The relation between MRI measures of inflammation and neurodegeneration in multiple sclerosis

The clinico-radiological paradox of cognitive function and MRI burden of white matter lesions in people with multiple sclerosis: A systematic review and meta-analysis

BACKGROUND

Moderate correlation exists between the imaging quantification of brain white matter lesions and cognitive performance in people with multiple sclerosis (MS). This may reflect the greater importance of other features, including subvisible pathology, or methodological limitations of the primary literature.

OBJECTIVES

To summarise the cognitive clinico-radiological paradox and explore the potential methodological factors that could influence the assessment of this relationship.

METHODS

Systematic review and meta-analysis of primary research relating cognitive function to white matter lesion burden.

RESULTS

Fifty papers met eligibility criteria for review, and meta-analysis of overall results was possible in thirty-two (2050 participants). Aggregate correlation between cognition and T2 lesion burden was r = -0.30 (95% confidence interval: -0.34, -0.26). Wide methodological variability was seen, particularly related to key factors in the cognitive data capture and image analysis techniques.

CONCLUSIONS

Resolving the persistent clinico-radiological paradox will likely require simultaneous evaluation of multiple components of the complex pathology using optimum measurement techniques for both cognitive and MRI feature quantification. We recommend a consensus initiative to support common standards for image analysis in MS, enabling benchmarking while also supporting ongoing innovation.

Mild Traumatic Brain Injury

Mild traumatic brain injury (MTBI) is a significant public health problem worldwide. Injured individuals have an increased relative risk of developing a variety of neuropsychiatric conditions associated with the profile of brain regions typically affected in TBI. Within a neurobiopsychosocial framework, this article reviews what is known about the neuropsychiatric sequelae of MTBI, with an emphasis on recent advances.

Sodium imaging as a marker of tissue injury in patients with multiple sclerosis

Recent studies have suggested that intra-axonal sodium accumulation contribute to axonal degeneration in patients with MS. Advances in MRI hardware and software allow acquisition of brain sodium signal in vivo. This review begins with a summary of the experimental evidence for impairment of sodium homeostasis in MS. Then, MRI methods for sodium acquisition are reviewed and the application of the techniques in patients with MS is discussed. Sodium imaging and ultra-high field MRI have the potential to provide tissue-specific markers of neurodegeneration in MS.

Female gender and reproductive factors affecting risk, relapses and progression in multiple sclerosis

Multiple sclerosis (MS), a chronic inflammatory demyelina-ting and degenerative disease of the central nervous system, is a frequent cause of neurological disability in young adults. Female predominance has increased over the last decades. Although female gender carries a higher risk of developing relapsing remitting MS, being female and at child-bearing age also appears to provide some protection against cognitive decline and against progressive onset MS, an adverse predictive factor when considering long-term disability in MS. The risk of MS in women has been associated with an earlier age at menarche. In most studies, parity did not impact MS risk. However, the recently published association of higher parity and offspring number with a reduced risk of a first demyelinating event suggests a potential suppressive effect. Pregnancy in MS patients has been associated with a reduced relapse rate and a reduction of neurological symptoms, especially in the third trimester. Despite the increased relapse risk in the postpartum period, there is no indication of an adverse effect of childbirth on the long-term course of MS. Fertility treatment in MS has been associated with an increased relapse risk in the following 3-month period, especially when the procedure did not result in pregnancy and gonadotrophin-releasing hormone agonists were used. Altogether, there is substantial evidence to support a regulatory role of sex steroid hormones in MS. In the absence of correlations with single hormone blood levels, we can only speculate about the underlying mechanisms. In conclusion, the increased MS risk in women and the changes in relapse and progression risk in association with reproductive events suggest significant and complex interactions between immune, neuroendocrine and reproductive systems in MS.

