD8+ T cells, microglia/macrophages (IBA-1+), demyelination (myelin oligodendrocyte glycoprotein+) and axon density (neurofilament-H+). Lymphoid-like structures containing follicular dendritic cell networks and dividing B cells were seen in the spinal meninges of 3 out of 11 F+ SPMS cases. CD4+ and CD20+ cell counts were increased in F+ SPMS compared to F- SPMS and controls, whilst axon loss was greatest in motor and sensory tracts of the F+ SPMS cases (P < 0.01). The density of CD20+ B cells of the spinal leptomeninges correlated with CD4+ T cells and total B and T cells of the meninges; with the density of white matter perivascular CD20+ and CD4+ lymphocytes (P < 0.05); with white matter lesion area (P < 0.05); and the extent of axon loss (P < 0.05) in F+ SPMS cases only. We show that the presence of lymphoid-like structures in the forebrain is associated with a profound spinal cord pathology and local B cell rich meningeal inflammation associates with the extent of cord pathology. Our work supports a principal role for B cells in sustaining inflammation and tissue injury throughout the CNS in the progressive disease stage.

Spinal Cord Involvement in MS and Other Demyelinating Diseases

Diagnostic accuracy is poor in demyelinating myelopathies, and therefore a challenge for neurologists in daily practice, mainly because of the multiple underlying pathophysiologic mechanisms involved in each subtype. A systematic diagnostic approach combining data from the clinical setting and presentation with magnetic resonance imaging (MRI) lesion patterns, cerebrospinal fluid (CSF) findings, and autoantibody markers can help to better distinguish between subtypes. In this review, we describe spinal cord involvement, and summarize clinical findings, MRI and diagnostic characteristics, as well as treatment options and prognostic implications in different demyelinating disorders including: multiple sclerosis (MS), neuromyelitis optica spectrum disorder, acute disseminated encephalomyelitis, anti-myelin oligodendrocyte glycoprotein antibody-associated disease, and glial fibrillary acidic protein IgG-associated disease. Thorough understanding of individual case etiology is crucial, not only to provide valuable prognostic information on whether the disorder is likely to relapse, but also to make therapeutic decision-making easier and reduce treatment failures which may lead to new relapses and long-term disability. Identifying patients with monophasic disease who may only require acute management, symptomatic treatment, and subsequent rehabilitation, rather than immunosuppression, is also important.

Detecting neurodegenerative pathology in multiple sclerosis before irreversible brain tissue loss sets in

Background

Multiple sclerosis (MS) is a complex chronic inflammatory and degenerative disorder of the central nervous system. Accelerated brain volume loss, or also termed atrophy, is currently emerging as a popular imaging marker of neurodegeneration in affected patients, but, unfortunately, can only be reliably interpreted at the time when irreversible tissue damage likely has already occurred. Timing of treatment decisions based on brain atrophy may therefore be viewed as suboptimal.

Main body

This Narrative Review focuses on alternative techniques with the potential of detecting neurodegenerative events in the brain of subjects with MS prior to the atrophic stage. First, metabolic and molecular imaging provide the opportunity to identify early subcellular changes associated with energy dysfunction, which is an assumed core mechanism of axonal degeneration in MS. Second, cerebral hypoperfusion has been observed throughout the entire clinical spectrum of the disorder but it remains an open question whether this serves as an alternative marker of reduced metabolic activity, or exists as an independent contributing process, mediated by endothelin-1 hyperexpression. Third, both metabolic and perfusion alterations may lead to repercussions at the level of network performance and structural connectivity, respectively assessable by functional and diffusion tensor imaging. Fourth and finally, elevated body fluid levels of neurofilaments are gaining interest as a biochemical mirror of axonal damage in a wide range of neurological conditions, with early rises in patients with MS appearing to be predictive of future brain atrophy.

Conclusions

Recent findings from the fields of advanced neuroradiology and neurochemistry provide the promising prospect of demonstrating degenerative brain pathology in patients with MS before atrophy has installed. Although the overall level of evidence on the presented topic is still preliminary, this Review may pave the way for further longitudinal and multimodal studies exploring the relationships between the abovementioned measures, possibly leading to novel insights in early disease mechanisms and therapeutic intervention strategies.

Aged hind-limb clasping experimental autoimmune encephalomyelitis models aspects of the neurodegenerative process seen in multiple sclerosis

Experimental autoimmune encephalomyelitis (EAE) is the most common model of multiple sclerosis (MS). This model has been instrumental in understanding the events that lead to the initiation of central nervous system (CNS) autoimmunity. Though EAE has been an effective screening tool for identifying novel therapies for relapsing-remitting MS, it has proven to be less successful in identifying therapies for progressive forms of this disease. Though axon injury occurs in EAE, it is rapid and acute, making it difficult to intervene for the purpose of evaluating neuroprotective therapies. Here, we describe a variant of spontaneous EAE in the 2D2 T cell receptor transgenic mouse (2D2⁺ mouse) that presents with hind-limb clasping upon tail suspension and is associated with T cell-mediated inflammation in the posterior spinal cord and spinal nerve roots. Due to the mild nature of clinical signs in this model, we were able to maintain cohorts of mice into middle age. Over 9 mo, these mice exhibited a relapsing-remitting course of hind-limb clasping with the development of progressive motor deficits. Using a combined approach of ex vivo magnetic resonance (MR) imaging and histopathological analysis, we observed neurological progression to associate with spinal cord atrophy, synapse degradation, and neuron loss in the gray matter, as well as ongoing axon injury in the white matter of the spinal cord. These findings suggest that mild EAE coupled with natural aging may be a solution to better modeling the neurodegenerative processes seen in MS.

