The effect of interferon beta-1b on quantities derived from MT MRI in secondary progressive MS

Quantitative magnetization transfer imaging in relapsing-remitting multiple sclerosis: a systematic review and meta-analysis

Myelin-sensitive MRI such as magnetization transfer imaging has been widely used in multiple sclerosis. The influence of methodology and differences in disease subtype on imaging findings is, however, not well established. Here, we systematically review magnetization transfer brain imaging findings in relapsing-remitting multiple sclerosis. We examine how methodological differences, disease effects and their interaction influence magnetization transfer imaging measures. Articles published before 06/01/2021 were retrieved from online databases (PubMed, EMBASE and Web of Science) with search terms including 'magnetization transfer' and 'brain' for systematic review, according to a pre-defined protocol. Only studies that used human in vivo quantitative magnetization transfer imaging in adults with relapsing-remitting multiple sclerosis (with or without healthy controls) were included. Additional data from relapsing-remitting multiple sclerosis subjects acquired in other studies comprising mixed disease subtypes were included in meta-analyses. Data including sample size, MRI acquisition protocol parameters, treatments and clinical findings were extracted and qualitatively synthesized. Where possible, effect sizes were calculated for meta-analyses to determine magnetization transfer (i) differences between patients and healthy controls; (ii) longitudinal change and (iii) relationships with clinical disability in relapsing-remitting multiple sclerosis. Eighty-six studies met inclusion criteria. MRI acquisition parameters varied widely, and were also underreported. The majority of studies examined the magnetization transfer ratio in white matter, but magnetization transfer metrics, brain regions examined and results were heterogeneous. The analysis demonstrated a risk of bias due to selective reporting and small sample sizes. The pooled random-effects meta-analysis across all brain compartments revealed magnetization transfer ratio was 1.17 per cent units (95% CI -1.42 to -0.91) lower in relapsing-remitting multiple sclerosis than healthy controls (z-value: -8.99, P < 0.001, 46 studies). Linear mixed-model analysis did not show a significant longitudinal change in magnetization transfer ratio across all brain regions [β = 0.12 (-0.56 to 0.80), t-value = 0.35, P = 0.724, 14 studies] or normal-appearing white matter alone [β = 0.037 (-0.14 to 0.22), t-value = 0.41, P = 0.68, eight studies]. There was a significant negative association between the magnetization transfer ratio and clinical disability, as assessed by the Expanded Disability Status Scale [r = -0.32 (95% CI -0.46 to -0.17); z-value = -4.33, P < 0.001, 13 studies]. Evidence suggests that magnetization transfer imaging metrics are sensitive to pathological brain changes in relapsing-remitting multiple sclerosis, although effect sizes were small in comparison to inter-study variability. Recommendations include: better harmonized magnetization transfer acquisition protocols with detailed methodological reporting standards; larger, well-phenotyped cohorts, including healthy controls; and, further exploration of techniques such as magnetization transfer saturation or inhomogeneous magnetization transfer ratio.

Effect of siponimod on magnetic resonance imaging measures of neurodegeneration and myelination in secondary progressive multiple sclerosis: Gray matter atrophy and magnetization transfer ratio analyses from the EXPAND phase 3 trial

BACKGROUND

Magnetic resonance imaging (MRI) measurements of gray matter (GM) atrophy and magnetization transfer ratio (MTR; correlate of myelination) may provide better insights than conventional MRI regarding brain tissue integrity/myelination in multiple sclerosis (MS).

OBJECTIVE

To examine the effect of siponimod in the EXPAND trial on whole-brain and GM atrophy, newly formed normalized magnetization transfer ratio (nMTR) lesions, and nMTR-assessed integrity of normal-appearing brain tissue (NABT), cortical GM (cGM), and normal-appearing white matter (NAWM).

METHODS

Patients with secondary progressive multiple sclerosis (SPMS) received siponimod (2 mg/day; n =1037) or placebo (n = 523). Endpoints included percentage change from baseline to months 12/24 in whole-brain, cGM, and thalamic volumes; change in nMTR from baseline to months 12/24 in NABT, cGM, and NAWM; MTR recovery in newly formed lesions.

RESULTS

Compared with placebo, siponimod significantly reduced progression of whole-brain and GM atrophy over 12/24 months, and was associated with improvements in brain tissue integrity/myelination within newly formed nMTR lesions and across NABT, cGM, and NAWM over 24 months. Effects were consistent across age, disease duration, inflammatory activity subgroups, and disease severity.

CONCLUSION

Siponimod reduced brain tissue damage in patients with SPMS as evidenced by objective measures of brain tissue integrity/myelination. This is consistent with central nervous system (CNS) effects observed in preclinical models. ClinicalTrials.gov number: NCT01665144.

Predictive MRI Biomarkers in MS—A Critical Review

Background and Objectives: In this critical review, we explore the potential use of MRI measurements as prognostic biomarkers in multiple sclerosis (MS) patients, for both conventional measurements and more novel techniques such as magnetization transfer, diffusion tensor, and proton spectroscopy MRI. Materials and Methods: All authors individually and comprehensively reviewed each of the aspects listed below in PubMed, Medline, and Google Scholar. Results: There are numerous MRI metrics that have been proven by clinical studies to hold important prognostic value for MS patients, most of which can be readily obtained from standard 1.5T MRI scans. Conclusions: While some of these parameters have passed the test of time and seem to be associated with a reliable predictive power, some are still better interpreted with caution. We hope this will serve as a reminder of how vast a resource we have on our hands in this versatile tool—it is up to us to make use of it.

Application of advanced MRI techniques to monitor pharmacologic and rehabilitative treatment in multiple sclerosis: current status and future perspectives

Introduction: Advances in magnetic resonance imaging (MRI) technology and analyses are improving our understanding of the pathophysiology of multiple sclerosis (MS). Due to their ability to grade the presence of irreversible tissue loss, microstructural tissue abnormalities, metabolic changes and functional plasticity, the application of these techniques is also expanding our knowledge on the efficacy and mechanisms of action of different pharmacological and rehabilitative treatments. Areas covered: This review discusses recent findings derived from the application of advanced MRI techniques to evaluate the structural and functional substrates underlying the effects of pharmacologic and rehabilitative treatments in patients with MS. Current applications as outcome in clinical trials and observational studies, their interpretation and possible pitfalls in their use are discussed. Finally, how these techniques could evolve in the future to improve monitoring of disease progression and treatment response is examined. Expert commentary: The number of treatments currently available for MS is increasing. The application of advanced MRI techniques is providing reliable and specific measures to better understand the targets of different treatments, including neuroprotection, tissue repair, and brain plasticity. This is a fundamental progress to move toward personalized medicine and individual treatment selection.

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.

The Role of Advanced Magnetic Resonance Imaging Techniques in Multiple Sclerosis Clinical Trials

Magnetic resonance imaging has been crucial in the development of anti-inflammatory disease-modifying treatments. The current landscape of multiple sclerosis clinical trials is currently expanding to include testing not only of anti-inflammatory agents, but also neuroprotective, remyelinating, neuromodulating, and restorative therapies. This is especially true of therapies targeting progressive forms of the disease where neurodegeneration is a prominent feature. Imaging techniques of the brain and spinal cord have rapidly evolved in the last decade to permit in vivo characterization of tissue microstructural changes, connectivity, metabolic changes, neuronal loss, glial activity, and demyelination. Advanced magnetic resonance imaging techniques hold significant promise for accelerating the development of different treatment modalities targeting a variety of pathways in MS.