White matter and deep gray matter hemodynamic changes in multiple sclerosis patients with clinically isolated syndrome

The dynamic susceptibility contrast magnetic resonance imaging perfusion technique was used to investigate possible hemodynamic changes in normal appearing white matter and deep gray matter (DGM) of 30 patients with clinically isolated syndrome (CIS) and 30 patients with relapsing-remitting multiple sclerosis. Thirty normal volunteers were studied as controls. Cerebral blood volume, cerebral blood flow (CBF), and mean transit time values were estimated. Normalization was achieved for each subject with respect to average values of CBF and mean transit time of the hippocampi's dentate gyrus. Measurements concerned three regions of normal white matter of normal volunteers, normal appearing white matter of CIS and patients with relapsing-remitting multiple sclerosis, and DGM regions, bilaterally. All measured normal appearing white matter and DGM regions of the patients with CIS had significantly higher cerebral blood volume and mean transit time values, while averaged DGM regions had significantly lower CBF values, compared to those of normal volunteers (P < 0.001). Regarding patients with relapsing-remitting multiple sclerosis, all measured normal appearing white matter and DGM regions showed lower CBF values than those of normal volunteers and lower cerebral blood volume and CBF values compared to patients with CIS (P < 0.001). These data provide strong evidence that hemodynamic changes--affecting both white and DGM--may occur even at the earliest stage of multiple sclerosis, with CIS patients being significantly different than relapsing-remitting multiple sclerosis patients.

Evidence for acute neurotoxicity after chemotherapy

OBJECTIVE

Chronic neurotoxicity is a recognized long-term complication following chemotherapy in a range of diseases. Neurotoxicity adversely affects patients' quality of life. The objective of this study is to examine whether there is evidence of acute neurotoxicity.

METHODS

This prospective study included patients with secondary progressive multiple sclerosis (SPMS-BMT, n = 14) and hematological malignancies (HM-BMT, n = 17) receiving chemotherapy as preconditioning for bone marrow transplant. The control groups included SPMS patients matched for demographic and clinical data (SPMS-PL, n = 14) and healthy controls (n = 14). Neurodegeneration was assessed at baseline and longitudinally (months 1, 2, 3, 6, 9, 12, 24, and 36), combining a clinical scale for disability (Expanded Disability Status Scale [EDSS]), a serum protein biomarker for neurodegeneration (neurofilaments, NfH-SMI35), and brain atrophy measures (magnetic resonance imaging).

RESULTS

Disability progression was significantly more acute and severe following chemotherapy compared to placebo. Immediately after starting chemotherapy, serum NfH-SMI35 levels increased in 79% (p < 0.0001) of SPMS-BMT patients and 41% (p < 0.01) of HM-BMT patients compared to 0% of SPMS-PL patients or healthy controls. In SPMS-BMT serum NfH-SMI35 levels were > 100-fold higher 1 month after chemotherapy (29.73ng/ml) compared to baseline (0.28ng/ml, p < 0.0001). High serum NfH-SMI35 levels persisting for at least 3 months were associated with sustained disability progression on the EDSS (p < 0.05). Brain atrophy rates increased acutely in SPMS-BMT (-2.09) compared to SPMS-PL (-1.18, p < 0.05).

INTERPRETATION

Neurotoxicity is an unwanted acute side effect of aggressive chemotherapy.

Rostrocaudal analysis of corpus callosum demyelination and axon damage across disease stages refines diffusion tensor imaging correlations with pathological features

Noninvasive assessment of the progression of axon damage is important for evaluating disease progression and developing neuroprotective interventions in multiple sclerosis patients. We examined the cellular responses correlated with diffusion tensor imaging-derived axial (lambda(parallel)) and radial (lambda(perpendicular)) diffusivity values throughout acute (4 weeks) and chronic (12 weeks) stages of demyelination and after 6 weeks of recovery using the cuprizone demyelination of the corpus callosum model in C57BL/6 and Thy1-YFP-16 mice. The rostrocaudal progression of pathological alterations in the corpus callosum enabled spatially and temporally defined correlations of pathological features with diffusion tensor imaging measurements. During acute demyelination, microglial/macrophage activation was most extensive and axons exhibited swellings, neurofilament dephosphorylation, and reduced diameters. Axial diffusivity values decreased in the acute phase but did not correlate with axonal atrophy during chronic demyelination. In contrast, radial diffusivity increased with the progression of demyelination but did not correlate with myelin loss or astrogliosis. Unlike other animal models with progressive neurodegeneration and axon loss, the acute axon damage did not progress to discontinuity or loss of axons even after a period of chronic demyelination. Correlations of reversible axon pathology, demyelination, microglia/macrophage activation, and astrogliosis with regional axial and radial diffusivity measurements will facilitate the clinical application of diffusion tensor imaging in multiple sclerosis patients.

