Iron deposition on SWI-filtered phase in the subcortical deep gray matter of patients with clinically isolated syndrome may precede structure-specific atrophy

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.

Central vein sign and paramagnetic rim sign: From radiologically isolated syndrome to multiple sclerosis

The widespread use of magnetic resonance imaging (MRI) has led to an increase in incidental findings in the central nervous system. Radiologically isolated syndrome (RIS) is a condition where imaging reveals lesions suggestive of demyelinating disease without any clinical episodes consistent with multiple sclerosis (MS). The prognosis for RIS patients is uncertain, with some remaining asymptomatic while others progress to MS. Several risk factors for disease progression have been identified, including male sex, younger age at diagnosis, and spinal cord lesions. This article reviews two promising biomarkers, the central vein sign (CVS) and the paramagnetic rim sign (PRS), and their potential role in the diagnosis and prognosis of MS and RIS. Both CVS and PRS have been shown to be accurate diagnostic markers in MS, with high sensitivity and specificity, and have been useful in distinguishing MS from other disorders. Further research is needed to validate these findings and determine the clinical utility of these biomarkers in routine practice.

Dialysis adequacy and hemoglobin levels predict cerebral atrophy in maintenance-hemodialysis patients

The pathogenesis of cerebral atrophy (CA) is not clear. Previous studies show a high incidence of preterm CA in hemodialysis patients. This study aims to investigate the factors influencing CA and to derive a CA prediction nomogram in maintenance-hemodialysis patients. First, brain volumes of hemodialysis patients (≤55 years) were compared against age- and sex-matched healthy controls, and differences were revealed in bilateral insular cisterns width, maximum cerebral sulci width, Evans index, ventricular-brain ratio, frontal atrophy index, and temporal lobe ratio. Then, the patients were divided equally into "no or mild" or "severe" CA groups. Potential factors influencing CA were screened. Kt/V (urea removal index) and hemoglobin levels negatively correlated with CA degree, and were used to establish a nomogram within randomly assigned training and validation patient groups. The areas under the receiver operating characteristic curves (AUROC) for training and validation groups were 0.703 and 0.744, respectively. When potassium and calcium were added to the nomogram, the AUROC for training/validation group increased to 0.748/0.806. The nomogram had optimal AUROC for training (0.759) and validation (0.804) groups when albumin was also included. Hemodialysis patients showed reduced anterior brain volumes and the nomogram established herein may have predictive value for developing CA.

Altered spontaneous brain activity patterns in patients with hyperthyroidism exophthalmos using amplitude of low-frequency fluctuation: a resting-state fMRI study

AIM

To assess changed spontaneous brain activity in hyperthyroid exophthalmos (HE) patients by the amplitude of the low-frequency fluctuation (ALFF) method, and to analyze the correlation between brain activity and ALFF values in these patients.

METHODS

Totally 18 HE and 18 hyperthyroid non-exophthalmos (HNE) patients were enrolled. The participants were tested by resting-state functional magnetic resonance imaging, and receiver operating characteristic (ROC) curves were generated to classify the ALFF values of the study population. Pearson's correlation analysis was utilized to evaluate the relationship between the ALFF values obtained from different brain areas and clinical manifestations.

RESULTS

Contrary to HNE patients, we observed lower ALFF values in the left calcarine fissure and surrounding cortex (LCFSC) in HE patients. In the ROC curve analysis of the LCFSC, the area under the curve reflected a high degree of accuracy. In addition, there was positive correlation between mean ALFF values of the LCFSC and the best-corrected visual acuity of the affected eyes.

CONCLUSION

The study displays abnormal brain activity in LCFSC in patients with HE, which might suggest pathological mechanism of visual impairment of HE patients.

Smoldering lesions in MS: if you like it then you should put a rim on it

PURPOSE

In multiple sclerosis (MS), chronic active/smoldering white matter lesions presenting with hypointense rims on susceptibility-weighted imaging (SWI) of the brain have been recognized as an important radiological feature. The aim of this work was to study the prevalence of paramagnetic rim lesions (RLs) in MS patients in a clinical setting and to assess differences in demographic and clinical variables regarding the presence of RLs.

METHODS

All 3 T brain magnetic resonance (MR) studies performed in MS patients between July 2020 and January 2021 were reviewed. In all patients, RLs were assessed on three-dimensional (3D) SWI images and the T2 FLAIR lesion load volume was assessed. Demographic, laboratory (oligoclonal bands in CSF), and clinical data, including functional status with Expanded Disability Status Scale (EDSS), were retrieved from the clinical files.

RESULTS

Of the 192 patients, 113 (59%) presented with at least 1 RL. In the RL-positive group, the mean RL count was 4.81 ranging from 1 to 37. There was no significant difference in the number of RLs between the different types of MS (p = 0.858). Regarding the presence of RLs, there were no significant differences based on gender (p = 0.083), disease duration (p = 0.520), treatment regime (p = 0.326), EDSS score (p = 0.103), and the associated T2 FLAIR lesion load volume.

CONCLUSION

SWI RLs were frequently detected in our cohort regardless of the MS type, T2 FLAIR lesion load volume, demographic features, disease duration, or clinical score. Our results suggest that RLs are not associated with more severe forms of the disease. Today, RLs can be seen on 3 T 3D SWI, although this is not a clinical standard sequence yet. Therefore, it should be considered an additional helpful MR sequence in the diagnostic workup of MS, although more studies are warranted to establish the role of RLs as prognostic markers.