Imaging primary progressive multiple sclerosis: the contribution of structural, metabolic, and functional MRI techniques

Patients with primary progressive multiple sclerosis (PPMS) typically experience a progressive disease course from onset, leading to the accumulation of severe neurological disability. This is in contrast with the observation that the burden and activity of lesions on conventional magnetic resonance imaging (MRI) scans of the brain are much lower in patients with PPMS than in those with other less disabling forms of the disease. Studies with structural and functional MRI techniques are providing relevant contributions to the understanding of the mechanisms underlying the accumulatio n of irreversible neurological deficits in patients with PPMS. The results of these studies underpin that the main factors possibly explaining the clinical/MRI discrepancy observed in patients with PPMS include the presence of a diffuse tissue damage that is beyond the resolution of conventional imaging, the extent of cervical cord damage, and the impairment of the adaptive capacity of the cortex to limit the functional consequences of subcortical pathology.

Causes, effects and connectivity changes in MS-related cognitive decline

Cognitive decline is a frequent but undervalued aspect of multiple sclerosis (MS). Currently, it remains unclear what the strongest determinants of cognitive dysfunction are, with grey matter damage most directly related to cognitive impairment. Multi-parametric studies seem to indicate that individual factors of MS-pathology are highly interdependent causes of grey matter atrophy and permanent brain damage. They are associated with intermediate functional effects (e.g. in functional MRI) representing a balance between disconnection and (mal) adaptive connectivity changes. Therefore, a more comprehensive MRI approach is warranted, aiming to link structural changes with functional brain organization. To better understand the disconnection syndromes and cognitive decline in MS, this paper reviews the associations between MRI metrics and cognitive performance, by discussing the interactions between multiple facets of MS pathology as determinants of brain damage and how they affect network efficiency.

Multiple sclerosis

Due to its sensitivity to the different multiple sclerosis (MS)-related abnormalities, magnetic resonance imaging (MRI) has become an established tool to diagnose MS and to monitor its evolution. MRI has been included in the diagnostic workup of patients with clinically isolated syndromes suggestive of MS, and ad hoc criteria have been proposed and are regularly updated. In patients with definite MS, the ability of conventional MRI techniques to explain patients' clinical status and progression of disability is still suboptimal. Several advanced MRI-based technologies have been applied to estimate overall MS burden in the different phases of the disease. Their use has allowed the heterogeneity of MS pathology in focal lesions, normal-appearing white matter and gray matter to be graded in vivo. Recently, additional features of MS pathology, including macrophage infiltration and abnormal iron deposition, have become quantifiable. All of this, combined with functional imaging techniques, is improving our understanding of the mechanisms associated with MS evolution. In the near future, the use of ultrahigh-field systems is likely to provide additional insight into disease pathophysiology. However, the utility of advanced MRI techniques in clinical trial monitoring and in assessing individual patients' response to treatment still needs to be assessed.

Nonconventional MRI and microstructural cerebral changes in multiple sclerosis

MRI has become the most important paraclinical tool for diagnosing and monitoring patients with multiple sclerosis (MS). However, conventional MRI sequences are largely nonspecific in the pathology they reveal, and only provide a limited view of the complex morphological changes associated with MS. Nonconventional MRI techniques, such as magnetization transfer imaging (MTI), diffusion-weighted imaging (DWI) and susceptibility-weighted imaging (SWI) promise to complement existing techniques by revealing more-specific information on microstructural tissue changes. Past years have witnessed dramatic advances in the acquisition and analysis of such imaging data, and numerous studies have used these tools to probe tissue alterations associated with MS. Other MRI-based techniques-such as myelin-water imaging, (23)Na imaging, magnetic resonance elastography and magnetic resonance perfusion imaging-might also shed new light on disease-associated changes. This Review summarizes the rapid technical progress in the use of MRI in patients with MS, with a focus on nonconventional structural MRI. We critically discuss the present utility of nonconventional MRI in MS, and provide an outlook on future applications, including clinical practice. This information should allow appropriate selection of advanced MRI techniques, and facilitate their use in future studies of this disease.

Evidence-based guidelines: MAGNIMS consensus guidelines on the use of MRI in multiple sclerosis--establishing disease prognosis and monitoring patients

The role of MRI in the assessment of multiple sclerosis (MS) goes far beyond the diagnostic process. MRI techniques can be used as regular monitoring to help stage patients with MS and measure disease progression. MRI can also be used to measure lesion burden, thus providing useful information for the prediction of long-term disability. With the introduction of a new generation of immunomodulatory and/or immunosuppressive drugs for the treatment of MS, MRI also makes an important contribution to the monitoring of treatment, and can be used to determine baseline tissue damage and detect subsequent repair. This use of MRI can help predict treatment response and assess the efficacy and safety of new therapies. In the second part of the MAGNIMS (Magnetic Resonance Imaging in MS) network's guidelines on the use of MRI in MS, we focus on the implementation of this technique in prognostic and monitoring tasks. We present recommendations on how and when to use MRI for disease monitoring, and discuss some promising MRI approaches that may be introduced into clinical practice in the near future.

Differentiation and quantification of inflammation, demyelination and axon injury or loss in multiple sclerosis

Axon injury/loss, demyelination and inflammation are the primary pathologies in multiple sclerosis lesions. Despite the prevailing notion that axon/neuron loss is the substrate of clinical progression of multiple sclerosis, the roles that these individual pathological processes play in multiple sclerosis progression remain to be defined. An imaging modality capable to effectively detect, differentiate and individually quantify axon injury/loss, demyelination and inflammation, would not only facilitate the understanding of the pathophysiology underlying multiple sclerosis progression, but also the assessment of treatments at the clinical trial and individual patient levels. In this report, the newly developed diffusion basis spectrum imaging was used to discriminate and quantify the underlying pathological components in multiple sclerosis white matter. Through the multiple-tensor modelling of diffusion weighted magnetic resonance imaging signals, diffusion basis spectrum imaging resolves inflammation-associated cellularity and vasogenic oedema in addition to accounting for partial volume effects resulting from cerebrospinal fluid contamination, and crossing fibres. Quantitative histological analysis of autopsied multiple sclerosis spinal cord specimens supported that diffusion basis spectrum imaging-determined cellularity, axon and myelin injury metrics closely correlated with those pathologies identified and quantified by conventional histological staining. We demonstrated in healthy control subjects that diffusion basis spectrum imaging rectified inaccurate assessments of diffusion properties of white matter tracts by diffusion tensor imaging in the presence of cerebrospinal fluid contamination and/or crossing fibres. In multiple sclerosis patients, we report that diffusion basis spectrum imaging quantitatively characterized the distinct pathologies underlying gadolinium-enhanced lesions, persistent black holes, non-enhanced lesions and non-black hole lesions, a task yet to be demonstrated by other neuroimaging approaches. Diffusion basis spectrum imaging-derived radial diffusivity (myelin integrity marker) and non-restricted isotropic diffusion fraction (oedema marker) correlated with magnetization transfer ratio, supporting previous reports that magnetization transfer ratio is sensitive not only to myelin integrity, but also to inflammation-associated oedema. Our results suggested that diffusion basis spectrum imaging-derived quantitative biomarkers are highly consistent with histology findings and hold promise to accurately characterize the heterogeneous white matter pathology in multiple sclerosis patients. Thus, diffusion basis spectrum imaging can potentially serve as a non-invasive outcome measure to assess treatment effects on the specific components of underlying pathology targeted by new multiple sclerosis therapies.