Intersubject Variability and Normalization Strategies for Spinal Cord Total Cross-Sectional and Gray Matter Areas

BACKGROUND AND PURPOSE

The quantification of spinal cord (SC) atrophy by MRI has assumed an important role in assessment of neuroinflammatory/neurodegenerative diseases and traumatic SC injury. Recent technical advances make possible the quantification of gray matter (GM) and white matter tissues in clinical settings. However, the goal of a reliable diagnostic, prognostic or predictive marker is still elusive, in part due to large intersubject variability of SC areas. Here, we investigated the sources of this variability and explored effective strategies to reduce it.

METHODS

One hundred twenty-nine healthy subjects (mean age: 41.0 ± 15.9) underwent MRI on a Siemens 3T Skyra scanner. Two-dimensional PSIR at the C2-C3 vertebral level and a sagittal 1 mm³ 3D T1-weighted brain acquisition extended to the upper cervical cord were acquired. Total cross-sectional area and GM area were measured at C2-C3, as well as measures of the vertebra, spinal canal and the skull. Correlations between the different metrics were explored using Pearson product-moment coefficients. The most promising metrics were used to normalize cord areas using multiple regression analyses.

RESULTS

The most effective normalization metrics were the V-scale (from SienaX) and the product of the C2-C3 spinal canal diameters. Normalization methods based on these metrics reduced the intersubject variability of cord areas of up to 17.74%. The measured cord areas had a statistically significant sex difference, while the effect of age was moderate.

CONCLUSIONS

The present work explored in a large cohort of healthy subjects the source of intersubject variability of SC areas and proposes effective normalization methods for its reduction.

Myelin in the Central Nervous System: Structure, Function, and Pathology

Oligodendrocytes generate multiple layers of myelin membrane around axons of the central nervous system to enable fast and efficient nerve conduction. Until recently, saltatory nerve conduction was considered the only purpose of myelin, but it is now clear that myelin has more functions. In fact, myelinating oligodendrocytes are embedded in a vast network of interconnected glial and neuronal cells, and increasing evidence supports an active role of oligodendrocytes within this assembly, for example, by providing metabolic support to neurons, by regulating ion and water homeostasis, and by adapting to activity-dependent neuronal signals. The molecular complexity governing these interactions requires an in-depth molecular understanding of how oligodendrocytes and axons interact and how they generate, maintain, and remodel their myelin sheaths. This review deals with the biology of myelin, the expanded relationship of myelin with its underlying axons and the neighboring cells, and its disturbances in various diseases such as multiple sclerosis, acute disseminated encephalomyelitis, and neuromyelitis optica spectrum disorders. Furthermore, we will highlight how specific interactions between astrocytes, oligodendrocytes, and microglia contribute to demyelination in hereditary white matter pathologies.

Additive Effect of Spinal Cord Volume, Diffuse and Focal Cord Pathology on Disability in Multiple Sclerosis

Introduction: Spinal cord (SC) pathology is strongly associated with disability in multiple sclerosis (MS). We aimed to evaluate the association between focal and diffuse SC abnormalities and spinal cord volume and to assess their contribution to physical disability in MS patients. Methods: This large sample-size cross-sectional study investigated 1,249 patients with heterogeneous MS phenotypes. Upper cervical-cord cross-sectional area (MUCCA) was calculated on an axial 3D-T2w-FatSat sequence acquired at 3T using a novel semiautomatic edge-finding tool. SC images were scored for the presence of sharply demarcated hyperintense areas (focal lesions) and homogenously increased signal intensity (diffuse changes). Patients were dichotomized according EDSS in groups with mild (EDSS up to 3.0) and moderate (EDSS ≥ 3.5) physical disability. Analysis of covariance was used to identify factors associated with dichotomized MUCCA. In binary logistic regression, the SC imaging parameters were entered in blocks to assess their individual contribution to risk of moderate disability. In order to assess the risk of combined SC damage in terms of atrophy and lesional pathology on disability, secondary analysis was carried out where patients were divided into four categories (SC phenotypes) according to median dichotomized MUCCA and presence/absence of focal and/or diffuse changes. Results: MUCCA was strongly associated with total intracranial volume, followed by presence of diffuse SC pathology, and disease duration. Compared to the reference group (normally appearing SC, MUCCA>median), patients with the most severe SC changes (SC affected with focal and/or diffuse lesions, MUCCA Collapse

Key Words

• diffuse abnormalities
• focal lesions
• magnetic resonance imaging
• spinal cord
• spinal cord reserve

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Affiliation(s)

Michaela Andelova Department of Neurology, First Faculty of Medicine, Center of Clinical Neuroscience, Charles University and General University Hospital in Prague, Prague, Czechia
Tomas Uher Department of Neurology, First Faculty of Medicine, Center of Clinical Neuroscience, Charles University and General University Hospital in Prague, Prague, Czechia
Jan Krasensky Department of Radiology, Charles University in Prague, 1st Faculty of Medicine and General University Hospital, Prague, Czechia
Lukas Sobisek Endowment Fund IMPULS, Prague, Czechia
Eliska Kusova Department of Radiology, Charles University in Prague, 1st Faculty of Medicine and General University Hospital, Prague, Czechia
Barbora Srpova Department of Neurology, First Faculty of Medicine, Center of Clinical Neuroscience, Charles University and General University Hospital in Prague, Prague, Czechia
Karolina Vodehnalova Department of Neurology, First Faculty of Medicine, Center of Clinical Neuroscience, Charles University and General University Hospital in Prague, Prague, Czechia
Lucie Friedova Department of Neurology, First Faculty of Medicine, Center of Clinical Neuroscience, Charles University and General University Hospital in Prague, Prague, Czechia
Jiri Motyl Department of Neurology, First Faculty of Medicine, Center of Clinical Neuroscience, Charles University and General University Hospital in Prague, Prague, Czechia
Jana Lizrova Preiningerova Department of Neurology, First Faculty of Medicine, Center of Clinical Neuroscience, Charles University and General University Hospital in Prague, Prague, Czechia
Eva Kubala Havrdova Department of Neurology, First Faculty of Medicine, Center of Clinical Neuroscience, Charles University and General University Hospital in Prague, Prague, Czechia
Dana Horakova Department of Neurology, First Faculty of Medicine, Center of Clinical Neuroscience, Charles University and General University Hospital in Prague, Prague, Czechia
Manuela Vaneckova Department of Radiology, Charles University in Prague, 1st Faculty of Medicine and General University Hospital, Prague, Czechia

