Signal intensity on MRI of basal ganglia in multiple sclerosis

An update on the role of magnetic resonance imaging in predicting and monitoring multiple sclerosis progression

INTRODUCTION

While magnetic resonance imaging (MRI) is established in diagnosing and monitoring disease activity in multiple sclerosis (MS), its utility in predicting and monitoring disease progression is less clear.

AREAS COVERED

The authors consider changing concepts in the phenotypic classification of MS, including progression independent of relapses; pathological processes underpinning progression; advances in MRI measures to assess them; how well MRI features explain and predict clinical outcomes, including models that assess disease effects on neural networks, and the potential role for machine learning.

EXPERT OPINION

Relapsing-remitting and progressive MS have evolved from being viewed as mutually exclusive to having considerable overlap. Progression is likely the consequence of several pathological elements, each important in building more holistic prognostic models beyond conventional phenotypes. MRI is well placed to assess pathogenic processes underpinning progression, but we need to bridge the gap between MRI measures and clinical outcomes. Mapping pathological effects on specific neural networks may help and machine learning methods may be able to optimize predictive markers while identifying new, or previously overlooked, clinically relevant features. The ever-increasing ability to measure features on MRI raises the dilemma of what to measure and when, and the challenge of translating research methods into clinically useable tools.

Magnetic resonance imaging detection of deep gray matter iron deposition in multiple sclerosis: A systematic review

Multiple sclerosis (MS) is a chronic inflammatory and neurodegenerative disease involving immune-mediated damage. Iron deposition in deep gray matter (DGM) structures like the thalamus and basal ganglia have been suggested to play a role in MS pathogenesis. Magnetic Resonance Imaging (MRI) imaging methods like T2 and T2* imaging, susceptibility-weighted imaging, and quantitative susceptibility mapping can track iron deposition storage in the brain primarily from ferritin and hemosiderin (paramagnetic iron storage proteins) with varying levels of tissue contrast and sensitivity. In this systematic review, we evaluated the role of DGM iron deposition as detected by MRI techniques in relation to MS-related neuroinflammation and its potential as a novel therapeutic target. We searched through PubMed, Embase, and Web of Science databases following the Preferred Reporting Items for Systematic Reviews and Meta-Analyses guidelines, against predetermined inclusion and exclusion criteria. We included 89 articles (n = 6630 patients), and then grouped them into different categories: i) methodological techniques to measure DGM iron, ii) cross-sectional and group comparison of DGM iron content, iii) longitudinal comparisons of DGM iron, iv) associations between DGM iron and other imaging and neurobiological markers, v) associations with disability, and vi) associations with cognitive impairment. The review revealed that iron deposition in DGM is independent yet concurrent with demyelination, and that these iron deposits contribute to MS-related cognitive impairment and disability. Variability in iron distributions appears to rely on a positive feedback loop between inflammation, and release of iron by oligodendrocytes. DGM iron seems to be a promising prognostic biomarker for MS pathophysiology.

Effects of Rhythmic Auditory Cueing in Gait Rehabilitation for Multiple Sclerosis: A Mini Systematic Review and Meta-Analysis

Rhythmic auditory cueing has been shown to enhance gait performance in several movement disorders. The "entrainment effect" generated by the stimulations can enhance auditory motor coupling and instigate plasticity. However, a consensus as to its influence over gait training among patients with multiple sclerosis is still warranted. A systematic review and meta-analysis was carried out to analyze the effects of rhythmic auditory cueing in studies gait performance in patients with multiple sclerosis. This systematic identification of published literature was performed according to PRISMA guidelines, from inception until Dec 2017, on online databases: Web of science, PEDro, EBSCO, MEDLINE, Cochrane, EMBASE, and PROQUEST. Studies were critically appraised using PEDro scale. Of 602 records, five studies (PEDro score: 5.7 ± 1.3) involving 188 participants (144 females/40 males) met our inclusion criteria. The meta-analysis revealed enhancements in spatiotemporal parameters of gait i.e., velocity (Hedge's g: 0.67), stride length (0.70), and cadence (1.0), and reduction in timed 25 feet walking test (-0.17). Underlying neurophysiological mechanisms, and clinical implications are discussed. This present review bridges the gaps in literature by suggesting application of rhythmic auditory cueing in conventional rehabilitation approaches to enhance gait performance in the multiple sclerosis community.