Magnetic resonance outcome measures in multiple sclerosis trials: time to rethink?

PURPOSE OF REVIEW

We summarize MRI measures currently available to assess treatment efficacy and safety in multiple sclerosis (MS) clinical trials and discuss novel metrics that could enter the clinical arena in the near future.

RECENT FINDINGS

In relapsing remitting MS, MRI measures of disease activity (new T2 and gadolinium-enhancing lesions) provide a good surrogacy of treatment effect on relapse rate and disability progression; however, their value in progressive MS remains elusive. For the progressive disease forms, these measures need to be combined with quantities assessing the extent of irreversible tissue loss, which have already been introduced in some clinical trials (e.g., evolution of active lesions into permanent black holes and brain atrophy). Novel measures (e.g., quantification of gray matter and spinal cord atrophy) have demonstrated a great value in explaining patients' clinical outcome, but still need to be fully validated. Despite showing promise, evaluations of cortical lesions, of microscopic tissue abnormalities, and of functional cortical reorganization are still some way off for monitoring of treatment effects.

SUMMARY

Trial outcomes in MS should include measures of inflammation and neurodegeneration, which should be combined according to the disease clinical phenotype, phase of the study, and the supposed mechanism of action of the drug tested.

MRI measures of neuroprotection and repair in multiple sclerosis

Magnetic resonance imaging (MRI) has had an enormous impact on multiple sclerosis, enabling early diagnosis and providing surrogate markers for monitoring treatment response in clinical trials. Despite these advantages, conventional MRI is limited by lack of pathological specificity and lack of sensitivity to grey matter lesions and to microscopic damage in normal appearing tissue. Quantitative MRI techniques such as measures of parenchymal volume loss, magnetisation transfer imaging, diffusion tensor imaging, and proton magnetic resonance spectroscopy have enhanced our understanding of the nature and mechanism of tissue injury and repair in multiple sclerosis, and provided more specific correlates of neurological deficits and disability accrual. Some of these techniques may be of potential use in clinical trials as surrogate outcome measures for measuring treatment effects on neurodegenerative injury, which is currently difficult to quantify in clinical trials. In this respect, measures of brain volume, T1 hypointensity and magnetisation transfer ratio, and optical coherence tomography appear to be the most promising in the short term. The evidence for a role of neurodegeneration in the pathogenesis of multiple sclerosis, and particularly in the accumulation of irreversible disability, has become increasingly strong over recent years. This has prompted the search for new treatments that can effectively slow down, halt or even reverse such neurodegenerative processes, and in this way restore nervous system function. For this reason, there has been much interest in the development and validation of surrogate markers of neurodegeneration and neuroprotection for use in clinical trials. Advances in magnetic resonance imaging (MRI) technology have allowed the development and implementation of a number of methods that may be promising in this respect. To assess the utility of these methods and to identify needs for further research, sixty experts in neuropathology, clinical measurement, imaging and statistics participated in a meeting held in Amsterdam in 2008 under the aegis of the National Multiple Sclerosis Society. In the proceedings of the meeting, published in 2009 [1], brain volume changes, T1 hypointensity, magnetisation transfer ratio and optical coherence tomography were deemed the most promising measures for screening the neuroprotective capacity of new agents. Other MRI techniques, such as DTI, (1)H-MRS and functional MRI, although potentially useful, require more observational data to help determine the optimal trial design. This article will review some of the issues that were discussed at this meeting, and present some of the imaging techniques that were considered to be the most promising.

Interferon-β1bfor multiple sclerosis

Interferon-beta1b (Betaseron/Betaferon) was the first approved therapy for relapsing-remitting multiple sclerosis. The US Food and Drug Administration has expanded the indication to include relapsing forms of multiple sclerosis which encompasses secondary-progressive multiple sclerosis if relapses are present. In one scientifically sound head-to-head comparison (Independent Comparison of Interferon trial), interferon-beta1b was shown to be clinically superior to low-dose interferon-beta1a (Avonex). Current studies are underway to compare it with a double dosage of interferon-beta1b [corrected] as well as glatiramer acetate. Neutralizing antibodies are more likely to occur with interferon-beta1b, but their clinical significance has shown conflicting and confusing results making the utility of measuring neutralizing antibodies uncertain. Up to 12 years of follow-up data suggest that the drug remains effective on T2 magnetic resonance imaging burden of disease in those who stay on therapy. Initially, the major problem with interferon-beta1b was a lack of tolerability due to high incidents of skin reactions and influenza-like side effects. Patient adherence has improved dramatically with the introduction of autoinjectors and protocol changes including initial dose escalation, prophylactic ibuprofen or acetaminophen, evening administration of drug and an attentive nurse support system. Interferon-beta1b remains a first-line treatment for relapsing-remitting multiple sclerosis and relapsing forms of secondary-progressive multiple sclerosis based on robust efficacy data and a long-term safety profile.

Interferon-β1bin multiple sclerosis

In 1993, interferon (IFN)-beta(1b) for subcutaneous injection became the first US FDA-approved immunomodulatory treatment for multiple sclerosis, a chronic inflammatory disease of the CNS. In this review of IFN-beta(1b), we first present a short introduction to multiple sclerosis and currently available therapeutics. We then summarize current knowledge about the biochemical structure of IFN-beta(1b), as well as pharmacokinetics and pharmacodynamics, including data on putative mechanisms underlying therapeutic as well as adverse effects. Furthermore, a critical review of ongoing and recently published clinical trials investigating IFN-beta(1b) in multiple sclerosis will be provided. Main topics are: trials investigating IFN-beta(1b) after a first clinical event, at higher dosages or in comparison to once-weekly subcutaneous IFN-beta(1a) injections, 16 years of long-term follow-up, IFN-beta(1b) in Japanese patients, the role of neutralizing antibodies, biomarkers for the prediction of therapy response, IFN-beta(1b) and pregnancy, and IFN-beta(1b) treatment of children with multiple sclerosis. Finally, we discuss how novel drugs, especially monoclonal antibodies and orally administered immunosuppressants, might soon challenge the position of this well-established agent on the multiple sclerosis therapeutics market.

Primary progressive multiple sclerosis: part of the MS disease spectrum or separate disease entity?

Multiple sclerosis (MS), the most frequent demyelinating disease, is characterized by a variable disease course. The majority of patients starts with relapsing remitting (RR) disease; approximately 50-60% of these patients progress to secondary progressive (SP) disease. Only about 15% of the patients develop a progressive disease course from onset, termed primary progressive multiple sclerosis (PPMS); the underlying pathogenic mechanisms responsible for onset of the disease with either PPMS or relapsing remitting multiple sclerosis (RRMS) are unknown. Patients with PPMS do not show a female predominance and usually have a later onset of disease compared to patients with RRMS. Monozygous twins can be concordant or discordant for disease courses indicating that the disease course is not only genetically determined. Primary progressive multiple sclerosis and secondary progressive multiple sclerosis (SPMS) share many similarities in imaging and pathological findings. Differences observed among the different disease courses are more of a quantitative than qualitative nature suggesting that the different phenotypes are part of a disease spectrum modulated by individual genetic predisposition and environmental influences. In this review, we summarize the knowledge regarding the clinical, epidemiological, imaging, and pathological characteristics of PPMS and compare those characteristics with RRMS and SPMS.