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Influence of CNS T2-focal lesions on cervical cord atrophy and disability in multiple sclerosis

Background:

Mechanisms associated with cervical spinal cord (CSC) and upper thoracic spinal cord (TSC) atrophy in multiple sclerosis (MS) are poorly understood.

Objective:

To assess the influence of brain, CSC and TSC T2-hyperintense lesions on cord atrophy and disability in MS.

Methods:

Thirty-four MS patients underwent 3T brain, cervical and thoracic cord magnetic resonance imaging (MRI) and Expanded Disability Status Scale (EDSS) score assessment. CSC/TSC lesion number and volume (LV), whole-brain and cortico-spinal tract (CST) LVs were obtained. Normalized whole CSC and upper TSC cross-sectional areas (CSAn) were also derived. Age- and sex-adjusted regression models assessed associations of brain/cord lesions with CSAn and EDSS and identified variables independently associated with CSAn and EDSS with a stepwise variable selection.

Results:

CSC CSAn (β = −0.36, p = 0.03) and TSC CSAn (β = −0.60, p < 0.001) were associated with CSC T2 LV. EDSS (median = 3.0) was correlated with CSC T2 LV (β = 0.42, p = 0.01), brain (β = 0.34, p = 0.04) and CST LV (β = 0.35, p = 0.03). The multivariate analysis retained CSC LV as significant predictor of CSC CSAn ( R2 = 0.20, p = 0.023) and TSC CSAn ( R2 = 0.51, p < 0.001) and retained CSC and CST LVs as significant predictors of EDSS ( R2 = 0.55, p = 0.001).

Conclusions:

CSC LV is an independent predictor of cord atrophy. When neurological impairment is relatively mild, central nervous system (CNS) lesion burden is a better correlate of disability than atrophy.

Advances in spinal cord imaging in multiple sclerosis

The spinal cord is frequently affected in multiple sclerosis (MS), causing motor, sensory and autonomic dysfunction. A number of pathological abnormalities, including demyelination and neuroaxonal loss, occur in the MS spinal cord and are studied in vivo with magnetic resonance imaging (MRI). The aim of this review is to summarise and discuss recent advances in spinal cord MRI. Advances in conventional spinal cord MRI include improved identification of MS lesions, recommended spinal cord MRI protocols, enhanced recognition of MRI lesion characteristics that allow MS to be distinguished from other myelopathies, evidence for the role of spinal cord lesions in predicting prognosis and monitoring disease course, and novel post-processing methods to obtain lesion probability maps. The rate of spinal cord atrophy is greater than that of brain atrophy (-1.78% versus -0.5% per year), and reflects neuroaxonal loss in an eloquent site of the central nervous system, suggesting that it can become an important outcome measure in clinical trials, especially in progressive MS. Recent developments allow the calculation of spinal cord atrophy from brain volumetric scans and evaluation of its progression over time with registration-based techniques. Fully automated analysis methods, including segmentation of grey matter and intramedullary lesions, will facilitate the use of spinal cord atrophy in trial designs and observational studies. Advances in quantitative imaging techniques to evaluate neuroaxonal integrity, myelin content, metabolic changes, and functional connectivity, have provided new insights into the mechanisms of damage in MS. Future directions of research and the possible impact of 7T scanners on spinal cord imaging will be discussed.

Comparison of Reported Spinal Cord Lesions in Progressive Multiple Sclerosis with Theiler's Murine Encephalomyelitis Virus Induced Demyelinating Disease

BACKGROUND

Spinal cord (SC) lesions in Theiler's murine encephalomyelitis virus induced demyelinating disease (TMEV-IDD) resemble important features of brain lesions in progressive multiple sclerosis (MS) including inflammation, demyelination, and axonal damage. The aim of the present study was a comparison of SC lesions in MS and TMEV-IDD focusing on spatial and temporal distribution of demyelination, inflammation, SC atrophy (SCA), and axonal degeneration/loss in major descending motor pathways.

METHODS

TMEV and mock-infected mice were investigated clinically once a week. SC tissue was collected at 42, 98, 147, and 196 days post infection, and investigated using hematoxylin and eosin (HE) staining, immunohistochemistry targeting myelin basic protein (demyelination), Mac3 (microglia/macrophages), phosphorylated neurofilaments (axonal damage) and transmission electron microscopy.

RESULTS

Demyelination prevailed in SC white matter in TMEV-IDD, contrasting a predominant gray matter involvement in MS. TMEV-infected mice revealed a significant loss of axons similar to MS. Ultrastructural analysis in TMEV-IDD revealed denuded axons, degenerative myelin changes, axonal degeneration, as well as remyelination. SCA is a consistent finding in the SC of MS patients and was also detected at a late time point in TMEV-IDD.

CONCLUSION

This comparative study further indicates the suitability of TMEV-IDD as animal model also for the investigation of progressive SC lesions in MS.