Thalamic Injury and Cognition in Multiple Sclerosis

Multiple sclerosis (MS) produces demyelination and degeneration in both gray and white matter. Both cortical and deep gray matter injury is observed during the course of MS. Among deep gray matter structures, the thalamus has received special attention, as it undergoes volume loss in different MS subtypes and is involved in the earliest form of the disease, radiologically isolated syndrome. The thalamus plays an important role as an information relay center, and involvement of the thalamus in MS has been associated with a variety of clinical manifestations in MS, including fatigue, movement disorders, pain, and cognitive impairment (CI). Similar to thalamic volume loss, CI is seen from the earliest stages of MS and is potentially one of the most debilitating manifestations of the disease. The thalamus, particularly the dorsomedial nucleus as part of the basolateral limbic circuit and anterior thalamic nuclei through connections with the prefrontal cortex, has been shown to be involved in CI. Specifically, several cognitive performance measures such as processing speed and memory correlate with thalamic volume. Thalamic atrophy is one of the most important predictors of CI in MS, and both thalamic volume, diffusion tensor imaging measures, and functional activation correlate with the degree of CI in MS. Although the exact mechanism of thalamic atrophy is not well-understood, it is hypothesized to be secondary to degeneration following white matter injury resulting in secondary neurodegeneration and neuronal loss. The thalamus may represent an ideal biomarker for studies aiming to test neuroprotective or restorative therapies aimed at cognition.

Detection of Cortical and Deep Gray Matter Lesions in Multiple Sclerosis Using DIR and FLAIR at 3T

BACKGROUND AND PURPOSE

The comparative detection rates of deep gray matter (GM) multiple sclerosis (MS) lesions using double inversion recovery (DIR) and fluid-attenuated inversion-recovery (FLAIR) on 3T MR imaging remain unknown. We aimed to assess the detectability of cortical and deep GM MS lesions using DIR and FLAIR on 3T clinical exams and evaluate the relationship between deep GM lesions and brain atrophy.

METHODS

One hundred fifty consecutive MS patients underwent routine brain MRI that included 3D DIR and 2D T2 FLAIR on the same 3T scanner. Three neuroradiologists independently reviewed all exams for cortical and deep GM lesions. Statistical parametric mapping (SPM) and FMRIB software library (FSL)-FIRST pipelines were used to determine normalized whole brain and deep GM volumes.

RESULTS

A total of 65 cortical and 98 deep lesions were detected on DIR versus 24 and 20, respectively, on FLAIR. Among all 150 patients, the number and percentage of patients with GM lesions on DIR and FLAIR were as follows: cortical 43 (28.7%) versus 24 (16.0%) (P < .001), thalamus 47 (31.3%) versus 20 (13.3%) (P < .001), putamen 10 (6.7%) versus 3 (2.0%) (P = .02), globus pallidus 9 (6.0%) versus 3 (1.3%) (P = .02), and caudate 5 (3.3%) versus 1 (0.7%) (P = .125). Presence of deep GM lesions weakly correlated with deep GM volume fractions.

CONCLUSION

Deep GM MS lesions can be detected using routine clinical brain MRI including DIR and FLAIR at 3T. Future studies to optimize these sequences may improve the detection rates of cortical and deep GM lesions. The presence of GM lesions showed weak correlation with GM atrophy.

Iron Rims as an Imaging Biomarker in MS: A Systematic Mapping Review

Background: Multiple sclerosis (MS) is an autoimmune, inflammatory, demyelinating and degenerative disease of the central nervous system (CNS). To date, there is no definitive imaging biomarker for diagnosing MS. The current diagnostic criteria are mainly based on clinical relapses supported by the presence of white matter lesions (WMLs) on MRI. However, misdiagnosis of MS is still a significant clinical problem. The paramagnetic, iron rims (IRs) around white matter lesions have been proposed to be an imaging biomarker in MS. This study aimed to carry out a systematic mapping review to explore the detection of iron rim lesions (IRLs), on clinical MR scans, and describe the characteristics of IRLs presence in MS versus other MS-mimic disorders. Methods: Publications from 2001 on IRs lesions were reviewed in three databases: PubMed, Web of Science and Embase. From the initial result set 718 publications, a final total of 38 papers were selected. Results: The study revealed an increasing interest in iron/paramagnetic rims lesions studies. IRs were more frequently found in periventricular regions and appear to be absent in MS-mimics. Conclusions IR is proposed as a promising imaging biomarker for MS.

Current Methods of Magnetic Resonance for Noninvasive Assessment of Molecular Aspects of Pathoetiology in Multiple Sclerosis

Multiple sclerosis (MS) is an autoimmune disease with expanding axonal and neuronal degeneration in the central nervous system leading to motoric dysfunctions, psychical disability, and cognitive impairment during MS progression. The exact cascade of pathological processes (inflammation, demyelination, excitotoxicity, diffuse neuro-axonal degeneration, oxidative and metabolic stress, etc.) causing MS onset is still not fully understood, although several accompanying biomarkers are particularly suitable for the detection of early subclinical changes. Magnetic resonance (MR) methods are generally considered to be the most sensitive diagnostic tools. Their advantages include their noninvasive nature and their ability to image tissue in vivo. In particular, MR spectroscopy (proton 1H and phosphorus 31P MRS) is a powerful analytical tool for the detection and analysis of biomedically relevant metabolites, amino acids, and bioelements, and thus for providing information about neuro-axonal degradation, demyelination, reactive gliosis, mitochondrial and neurotransmitter failure, cellular energetic and membrane alternation, and the imbalance of magnesium homeostasis in specific tissues. Furthermore, the MR relaxometry-based detection of accumulated biogenic iron in the brain tissue is useful in disease evaluation. The early description and understanding of the developing pathological process might be critical for establishing clinically effective MS-modifying therapies.

MRI biomarkers of disease progression and conversion to secondary-progressive multiple sclerosis

INTRODUCTION

Conventional imaging measures remain a key clinical tool for the diagnosis multiple sclerosis (MS) and monitoring of patients. However, most measures used in the clinic show unsatisfactory performance in predicting disease progression and conversion to secondary progressive MS.