Multiple sclerosis normal-appearing white matter: pathology-imaging correlations

OBJECTIVE

The study was undertaken to determine the pathologic basis of subtle abnormalities in magnetization transfer ratio (MTR) and diffusion tensor imaging (DTI) parameters observed in normal-appearing white matter (NAWM) in multiple sclerosis brains.

METHODS

Brain tissues were obtained through a rapid postmortem protocol that included in situ magnetic resonance imaging (MRI). Four types of MRI-defined regions of interest (ROIs) were analyzed: (1) regions that were abnormal on all images (T2T1MTR lesions); (2) NAWM regions with slightly abnormal MTR located close to white matter lesions (sa-WM Close); (3) NAWM regions with slightly abnormal MTR located far from lesions (sa-WM Far); and (4) NAWM regions with normal MTR (NAWM). Immunohistochemical analysis for each ROI comprised immunostaining for myelin, axonal markers, activated microglia/macrophages, astrocytes, plasma proteins, and blood vessels.

RESULTS

Forty-eight ROIs from 4 secondary progressive MS brains were analyzed. sa-WM Close ROIs were associated with significantly more axonal swellings. There were more enlarged major histocompatibility complex II(+) microglia and macrophages detected in sa-WM Far, sa-WM Close, and T2T1MTR lesions than in NAWM. Across all ROIs, MTR and DTI measures were moderately correlated with myelin density, axonal area, and axonal counts. Excluding T2T1MTR lesions from analysis revealed that MTR and DTI measures in nonlesional white matter (WM) were correlated with activated microglia, but not with axonal or myelin integrity.

INTERPRETATION

The pathologic substrates for MRI abnormalities in NAWM vary based on distance from focal WM lesions. Close to WM lesions, axonal pathology and microglial activation may explain subtle MRI changes. Distant from lesions, microglial activation associated with proximity to cortical lesions might underlie MRI abnormalities.

Interferon beta for secondary progressive multiple sclerosis

BACKGROUND

Therapy with either recombinant beta-1a or beta-1b interferons (IFNs) is worldwide approved for Relapsing Remitting Multiple Sclerosis (RRMS). A major unanswered question is whether this treatment is able to safely reverse or retard the progressive phase of the disease.

OBJECTIVES

The main objective was to verify whether IFNs treatment in Secondary Progressive Multiple Sclerosis (SPMS) is more effective than placebo in reducing the number of patients who experience disability progression.

SEARCH METHODS

We searched the Cochrane Multiple Sclerosis Group's Trials Register (1995 to 15 February 2011), the reference lists of relevant articles and conference proceedings. Regulatory agencies were used as additional sources of information.

SELECTION CRITERIA

We included all randomised, double or single blind, placebo-controlled trials (RCTs) evaluating the efficacy of IFNs versus placebo in SPMS patients.

DATA COLLECTION AND ANALYSIS

Two review authors independently assessed all reports retrieved from the search. They independently extracted clinical, safety and MRI data, using a predefined data extraction form, resolving disagreements after discussion with a third reviewer. Risk of bias was evaluated to assess the quality of the studies. Treatment effect was measured using Risk Ratio (RR) with 95% confidence intervals (CI) for the binary outcomes and Standard Mean Difference with 95% CI for the continuous outcomes.

MAIN RESULTS

Five RCTs met the inclusion criteria, from which 3122 (1829 IFN and 1293 placebo) treated patients contributed to the analysis. Included population was heterogeneous in terms of baseline clinical characteristics of the disease, in particular the percentage of patients affected by secondary progression with superimposed relapse ranging from 72% to 44%. IFN beta 1a and 1b did not decrease the risk of progression sustained at 6 months (RR, 95% CI: 0.98, [0.82-1.16]) after three years of treatment. A significant decrease of the risk of progression sustained at 3 months (RR, 95% CI: 0.88 [0.80, 0.97]) and of the risk of developing new relapses at three years (RR 0.91, [0.84-0.97]) were found. The risk of developing new active brain lesions decreased over time but this data was obtained from single studies on Magnetic Resonance Imaging (MRI), performed in subgroups of patients; in spite of no effect on progression, the radiological data supported an effect on MRI parameters. The safety profile reflects what is commonly reported in MS IFN-treated patients.

AUTHORS' CONCLUSIONS

Well designed RCTs, evaluating a high number of patients were included in the review. Recombinant IFN beta does not prevent the development of permanent physical disability in SPMS. We were unable to verify the effect on cognitive function for the lack of comparable data. This treatment significantly reduces the risk of relapse and of short -term relapse-related disability.Overall, these results show that IFNs' anti-inflammatory effect is unable to retard progression, when established. In the future, no new RCTs for IFNs versus placebo in SPMS will probably be undertaken, because research is now focusing on innovative drugs. We believe that this review gives conclusive evidence on the clinical efficacy of IFNs versus placebo in SPMS.

Longitudinal changes in magnetisation transfer ratio in secondary progressive multiple sclerosis: data from a randomised placebo controlled trial of lamotrigine

Sodium blockade with lamotrigine is neuroprotective in animal models of central nervous system demyelination. This study evaluated the effect of lamotrigine on magnetisation transfer ratio (MTR), a putative magnetic resonance imaging measure of intact brain tissue, in a group of subjects with secondary progressive multiple sclerosis (MS). In addition, the utility of MTR measures for detecting change in clinically relevant pathology was evaluated. One hundred seventeen people attending the National Hospital for Neurology and Neurosurgery or the Royal Free Hospital, London, UK, were recruited into a double-blind, parallel-group trial. Subjects were randomly assigned by minimisation to receive lamotrigine (target dose 400 mg/day) or placebo for 2 years. Treating and assessing physicians and patients were masked to treatment allocation. Results of the primary endpoint, central cerebral volume, have been published elsewhere. Significant differences between the verum and placebo arms were seen in only two measures [normal appearing grey matter (NAGM) p = 0.036 and lesion peak height (PH) p = 0.004], and in both cases there was a greater reduction in MTR in the verum arm. Significant correlations were found of change in MS functional composite with all MTR measures except lesion and normal appearing white matter (NAWM) PH. However, the change in MTR measures over 2 years were small, with only NAGM mean (p = 0.001), lesion peak location (p = 0.11) and mean (p < 0.0001) changing significantly from baseline. These data did not show that lamotrigine was neuroprotective. The clinical correlation of MTR measures was consistent, but the responsiveness to change was limited.

Progressive multiple sclerosis and gray matter pathology: an MRI perspective

The evidence suggesting a role of extensive cortical demyelization and atrophy in progressive multiple sclerosis is rapidly increasing. Although conventional magnetic resonance imaging has had a huge impact on multiple sclerosis by enabling an earlier diagnosis, and by providing surrogate markers for monitoring disease response to anti-inflammatory/immunomodulatory treatments, it is limited by the low pathological specificity and the low sensitivity to both diffuse damage in normal-appearing white matter and focal and diffuse damage in gray matter. Advanced magnetic resonance imaging techniques can partially overcome these limitations by providing markers more specific to the underlying pathologic substrates and more sensitive to the structural and functional "occult" brain tissue damage in patients with multiple sclerosis. This review describes brain and spinal cord imaging studies of multiple sclerosis with particular emphasis on gray matter imaging in both secondary progressive and primary progressive multiple sclerosis, discusses the clinical implications of gray matter damage, and outlines current magnetic resonance imaging developments at high and ultrahigh magnetic field strength.