Neurodegeneration Induced by Metals in Caenorhabditis elegans

Metals are a component of a variety of ecosystems and organisms. They can generally be divided into essential and nonessential metals. The essential metals are involved in physiological processes once the deficiency of these metals has been associated with diseases. Although iron, manganese, copper, and zinc are important for life, it has been evidenced that they are also involved in neuronal damage in many neurodegenerative disorders. Nonessential metals, which are metals without physiological functions, are present in trace or higher levels in living organisms. Occupational, environmental, or deliberate exposures to lead, mercury, aluminum, and cadmium are clearly correlated with the increase of toxicity and varied kinds of pathological situations. Actually, the field of neurotoxicology needs to satisfy two opposing demands: the testing of a growing list of chemicals and resource limitations and ethical concerns associated with testing using traditional mammalian species. Toxicological assays using alternative animal models may relieve some of this pressure by allowing testing of more compounds while reducing expenses and using fewer mammals. The nervous system is by far the more complex system in C. elegans. Almost a third of their cells are neurons (302 neurons versus 959 cells in adult hermaphrodite). It initially underwent extensive development as a model organism in order to study the nervous system, and its neuronal lineage and the complete wiring diagram of its nervous system are stereotyped and fully described. The neurotransmission systems are phylogenetically conserved from nematodes to vertebrates, which allows for findings from C. elegans to be extrapolated and further confirmed in vertebrate systems. Different strains of C. elegans offer a new perspective on neurodegenerative processes. Some genes have been found to be related to neurodegeneration induced by metals. Studying these interactions may be an effective tool to slow neuronal loss and deterioration.

Iron dysregulation in Huntington's disease

Huntington's disease (HD) is one of many neurodegenerative diseases with reported alterations in brain iron homeostasis that may contribute to neuropathogenesis. Iron accumulation in the specific brain areas of neurodegeneration in HD has been proposed based on observations in post-mortem tissue and magnetic resonance imaging studies. Altered magnetic resonance imaging signal within specific brain regions undergoing neurodegeneration has been consistently reported and interpreted as altered levels of brain iron. Biochemical studies using various techniques to measure iron species in human samples, mouse tissue, or in vitro has generated equivocal data to support such an association. Whether elevated brain iron occurs in HD, plays a significant contributing role in HD pathogenesis, or is a secondary effect remains currently unclear.

Neuroradiological evaluation of demyelinating disease

Central nervous system inflammatory demyelinating disease can affect patients across the life span. Consensus definitions and criteria of all of the different acquired demyelinating diseases that fall on this spectrum have magnetic resonance imaging criteria. The advances of both neuroimaging techniques and important discoveries in immunology have produced an improved understanding of these conditions and classification. Neuroimaging plays a central role in the accurate diagnosis, prognosis, disease monitoring and research efforts that are being undertaken in this disease. This review focuses on the imaging spectrum of acquired demyelinating disease.

Pathogenic implications of iron accumulation in multiple sclerosis

Iron, an essential element used for a multitude of biochemical reactions, abnormally accumulates in the CNS of patients with multiple sclerosis (MS). The mechanisms of abnormal iron deposition in MS are not fully understood, nor do we know whether these deposits have adverse consequences, that is, contribute to pathogenesis. With some exceptions, excess levels of iron are represented concomitantly in multiple deep gray matter structures often with bilateral representation, whereas in white matter, pathological iron deposits are usually located at sites of inflammation that are associated with veins. These distinct spatial patterns suggest disparate mechanisms of iron accumulation between these regions. Iron has been postulated to promote disease activity in MS by various means: (i) iron can amplify the activated state of microglia resulting in the increased production of proinflammatory mediators; (ii) excess intracellular iron deposits could promote mitochondria dysfunction; and (iii) improperly managed iron could catalyze the production of damaging reactive oxygen species (ROS). The pathological consequences of abnormal iron deposits may be dependent on the affected brain region and/or accumulation process. Here, we review putative mechanisms of enhanced iron uptake in MS and address the likely roles of iron in the pathogenesis of this disease.

Iron and neurodegeneration in multiple sclerosis

Increased iron deposition might be implicated in multiple sclerosis (MS). Recent development of MRI enabled to determine brain iron levels in a quantitative manner, which has put more interest on studying the role of iron in MS. Evidence for abnormal iron homeostasis in MS comes also from analyses of iron and iron-related proteins in CSF and blood and postmortem MS brain sections. However, it is not yet clear if iron accumulation is implicated in MS pathology or merely reflects an epiphenomenon. Further interest has been generated by the idea of chronic cerebrospinal venous insufficiency that might be associated with brain iron accumulation due to a reduction in venous outflow, but its existence and etiologic role in MS are currently controversially debated. In future studies, combined approaches applying quantitative MRI together with CSF and serum analyses of iron and iron-related proteins in a clinical followup setting might help to elucidate the implication of iron accumulation in MS.