AREAS COVERED

Sophisticated imaging techniques have facilitated the identification of imaging biomarkers associated with disease progression, such as global and regional brain volume measures, and with conversion to secondary progressive MS, such as leptomeningeal contrast enhancement and chronic inflammation. The relevance of emerging imaging approaches partially overcoming intrinsic limitations of traditional techniques is also discussed.

EXPERT OPINION

Imaging biomarkers capable of detecting tissue damage early on in the disease, with the potential to be applied in multicenter trials and at an individual level in clinical settings, are strongly needed. Several measures have been proposed, which exploit advanced imaging acquisitions and/or incorporate sophisticated post-processing, can quantify irreversible tissue damage. The progressively wider use of high-strength field MRI and the development of more advanced imaging techniques will help capture the missing pieces of the MS puzzle. The ability to more reliably identify those at risk for disability progression will allow for earlier intervention with the aim to favorably alter the disease course.

Targeting Iron Dyshomeostasis for Treatment of Neurodegenerative Disorders

While iron has an important role in the normal functioning of the brain owing to its involvement in several physiological processes, dyshomeostasis has been found in many neurodegenerative disorders, as evidenced by both histopathological and imaging studies. Although the exact causes have remained elusive, the fact that altered iron levels have been found in disparate diseases suggests that iron may contribute to their development and/or progression. As such, the processes involved in iron dyshomeostasis may represent novel therapeutic targets. There are, however, many questions about the exact interplay between neurodegeneration and altered iron homeostasis. Some insight can be gained by considering the parallels with respect to what occurs in healthy aging, which is also characterized by increased iron throughout many regions in the brain along with progressive neurodegeneration. Nevertheless, the exact mechanisms of iron-mediated damage are likely disease specific to a certain degree, given that iron plays a crucial role in many disparate biological processes, which are not always affected in the same way across different neurodegenerative disorders. Moreover, it is not even entirely clear yet whether iron actually has a causative role in all of the diseases where altered iron levels have been noted. For example, there is strong evidence of iron dyshomeostasis leading to neurodegeneration in Parkinson's disease, but there is still some question as to whether changes in iron levels are merely an epiphenomenon in multiple sclerosis. Recent advances in neuroimaging now offer the possibility to detect and monitor iron levels in vivo, which allows for an improved understanding of both the temporal and spatial dynamics of iron changes and associated neurodegeneration compared to post-mortem studies. In this regard, iron-based imaging will likely play an important role in the development of therapeutic approaches aimed at addressing altered iron dynamics in neurodegenerative diseases. Currently, the bulk of such therapies have focused on chelating excess iron. Although there is some evidence that these treatment options may yield some benefit, they are not without their own limitations. They are generally effective at reducing brain iron levels, as assessed by imaging, but clinical benefits are more modest. New drugs that specifically target iron-related pathological processes may offer the possibility to prevent, or at the least, slow down irreversible neurodegeneration, which represents an unmet therapeutic target.

Primary biliary cholangitis patients exhibit MRI changes in structure and function of interoceptive brain regions

Background

Many patients with primary biliary cholangitis (PBC) experience non-hepatic symptoms that are possibly linked to altered interoception, the sense of the body’s internal state. We used magnetic resonance imaging (MRI) to determine if PBC patients exhibit structural and functional changes of the thalamus and insula, brain regions that process signals related to interoception.

Methods

Fifteen PBC patients with mild disease and 17 controls underwent 3 Tesla T₁-weighted MRI, resting-state functional MRI, and quantitative susceptibility mapping (QSM), to measure thalamic and insular volume, neuronal activity and iron deposition, respectively. Group differences were assessed using analysis of covariance, and stepwise linear regression was used to determine the predictive power of clinical indicators of disease.

Results

PBC patients exhibited reduced thalamic volume (p < 0.01), and ursodeoxycholic acid (UDCA) non-responders exhibited lower left thalamus activity (p = 0.05). PBC patients also exhibited reduced anterior insula activity (p = 0.012), and liver stiffness positively correlated with MRI indicators of anterior insula iron deposition (p < 0.02).

Conclusions

PBC affects structure and function of brain regions critically important to interoception. Moreover, these brain changes occur in patients with early, milder disease and thus may potentially be reversible.

A Radiodensity Histogram Study of the Brain in Multiple Sclerosis

Multiple sclerosis (MS) is a progressive neurodegenerative disease, affecting 1 million Americans and 2.5 million people globally. Although the diagnosis is made clinically, imaging plays a major role in diagnosing and monitoring disease progression and treatment response. Magnetic resonance imaging (MRI) has proven sensitive in imaging MS lesions, but the characterization offered by routine clinical MRI remains qualitative and with discrepancies between imaging and clinical findings. We investigated the ability of digital analysis of noncontrast head computed tomography (CT) images to detect global brain changes of MS. All routine diagnostic head CTs obtained on patients with known MS obtained from 1 of 2 scan platforms from 6/1/2011 to 6/1/2015 were reviewed. Head CT images from 54 patients with MS met inclusion criteria. Head CT images were processed and histogram metrics were compared to age- and gender- matched control subjects from the same CT scanners during the same time interval. Histogram metrics were correlated with plaque burden as seen on MRI studies. Compared with control subjects, patients had increased total brain radiodensity (P < .0001), further characterized as an increased histogram modal radiodensity (P < .0001) with decrease in histogram skewness (P < .0001). Radiodensity decreased with increasing plaque burden. Similar findings were seen in the patients with only mild plaque burden sub- group. Radiodensity is a unique tissue metric that is not measured by other imaging techniques. Our study finds that brain radiodensity histogram metrics highly correlate with MS, even in cases with minimal plaque burden.