Bimonthly assessment of magnetization transfer magnetic resonance imaging parameters in multiple sclerosis: a 14-month, multicentre, follow-up study

This study was performed to assess the temporal evolution of damage within lesions and the normal-appearing white matter, measured using frequent magnetization transfer (MT) MRI, in relapsing-remitting multiple sclerosis (RRMS). The relationship of MT ratio (MTR) changes with measures of lesion burden, and the sample sizes needed to demonstrate a treatment effect on MTR metrics in placebo-controlled MS trials were also investigated. Bimonthly brain conventional and MT MRI scans were acquired from 42 patients with RRMS enrolled in the placebo arm of a 14-month, double-blind trial. Longitudinal MRI changes were evaluated using a random effect linear model accounting for repeated measures, and adjusted for centre effects. The Expanded Disability Status Scale (EDSS) score remained stable over the study period. A weak, but not statistically significant, decrease over time was detected for normal-appearing brain tissue (NABT) average MTR (-0.02% per visit; p = 0.14), and MTR peak height (-0.15 per visit; p = 0.17), while average lesion MTR showed a significant decrease over the study period (-0.07% per visit; p = 0.03). At each visit, all MTR variables were significantly correlated with T2 lesion volume (LV) (average coefficients of correlation ranging from -0.54 to -0.28, and p-values from <0.001 to 0.02). At each visit, NABT average MTR was also significantly correlated with T1-hypointense LV (average coefficient of correlation = -0.57, p < 0.001). The estimation of the sample sizes required to demonstrate a reduction of average lesion MTR (the only parameter with a significant decrease over the follow-up) ranged from 101 to 154 patients to detect a treatment effect of 50% in a 1-year trial with a power of 90%. The steady correlation observed between conventional and MT MRI measures over time supports the hypothesis of axonal degeneration of fibres passing through focal lesions as one of the factors contributing to the overall MS burden.

Current approaches to the identification and management of breakthrough disease in patients with multiple sclerosis

Disease-modifying drugs (DMDs) for relapsing-remitting multiple sclerosis (RRMS) are only partly effective -- breakthrough disease commonly occurs despite treatment. Breakthrough disease is predictive of continued disease activity and a poor prognosis. Availability of several DMDs offers the possibility of tailoring treatment to individual patients with RRMS and altering treatment in patients with breakthrough disease. However, no biological or imaging markers have been validated to guide initial treatment, markers of individual responsiveness to DMDs are scarce, and there is no class 1 evidence to guide alternative therapy in patients with breakthrough disease. In this Review, we discuss proposed strategies to monitor patients with RRMS being treated with DMDs, outline approaches to identifying therapeutic response in individual patients, review MRI and biological markers of treatment response, and summarise the role of antibodies in biological therapies. We also outline possible strategies for the management of patients with breakthrough disease and highlight areas in which research is needed.

Characterizing iron deposition in multiple sclerosis lesions using susceptibility weighted imaging

PURPOSE

To investigate whether the variable forms of putative iron deposition seen with susceptibility weighted imaging (SWI) will lead to a set of multiple sclerosis (MS) lesion characteristics different than that seen in conventional MR imaging.

MATERIALS AND METHODS

Twenty-seven clinically definite MS patients underwent brain scans using magnetic resonance imaging including: pre- and postcontrast T1-weighted imaging, T2-weighted imaging, FLAIR, and SWI at 1.5 T, 3 T, and 4 T. MS lesions were identified separately in each imaging sequence. Lesions identified in SWI were reevaluated for their iron content using the SWI filtered phase images.

RESULTS

There were a variety of new lesion characteristics identified by SWI, and these were classified into six types. A total of 75 lesions were seen only with conventional imaging, 143 only with SWI, and 204 by both. From the iron quantification measurements, a moderate linear correlation between signal intensity and iron content (phase) was established.

CONCLUSION

The amount of iron deposition in the brain may serve as a surrogate biomarker for different MS lesion characteristics. SWI showed many lesions missed by conventional methods and six different lesion characteristics. SWI was particularly effective at recognizing the presence of iron in MS lesions and in the basal ganglia and pulvinar thalamus.

Magnetization transfer MR imaging in multiple sclerosis

We introduce the fundamental aspects of MT, of MT MR imaging, and the respective analysis techniques. We then review the applications of MT MR imaging to multiple sclerosis. Finally we review the technique's contribution to our understanding of this disease.

Grey matter magnetization transfer ratio independently correlates with neurological deficit in secondary progressive multiple sclerosis

Although there is substantial brain grey matter pathology in secondary progressive multiple sclerosis (MS), there has been limited investigation of its contribution to disability.This study investigated the correlation of magnetization transfer ratio (MTR) measures taken from brain grey matter, normal appearing white matter (NAWM) and lesions with neurological deficit and disability in 113 people with secondary progressive MS. In order to adjust for the potential effects of focal white matter lesions and global brain atrophy, T2 lesion volume and normalized brain volume (NBV) were also calculated for each subject. Clinical measures included the expanded disability status scale (EDSS) and the multiple sclerosis functional composite (MSFC) scores. Linear regression analysis was used to assess the age- and gender-adjusted correlation of MTR histogram mean, peak height and peak location with the MSFC and individual component measures. Logistic regression analysis was used to determine whether imaging measures could be used to predict if subjects were in the higher disability group (EDSS > or = 6.5).Significant correlations were detected between MSFC composite and mean MTR in (i) normal appearing white matter (NAWM; r = 0.327, p < 0.0001), (ii) grey matter (r = 0.460, p < 0.0001) and (iii) lesions (r = 0.394, p < 0.0001). Although NBV and T2 lesion volume correlated significantly with MSFC, grey matter histogram mean emerged as the best predictor of MSFC score. None of the MRI measures significantly predicted higher EDSS.These results suggest that brain grey matter pathology plays an important role in determining neurological impairment. The apparent paucity of correlation between MRI measures and EDSS is likely to represent the relative insensitivity of the latter measure in this study group.

The use of MR imaging as an outcome measure in multiple sclerosis clinical trials

MR imaging is an integral part of multiple sclerosis (MS) clinical trials. It provides the primary efficacy outcome of preliminary proof-of-concept studies and important corroborating data as secondary and exploratory outcomes in pivotal trials. At all stages of drug development, MR imaging provides important information on the kinetics and magnitude of treatment effect and insight into potential mechanisms of action. Attention to issues in scan acquisition, quantitative image processing, and statistical analysis is critical to generate high-quality data. Although it is unlikely that one single outcome measure can capture all aspects of the MS disease process, there is potential for MR imaging outcomes to evaluate inflammatory and degenerative components within clinical trials.