Towards a unifying, systems biology understanding of large-scale cellular death and destruction caused by poorly liganded iron: Parkinson's, Huntington's, Alzheimer's, prions, bactericides, chemical toxicology and others as examples

Exposure to a variety of toxins and/or infectious agents leads to disease, degeneration and death, often characterised by circumstances in which cells or tissues do not merely die and cease to function but may be more or less entirely obliterated. It is then legitimate to ask the question as to whether, despite the many kinds of agent involved, there may be at least some unifying mechanisms of such cell death and destruction. I summarise the evidence that in a great many cases, one underlying mechanism, providing major stresses of this type, entails continuing and autocatalytic production (based on positive feedback mechanisms) of hydroxyl radicals via Fenton chemistry involving poorly liganded iron, leading to cell death via apoptosis (probably including via pathways induced by changes in the NF-κB system). While every pathway is in some sense connected to every other one, I highlight the literature evidence suggesting that the degenerative effects of many diseases and toxicological insults converge on iron dysregulation. This highlights specifically the role of iron metabolism, and the detailed speciation of iron, in chemical and other toxicology, and has significant implications for the use of iron chelating substances (probably in partnership with appropriate anti-oxidants) as nutritional or therapeutic agents in inhibiting both the progression of these mainly degenerative diseases and the sequelae of both chronic and acute toxin exposure. The complexity of biochemical networks, especially those involving autocatalytic behaviour and positive feedbacks, means that multiple interventions (e.g. of iron chelators plus antioxidants) are likely to prove most effective. A variety of systems biology approaches, that I summarise, can predict both the mechanisms involved in these cell death pathways and the optimal sites of action for nutritional or pharmacological interventions.

Quantitative assessment of brain iron by R2* relaxometry in patients with clinically isolated syndrome and relapsing–remitting multiple sclerosis

Background

Increased iron deposition has been implicated in the pathophysiology of multiple sclerosis (MS), based on visual analysis of signal reduction on T2-weighted images. R2* relaxometry allows to assess brain iron accumulation quantitatively.

Objective

To investigate regional brain iron deposition in patients with a clinically isolated syndrome (CIS) or relapsing–remitting MS (RRMS) and its associations with demographical, clinical, and conventional magnetic resonance imaging (MRI) parameters.

Methods

We studied 69 patients (CIS, n = 32; RRMS, n = 37) with 3T MRI and analyzed regional R2* relaxation rates and their correlations with age, disease duration, disability, T2 lesion load, and normalized brain volumes.

Results

Basal ganglia R2* relaxation rates increased in parallel with age ( r = 0.3–0.6; P < 0.01) and were significantly higher in RRMS than in CIS ( P < 0.05). Using multivariate linear regression analysis, the rate of putaminal iron deposition was independently predicted by the patients’ age, disease duration, and gray matter atrophy.

Conclusions

Quantitative assessment by R2* relaxometry suggests increased iron deposition in the basal ganglia of MS patients, which is associated with disease duration and brain atrophy. This technique together with long-term follow-up thus appears suited to clarify whether regional iron accumulation contributes to MS morbidity or merely reflects an epiphenomenon.

Multiple sclerosis: hyperintense dentate nucleus on unenhanced T1-weighted MR images is associated with the secondary progressive subtype

PURPOSE

To describe the occurrence of abnormal hyperintensity in the dentate nucleus on T1-weighted magnetic resonance (MR) images in patients with multiple sclerosis (MS) as a neuroradiologic sign of gray matter involvement. Presence of the finding was evaluated for association with disability, clinical MS subtype, total lesion volume on T1- and T2-weighted MR images (lesion load), and brain atrophy.

MATERIALS AND METHODS

Written informed consent was waived by the Ethics Committee because of the retrospective nature of this single-center Institutional Review Board-approved study. MR examinations of 185 patients with MS were reviewed, and 119 patients were included for analysis. Two neuroimagers, who were blinded to clinical data, assessed the presence of a hyperintense dentate nucleus on T1-weighted MR images. The presence of this radiologic alteration was then evaluated in relation to MS subtype, clinical disability, T1 and T2 lesion load, and whole-brain atrophy measurements. Fisher exact, chi(2), and Mann-Whitney U tests were used to evaluate differences in clinical and imaging features between patients with and those without a T1 hyperintense dentate nucleus.

RESULTS

Twenty-three (19.3%) of the 119 patients had a hyperintense dentate nucleus on unenhanced T1-weighted MR images. This finding was related to the secondary progressive subtype of the disease, a higher score on the Expanded Disability Status Scale, a higher brain lesion load, and tissue loss. None of the patients with primary progressive MS had a hypterintense dentate nucleus.

CONCLUSION

Hyperintensity of the dentate nucleus may be present on unenhanced T1-weighted MR images of patients with MS and is associated with the secondary progressive disease subtype and with increased clinical disability, lesion load, and brain atrophy.