Monitoring Progressive Multiple Sclerosis with Novel Imaging Techniques

Imaging markers for monitoring disease progression in progressive multiple sclerosis (PMS) are scarce, thereby limiting the possibility to monitor disease evolution and to test effective treatments in clinical trials. Advanced imaging techniques that have the advantage of metrics with increased sensitivity to short-term tissue changes and increased specificity to the structural abnormalities characteristic of PMS have recently been applied in clinical trials of PMS. In this review, we (1) provide an overview of the pathological features of PMS, (2) summarize the findings of research and clinical trials conducted in PMS which have applied conventional and advanced magnetic resonance imaging techniques and (3) discuss recent advancements and future perspectives in monitoring PMS with imaging techniques.

Multiple sclerosis

Multiple sclerosis (MS) is the most common chronic inflammatory, demyelinating and neurodegenerative disease of the central nervous system in young adults. This disorder is a heterogeneous, multifactorial, immune-mediated disease that is influenced by both genetic and environmental factors. In most patients, reversible episodes of neurological dysfunction lasting several days or weeks characterize the initial stages of the disease (that is, clinically isolated syndrome and relapsing-remitting MS). Over time, irreversible clinical and cognitive deficits develop. A minority of patients have a progressive disease course from the onset. The pathological hallmark of MS is the formation of demyelinating lesions in the brain and spinal cord, which can be associated with neuro-axonal damage. Focal lesions are thought to be caused by the infiltration of immune cells, including T cells, B cells and myeloid cells, into the central nervous system parenchyma, with associated injury. MS is associated with a substantial burden on society owing to the high cost of the available treatments and poorer employment prospects and job retention for patients and their caregivers.

Spinal cord volume loss: A marker of disease progression in multiple sclerosis

OBJECTIVE

Cross-sectional studies have shown that spinal cord volume (SCV) loss is related to disease severity in multiple sclerosis (MS). However, long-term data are lacking. Our aim was to evaluate SCV loss as a biomarker of disease progression in comparison to other MRI measurements in a large cohort of patients with relapse-onset MS with 6-year follow-up.

METHODS

The upper cervical SCV, the total brain volume, and the brain T2 lesion volume were measured annually in 231 patients with MS (180 relapsing-remitting [RRMS] and 51 secondary progressive [SPMS]) over 6 years on 3-dimensional, T1-weighted, magnetization-prepared rapid-acquisition gradient echo images. Expanded Disability Status Scale (EDSS) score and relapses were recorded at every follow-up.

RESULTS

Patients with SPMS had lower baseline SCV (p < 0.01) but no accelerated SCV loss compared to those with RRMS. Clinical relapses were found to predict SCV loss over time (p < 0.05) in RRMS. Furthermore, SCV loss, but not total brain volume and T2 lesion volume, was a strong predictor of EDSS score worsening over time (p < 0.05). The mean annual rate of SCV loss was the strongest MRI predictor for the mean annual EDSS score change of both RRMS and SPMS separately, while correlating stronger in SPMS. Every 1% increase of the annual SCV loss rate was associated with an extra 28% risk increase of disease progression in the following year in both groups.

CONCLUSION

SCV loss over time relates to the number of clinical relapses in RRMS, but overall does not differ between RRMS and SPMS. SCV proved to be a strong predictor of physical disability and disease progression, indicating that SCV may be a suitable marker for monitoring disease activity and severity.

Cervical spinal cord atrophy: An early marker of progressive MS onset

Objective

To assess whether cervical spinal cord atrophy heralds the onset of progressive MS.

Methods

We studied 34 individuals with radiologically isolated syndrome (RIS) and 31 patients with relapsing-remitting MS (RRMS) age matched to 25 patients within a year of onset of secondary progressive MS (SPMS). Two raters independently measured (twice per rater) the cervical spinal cord average segmental area (CASA) (mm²) of axial T2-weighted images between C2 and C7 landmarks. The midsagittal T2-weighted image from the end of C2 to the end of C7 vertebra was used to measure the cervical spine (c-spine) length (mm). Sex, age at cervical MRI, number and location of cervical spinal cord lesions, c-spine length, and diagnoses were analyzed against the outcome measures of CASA and C2 and C7 slice segmental areas.

Results

Intrarater and interrater agreement was excellent (intraclass correlation coefficient >0.97). The CASA area (p = 0.03) and C7 area (p = 0.002) were smaller in SPMS compared with RRMS. The C2 area (p = 0.027), CASA (p = 0.004), and C7 area (p = 0.003) were smaller in SPMS compared with RIS. The C2 area did not differ between SPMS and RRMS (p = 0.09). The C2 area (p = 0.349), CASA (p = 0.136), and C7 area (p = 0.228) did not differ between RIS and MS (SPMS and RRMS combined). In the multivariable model, ≥2 cervical spinal cord lesions were associated with the C2 area (p = 0.008), CASA (p = 0.009), and C7 area independent of disease course (p = 0.017). Progressive disease course was associated with the C7 area independent of the cervical spinal cord lesion number (p = 0.004).

Conclusion

Cervical spinal cord atrophy is evident at the onset of progressive MS and seems partially independent of the number of cervical spinal cord lesions.

Classification of evidence

This study provides Class III evidence that MRI cervical spinal cord atrophy distinguishes patients at the onset of progressive MS from those with RIS and RRMS.