[Anemia and dysregulation of iron metabolism in multiple sclerosis]

Anemia is one of the common diseases comorbid with multiple sclerosis (MS). This article reviews the prevalence and types of anemia in MS patients. It has been shown that anemia is often accompanied by a decrease in serum iron level. The authors present the data on iron metabolism in patients with MS and MRI findings concerning deposits of iron in the gray matter of the brain. The causal relationship between abnormalities in iron metabolism and MS remains unclear; this study allows to approach the understanding of the MS pathogenesis and to increase the efficacy of therapy for this disease.

Quantitative Susceptibility Mapping of the Thalamus: Relationships with Thalamic Volume, Total Gray Matter Volume, and T2 Lesion Burden

BACKGROUND AND PURPOSE

Both thalamic iron deposition and atrophy have been reported in patients with multiple sclerosis compared with healthy controls, but how they are related is unclear. The purpose of this study was to understand the pathophysiologic basis for this iron deposition.

MATERIALS AND METHODS

Ninety-five patients with relapsing-remitting multiple sclerosis underwent 3T MR imaging with a standardized protocol that included quantitative susceptibility mapping to measure iron concentration and a 3D T1 echo-spoiled gradient-echo sequence to obtain thalamic volumes. Volumes of interest were manually delineated on the quantitative susceptibility map to encompass both thalami. Multivariate regression analyses were performed to identify the association between thalamic susceptibility and volume. Associations between thalamic susceptibility and total gray matter volume, cortical thickness, and T2 lesion volume were also assessed.

RESULTS

The relative susceptibility of the thalamus was associated with T2 lesion volume (P = .015) and was higher in the presence of enhancing lesions (P = .013). The relative susceptibility of the thalami was not associated with thalamic volumes, total gray matter volumes, or cortical thickness (P > .05).

CONCLUSIONS

Iron levels in the thalami are associated with T2 lesion burden and the presence of enhancing lesions, but not with thalamic or gray matter volumes, suggesting that iron accumulation is associated with white matter inflammation rather than gray matter neurodegeneration.

Mapping of thalamic magnetic susceptibility in multiple sclerosis indicates decreasing iron with disease duration: A proposed mechanistic relationship between inflammation and oligodendrocyte vitality

Recent advances in susceptibility MRI have dramatically improved the visualization of deep gray matter brain regions and the quantification of their magnetic properties in vivo, providing a novel tool to study the poorly understood iron homeostasis in the human brain. In this study, we used an advanced combination of the recent quantitative susceptibility mapping technique with dedicated analysis methods to study intra-thalamic tissue alterations in patients with clinically isolated syndrome (CIS) and multiple sclerosis (MS). Thalamic pathology is one of the earliest hallmarks of MS and has been shown to correlate with cognitive dysfunction and fatigue, but the mechanisms underlying the thalamic pathology are poorly understood. We enrolled a total of 120 patients, 40 with CIS, 40 with Relapsing Remitting MS (RRMS), and 40 with Secondary Progressive MS (SPMS). For each of the three patient groups, we recruited 40 controls, group matched for age- and sex (120 total). We acquired quantitative susceptibility maps using a single-echo gradient echo MRI pulse sequence at 3 T. Group differences were studied by voxel-based analysis as well as with a custom thalamus atlas. We used threshold-free cluster enhancement (TFCE) and multiple regression analyses, respectively. We found significantly reduced magnetic susceptibility compared to controls in focal thalamic subregions of patients with RRMS (whole thalamus excluding the pulvinar nucleus) and SPMS (primarily pulvinar nucleus), but not in patients with CIS. Susceptibility reduction was significantly associated with disease duration in the pulvinar, the left lateral nuclear region, and the global thalamus. Susceptibility reduction indicates a decrease in tissue iron concentration suggesting an involvement of chronic microglia activation in the depletion of iron from oligodendrocytes in this central and integrative brain region. Not necessarily specific to MS, inflammation-mediated iron release may lead to a vicious circle that reduces the protection of axons and neuronal repair.

Susceptibility Weighted MRI in Rodents at 9.4 T

Susceptibility Weighted Imaging (SWI) is an established part of the clinical neuroimaging toolbox and, since its inception, has also successfully been used in various preclinical studies. Exploiting the effect of variations of magnetic susceptibility between different tissues on the externally applied, static, homogeneous magnetic field, the method visualizes venous vasculature, hemorrhages and blood degradation products, calcifications, and tissue iron deposits. The chapter describes in vivo and ex vivo protocols for preclinical SWI in rodents.

Iron-related gene variants and brain iron in multiple sclerosis and healthy individuals

Brain iron homeostasis is known to be disturbed in multiple sclerosis (MS), yet little is known about the association of common gene variants linked to iron regulation and pathological tissue changes in the brain. In this study, we investigated the association of genetic determinants linked to iron regulation with deep gray matter (GM) magnetic susceptibility in both healthy controls (HC) and MS patients. Four hundred (400) patients with MS and 150 age- and sex-matched HCs were enrolled and obtained 3 T MRI examination. Three (3) single nucleotide polymorphisms (SNPs) associated with iron regulation were genotyped: two SNPs in the human hereditary hemochromatosis protein gene HFE: rs1800562 (C282Y mutation) and rs1799945 (H63D mutation), as well as the rs1049296 SNP in the transferrin gene (C2 mutation). The effects of disease and genetic status were studied using quantitative susceptibility mapping (QSM) voxel-based analysis (VBA) and region-of-interest (ROI) analysis of the deep GM. The general linear model framework was used to compare groups. Analyses were corrected for age and sex, and adjusted for false discovery rate. We found moderate increases in susceptibility in the right putamen of participants with the C282Y (+ 6.1 ppb) and H63D (+ 6.9 ppb) gene variants vs. non-carriers, as well as a decrease in thalamic susceptibility of progressive MS patients with the C282Y mutation (left: − 5.3 ppb, right: − 6.7 ppb, p < 0.05). Female MS patients had lower susceptibility in the caudate (− 6.0 ppb) and putamen (left: − 3.9 ppb, right: − 4.6 ppb) than men, but only when they had a wild-type allele (p < 0.05). Iron-gene linked increases in putamen susceptibility (in HC and relapsing remitting MS) and decreases in thalamus susceptibility (in progressive MS), coupled with apparent sex interactions, indicate that brain iron in healthy and disease states may be influenced by genetic factors.