Enhancing the ability of experimental autoimmune encephalomyelitis to serve as a more rigorous model of multiple sclerosis through refinement of the experimental design

Advancing the understanding of the mechanisms involved in the pathogenesis of multiple sclerosis (MS) likely will lead to new and better therapeutics. Although important information about the disease process has been obtained from research on pathologic specimens, peripheral blood lymphocytes and MRI studies, the elucidation of detailed mechanisms has progressed largely through investigations using animal models of MS. In addition, animal models serve as an important tool for the testing of putative interventions. The most commonly studied model of MS is experimental autoimmune encephalomyelitis (EAE). This model can be induced in a variety of species and by various means, but there has been concern that the model may not accurately reflect the disease process, and more importantly, it may give rise to erroneous findings when it is used to test possible therapeutics. Several reasons have been given to explain the shortcomings of this model as a useful testing platform, but one idea provides a framework for improving the value of this model, and thus, it deserves careful consideration. In particular, the idea asserts that EAE studies are inadequately designed to enable appropriate evaluation of putative therapeutics. Here we discuss problem areas within EAE study designs and provide suggestions for their improvement. This paper is principally directed at investigators new to the field of EAE, although experienced investigators may find useful suggestions herein.

Quantitative assessment of iron accumulation in the deep gray matter of multiple sclerosis by magnetic field correlation imaging

BACKGROUND AND PURPOSE

Deposition of iron has been recognized recently as an important factor of pathophysiologic change including neurodegenerative processes in multiple sclerosis (MS). We propose that there is an excess accumulation of iron in the deep gray matter in patients with MS that can be measured with a newly developed quantitative MR technique--magnetic field correlation (MFC) imaging.

MATERIALS AND METHODS

With a 3T MR system, we studied 17 patients with relapsing-remitting MS and 14 age-matched healthy control subjects. We acquired MFC imaging using an asymmetric single-shot echo-planar imaging sequence. Regions of interest were selected in both deep gray matter and white matter regions, and the mean MFC values were compared between patients and controls. We also correlated the MFC data with lesion load and neuropsychologic tests in the patients.

RESULTS

MFC measured in the deep gray matter in patients with MS was significantly higher than that in the healthy controls (P < or = .03), with an average increase of 24% in the globus pallidus, 39.5% in the putamen, and 30.6% in the thalamus. The increased iron deposition measured with MFC in the deep gray matter in the patients correlated positively with the total number of MS lesions (thalamus: r = 0.61, P = .01; globus pallidus: r = 0.52, P = .02). A moderate but significant correlation between the MFC value in the deep gray matter and the neuropsychologic tests was also found.

CONCLUSION

Quantitative measurements of iron content with MFC demonstrate increased accumulation of iron in the deep gray matter in patients with MS, which may be associated with the disrupted iron outflow pathway by lesions. Such abnormal accumulation of iron may contribute to neuropsychologic impairment and have implications for neurodegenerative processes in MS.

Seeing is believing: in vivo evolution of multiple sclerosis pathology with magnetic resonance

Multiple sclerosis (MS) is considered a prototypical inflammatory autoimmune disease of the central nervous system that affects both myelin and axon. One of the most challenging aspects of MS is understanding the nature and mechanism of tissue injury because inflammation, demyelination, axonal degeneration, microvascular injury, and atrophy are all identified in histopathologic studies. Magnetic resonance (MR) imaging provides an in vivo examination of the brain that directly defines the extent of the pathology. In recent years, extensive MR studies have had a major impact on MS not only in making an early diagnosis but also in understanding of the disease. By exploiting the natural history and histopathologic correlation, conventional and various novel quantitative MR techniques have demonstrated the ability to image underlying pathological processes in MS. This review examines the role of different MR techniques in going beyond anatomical imaging and produces a more comprehensive overview of the pathophysiological changes which occur and evolve in MS.

Deferiprone, an orally deliverable iron chelator, ameliorates experimental autoimmune encephalomyelitis

The iron chelator, Desferal, suppressed disease activity of experimental autoimmune encephalomyelitis (EAE), an animal model of multiple sclerosis (MS), and it has been tested in pilot trials for MS. The administration regimen of Desferal is cumbersome and prone to complications. Orally-deliverable, iron chelators have been developed that circumvent these difficulties, and the objective of this study was to test an oral chelator in EAE. SJL mice with active EAE were randomly assigned to receive deferiprone (150 mg/kg) or vehicle (water) 2×/day via gavage. EAE mice given deferiprone had significantly less disease activity and lower levels of inflammatory cell infiltrates (revealed by H&E staining) than EAE mice administered vehicle. T-cell infiltration, assessed by anti-CD3 immunohistochemical staining, also was reduced, although not significantly. Splenocytes cultured from naïve SJL mice were stimulated with anti-CD3 and anti-CD28 with or without 250 μM deferiprone. While ~39% of costimulated splenocytes without deferiprone underwent division, only ~2.8% of costimulated splenocytes with deferiprone divided and the latter cells were only 53% as viable as the former. Deferiprone had no effect on proliferation or viability of cells that were not costimulated. In summary, deferiprone effectively suppressed active EAE disease and it inhibited T-cell function. Multiple Sclerosis 2007; 13: 1118—1126. http://msj.sagepub.com