Understanding a role for hypoxia in lesion formation and location in the deep and periventricular white matter in small vessel disease and multiple sclerosis

The deep and periventricular white matter is preferentially affected in several neurological disorders, including cerebral small vessel disease (SVD) and multiple sclerosis (MS), suggesting that common pathogenic mechanisms may be involved in this injury. Here we consider the potential pathogenic role of tissue hypoxia in lesion development, arising partly from the vascular anatomy of the affected white matter. Specifically, these regions are supplied by a sparse vasculature fed by long, narrow end arteries/arterioles that are vulnerable to oxygen desaturation if perfusion is reduced (as in SVD, MS and diabetes) or if the surrounding tissue is hypoxic (as in MS, at least). The oxygen crisis is exacerbated by a local preponderance of veins, as these can become highly desaturated 'sinks' for oxygen that deplete it from surrounding tissues. Additional haemodynamic deficiencies, including sluggish flow and impaired vasomotor reactivity and vessel compliance, further exacerbate oxygen insufficiency. The cells most vulnerable to hypoxic damage, including oligodendrocytes, die first, resulting in demyelination. Indeed, in preclinical models, demyelination is prevented if adequate oxygenation is maintained by raising inspired oxygen concentrations. In agreement with this interpretation, there is a predilection of lesions for the anterior and occipital horns of the lateral ventricles, namely regions located at arterial watersheds, or border zones, known to be especially susceptible to hypoperfusion and hypoxia. Finally, mitochondrial dysfunction due to genetic causes, as occurs in leucodystrophies or due to free radical damage, as occurs in MS, will compound any energy insufficiency resulting from hypoxia. Viewing lesion formation from the standpoint of tissue oxygenation not only reveals that lesion distribution is partly predictable, but may also inform new therapeutic strategies.

Pharmacological Approaches to the Management of Secondary Progressive Multiple Sclerosis

It is well recognised that the majority of the impact of multiple sclerosis (MS), both personal and societal, arises in the progressive phase where disability accumulates inexorably. As such, progressive MS (PMS) has been the target of pharmacological therapies for many years. However, there are no current licensed treatments for PMS. This stands in marked contrast to relapsing remitting MS (RRMS) where trials have resulted in numerous licensed therapies. PMS has proven to be a more difficult challenge compared to RRMS and this review focuses on secondary progressive MS (SPMS), where relapses occur before the onset of gradual, irreversible disability, and not primary progressive MS where disability accumulation occurs without prior relapses. Although there are similarities between the two forms, in both cases pinpointing when PMS starts is difficult in a condition in which disability can vary from day to day. There is also an overlap between the pathology of relapsing and progressive MS and this has contributed to the lack of well-defined outcomes, both surrogates and clinically relevant outcomes in PMS. In this review, we used the search term 'randomised controlled clinical drug trials in secondary progressive MS' in publications since 1988 together with recently completed trials where results were available. We found 34 trials involving 21 different molecules, of which 38% were successful in reaching their primary outcome. In general, the trials were well designed (e.g. double blind) with sample sizes ranging from 35 to 1949 subjects. The majority were parallel group, but there were also multi-arm and multidose trials as well as the more recent use of adaptive designs. The disability outcome most commonly used was the Expanded Disability Status Scale (EDSS) in all phases, but also magnetic resonance imaging (MRI)-measured brain atrophy has been utilised as a surrogate endpoint in phase II studies. The majority of the treatments tested in SPMS over the years were initially successful in RRMS. This has a number of implications in terms of targeting SPMS, but principally implies that the optimal strategy to target SPMS is to utilise the prodrome of relapses to initiate a therapy that will aim to both prevent progression and slow its accumulation. This approach is in agreement with the early targeting of MS but requires treatments that are both effective and safe if it is to be used before disability is a major problem. Recent successes will hopefully result in the first licensed therapy for PMS and enable us to test this approach.

Spinal cord atrophy as a primary outcome measure in phase II trials of progressive multiple sclerosis

Objectives:

To measure the development of spinal cord (SC) atrophy over 1 year in patients with progressive multiple sclerosis (PMS) and determine the sample sizes required to demonstrate a reduction in spinal cord cross-sectional area (SC-CSA) as an outcome measure in clinical trials.

Methods:

In total, 44 PMS patients (26 primary progressive multiple sclerosis (PPMS), 18 secondary progressive multiple sclerosis (SPMS)) and 29 healthy controls (HCs) were studied at baseline and 12 months. SC-CSA was measured using the three-dimensional (3D) fast field echo sequences acquired at 3T and the active surface model. Multiple linear regressions were used to investigate changes in imaging measurements.

Results:

PPMS patients had shorter disease duration, lower Expanded Disability Status Scale (EDSS) and larger SC-CSA than SPMS patients. All patients together showed a significantly greater decrease in percentage SC-CSA change than HCs, which was driven by the PPMS. All patients deteriorated over 1 year, but no association was found between percentage SC-CSA change and clinical changes. The sample size per arm required to detect a 50% treatment effect over 1 year, at 80% power, was 57 for PPMS and 546 for SPMS.

Conclusion:

SC-CSA may become an outcome measure in trials of PPMS patients, when they are at an early stage of the disease, have moderate disability and modest SC atrophy.

Autoantibodies to heterogeneous nuclear ribonuclear protein A1 (hnRNPA1) cause altered 'ribostasis' and neurodegeneration; the legacy of HAM/TSP as a model of progressive multiple sclerosis

Several years following its discovery in 1980, infection with human T-lymphotropic virus type 1 (HTLV-1) was shown to cause HTLV-1 associated myelopathy/tropical spastic paraparesis (HAM/TSP), a disease biologically similar to progressive forms of multiple sclerosis (MS). In this manuscript, we review some of the clinical, pathological, and immunological similarities between HAM/TSP and MS with an emphasis on how autoantibodies to an RNA binding protein, heterogeneous nuclear ribonuclear protein A1 (hnRNP A1), might contribute to neurodegeneration in immune mediated diseases of the central nervous system.