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Magnetic susceptibility and common gene variants linked to iron were investigated.

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The C282Y and H63D alleles were associated with putamen and thalamus susceptibility changes.

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Dependent on allele status, men and women differed in deep GM susceptibility in MS.

Heterogeneous pathological processes account for thalamic degeneration in multiple sclerosis: Insights from 7 T imaging

BACKGROUND

Thalamic degeneration impacts multiple sclerosis (MS) prognosis.

OBJECTIVE

To investigate heterogeneous thalamic pathology, its correlation with white matter (WM), cortical lesions and thickness, and as function of distance from cerebrospinal fluid (CSF).

METHODS

In 41 MS subjects and 17 controls, using 3 and 7 T imaging, we tested for (1) differences in thalamic volume and quantitative T₂* (q-T₂*) (2) globally and (3) within concentric bands originating from the CSF/thalamus interface; (4) the relation between thalamic, cortical, and WM metrics; and (5) the contribution of magnetic resonance imaging (MRI) metrics to clinical scores. We also assessed MS thalamic lesion distribution as a function of distance from CSF.

RESULTS

Thalamic lesions were mainly located next to the ventricles. Thalamic volume was decreased in MS versus controls ( p < 10^-2); global q-T₂* was longer in secondary progressive multiple sclerosis (SPMS) only ( p < 10^-2), indicating myelin and/or iron loss. Thalamic atrophy and longer q-T₂* correlated with WM lesion volume ( p < 0.01). In relapsing-remitting MS, q-T₂* thalamic abnormalities were located next to the WM ( p < 0.01 (uncorrected), p = 0.09 (corrected)), while they were homogeneously distributed in SPMS. Cortical MRI metrics were the strongest predictors of clinical outcome.

CONCLUSION

Heterogeneous pathological processes affect the thalamus in MS. While focal lesions are likely mainly driven by CSF-mediated factors, overall thalamic degeneration develops in association with WM lesions.

Heterogeneity of Cortical Lesion Susceptibility Mapping in Multiple Sclerosis

BACKGROUND AND PURPOSE

Quantitative susceptibility mapping has been used to characterize iron and myelin content in the deep gray matter of patients with multiple sclerosis. Our aim was to characterize the susceptibility mapping of cortical lesions in patients with MS and compare it with neuropathologic observations.

MATERIALS AND METHODS

The pattern of microglial activation was studied in postmortem brain tissues from 16 patients with secondary-progressive MS and 5 age-matched controls. Thirty-six patients with MS underwent 3T MR imaging, including 3D double inversion recovery and 3D-echo-planar SWI.

RESULTS

Neuropathologic analysis revealed the presence of an intense band of microglia activation close to the pial membrane in subpial cortical lesions or to the WM border of leukocortical cortical lesions. The quantitative susceptibility mapping analysis revealed 131 cortical lesions classified as hyperintense; 33, as isointense; and 84, as hypointense. Quantitative susceptibility mapping hyperintensity edge found in the proximity of the pial surface or at the white matter/gray matter interface in some of the quantitative susceptibility mapping-hyperintense cortical lesions accurately mirrors the microglia activation observed in the neuropathology analysis.

CONCLUSIONS

Cortical lesion susceptibility maps are highly heterogeneous, even at individual levels. Quantitative susceptibility mapping hyperintensity edge found in proximity to the pial surface might be due to the subpial gradient of microglial activation.

Changes of deep gray matter magnetic susceptibility over 2 years in multiple sclerosis and healthy control brain

In multiple sclerosis, pathological changes of both tissue iron and myelin occur, yet these factors have not been characterized in a longitudinal fashion using the novel iron- and myelin-sensitive quantitative susceptibility mapping (QSM) MRI technique. We investigated disease-relevant tissue changes associated with myelin loss and iron accumulation in multiple sclerosis deep gray matter (DGM) over two years. One-hundred twenty (120) multiple sclerosis patients and 40 age- and sex-matched healthy controls were included in this prospective study. Written informed consent and local IRB approval were obtained from all participants. Clinical testing and QSM were performed both at baseline and at follow-up. Brain magnetic susceptibility was measured in major DGM structures. Temporal (baseline vs. follow-up) and cross-sectional (multiple sclerosis vs. controls) differences were studied using mixed factorial ANOVA analysis and appropriate t-tests. At either time-point, multiple sclerosis patients had significantly higher susceptibility in the caudate and globus pallidus and lower susceptibility in the thalamus. Over two years, susceptibility increased significantly in the caudate of both controls and multiple sclerosis patients. Inverse thalamic findings among MS patients suggest a multi-phase pathology explained by simultaneous myelin loss and/or iron accumulation followed by iron depletion and/or calcium deposition at later stages.

An illustrated comparison of processing methods for MR phase imaging and QSM: combining array coil signals and phase unwrapping

Phase imaging benefits from strong susceptibility effects at very high field and the high signal-to-noise ratio (SNR) afforded by multi-channel coils. Combining the information from coils is not trivial, however, as the phase that originates in local field effects (the source of interesting contrast) is modified by the inhomogeneous sensitivity of each coil. This has historically been addressed by referencing individual coil sensitivities to that of a volume coil, but alternative approaches are required for ultra-high field systems in which no such coil is available. An additional challenge in phase imaging is that the phase that develops up to the echo time is "wrapped" into a range of 2π radians. Phase wraps need to be removed in order to reveal the underlying phase distribution of interest. Beginning with a coil combination using a homogeneous reference volume coil - the Roemer approach - which can be applied at 3 T and lower field strengths, we review alternative methods for combining single-echo and multi-echo phase images where no such reference coil is available. These are applied to high-resolution data acquired at 7 T and their effectiveness assessed via an index of agreement between phase values over channels and the contrast-to-noise ratio in combined images. The virtual receiver coil and COMPOSER approaches were both found to be computationally efficient and effective. The main features of spatial and temporal phase unwrapping methods are reviewed, placing particular emphasis on recent developments in temporal phase unwrapping and Laplacian approaches. The features and performance of these are illustrated in application to simulated and high-resolution in vivo data. Temporal unwrapping was the fastest of the methods tested and the Laplacian the most robust in images with low SNR. © 2016 The Authors. NMR in Biomedicine published by John Wiley & Sons Ltd.