Magnetic resonance imaging of iron deposition in neurological disorders

Deposition of iron in the brain is proposed to play a role in the pathophysiology of the normal aging process and neurodegenerative diseases. Whereas iron is required for normal neuronal metabolism, excessive levels can contribute to the formation of free radicals, leading to lipid peroxidation and neurotoxicity. Magnetic resonance imaging (MRI) is a powerful tool to detect excessive iron in the brain and longitudinally monitor changes in iron levels. Iron deposition is associated with a reduction in the T2 relaxation time, leading to hypointensity on spin-echo and gradient-echo T2-weighted images. The MRI changes associated with iron deposition have been observed both in normal aging and in various chronic neurological diseases, including multiple sclerosis, Alzheimer disease, and Parkinson disease. Magnetic resonance imaging metrics providing information about iron concentrations include R2, R2', and R2*. The purpose of this review is to discuss the role of iron and its detection by MRI in various neurological disorders. We will review the basic biochemical properties of iron and its influence on MRI signal. We will also summarize the sensitivity and specificity of MRI techniques in detecting iron. The MRI and pathological findings pertaining to brain iron will be reviewed with respect to normal aging and a variety of neurological disorders. Finally, the biochemistry and pathophysiology surrounding iron, oxidative stress, free radicals, and lipid peroxidation in the brain will be discussed, including therapeutic implications. The potential role of iron deposition and its assessment by MRI provides exciting potential applications to the diagnosis, longitudinal monitoring, and therapeutic development for disorders of the brain.

Voxel-based analysis of MTR images: a method to locate gray matter abnormalities in patients at the earliest stage of multiple sclerosis

PURPOSE

To determine whether voxel-based analysis of magnetization transfer ratio (MTR) maps can provide evidence of a coherent pattern of gray matter (GM) macroscopic and microscopic tissue damage in patients at the earliest stage of multiple sclerosis (MS).

MATERIALS AND METHODS

We acquired GM MTR maps in 18 patients with clinically isolated syndrome suggestive of MS (CISSMS), and 18 sex- and age-matched healthy controls. We evaluated the clinical status of the patients using the MS functional composite score and the expanded disability status scale. A two-sample t-test (P <0.0001, k=20, uncorrected for height threshold) was used to compare GM MTR maps from patients and controls on a voxel-by-voxel basis. We then extracted data from regions with t-values above the statistical threshold to verify the significance of differences using a nonparametric Mann-Whitney U-test.

RESULTS

A between-groups comparison of GM maps revealed large abnormalities in the basal ganglia, including the bilateral thalamus, bilateral lenticular nucleus, bilateral head of caudate, and protuberance, and smaller abnormalities in the right insula, right BA 4, and left BA 40. The MTR measured in the left caudate and right insula was inversely correlated with duration following the first clinical event.

CONCLUSION

These results suggest that although MS is a multifocal demyelinating disease that affects white matter (WM), a pattern of tissue damage is present inside the GM involving predominantly basal ganglia at the earliest stage of the disease.

Biomarkers and surrogate outcomes in neurodegenerative disease: lessons from multiple sclerosis

Multiple sclerosis (MS) is a chronic disease of the CNS that most commonly affects young adults. It is usually characterized in the early years by acute relapses followed by partial or complete remission; in later years progressive and irreversible disability develops. Because of the protracted and unpredictable clinical course, biological surrogate markers are much needed to make clinical trials of potential disease-modifying treatments more efficient. Magnetic resonance (MR) outcome measures are now widely used to monitor treatment outcome in MS trials. Areas of multifocal inflammation are detected with a high sensitivity as new areas of gadolinium enhancement and T2 abnormality, and these may be considered as surrogate markers for clinical relapses. However, progressive disability is not clearly related to inflammatory lesions but rather to a progressive and diffuse process with increasing neuroaxonal loss. MR surrogate measures for neuroaxonal loss include atrophy (tissue loss in brain and spinal cord), N-acetyl aspartate, and T1 hypointense lesions. Diffuse abnormality in normal appearing brain tissue may also be monitored using magnetization transfer ratio and other quantitative MR measures. For treatment trials of new agents aimed at preventing disability, measures of neuroaxonal damage should be acquired, especially atrophy, which occurs at all stages of MS and which can be quantified in a sensitive and reproducible manner. Because the MR surrogates for neuroaxonal loss are not yet validated as predicting future disability, definitive trials should continue to monitor an appropriate disability endpoint.