Smoking is associated with progressive disease course and increased progression in clinical disability in a prospective cohort of people with multiple sclerosis

BACKGROUND

Multiple sclerosis has a variable disease course. The contribution of modifiable lifestyle factors to disease course has not been well studied, although one cohort has reported that smoking is associated with conversion to secondary progressive MS course and another that smoking is not.

METHODS

We conducted a prospective cohort study of people with MS in Southern Tasmania from 2002 to 2004 with 78% (203/259) of eligible participating and 198 with one or more reviews and confirmed MS. The cohort had a high retention rate (90% (183/203)). The median follow-up time was 909 days. Smoking data were collected at baseline and six-monthly reviews. Clinical disability assessments were conducted annually in conjunction with a real time clinical notification system for relapses. A repeated measures analysis and other statistical methods were used.

RESULTS

Cumulative pack-years (p-y) smoked after cohort entry was associated with an increase in longitudinal MSSS (p < 0.001). Relative to the 0 pack years (p-y) category (in the year prior to the MSSS measure) those in the 0 to 1 p-y category had an adjusted mean difference in MSSS of 0.34 (95% CI 0.28, 0.66); those in the 1 to 2 p-y category had a 0.41 (95% CI -0.03, 0.85) increase; and those in the 2 or more p-y category had a 0.99 (95% CI 0.41, 1.58) increase in MSSS. Similar results were found using a variety of statistical approaches or EDSS as a clinical outcome. Smoking during the cohort period was not associated with relapse (cumulative pack years smoked after cohort entry, HR 0.94 (0.69, 1.26) per pack year).

CONCLUSION

A better understanding of the mechanisms underlying smoking and multiple sclerosis, particularly progressive forms of the disease, may provide new insights for the eventual goal of better treatment and prevention of multiple sclerosis.

Interferon-β is neuroprotective against the toxicity induced by activated microglia

Multiple sclerosis (MS) is a chronic inflammatory disorder of the central nervous system characterized by demyelination, T lymphocyte infiltration, and neuronal degeneration. Interferon-beta (IFN)-beta reduces symptoms of the relapsing-remitting form of MS. In this study, we investigated whether IFN-beta is neuroprotective against the toxicity induced by activated microglia in cortical neurons and microglia co-cultures. IFN-beta suppressed the production of glutamate and superoxide by activated microglia to 70% and 75% of lipopolysaccharide stimulation, respectively, and prevented microglial-induced neuronal cell death. Although IFN-beta enhanced the production of tumor necrosis factor (TNF)-alpha, interleukin (IL)-1beta, and nitric oxide (NO) by activated microglia, these molecules did not directly induce neurotoxicity in cultured cortical neurons. IFN-beta did not prevent neuronal cell death induced by the peroxynitrite donor 3-morpholinosydnonimine (SIN-1) or ionotropic glutamate receptor agonists such as N-methyl-D-aspartic acid (NMDA) and alpha-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid (AMPA). These results suggest that IFN-beta may be a useful agent counteracting neurotoxicity associated with activated microglia.

A three-year study of brain atrophy after autologous hematopoietic stem cell transplantation in rapidly evolving secondary progressive multiple sclerosis

BACKGROUND AND PURPOSE

In multiple sclerosis (MS), autologous hematopoietic stem cell transplantation (AHSCT) induces a profound suppression of clinical activity and MR imaging-detectable inflammation, but it may be associated with a rapid brain volume loss in the months subsequent to treatment. The aim of this study was to assess how AHSCT affects medium-term evolution of brain atrophy in MS.

MATERIALS AND METHODS

MR imaging scans of the brain from 14 patients with rapidly evolving secondary-progressive MS obtained 3 months before and every year after AHSCT for 3 years were analyzed. Baseline normalized brain volumes and longitudinal percentage of brain volume changes (PBVCs) were assessed using the Structural Image Evaluation of Normalized Atrophy software.

RESULTS

The median decrease of brain volume was 1.92% over the first year after AHSCT and then declined to 1.35% at the second year and to 0.69% at the third year. The number of enhancing lesions seen on the pretreatment scans was significantly correlated with the PBVCs between baseline and month 12 (r = -0.62; P = .02); no correlation was found with the PBVCs measured over the second and third years.