Inversion recovery ultrashort echo time magnetic resonance imaging: A method for simultaneous direct detection of myelin and high signal demonstration of iron deposition in the brain - A feasibility study

Multiple sclerosis (MS) causes demyelinating lesions in the white matter and increased iron deposition in the subcortical gray matter. Myelin protons have an extremely short T2* (<1ms) and are not directly detected with conventional clinical magnetic resonance (MR) imaging sequences. Iron deposition also reduces T2*, leading to reduced signal on clinical sequences. In this study we tested the hypothesis that the inversion recovery ultrashort echo time (IR-UTE) pulse sequence can directly and simultaneously image myelin and iron deposition using a clinical 3T scanner. The technique was first validated on a synthetic myelin phantom (myelin powder in D₂O) and a Feridex iron phantom. This was followed by studies of cadaveric MS specimens, healthy volunteers and MS patients. UTE imaging of the synthetic myelin phantom showed an excellent bi-component signal decay with two populations of protons, one with a T2* of 1.2ms (residual water protons) and the other with a T2* of 290μs (myelin protons). IR-UTE imaging shows sensitivity to a wide range of iron concentrations from 0.5 to ~30mM. The IR-UTE signal from white matter of the brain of healthy volunteers shows a rapid signal decay with a short T2* of ~300μs, consistent with the T2* values of myelin protons in the synthetic myelin phantom. IR-UTE imaging in MS brain specimens and patients showed multiple white matter lesions as well as areas of high signal in subcortical gray matter. This in specimens corresponded in position to Perl's diaminobenzide staining results, consistent with increased iron deposition. IR-UTE imaging simultaneously detects lesions with myelin loss in the white matter and iron deposition in the gray matter.

Hippocampal microstructural damage correlates with memory impairment in clinically isolated syndrome suggestive of multiple sclerosis

OBJECTIVE

We investigated whether diffusion tensor imaging (DTI) could reveal early hippocampal damage and clinically relevant correlates of memory impairment in persons with clinically isolated syndrome (CIS) suggestive of multiple sclerosis (MS).

METHODS

A total of 37 persons with CIS, 32 with MS and 36 controls prospectively included from 2011 to 2014 were tested for cognitive performances and scanned with 3T-magnetic resonance imaging (MRI) to assess volumetric and DTI changes within the hippocampus, whole brain volume and T2-lesion load.

RESULTS

While there was no hippocampal atrophy in the CIS group, hippocampal fractional anisotropy (FA) was significantly decreased compared to controls. Decrease in hippocampal FA together with increased mean diffusivity (MD) was even more prominent in MS patients. In CIS, hippocampal MD was correlated with episodic verbal memory performance ( r = -0.57, p = 0.0002 and odds ratio (OR) = 0.058, 95% confidence interval (CI) = 0.0057-0.59, p = 0.016 adjusted for age, gender, depression and T2-lesion load), but not with cognitive tasks unrelated to hippocampal functions. Hippocampal MD was the only variable discriminating memory-impaired from memory-preserved persons with CIS (area under the curve (AUC) = 0.77, sensitivity = 90.0%, specificity = 70.3%, positive predictive value (PPV) = 52.9%, negative predictive value (NPV) = 95.0%).

CONCLUSION

DTI alterations within the hippocampus might reflect early neurodegenerative processes that are correlated with episodic memory performance, discriminating persons with CIS according to their memory status.

Early silent microstructural degeneration and atrophy of the thalamocortical network in multiple sclerosis

Recent studies on patients with clinically isolated syndrome (CIS) and multiple sclerosis (MS) demonstrated thalamic atrophy. Here we addressed the following question: Is early thalamic atrophy in patients with CIS and relapsing-remitting MS (RRMS) mainly a direct consequence of white matter (WM) lesions-as frequently claimed-or is the atrophy stronger correlated to "silent" (nonlesional) microstructural thalamic alterations? One-hundred and ten patients with RRMS, 12 with CIS, and 30 healthy controls were admitted to 3 T magnetic resonance imaging. Fractional anisotropy (FA) was computed from diffusion tensor imaging (DTI) to assess thalamic and WM microstructure. The relative thalamic volume (RTV) and thalamic FA were significantly reduced in patients with CIS and RRMS relative to healthy controls. Both measures were also correlated. The age, gender, WM lesion load, thalamic FA, and gray matter volume-corrected RTV were reduced even in the absence of thalamic and extensive white matter lesions-also in patients with short disease duration (≤24 months). A voxel-based correlation analysis revealed that the RTV reduction had a significant effect on local WM FA-in areas next to the thalamus and basal ganglia. These WM alterations could not be explained by WM lesions, which had a differing spatial distribution. Early thalamic atrophy is mainly driven by silent microstructural thalamic alterations. Lesions do not disclose the early damage of thalamocortical circuits, which seem to be much more affected in CIS and RRMS than expected. Thalamocortical damage can be detected by DTI in normal appearing brain tissue. Hum Brain Mapp 37:1866-1879, 2016. © 2016 Wiley Periodicals, Inc.