Diffusion tensor imaging in early relapsing-remitting multiple sclerosis

Diffusion tensor magnetic resonance imaging (DTI) indices are abnormal in patients with established multiple sclerosis (MS). The objective of this study was to examine the diffusion characteristics of MS lesions, normal appearing white matter (NAWM) and normal appearing grey matter (NAGM) in MS patients with early relapsing-remitting disease. A further objective was to investigate the relationship between three DTI parameters (fractional anisotropy (FA), mean diffusivity (MD) and volume ratio (VR)) and clinical outcome measures (Kurtzke expanded disability status scale (EDSS) and MS Functional Composite Measure) in early disease. DTI was performed in 28 patients and 27 controls. Analysis was carried out using a region of interest (ROI) approach. ROIs were placed in 12 NAWM and nine NAGM regions. Significant differences were found in FA, MD and VR between lesions and NAWM (P< 0.001 for all three DTI parameters). No significant differences were found between patients and controls when examining NAWM or NAGM, although there was a trend for abnormal NAWM FA and VR in some regions. No correlation was found between DTI parameters in lesions, NAWM or NAGM and the clinical outcome measures. The lack of significant DTI abnormality in the NAWM and NAGM may reflect a lack of pathological change or a limited sensitivity of DTI using ROI methodology. Previous studies have shown abnormalities in TI relaxation time, magnetisation transfer ratio (MTR) and N-Acetyl aspartate (NM) in this cohort of patients, and as such, DTI using a region of interest (ROI) approach may not be as sensitive as other MR techniques in detecting subtle changes in normal appearing brain

Investigation of MS normal-appearing brain using diffusion tensor MRI with clinical correlations

OBJECTIVE

To quantitatively investigate water diffusion changes in normal-appearing white matter (NAWM) and gray matter in patients with MS, and to evaluate whether these changes are correlated with clinical disability and disease duration.

BACKGROUND

Diffusion tensor imaging provides quantitative information about the magnitude and directionality (anisotropy) of water diffusion in vivo and detects pathologic changes in MS brain tissue.

METHODS

Diffusion tensor imaging was performed in 39 patients with MS and in 21 age-matched control subjects. Quantitative indices, including fractional anisotropy, volume ratio, and mean diffusivity, were obtained in 30 regions of interest located in normal-appearing basal ganglia, cerebellar gray matter, and supratentorial and infratentorial NAWM.

RESULTS

Patients with MS showed significantly reduced anisotropy and a trend toward increased diffusivity in the infratentorial and supratentorial NAWM, and significantly increased anisotropy in the basal ganglia. In all patients with MS, both fractional anisotropy and mean diffusivity in the cerebral peduncles were inversely correlated with the Expanded Disability Status Scale and pyramidal functional scores. In patients with relapsing-remitting MS, there was a strong correlation between Expanded Disability Status Scale score and fractional anisotropy in both supratentorial and infratentorial NAWM. In primary and secondary progressive MS, disease duration correlated strongly with mean diffusivity in infratentorial NAWM and fractional anisotropy in the cerebral peduncles, respectively.

CONCLUSION

The most striking finding of decreased fractional anisotropy in supratentorial and infratentorial NAWM and increased fractional anisotropy in basal ganglia may result from axonal degeneration due to fiber transection in remote focal lesions. Diffusion tensor imaging indices, in particular fractional anisotropy, appear sensitive to structural damage in NAWM that is associated with disability and progression in MS.

Gray matter T2 hypointensity is related to plaques and atrophy in the brains of multiple sclerosis patients

Cortical and subcortical gray matter hypointensities on T2-weighted MR images (T2WI) occur commonly in MS brains and have been related to disease duration, clinical course, and the level of neurologic disability. These hypointensities have been reported to occur in the thalamus, basal ganglia, and rolandic cortex. We assessed whether T2 hypointensity is associated with the severity of white matter plaques and atrophy of MS brains. In 114 MS patients, hypointensity of the thalamus, putamen, caudate, and sensorimotor cortex was ordinally rated against age- and gender-matched normal controls on 1.5-T MRI fast spin-echo axial T2WI. Regional and global T2 hyperintense and T1 hypointense parenchymal lesion loads were ordinally rated. Enlargement of subarachnoid and ventricular spaces (atrophy) was ordinally rated vs. age- and gender-matched normal controls. T2 hypointensity was highly, positively correlated with many other MRI variables. Regression modeling showed that T2 hypointensity was related to total atrophy, total T2 lesion load, third ventricular enlargement, parietal atrophy, and to a lesser extent, frontal T1 lesions and cerebellar T2 lesions, but not related to gadolinium enhancement. Ordinal ratings of T2 lesions and central atrophy showed high correlations with quantitative computerized assessments. We conclude that gray matter hypointensity on T2WI may reflect pathologic iron deposition and brain degeneration in MS. This T2 hypointensity is associated with brain atrophy and other MR markers of tissue damage. Further study is warranted to determine if T2 hypointensity is predictive of disease course in MS and is a useful surrogate outcome measure in therapeutic trials.