The role of MRI in the evaluation of secondary progressive multiple sclerosis

Magnetic resonance imaging already has an established role in the diagnosis of multiple sclerosis, but it also has the potential to provide prognostic information, and to monitor [corrected] disease progression in clinical trials and practice. Magnetic resonance imaging measures are increasingly being used as the primary outcome in early phase clinical trials of immunomodulatory therapies (for example brain white matter lesion counts or volumes, and gadolinium contrast enhancing lesions) and putatively neuroprotective agents (for example measures of whole brain atrophy), and trials of agents that promote remyelination are also likely to follow suit. In this review we consider the use of magnetic resonance imaging measures as predictors and markers of disease progression in multiple sclerosis, and explore possible future directions in this rapidly developing field.

Spinal cord MRI in multiple sclerosis--diagnostic, prognostic and clinical value

Multiple sclerosis (MS) is an inflammatory disorder of the CNS that affects both the brain and the spinal cord. MRI studies in MS focus more often on the brain than on the spinal cord, owing to the technical challenges in imaging this smaller, mobile structure. However, spinal cord abnormalities at disease onset have important implications for diagnosis and prognosis. Furthermore, later in the disease course, in progressive MS, myelopathy becomes the primary characteristic of the clinical presentation, and extensive spinal cord pathology--including atrophy, diffuse abnormalities and numerous focal lesions--is common. Recent spinal cord imaging studies have employed increasingly sophisticated techniques to improve detection and quantification of spinal cord lesions, and to elucidate their relationship with physical disability. Quantitative MRI measures of cord size and tissue integrity could be more sensitive to the axonal loss and other pathological processes in the spinal cord than is conventional MRI, putting quantitative MRI in a key role to elucidate the association between disability and spinal cord abnormalities seen in people with MS. In this Review, we summarize the most recent MS spinal cord imaging studies and discuss the new insights they have provided into the mechanisms of neurological impairment. Finally, we suggest directions for further and future research.

Putaminal alteration in multiple sclerosis patients with spinal cord lesions

Typical multiple sclerosis (MS) lesions occur in the brain as well as in the spinal cord. However, two extreme magnetic resonance imaging phenotypes appear occasionally: those with predominantly spinal cord lesions (MS + SL) and those with cerebral lesions and no detectable spinal lesions (MS + CL). We assessed whether morphological differences can be found between these two extreme phenotypes. We examined 19 patients with MS + SL, 18 with MS + CL and 20 controls. All subjects were examined using magnetic resonance imaging, including anatomical and diffusion tensor imaging sequences. Voxel-based morphologic and regions of interest-based analyses and tract-based spatial statistics were performed. Patients also underwent neuropsychological testing. Demographic, clinical and neuropsychological characteristics did not differ between MS + SL and MS + CL patients. Patients with MS + SL showed significantly larger putamen volumes than those with MS + CL which correlated negatively with disability. Compared to controls, only MS + CL revealed clear cortical and deep gray matter atrophy, which correlated with cerebral lesion volume. Additionally, extensive white matter microstructural damage was found only in MS + CL compared to MS + SL and controls in the tract-based spatial statistics. Higher putamen volumes in MS + SL could suggest compensatory mechanisms in this area responsible for motor control. Widely reduced fractional anisotropy values in MS + CL were caused by higher cerebral lesion volume and thus presumably stronger demyelination, which subsequently leads to higher global gray matter atrophy.

MRI monitoring of pathological changes in the spinal cord in patients with multiple sclerosis

The spinal cord is a clinically important site that is affected by pathological changes in most patients with multiple sclerosis; however, imaging of the spinal cord with conventional MRI can be difficult. Improvements in MRI provide a major advantage for spinal cord imaging, with better signal-to-noise ratio and improved spatial resolution. Through the use of multiplanar MRI, identification of diffuse and focal changes in the whole spinal cord is now routinely possible. Corroborated by related histopathological analyses, several new techniques, such as magnetisation transfer, diffusion tension imaging, functional MRI, and proton magnetic resonance spectroscopy, can detect non-focal, spinal cord pathological changes in patients with multiple sclerosis. Additionally, functional MRI can reveal changes in the response pattern to sensory stimulation in patients with multiple sclerosis. Through use of these techniques, findings of cord atrophy, intrinsic cord damage, and adaptation are shown to occur largely independently of focal spinal cord lesion load, which emphasises their relevance in depiction of the true burden of disease. Combinations of magnetisation transfer ratio or diffusion tension imaging indices with cord atrophy markers seem to be the most robust and meaningful biomarkers to monitor disease evolution in early multiple sclerosis.

Pathological mechanisms in progressive multiple sclerosis

A better understanding of the pathological mechanisms that drive neurodegeneration in individuals with multiple sclerosis is needed to develop therapies that will effectively treat patients in the primary and secondary progressive stages of the disease. We propose that the inflammatory demyelinating disease process in early multiple sclerosis triggers a cascade of events that lead to neurodegeneration and are amplified by pathogenic mechanisms related to brain ageing and accumulated disease burden. Key elements driving neurodegeneration include microglia activation, chronic oxidative injury, accumulation of mitochondrial damage in axons, and age-related iron accumulation in the human brain. Altered mitochondrial function in axons might be of particular importance. This process leads to chronic cell stress and imbalance of ionic homoeostasis, resulting in axonal and neuronal death. The evidence suggests that treatment of progressive multiple sclerosis should be based on a combination of anti-inflammatory, regenerative, and neuroprotective strategies.