Characterization of white matter damage in animal models of multiple sclerosis by magnetization transfer ratio and quantitative mapping of the apparent bound proton fraction f*

Quantitative magnetization transfer magnetic resonance imaging (qMT-MRI) can be used to improve detection of white matter tissue damage in multiple sclerosis (MS) and animal models thereof. To study the correlation between MT parameters and tissue damage, the magnetization transfer ratio (MTR), the parameter f* (closely related to the bound proton fraction) and the bound proton transverse relaxation time T2B of lesions in a model of focal experimental autoimmune encephalomyelitis (EAE) were measured on a 7T animal scanner and data were compared with histological markers indicative for demyelination, axonal density, and tissue damage. A clear spatial correspondence was observed between reduced values of MTR and demyelination in this animal model. We observed two different levels of MTR and f* reduction for these lesions. One was characterized by a pronounced demyelination and the other corresponded to a more severe loss of the cellular matrix. Changes in f* were generally more pronounced than those of MTR in areas of demyelination. Moreover, a reduction of f* was already observed for tissue where MTR was virtually normal. No changes in T2B were observed for the lesions. We conclude that MTR and qMT mapping are efficient and reliable readouts for studying demyelination in animal models of MS, and that the analysis of regional f* might be even superior to the analysis of MTR values. Therefore, quantitative mapping of f* from human brains might also improve the detection of white matter damage in MS.

Magnetic resonance imaging in clinical trials

PURPOSE OF REVIEW

The aim of this article is to review the latest clinical trials in neurological diseases where magnetic resonance imaging was used to assess treatment outcome.

RECENT FINDINGS

The unique sensitivity of magnetic resonance imaging for detecting disorders in the brain has made it an attractive noninvasive tool for assessing treatment efficacy in several diseases. Volumetric and functional magnetic resonance imaging have proved to represent robust biomarkers for the evaluation of anti-Alzheimer treatments, and have demonstrated a significant impact of cholinesterase inhibitors. The optimization of thrombolytic therapy in acute ischemic stroke has concentrated on the quantification of the ischemic penumbra, using perfusion-weighted and diffusion-weighted imaging. Standard assessment of T2 or fluid-attenuated inversion recovery lesion load remains the method of choice to evaluate new therapeutic strategy in multiple sclerosis. Other nonconventional quantitative magnetic resonance imaging techniques such as magnetic resonance volumetry, magnetization transfer imaging, diffusion-weighted imaging, or magnetic resonance spectroscopy are increasingly used in the field.

SUMMARY

Magnetic resonance imaging has become a major surrogate marker of treatment response in clinical trials of neurological disorders, offering the possibility to reduce the required sample size or to shorten the duration of the trial.

Magnetic resonance imaging metrics and their correlation with clinical outcomes in multiple sclerosis: a review of the literature and future perspectives

Magnetic resonance imaging (MRI) has revolutionized the diagnosis and management of patients with multiple sclerosis (MS). Conventional MRI metrics are employed as primary endpoints in proof-of-concept clinical trials evaluating new drugs for MS and as secondary endpoints in definitive phase III trials. Metrics derived from non-conventional MRI techniques are now emerging and hold significant promise since they appear to be more correlated with the most disabling features of MS. However, none of these has been approved for use as a surrogate endpoint for accumulation of physical disability, which is the most important clinical endpoint of this disease. Taking into account the large numbers of patients needed, the extensive exposure to placebo, and the relatively long duration required for phase III clinical trials to show a meaningful effect on progression of disability, the need for a valid, reliable, and objective paraclinical marker of disease evolution cannot be overemphasized. This paper reviews the most up-to-date data regarding MRI techniques, their relationship with central nervous system pathology, as well as with clinical endpoints, and proposes future insights into the use of MRI metrics as surrogate endpoints in clinical trials of MS.

Imaging of remyelination and neuronal health

Remyelination of axons that have been demyelinated due to multiple sclerosis (MS) may be a critical step in restoring the damaged axons and reversing the disease process. While it is possible to establish the presence of remyelination with microscopy of tissue samples, it is important to have noninvasive or minimally invasive methods to measure remyelination in living animals and humans. Such tools are critical to establishing the efficacy of agents purported to promote or enhance remyelination. This chapter reviews the technology of imaging of the brain, its application to MS, and the current state of imaging techniques for measuring remyelination and the health of the associated neurons in the setting of MS.

Large-scale, multicentre, quantitative MRI study of brain and cord damage in primary progressive multiple sclerosis

Although the mechanisms underlying the accumulation of disability in primary progressive (PP) multiple sclerosis (MS) are still unclear, a major role seems to be played by `occult' tissue damage. We investigated whether conventional and magnetization transfer (MT) MRI may provide complementary information for the assessment of PPMS severity. Conventional and MT MRI scans from 226 PPMS patients and 84 healthy controls were collected for centralized analysis. The expanded disability status scale (EDSS) score was rated at the time of MRI acquisition. T2 lesion volume, normalized brain volume (NBV) and cervical cord cross-sectional area (CSA) were measured. Magnetization transfer ratio (MTR) histograms from whole brain tissue, normal-appearing white matter and grey matter (NAGM) were also obtained. Mean NBV, CSA and MTR histogram-derived metrics showed significant inter-centre heterogeneity. After correcting for the acquisition centre, pooled average MTR and histogram peak height values were different between PPMS patients and controls for all tissue classes ( P-values between 0.03 and 0.0001). More severe brain and cord atrophy and MT MRI-detectable NAGM damage were found in patients who required walking aids than in those who did not ( P-values: 0.03, 0.001 and 0.016). A composite score of NBV, CSA, whole brain and NAGM MTR histogram peak height z-scores was correlated with patients' EDSS ( r = 0.37, P 0.001). Magnetization transfer MRI might provide information complementary to that given by conventional MRI when assessing PPMS severity. Sequence-related variability of measurements makes the standardization of MT MRI acquisition essential for the design of multicentre studies. Multiple Sclerosis 2008; 14: 455—464. http://msj.sagepub.com

Effect of intravenous methylprednisolone on the number, size and confluence of plaques in relapsing-remitting multiple sclerosis

The aim of the present study was to evaluate whether intravenous methylprednisolone (IVMP) pulses affect the confluence and enlargement of T2 lesions in the long term in patients with relapsing-remitting (RR) multiple sclerosis (MS). Of 88 RR MS patients, randomly assigned to regular pulses of IVMP (1 g/day for 5 days with an oral prednisone taper) or IVMP on the same dose schedule only for relapses, and followed up without other disease-modifying drug therapy for 5 years, 81 patients completed the trial as planned. Pulsed IVMP was given every 4 months for 3 years, and then every 6 months for the subsequent 2 years. Calculations were performed for number, size and lesion volume (LV) of T2- and confluent T2-lesions. At study entry, the number, size and LV of T2- and confluent T2-lesions were well matched in the two study arms. At the end of the study, patients who received IVMP pulses every 4-6 months for 5 years had significantly fewer confluent T2 lesions (105 vs. 270, p<0.0001), lower confluent T2-LV (5.4 ml vs. 17.4 ml, p<0.00001), fewer large T2 lesions (>10 mm) (165 vs. 541, p<0.00001), and lower T2-LV/N degrees T2 lesion index (0.52 vs. 1.1, p=0.007) when compared to patients who received IVMP only for relapses. There were more small T2 lesions (1082 vs. 288, p<0.000001) in the IVMP pulsed arm. Patients who received higher total doses of IVMP showed the smallest changes in confluent T2-LV during the study. This study suggests that treatment with pulses of IVMP may prevent the confluence of T2 lesions, which may in turn contribute to slower progression of disability in the long term. However, pulsed IVMP treatment did not significantly slow down accumulation of overall T2-LV and there were more smaller T2 lesions in the IVMP pulsed arm at the end of the study.