Increased brain iron deposition is a risk factor for brain atrophy in patients with haemodialysis: a combined study of quantitative susceptibility mapping and whole brain volume analysis

To explore the correlation between increased brain iron deposition and brain atrophy in patients with haemodialysis and their correlation with clinical biomarkers and neuropsychological test. Forty two patients with haemodialysis and forty one age- and gender-matched healthy controls were recruited in this prospective study. 3D whole brain high resolution T1WI and susceptibility weighted imaging were scanned on a 3 T MRI system. The brain volume was analyzed using voxel-based morphometry (VBM) in patients and to compare with that of healthy controls. Quantitative susceptibility mapping was used to measure and compare the susceptibility of different structures between patients and healthy controls. Correlation analysis was used to investigate the relationship between the brain volume, iron deposition and neuropsychological scores. Stepwise multiple regression analysis was used to explore the effect of clinical biomarkers on the brain volumes in patients. Compared with healthy controls, patients with haemodialysis showed decreased volume of bilateral putamen and left insular lobe (All P < 0.05). Susceptibilities of bilateral caudate head, putamen, substantia nigra, red nucleus and dentate nucleus were significantly higher (All P < 0.05). The increased brain iron deposition is negatively correlated with the decreased volume of bilateral putamen (P < 0.01). Neuropsychological scores positively correlated with decreased volume of left insular lobe (P < 0.05). Dialysis duration was negatively associated with decreased volume of bilateral putamen (P < 0.05). Our study indicated increased brain iron deposition and dialysis duration was risk factors for brain atrophy in patients with haemodialysis. The decreased gray matter volume of the left insular lobe was correlated with neurocognitive impairment.

Iron deposition in the gray matter in patients with relapse-remitting multiple sclerosis: A longitudinal study using three-dimensional (3D)-enhanced T2*-weighted angiography (ESWAN)

PURPOSE

To investigate the relationship between the iron content by magnetic resonance imaging (MRI) and clinic correlation in patients with relapse-remitting multiple sclerosis (RRMS) over a two-year period.

METHODS

Thirty RRMS patients and 30 healthy control subjects were examined twice, two years apart, by undergoing brain conventional MRI and three-dimensional (3D)-enhanced T2*-weighted angiography (ESWAN) sequences at 3.0T. Quantitative differences in iron content in deep gray matter (GM) nuclei and precentral gyrus GM between patients and control subjects with repeated-measures the mean phase values (MPVs) for ESWAN-filtered phase images. Spearman's rank correlation coefficient analysis was used to evaluate correlations of the MPVs, both 2-year-difference and single-time measurements, to disease duration, expanded disability status scale (EDSS) and times of recurrence.

RESULTS

The RRMS patients had higher GM iron concentration than that of the healthy control subjects in both single-time measurements, but only the substantia nigra (SN), and the precentral gyrus GM (PGM) showed a significant statistical difference (p<0.05). Using the paired samples t test, we found that there were significant differences in two-year-difference measurements of the MPVs in the putamen (PUT), the globus pallidus (GP), the head of the caudate nucleus (HCN), the thalamus (THA), SN, the red nucleus (RN), the dentate nucleus (DN) and PGM, especially in SN (t=2.92, p=0.007) in RRMS patients. The MPVs of the PUT, GP, HCN, THA, SN, RN, DN and PGM for the subgroup with RRMS patients in times of recurrence less than twice were similar to the healthy controls. There was no significant difference in all regions of interests (ROIs). However, there were significant differences in all ROIs except THA and GP for the other subgroup with RRMS patients in times of recurrence more than and equal to twice. Spearman's rank correlation coefficient analysis showed there were significant negative correlations between disease duration and the MPVs in the HCN (r=-0.516, p=0.004), DN (r=-0.468, p=0.009) and PGM (r=-0.84, p=0). However, no correlations were found between the EDSS scores and the MPVs.

CONCLUSIONS

Iron content in the GM can be measurable using MRI and our results confirmed that iron concentration was increasing in the GM of MS patients during two-year period compared to healthy controls. Furthermore, this study had also shown significant and substantial correlation of iron concentration with disease severity.

A pilot, longitudinal, 24-week study to evaluate the effect of interferon beta-1a subcutaneous on changes in susceptibility-weighted imaging-filtered phase assessment of lesions and subcortical deep-gray matter in relapsing-remitting multiple sclerosis

BACKGROUND

Studies have shown a relationship between increased iron content and clinical progression, cognitive impairment, and brain atrophy in patients with multiple sclerosis. Altered phase, as determined by susceptibility-weighted imaging (SWI), can potentially capture iron content changes.

OBJECTIVE

The objective of this study was to investigate phase changes in white matter (WM) lesions and subcortical deep-gray matter (SDGM) of patients with relapsing-remitting (RR) MS treated with interferon beta-1a administered subcutaneously versus untreated healthy controls (HCs).

METHODS

We conducted a 24-week, nonrandomized, open-label pilot study of 23 patients with RRMS receiving interferon beta-1a administered subcutaneously and 15 HCs. Patients were imaged on a 3T scanner at baseline, 12, and 24 weeks; changes in phase behavior in WM lesions and regional SDGM [mean phase of low-phase voxels (MP-LPV)], and in SDGM volumes, were measured. Between- and within-group changes were tested using nonparametric statistics adjusted for multiple comparisons.

RESULTS

The number (p = 0.003) and volume (p < 0.001) of phase WM lesions both significantly decreased among RRMS patients over 24 weeks. At baseline, MP-LPV was lower (suggestive of greater iron content) in total SDGM among RRMS patients versus HCs (p = 0.002). Week 24 MP-LPV changes from baseline were not significantly different between groups in total SDGM or any region except the putamen (-0.0025 radians in RRMS patients versus 0.0035 radians in HCs; p = 0.041).