Clinical trials in progressive multiple sclerosis: lessons learned and future perspectives

Progressive multiple sclerosis is characterised clinically by the gradual accrual of disability independent of relapses and can occur with disease onset (primary progressive) or can be preceded by a relapsing disease course (secondary progressive). An effective disease-modifying treatment for progressive multiple sclerosis has not yet been identified, and so far the results of clinical trials have generally been disappointing. Ongoing advances in the knowledge of pathogenesis, in the identification of novel targets for neuroprotection, and in improved outcome measures could lead to effective treatments for progressive multiple sclerosis. In this Series paper, we summarise the lessons learned from completed clinical trials and perspectives from trials in progress in progressive multiple sclerosis. We review promising clinical, imaging, and biological markers, along with novel designs, for clinical trials. The use of more refined outcomes and truly neuroprotective drugs, coupled with more efficient trial design, has the capacity to deliver a new era of therapeutic discovery in this challenging area.

Multiple sclerosis risk loci correlate with cervical cord atrophy and may explain the course of disability

Genome-wide association studies (GWAS) underscore the genetic basis of multiple sclerosis (MS); however, only few of the newly reported genetic variations relevant in MS have been replicated or correlated for clinical/paraclinical phenotypes such as spinal cord atrophy in independent patient cohorts. We genotyped 141 MS patients for 58 variations reported to reach significance in GWAS. Expanded disability status scale (EDSS) and disease duration (DD) are available from regular clinical examinations. MRI included sagittal high-resolution 3D T1-weighted magnetization-prepared rapid acquisition gradient echo of the cervical cord region used for volumetry. Due dependency of mean upper cervical cord area (MUCCA) with EDSS and/or DD, correction operations were performed compensating for EDSS/DD. We assessed each MS risk locus for possible MUCCA association. We identified twelve risk loci that significantly correlated with MUCCA. For nine loci-BATF, CYP27B1, IL12B, NFKB1, IL7, PLEK, EVI5, TAGAP and nrs669607-patients revealed significantly higher degree of atrophy; TYK2, RGS1 and CLEC16A revealed inverse effects. The weighted genetic risk score over the twelve loci showed significant correlation with MUCCA. Our data reveal a risk gene depending paraclinical/clinical phenotype. Since MUCCA clearly correlates with disability, the candidates identified here may serve as prognostic markers for disability progression.

Thoracic spinal cord lesions are influenced by the degree of cervical spine involvement in multiple sclerosis

STUDY DESIGN

Cross-sectional analyses.

OBJECTIVE

To determine whether cervical spinal cord lesions predict the presence of thoracic cord lesions in multiple sclerosis (MS) patients.

SETTING

Single MS Clinic, AZ, USA.

METHODS

All MS patients, with MRI studies of the brain, cervical and thoracic spine obtained during a single scanning session, were acquired during a 1-year period. Clinical, demographic and imaging covariates were used in a multivariate regression model to refine predictors of thoracic cord involvement.

RESULTS

A total of 687 patients were evaluated, and patients were excluded because of a diagnosis of other neurological disorders, not meeting the 2010 McDonald criteria for MS (n=222) or incomplete neuraxis imaging (n=339). The study cohort comprised 126 patients. There was an increase in the odds ratio (OR) of thoracic spine involvement when any cervical spine lesion was present (OR=6.08, 95% confidence interval (2.21-16.68), P<0.001). The multivariate logistic regression model demonstrated a substantial and significant increase in the odds of thoracic spine involvement when more than two cervical spine lesions were present, two lesions (OR 4.44, (0.91-21.60), P=0.06), three lesions (OR 19.76, (3.51-111.17), P=0.001), four or more lesions (OR 20.49, (1.97-213.23), P=0.012) and diffuse lesions (OR 71.94, (5.28-979.88), P=0.001), when adjusting for significant covariates including clinical symptoms, brain lesions, disease duration and treatment exposure.

CONCLUSIONS

Thoracic spinal cord lesions appear to be predicated on the degree of cervical spine involvement in patients with MS, a risk that appears to be independent of brain findings or clinical features.

Spinal cord atrophy in multiple sclerosis and relationship with disability across clinical phenotypes

BACKGROUND

Several studies have shown a relationship between spinal cord atrophy and clinical disability in patients with multiple sclerosis (MS).

OBJECTIVES

We examined the correlation between cervical cord cross-sectional area at the C2 vertebral level (CSA-C2) and the expanded disability status scale (EDSS) in patients with relapsing-remitting and progressive forms of MS. The latter included both secondary and primary progressive MS patients.

METHODS

A total of 150 patients with MS were recruited from the Wayne State University MS clinic. Ninety-three had relapsing-remitting MS and 57 patients had progressive MS. MRI scan of the cervical cord was obtained for each patient. Correlation studies and multivariate regression analysis was performed, blinded to clinical status.

RESULTS

The mean age was 41.3 year old, 64.6% were women, mean disease duration was 11.2 years, CSA-C2 was 80.2mm(2) and mean EDSS was 3.8. There was significant correlation between CSA-C2 and EDSS (r -0.75, p<0.0001). Sub-group analysis showed CSA-C2 was 68.6mm(2) and 87.3mm(2) in the progressive and relapsing-remitting groups, respectively (p<0.0001). Multivariable regression showed that CSA-C2 was a significant predictor of disability independent of disease duration, and phenotype.

CONCLUSIONS

Our study demonstrates that CSA-C2 has a strong correlation with clinical disability in both RRMS and progressive MS. Greater spinal cord atrophy was seen in patients with progressive than relapsing-remitting MS. CSA-C2, disease duration, and phenotype are independent predictors of disability.