Whole brain and localized magnetization transfer measurements are associated with cognitive impairment in patients infected with human immunodeficiency virus

BACKGROUND AND PURPOSE

Patients infected with human immunodeficiency virus (HIV) are susceptible to cognitive deterioration. This study investigated the utility of magnetization transfer (MT) imaging for quantification of brain tissue alterations associated with cognitive deficits in patients with HIV.

MATERIALS AND METHODS

MT ratios (MTR) were derived for whole brain and for regions of interest (ROIs) in the basal ganglia and white matter in 11 HIV and 12 control subjects. Relationships with severity of cognitive impairment and specific neuropsychological deficits were also evaluated.

RESULTS

MTR values for normalized whole brain histogram peak height, whole brain histogram mean, and all examined ROIs were reduced in the HIV subjects. Normalized histogram peak height and mean for whole brain, as well as means for the corpus callosum, basal ganglia, and frontal white matter (FWM), were significantly correlated with severity of cognitive impairment. MTR values for white matter regions (corpus callosum, FWM, and centrum semiovale) were correlated with specific cognitive deficits.

CONCLUSION

Quantitative MTR measurements, determined for the whole brain and for vulnerable ROIs, are sensitive to neuropathologic changes associated with cognitive impairment in HIV-infected patients.

Magnetization transfer magnetic resonance imaging of the brain, spinal cord, and optic nerve

Magnetic resonance imaging is highly sensitive in revealing CNS abnormalities associated with several neurological conditions, but lacks specificity for their pathological substrates. In addition, MRI does not allow evaluation of the presence and extent of damage in regions that appear normal on conventional MRI sequences and that postmortem studies have shown to be affected by pathology. Quantitative MR-based techniques with increased pathological specificity to the heterogeneous substrates of CNS pathology have the potential to overcome such limitations. Among these techniques, one of the most extensively used for the assessment of CNS disorders is magnetization transfer MRI (MT-MRI). The application of this technique for the assessment of damage in macroscopic lesions, in normal-appearing white and gray matter, and in the spinal cord and optic nerve of patients with several neurological conditions is providing important in vivo information-dramatically improving our understanding of the factors associated with the appearance of clinical symptoms and the accumulation of irreversible disability. MT-MRI also has the potential to contribute to the diagnostic evaluation of several neurological conditions and to improve our ability to monitor treatment efficacy in experimental trials.

MRI to monitor treatment efficacy in multiple sclerosis

It is the primary goal of disease modifying treatments in multiple sclerosis (MS) to prevent the occurrence of new clinical deficits and lessen or prevent accumulation of disability. As a consequence, clinical aspects constitute the major outcome variables in treatment trials and are also the leading factor for treatment decisions in individual patients. However, determining treatment efficacy by clinical evaluation suffers from limited objectivity, sensitivity, and specificity for the underlying pathophysiologic aspects, which may constitute the target of a given therapy. Magnetic resonance imaging (MRI) can partly overcome these limitations by showing morphologic aspects of the disease with clinical relevance and responsiveness to therapy. Within the past 10 years sufficient data have been collected to establish the accumulation of new/enlarging T2 lesions and gadolinium enhancing lesions, T2 lesion load, T1-hypointense lesions, and brain volume changes as reasonably well-defined markers of disease processes, which may serve to monitor treatment efficacy. Accordingly, these variables have been extensively used for probing the efficacy of disease modifying treatments. In part they are also suited to guide therapeutic decisions in the individual patient. Further options may come from the use of advanced techniques like magnetization transfer MRI, diffusion-weighted MRI, and proton magnetic resonance spectroscopy, which detect more subtle MS related tissue abnormalities. Irrespective of the technique employed, great care has to be given to the standardization and reproducibility of both data acquisition and interpretation when using MRI to monitor treatment efficacy. For the individual patient therapeutic decisions based on MRI need experience and caution.

Magnetization Transfer MRI in Multiple Sclerosis

In multiple sclerosis (MS), conventional magnetic resonance imaging (cMRI) has proved to be sensitive for detecting lesions and their changes over time. However, cMRI is not able to characterize and quantify the tissue damage within and outside such lesions. Magnetization transfer (MT) MRI is a quantitative technique with the potential to overcome this limitation and, as a consequence, to provide additional information about the nature and the extent of tissue damage associated to this disease. During the last 10 years, MT MRI indeed has allowed us to quantify the structural changes occurring within and outside lesions visible on cMRI scans, thus providing a more accurate in vivo picture of the heterogeneity of MS and, as a consequence, improving our ability to monitor the evolution of the disease. The application of MT MRI to the study of MS has contributed to change our understanding of how MS causes irreversible disability by showing that MS is more than an inflammatory-demyelinating condition of the white matter of the central nervous system.

EFNS guidelines on the use of neuroimaging in the management of multiple sclerosis

Magnetic resonance (MR)-based techniques are widely used for the assessment of patients with suspected and definite multiple sclerosis (MS). However, despite the publication of several position papers, which attempted to define the utility of MR techniques in the management of MS, their application in everyday clinical practice is still suboptimal. This is probably related, not only, to the fact that the majority of published guidelines focused on the optimization of MR technology in clinical trials, but also to the continuing development of modern, quantitative MR-based techniques, that have not as yet entered the clinical arena. The present report summarizes the conclusions of the 'EFNS Expert Panel of Neuroimaging of MS' on the application of conventional and non-conventional MR techniques to the clinical management of patients with MS. These guidelines are intended to assist in the use of conventional MRI for the diagnosis and longitudinal monitoring of patients with MS. In addition, they should provide a foundation for the development of more widespread but rational clinical applications of non-conventional MR-based techniques in studies of MS patients.

Secondary progressive multiple sclerosis: current knowledge and future challenges

The secondary progressive phase of multiple sclerosis (MS), which is characterised by a steady accrual of fixed disability after an initial relapsing remitting course, is not clearly understood. Although there is no consensus on the mechanisms underlying such a transition to the progressive phase, epidemiological and neuroimaging studies indicate that it is probably driven by the high prevalence of neurodegenerative compared with inflammatory pathological changes. This notion is lent support by the limited efficacy of available immunomodulating and immunosuppressive treatment strategies, which seems to be further decreased in the late stages of secondary progressive MS. No established clinical or paraclinical predictors of the transition from relapsing remitting to secondary progressive MS have been described. However, the use of quantitative MRI-derived measures is warranted to monitor natural history studies and therapeutic trials of secondary progressive MS with increased reliability. In view of the small effects of immunomodulating and immunosuppressive treatments in preventing the transition to secondary progression, the development of treatments promoting neuroaxonal repair remains an important goal in this disease.

Magnetization transfer imaging in multiple sclerosis

Magnetization transfer (MT) is a relatively new way of generating contrast in magnetic resonance (MR) images that is sensitive to the density of the macromolecules found throughout tissue structures such as membranes, myelin, and organelles. MT imaging (MTI) can provide a quantitative measure of macromolecular density, and therefore of tissue damage, and has been applied in the central nervous system in multiple sclerosis (MS) and other diseases. This article introduces the contrast mechanisms behind MTI and gives some practical guidance about implementing MTI and about quantitative analysis of the MT scans. An overview of MT measurements made in animal studies, in postmortem tissue samples, and in other demyelinating diseases attempts to rationalize the pathological basis of changes in MT contrast in MS. The application of MTI to MS is reviewed, with emphasis on the contribution that MTI has made to the current understanding of the MS disease process, both its natural history and the response to treatment. The pathological basis of abnormal MT contrast is still open to debate, with many conflicting reports; indeed, it is unlikely that a simple measure of MT effect will reveal the details of pathology that is a combination of inflammation, demyelination, remyelination, and axonal loss. There is no doubt, however, that MT measurements have contributed to the current understanding of both disease progression and the response to treatment and will prove to be a valuable tool in the future, particularly if more refined techniques can be applied practically in multicenter studies.