CONCLUSIONS

After AHSCT, the rate of brain tissue loss in patients with MS declines dramatically after the first 2 years. The initial rapid development of brain atrophy may be a late consequence of the pretransplant disease activity and/or a transient result of the intense immunoablative conditioning procedure.

Inflammatory demyelination and neurodegeneration in early multiple sclerosis

A number of recent magnetic resonance imaging studies have challenged the classical view of multiple sclerosis (MS) as a "two-stage" disease where an early inflammatory demyelinating phase with focal macroscopic lesions formed in the white matter (WM) of the central nervous system is followed by a late neurodegenerative phase, which is believed to be a mere consequence of repeated inflammatory insults and irreversible demyelination. These studies have consistently shown the presence of diffuse normal-appearing WM damage, marked gray matter involvement and significant cortical functional reorganization, as well as the occurrence of the neurodegenerative component of MS from the earliest clinical stages of the disease with only a partial relation to MRI markers of inflammatory demyelination. The present review argues that MS can no longer be viewed as a "two-stage" disease, which suggests that the two pathological components are dissociated in time, but rather as a "simultaneous two-component" disease, where the relative contributions of the various pathological processes of the disease to the development of "fixed" disability, their relationship and their evolution over time need to be clarified. This new view of MS should inform the development of future research protocols to define its actual physiopathology and prompt the institution of early treatment which should ideally target not only inflammatory demyelination, but also the neurodegenerative aspects of the disease, as well as promote neuroprotection and enhance reparative mechanisms and adaptive functional reorganization of the cortex.

[Future of non conventional MR techniques in MS]

Although conventional magnetic resonance imaging (MRI) is used for diagnosing multiple sclerosis (MS) and monitoring disease activity and course, the correlation between conventional MRI data and clinical findings remains weak. This "clinical-MRI paradox" could be partly due to the lack of MRI specificity related to the heterogeneous pathological substrates of MS and to its inability to quantify the extent of damage in the normal-appearing tissue. Recently, non-conventional MRI techniques, including magnetization transfer MRI, diffusion tensor MRI, and proton MR spectroscopy have been applied to improve our understanding of the pathophysiology of MS. These techniques may provide information about structural and biochemical changes occurring within and outside macroscopic MS lesions (inflammation, demyelination, axonal loss), in particular in the normal-appearing white and grey matter. These techniques could also significantly improve our ability to monitor inflammatory demyelination and axonal injury. In the same way, functional MRI gives us the potential substrate to assess the mechanisms of adaptive cortical reorganization, which may limit the irreversible consequences of MS tissue injury.

The involvement of mitochondria in the pathogenesis of multiple sclerosis

Multiple sclerosis is an immune-mediated disorder of the central nervous system. Major pathological characteristics include the loss of oligodendrocytes, demyelination and neuroaxonal depletion in association with inflammation. The complex pathophysiology of tissue loss is only partially understood. Here we discuss a variety of mitochondrion-driven mechanisms involved in immune regulation, oligodendrocyte depletion and neurodegeneration. The recognition of a mitochondrial link between inflammation and neurodegeneration underscores the importance of an early aggressive intervention for halting inflammation and preventing neurodegeneration, and identifies the mitochondrion as a potential target in neuroprotection.

Long-term follow-up of patients treated with glatiramer acetate: a multicentre, multinational extension of the European/Canadian double-blind, placebo-controlled, MRI-monitored trial

Glatiramer acetate (GA) is effective in reducing clinical and magnetic resonance imaging (MRI) activity in relapsing-remitting multiple sclerosis (RRMS). Serial long-term MRI data are lacking for large cohorts of GA-treated patients. The European/Canadian GA study consisted of two consecutive phases, each lasting nine months. The first treatment phase was randomized, double-blind and placebo-controlled. The second was an open-label, active treatment phase with daily administration of 20 mg GA subcutaneously for all patients. For the long-term follow-up (LTFU), dual echo, pre- and postgadolinium T1-weighted brain MRI scans were obtained with the same acquisition scheme as for the original trial and a neurological assessment was performed. Lesion volumes, normalized brain volumes and percentage brain volume changes (PBVC) were measured. One hundred and forty-two (63.4%) of the 224 patients who completed the two phases of the European/Canadian study underwent the LTFU after a mean period of 5.8 years (range: 5.3-6.4); 73 were treated with GA from study initiation. MRI measures at LTFU did not significantly differ between patients originally assigned to placebo and those who were always treated with GA, but the proportion of patients who did not require walking aids at LTFU was lower in the latter group (P=0.034). PBVC between baseline and LTFU was significantly correlated with lesion load at study entry. An earlier initiation of GA treatment in patients with active RRMS might, at least partially, have a favourable impact on long-term disease evolution. Multiple Sclerosis 2007; 13: 502-508. http://msj.sagepub.com