Challenges in multiple sclerosis; how to define occurence of progression

The challenges in MS are related to number of controversies in various aspects of disease but the relationship between relapses and disability progression, or aspects of MS as an inflammatory and/or neurodegenerative disease are extremely important because of its implications on prognosis and therapy of MS. MS was classically regarded as white matter inflammatory disease, while disability progression, brain and spinal cord atrophy were regarded as a consequence of global inflammation of NAWM and secondary involvement of grey matter. More recent histopathology studies, but also new, modern MRI techniques changed this view in MS as a prominent grey and white matter disease. Inflammatory demyelination of grey matter occurs early in MS sometimes even before occurrence of white matter lesions. Inspite of early therapy of MS with immunomodulatory drugs disability progression and neurodegeneration are still important and common part of MS pathogenesis. This indicate that treatment is not adequate to the predicted severity of MS, or perhaps to the basic pathogenetic mechanisms in MS. Beside acute clinical symptoms, conclusions about the severity of the disease are reflection of MRI sensitivity to detect focal WM lesions and insensitivity to detect grey matter lesions which correlate better with clinical symptoms. All presented studies and evaluations point to the necessity of changing the established diagnostic evaluation and treatment in MS. At the earliest stage of MS as well as in follow up of disease it would be necessary to apply a new MRI techniques more available for clinical practice such as DIR brain MR imaging at 3T because of their sensitivity to detect grey matter lesions. In patient with present cortical lesions even in earliest stages of MS depending on severity of grey matter involvement more efficacious therapy like second or even third line therapy should start.

Pathology of multiple sclerosis and related inflammatory demyelinating diseases

This article provides a comprehensive overview of the pathology of multiple sclerosis (MS), including recent insights into its molecular neuropathology and immunology. It shows that all clinical manifestations of relapsing and progressive MS display the same basic features of pathology, such as chronic inflammation, demyelination in the white and gray matter, and diffuse neurodegeneration within the entire central nervous system. However, the individual components of the pathological spectrum vary quantitatively between early relapsing and late progressive MS. Widespread confluent and plaque-like demyelination with oligodendrocyte destruction is the unique pathological hallmark of the disease, but axonal injury and neurodegeneration are additionally present and in part extensive. Remyelination of existing lesions may occur in MS brains; it is extensive in a subset of patients, while it fails in others. Active tissue injury in MS is always associated with inflammation, consistent with T-cell and macrophage infiltration and microglia activation. Recent data suggest that oxidative injury and subsequent mitochondrial damage play a major pathogenetic role in neurodegeneration. Finally we discuss similarities and differences of the pathology between classical MS and other inflammatory demyelinating diseases, such as neuromyelitis optica, concentric sclerosis, or acute disseminated encephalomyelitis.

Spinal cord gray matter atrophy correlates with multiple sclerosis disability

OBJECTIVE

In multiple sclerosis (MS), cerebral gray matter (GM) atrophy correlates more strongly than white matter (WM) atrophy with disability. The corresponding relationships in the spinal cord (SC) are unknown due to technical limitations in assessing SC GM atrophy. Using phase-sensitive inversion recovery (PSIR) magnetic resonance imaging, we determined the association of the SC GM and SC WM areas with MS disability and disease type.

METHODS

A total of 113 MS patients and 20 healthy controls were examined at 3T with a PSIR sequence acquired at the C2/C3 disk level. Two independent, clinically masked readers measured the cord WM and GM areas. Correlations between cord areas and Expanded Disability Status Score (EDSS) were determined. Differences in areas between groups were assessed with age and sex as covariates.

RESULTS

Relapsing MS (RMS) patients showed smaller SC GM areas than age- and sex-matched controls (p = 0.008) without significant differences in SC WM areas. Progressive MS patients showed smaller SC GM and SC WM areas compared to RMS patients (all p ≤ 0.004). SC GM, SC WM, and whole cord areas inversely correlated with EDSS (rho: -0.60, -0.32, -0.42, respectively; all p ≤ 0.001). The SC GM area was the strongest correlate of disability in multivariate models including brain GM and WM volumes, fluid-attenuated inversion recovery lesion load, T1 lesion load, SC WM area, number of SC T2 lesions, age, sex, and disease duration. Brain and spinal GM independently contributed to EDSS.

INTERPRETATION

SC GM atrophy is detectable in vivo in the absence of WM atrophy in RMS. It is more pronounced in progressive MS than RMS and contributes more to patient disability than SC WM or brain GM atrophy.

Atrophy and structural variability of the upper cervical cord in early multiple sclerosis

BACKGROUND

Despite agreement about spinal cord atrophy in progressive forms of multiple sclerosis (MS), data on clinically isolated syndrome (CIS) and relapsing-remitting MS (RRMS) are conflicting.

OBJECTIVE

To determine the onset of spinal cord atrophy in the disease course of MS.

METHODS

Structural brain magnetic resonance imaging (MRI) was acquired from 267 patients with CIS (85) or RRMS (182) and 64 healthy controls (HCs). The upper cervical cord cross-sectional area (UCCA) was determined at the level of C2/C3 by a segmentation tool and adjusted for focal MS lesions. The coefficient of variation (CV) was calculated from all measurements between C2/C3 and 13 mm above as a measure of structural variability.

RESULTS

Compared to HCs (76.1±6.9 mm(2)), UCCA was significantly reduced in CIS patients (73.5±5.8 mm(2), p=0.018) and RRMS patients (72.4±7.0 mm(2), p<0.001). Structural variability was higher in patients than in HCs, particularly but not exclusively in case of focal lesions (mean CV HCs/patients without/with lesions: 2.13%/2.55%/3.32%, all p-values<0.007). UCCA and CV correlated with Expanded Disability Status Scale (EDSS) scores (r =-0.131/0.192, p=0.044/<0.001) and disease duration (r=-0.134/0.300, p=0.039/< 0.001). CV additionally correlated with hand and arm function (r=0.180, p=0.014).

CONCLUSION

In MS, cervical cord atrophy already occurs in CIS. In early stages, structural variability may be a more meaningful marker of spinal cord pathology than atrophy.