Clinical trials in multiple sclerosis: methodological issues

PURPOSE OF REVIEW

The availability of partially effective immunomodulatory and immunosuppressive treatments for relapsing multiple sclerosis (MS) opens important ethical, methodological and practical issues in the design and conduct of new clinical trials in these patients.

RECENT FINDINGS

The recommendation of the National Health Authorities to prioritize phase III clinical trials using placebo arm raises ethical questions. In addition, patients are reluctant to be involved in such trials. Alternative clinical trial designs will be discussed. Relapses and active lesions are accepted measures of disease activity; new/enlarging T2 lesions and/or enhancing lesions are accepted surrogate markers of disease activity in phase II clinical trials. On the contrary, there are no accepted magnetic resonance imaging (MRI) surrogate markers of disease progression and also the clinical measures to monitor the degenerative aspects of the disease are not without important limitations. New scales of impairment, disability and quality of life will be reviewed extensively. We will also focus on the value of modern and quantitative MRI techniques, which hold substantial promise as tools to estimate the extent of MS-related irreversible tissue loss.

SUMMARY

The use of an active comparator in a superior clinical-trial design is becoming an attractive option for testing the efficacy of new drugs in relapsing MS. At present there are no fully reliable and sensitive clinical markers of the accumulation of irreversible tissue damage in MS. Although additional extensive application in longitudinal studies is needed, modern MRI techniques are promising tools to monitor the neurodegenerative aspects of MS.

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

Gadolinium-enhanced magnetic resonance imaging (MRI) and measures of brain volume have been extensively applied in large-scale studies to assess disease activity and irreversible tissue damage in multiple sclerosis (MS). Although histopathological studies of MS demonstrated that axonal transection occurs at sites of inflammatory changes, the correlation between brain tissue loss and gadolinium enhancement was found to be either absent or poor in virtually all in vivo MRI studies. This review discusses the reasons of this "inflammation/neurodegeneration mismatch" in MS and proposes possible strategies for a better in vivo characterization of the complex pathological process of this disease.

Increasing normal-appearing grey and white matter magnetisation transfer ratio abnormality in early relapsing-remitting multiple sclerosis

Abnormalities within normal-appearing grey and white matter (NAGM and NAWM) occur early in the clinical course of multiple sclerosis (MS) and can be detected in-vivo using the magnetisation transfer ratio (MTR). To better characterize the rates of change in both tissues and to ascertain when such changes begin, we serially studied a cohort of minimally disabled, early relapsing-remitting MS patients, using NAGM and NAWM MTR histograms. Twenty-three patients with clinically definite early relapsing-remitting MS (mean disease duration at baseline 1.9 years), and 19 healthy controls were studied. A magnetisation transfer imaging sequence was acquired yearly for two years. Twenty-one patients and 10 controls completed followup. NAWM and NAGM MTR histograms were derived and mean MTR calculated. A hierarchical regression analysis, adjusting for brain parenchymal fraction,was used to assess MTR change over time. MS NAWM and NAGM MTR were significantly reduced in comparison with controls at baseline and, in patients, both measures decreased further during follow-up: (-0.10 pu/year, p=0.001 and -0.18 pu/year, p<0.001 respectively). The rate of MTR decrease was significantly greater in NAGM than NAWM (p=0.004). Under the assumption that such changes are linear, backward extrapolation of the observed rates of change suggested that NAWM abnormality began before symptom onset. We conclude that increasing MTR abnormalities in NAWM and NAGM are observed early in the course of relapsing-remitting MS. It is now important to investigate whether these measures are predictive of future disability, and consequently, whether MTR could be used as a surrogate marker in therapeutic trials.

Imaging of multiple sclerosis: role in neurotherapeutics

Magnetic resonance imaging (MRI) plays an ever-expanding role in the evaluation of multiple sclerosis (MS). This includes its sensitivity for the diagnosis of the disease and its role in identifying patients at high risk for conversion to MS after a first presentation with selected clinically isolated syndromes. In addition, MRI is a key tool in providing primary therapeutic outcome measures for phase I/II trials and secondary outcome measures in phase III trials. The utility of MRI stems from its sensitivity to longitudinal changes including those in overt lesions and, with advanced MRI techniques, in areas affected by diffuse occult disease (the so-called normal-appearing brain tissue). However, all current MRI methodology suffers from limited specificity for the underlying histopathology. Conventional MRI techniques, including lesion detection and measurement of atrophy from T1- or T2-weighted images, have been the mainstay for monitoring disease activity in clinical trials, in which the use of gadolinium with T1-weighted images adds additional sensitivity and specificity for areas of acute inflammation. Advanced imaging methods including magnetization transfer, fluid attenuated inversion recovery, diffusion, magnetic resonance spectroscopy, functional MRI, and nuclear imaging techniques have added to our understanding of the pathogenesis of MS and may provide methods to monitor therapies more sensitively in the future. However, these advanced methods are limited by their cost, availability, complexity, and lack of validation. In this article, we review the role of conventional and advanced imaging techniques with an emphasis on neurotherapeutics.

The use of magnetic resonance imaging in multiple sclerosis: lessons learned from clinical trials

Magnetic resonance imaging (MRI) is an important paraclinical tool for the diagnosis of multiple sclerosis (MS) and for monitoring its disease course. The efficacy of most of the available MS disease-modifying treatments has been tested in clinical trials where MRI-derived quantities served as primary or secondary outcome measures. However, conventional MRI measures (i.e., the number and volume of contrast-enhancing, the volumes of T2-hyperintense and T1-hypointense lesions and the assessment of brain volume changes) are limited in terms of pathological specificity and, as a consequence, are modestly correlated with clinical measures of disease activity and have a modest prognostic value as predictors of MS evolution. In the present review, we discuss the main factors potentially responsible for the so-called 'clinical MRI paradox' and how modern quantitative MR-based techniques might contribute to, at least partially, overcome it. The lessons learned from MS trials suggest that future applications of MRI to assess MS evolution should rely upon the use of composite measures thought to reflect the various components of the disease, as well as on study protocols specifically designed on the individual trial characteristics.

The use of quantitative magnetic-resonance-based techniques to monitor the evolution of multiple sclerosis

Conventional MRI can improve accuracy in the diagnosis of multiple sclerosis (MS) and monitor the efficacy of experimental treatments. However, conventional MRI provides only gross estimates of the extent and nature of tissue damage associated with this disease. Other quantitative magnetic-resonance-based techniques have the potential to overcome the limitations of conventional MRI and, as a consequence, to improve our understanding of the natural history of MS. Magnetisation-transfer, diffusion-weighted, and functional MRI--as well as proton magnetic-resonance spectroscopy--are helping us to elucidate the mechanisms that underlie injury, repair, and functional adaptation in patients with MS. These techniques are substantially changing our understanding of how MS causes irreversible disability and should be used more extensively in clinical trials and in studies of disease progression.