Magnetization transfer and diffusion tensor MR imaging of basal ganglia from patients with multiple sclerosis

Although post-mortem studies have shown that lesions of multiple sclerosis (MS) can be detected in the basal ganglia, conventional T2-weighted magnetic resonance (MR) imaging is poorly sensitive for detecting such abnormalities. This study was performed to investigate whether magnetization transfer (MT) and diffusion tensor MR imaging are able to detect in vivo basal ganglia changes in patients with MS. After image coregistration, MT ratio (MTR) and mean diffusivity (&Dmacr;) maps were obtained and MTR and &Dmacr; values of the putamen, head of the caudatus and thalamus measured from 31 patients with clinically definite MS and 14 age- and sex-matched healthy volunteers using region of interest analysis. Although we found slightly decreased MTR and increased &Dmacr; in the basal ganglia from patients compared to controls, suggesting increased extra-cellular water and reduced amount of 'barriers' restricting water molecular motion in the basal ganglia of patients with MS, none of the differences was statistically significant. These data suggest that the more sophisticated MR probes of tissue disruption and cellular integrity are no more sensitive than current conventional imaging for detecting basal ganglia abnormalities in patients with MS.

Prognostic value of MR and magnetization transfer imaging findings in patients with clinically isolated syndromes suggestive of multiple sclerosis at presentation

BACKGROUND AND PURPOSE

The extent of abnormalities on T2-weighted MR images of the brain of patients with clinically isolated syndromes (CIS) suggestive of multiple sclerosis (MS) at presentation is associated with an increased risk of developing clinically definite MS (CDMS). We evaluated whether subtle changes outside T2-visible lesions are present in the brain of these patients and whether their extent increases the risk of subsequent development of CDMS.

METHODS

Dual-echo, T1-weighted, and magnetization transfer (MT) images of the brain were obtained from 24 patients with CIS at presentation. These patients were followed up for a mean period of 33 months (range, 25-42 months). Twenty age- and sex-matched healthy volunteers served as control subjects. To create MT histograms of the normal-appearing brain tissue (NABT), macroscopic lesions were segmented from dual-echo images, were superimposed automatically, and were nulled out from the coregistered and scalp-stripped MT ratio (MTR) maps. The following MTR histogram-derived measures were considered: average MTR, MTR(25), MTR(50), MTR(75), peak height, and peak position. T2 and T1 lesion loads, average lesion MTR, and brain volume were also measured.

RESULTS

Patients with CIS had lower average NABT-MTR (P < .0001) and peak position (P = .002) than did control volunteers, but patient brain size was similar to that of volunteers. At follow-up, 10 (41%) patients developed CDMS. Patients who developed CDMS during the follow-up period had higher T2 lesion volume (P = .003) and lower average NABT-MTR (P = .005) and peak position (P = .006) than did those who did not develop CDMS. T2 lesion volume (odd ratio, 3.54; P = .0005) and average NABT-MTR (odd ratio, 0.81; P = .01) were independent predictors of the subsequent development of CDMS.

CONCLUSION

Subtle changes occur outside lesions visible on conventional MR images among patients with CIS suggestive of MS at presentation. The greater the extent of such abnormalities is, the higher is the risk of subsequent development of CDMS.

Changes in the normal appearing brain tissue and cognitive impairment in multiple sclerosis

OBJECTIVES

To assess (a) whether the changes in the normal appearing brain tissue (NABT), as revealed by magnetisation transfer (MT) histogram analysis, correlates with cognitive dysfunction in patients with multiple sclerosis and (b) the relative contribution of these changes by comparison with that of multiple sclerosis lesions visible on conventional MRI.

METHODS

Dual echo, T1 weighted and MT scans of the brain were obtained in 12 patients with multiple sclerosis with cognitive impairment and in seven without cognitive impairment. Lesion loads were assessed from T2 and T1 weighted scans. To create MT histograms of the NABT, multiple sclerosis lesion outlines from dual echo scans were superimposed automatically and nulled out from the coregistered and scalp stripped MTR maps. Average lesion MT ratio (MTR) and brain size were also measured.

RESULTS

T2 and T1 lesion loads were significantly higher and the average lesion MTR and brain size were significantly lower in the group of cognitively impaired patients. Patients with cognitive deficits also had significantly lower average MTR and peak location of the NABT histogram. Logistic regression analysis showed that 68% of the total variance was explained by average NABT-MTR alone. A multivariable regression model showed that NABT-MTR was the only factor that significantly correlated with cognitive impairment in these patients (p=0.001).

CONCLUSIONS

The extent of abnormalities which go undetected when using conventional MRI is relevant in determining cognitive impairment in multiple sclerosis.

Does the extent of axonal loss and demyelination from chronic lesions in multiple sclerosis correlate with the clinical subgroup?

OBJECTIVE

To determine non-invasively the relation between the degree of axonal loss and the extent of demyelination in chronic lesions visible on MRI in patients with different subgroups of clinically definite multiple sclerosis using (1)H magnetic resonance spectroscopy ((1)H MRS) and magnetisation transfer imaging (MT). Conventional MRI is unable to differentiate between the various pathological processes occurring in the multiple sclerosis lesion. There are, however, newer MR techniques which show promise in this respect.