Functional magnetic resonance imaging and multiple sclerosis

There is increasing evidence that the severity of the clinical manifestations of multiple sclerosis (MS) does not result simply from the extent of tissue destruction, rather it represents a complex balance between tissue damage, tissue repair and cortical reorganization. Functional magnetic resonance imaging provides information regarding the extent and nature of brain plasticity following MS-related structural injury, with the potential to limit the clinical manifestations of the disease. An altered recruitment of regions devoted normally to the performance of a given task and/or the recruitment of additional areas that are not typically activated by healthy people for performing that given task have been described in patients with MS, independent of their clinical phenotype, when investigating visual, cognitive and motor systems. These functional changes have been related not only to the extent and severity of brain damage within and outside T2-visible lesions and to the involvement of specific brain structures, but also to the degree of spinal cord and optic nerve involvement. It has also been suggested that an altered recruitment of specific brain regions might be associated with the appearance of clinical symptoms in MS, such as fatigue. Brain functional changes have been shown to be dynamic over time, not only after an acute relapse, but also in clinically stable patients. More recently, in patients at the earliest clinical stage of the disease, it has been shown that such changes might contribute to predicting the evolution to definite MS, and it has been postulated that dynamic changes of brain cortical activations might occur with the progression of the disease. An increased recruitment of the cerebral networks might represent the first step of cortical reorganization with the potential to maintain a normal level of function in the course of MS. The progressive failure of these mechanisms might, on the one hand, result in the activation of previously silent second-order compensatory areas, and on the other, contribute to the accumulation of irreversible disability.

MRI evidence for multiple sclerosis as a diffuse disease of the central nervous system

The classical view of MS as a chronic inflammatory demyelinating disease leading to the formation of focal central nervous system (CNS) white matter (WM) lesions has been recently challenged by pathological studies and by the extensive application of modern MRI-based techniques. There is now overwhelming evidence supporting the following statements: MS causes widespread tissue damage in the normal-appearing white matter (NAWM) of the brain and spinal cord, whose extent and severity is more strictly associated to the clinical manifestations of the disease than the extent of focal pathology. Discrete, macroscopic lesions are just the tip of the iceberg of MS pathology. Grey matter (GM) damage is a consistent feature of all MS phenotypes, which is progressive from the start of the relapsing-remitting phase of the disease. As is the case for WM, GM damage is also a mixture of focal lesions and diffuse pathology. High-field strength MR scanners are improving our ability to image focal GM lesions and modern MR-based techniques are enabling us to quantify in vivo the extent and severity of GM pathology, which have been shown to correlate only moderately with the amount of WM changes. At least part of GM pathology in MS is not secondary to retrograde degeneration of fibers traversing WM lesions. The neurodegenerative component of the disease is not a late phenomenon and it is not completely driven by inflammatory demyelination. In fact, neurodegeneration occurs very early in the course of MS and the correlation between MRI measures of inflammation and neurodegeneration is weak in all disease phases. The interplay of inflammation and neurodegeneration is a complex and still poorly understood phenomenon. At least part of MS-related neurodegeneration is not directly driven by Wallerian degeneration. Functional cortical changes can be seen in virtually all MS patients and are likely to play a central role in the ability of the MS brain to respond to tissue injury and, hence, limit the functional consequences of structural damage. MS disability is not just the result of tissue destruction but rather a balance between tissue destruction, tissue repair and adaptive cortical reorganization. All of this calls for the concept of MS as a focal, inflammatory demyelinating, WM disease to be reexamined and to start viewing MS as a diffuse CNS disease with an important neurodegenerative component. This is central for identifying novel and effective treatment strategies.