METHODS

(1)H MRS and MT were performed in 18 patients with clinically definite multiple sclerosis who had a wide range of disability and disease duration.

RESULTS

A significant correlation was found between a reduction in the concentration of N-acetyl aspartate (NAA; an in vivo marker of axonal loss or dysfunction) and a reduction in MT ratio (a probable marker of demyelination) in patients who had entered the secondary progressive stage of the disease. Patients with minimal disability after a disease duration of greater than 10 years-so called benign multiple sclerosis-showed a relative preservation of NAA and MT.

CONCLUSIONS

Because a reduction in MT seems to be a relative marker for demyelination and a reduction of NAA from chronic lesions is indicative of axonal loss, this study supports the hypothesis that demyelination and axonal loss occur in the same chronic multiple sclerosis lesions. In addition, the degree of axonal loss and demyelination correlates with clinical heterogeneity.

Relevance of hypointense lesions on fast fluid-attenuated inversion recovery MR images as a marker of disease severity in cases of multiple sclerosis

BACKGROUND AND PURPOSE

Hypointense lesions can be visible on fast fluid-attenuated inversion recovery (FLAIR) MR images of the brain of patients with multiple sclerosis (MS), and they may be produced by severely damaged white matter. To test the role of these lesions as an MR marker of MS severity, we assessed their relationship with clinical findings and other MR measures.

METHODS

Using a 1.5-T scanner, dual-echo rapid acquisition with relaxation enhancement, fast FLAIR, and T1-weighted MR images (24 axial, 5-mm-thick contiguous interleaved sections) were obtained from 50 patients (32 with relapsing-remitting and 18 with secondary progressive MS).

RESULTS

Hypointense lesions were visible on the fast FLAIR images of 19 patients (mean number of lesions, 7.8; range 1-22); their median load was 1.4 mL (range, 0.05-12.6 mL). The median lesion load was significantly higher in patients with secondary progressive MS than in those with relapsing-remitting MS on the T1-weighted images. Both the number and the load of hypointense lesions shown by fast FLAIR imaging were significantly higher in patients with secondary progressive MS. Significant correlations were found between Expanded Disability Status Scale scores and MR lesion load. A multivariate analysis showed that only the presence of hypointense lesions on fast FLAIR images significantly separated cases of relapsing-remitting MS from cases of secondary progressive MS (relative risk, 7.1; 95% confidence interval, 2.0-25.9).

CONCLUSION

The presence of hypointense lesions on fast FLAIR images was a strong predictor of disease severity in cases of MS, although the low sensitivity of this approach might limit its use for the assessment of MS evolution.

1H magnetic resonance spectroscopy of chronic cerebral white matter lesions and normal appearing white matter in multiple sclerosis

OBJECTIVES

To test the hypothesis that irrecoverable neurological deficit in multiple sclerosis is associated with axonal loss.

METHODS

1H magnetic resonance spectroscopy (MRS) was carried out in a group of patients with clinically definite multiple sclerosis (n=31). Using this technique, the apparent concentration of NA ([NA] the sum of N-acetyl aspartate (NAA), a neuronal marker, and N-acetylaspartylglutamate has been compared in four groups of patients with multiple sclerosis classified as relapsing-remitting, secondary progressive, primary progressive, benign, and a control group.

RESULTS

In the patients with relapsing-remitting disease (n=9) there was a highly significant reduction of apparent NA (median 8.73 mM, range 6.86 mM-10.74 mM, P=0.0008) from an area of high signal compared with the control group (median 11.97 mM, range 10.55 mM-14.5 mM). In the patients with secondary progressive disease (n=10), there was again a highly significant reduction of apparent NA (median 7.82 mM, range 3.5 mM-10.3 mM, P=0.0003) from an area of high signal compared with the control group. In the patients with primary progressive disease (n=6) there was once again a highly significant reduction of apparent NA (median 8.83 mM, range 6.95 mM-9.89 mM, P<0.002) from an area of high signal compared with the control group. In the patients with benign disease, however, there was no significant difference in the apparent NA (median 10.5 mM, range 8.53 mM-12.8 mM, P>0.05) from an area of high signal compared with the control group. In the patients with benign disease (n=5) there was also no significant difference in the apparent NA (median 10.74 mM, range 8.58 mM-13.4 mM, P>0.3) from an area of normal appearing white matter compared with the control group. In the patients with primary progressive disease, however, there was a significant reduction of apparent NA from an area of normal appearing white matter (median 8.78 mM, range 8.7 mM-12.38 mM, P< 0.025) compared with the control group. There was a significant inverse correlation between [NA] from lesions in the patients with multiple sclerosis and disability as measured on the Kurtzke expanded disability scale score (r= -0.364, 0.05>P>0.02).

CONCLUSION

These findings support the hypothesis that axonal loss is important in the development of disability in multiple sclerosis. They also provide evidence for axonal loss in normal appearing white matter in patients with primary progressive disease.