CONCLUSIONS

Over 24 weeks, phase lesions were reduced significantly in the RRMS group. These preliminary results suggest that SWI-filtered phase may become a useful tool for monitoring RRMS disease activity.

Relationship between iron accumulation and white matter injury in multiple sclerosis: a case-control study

Despite the increasing development and applications of iron imaging, the pathophysiology of iron accumulation in multiple sclerosis (MS), and its role in disease progression and development of clinical disability, is poorly understood. The aims of our study were to determine the presence and extent of iron in T2 visible lesions and gray and white matter using magnetic field correlation (MFC) MRI and correlate with microscopic white matter (WM) injury as measured by diffusion tensor imaging (DTI). This is a case-control study including a series of 31 patients with clinically definite MS. The mean age was 39 years [standard deviation (SD) = 9.55], they were 11 males and 20 females, with a disease duration average of 3 years (range 0-13) and a median EDSS of 2 (0-4.5). Seventeen healthy volunteers (6 males and 11 females) with a mean age of 36 years (SD = 11.4) were recruited. All subjects underwent MR imaging on a 3T scanner using T2-weighted sequence, 3D T1 MPRAGE, MFC, single-shot DTI and post-contrast T1. T2-lesion volumes, brain volumetry, DTI parameters and iron quantification were calculated and multiple correlations were exploited. Increased MFC was found in the putamen (p = 0.061), the thalamus (p = 0.123), the centrum semiovale (p = 0.053), globus pallidus (p = 0.008) and gray matter (GM) (p = 0.004) of MS patients compared to controls. The mean lesional MFC was 121 s(-2) (SD = 67), significantly lower compared to the GM MFC (<0.0001). The GM mean diffusivity (MD) was inversely correlated with the MFC in the centrum semiovale (p < 0.001), and in the splenium of the corpus callosum (p < 0.001). Patients with MS have increased iron in the globus pallidus, putamen and centrum with a trend toward increased iron in all the brain structures. Quantitative iron evaluation of WM and GM may improve the understanding of MS pathophysiology, and might serve as a surrogate marker of disease progression.

Subcortical brain segmentation of two dimensional T1-weighted data sets with FMRIB's Integrated Registration and Segmentation Tool (FIRST)

Brain atrophy has been identified as an important contributing factor to the development of disability in multiple sclerosis (MS). In this respect, more and more interest is focussing on the role of deep grey matter (DGM) areas. Novel data analysis pipelines are available for the automatic segmentation of DGM using three-dimensional (3D) MRI data. However, in clinical trials, often no such high-resolution data are acquired and hence no conclusions regarding the impact of new treatments on DGM atrophy were possible so far. In this work, we used FMRIB's Integrated Registration and Segmentation Tool (FIRST) to evaluate the possibility of segmenting DGM structures using standard two-dimensional (2D) T1-weighted MRI. In a cohort of 70 MS patients, both 2D and 3D T1-weighted data were acquired. The thalamus, putamen, pallidum, nucleus accumbens, and caudate nucleus were bilaterally segmented using FIRST. Volumes were calculated for each structure and for the sum of basal ganglia (BG) as well as for the total DGM. The accuracy and reliability of the 2D data segmentation were compared with the respective results of 3D segmentations using volume difference, volume overlap and intra-class correlation coefficients (ICCs). The mean differences for the individual substructures were between 1.3% (putamen) and −25.2% (nucleus accumbens). The respective values for the BG were −2.7% and for DGM 1.3%. Mean volume overlap was between 89.1% (thalamus) and 61.5% (nucleus accumbens); BG: 84.1%; DGM: 86.3%. Regarding ICC, all structures showed good agreement with the exception of the nucleus accumbens. The results of the segmentation were additionally validated through expert manual delineation of the caudate nucleus and putamen in a subset of the 3D data. In conclusion, we demonstrate that subcortical segmentation of 2D data are feasible using FIRST. The larger subcortical GM structures can be segmented with high consistency. This forms the basis for the application of FIRST in large 2D MRI data sets of clinical trials in order to determine the impact of therapeutic interventions on DGM atrophy in MS.

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Segmentation of deep grey matter (DGM) using 2-dimensional MRI data is challenging.

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We performed a systematic comparison between 2 and 3D data segmentation using FIRST.

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The DGM volumes of 70 multiple sclerosis patients were statistically compared.

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We found a good agreement of the segmentation results for the large DGM structures.

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Our results indicate that FIRST is suitable for the segmentation of 2D data sets acquired in multicentre studies.

Iron and volume in the deep gray matter: association with cognitive impairment in multiple sclerosis

BACKGROUND AND PURPOSE

There is a well-established correlation between deep gray matter atrophy and cognitive dysfunction in MS. However, the cause of these signs of neurodegeneration is poorly understood. Iron accumulation in the deep gray matter is higher in patients with MS compared with age- and sex-matched healthy controls, and could contribute to disease progression. Our objective was to evaluate the relationship between iron and cognition in several deep gray matter structures while accounting for the influence of volume loss.

MATERIALS AND METHODS

Eighty-five patients with MS and 27 healthy volunteers underwent 3T MR imaging and neuropsychological examination. We used SWI filtered phase to analyze the mean phase of low-phase voxels, indicative of abnormal iron accumulation.

RESULTS

Correlations between mean phase of low-phase voxels and cognitive tests were found in the caudate nucleus (r = 0.240 and 0.232), putamen (r = 0.368, 0.252, and 0.238), globus pallidus (r = 0.235), and pulvinar nucleus of thalamus (r = 0.244, 0.255, and 0.251) (P < .05). However, correlations between structure volume and cognition were more robust. Furthermore, the introduction of structure volume into hierarchical regression analyses after iron metrics significantly improved most models, and mean phase of low-phase voxels did not account for significant variance after volume.

CONCLUSIONS

These findings suggest that iron accumulation plays a significant, if minor, role in MS cognitive decline.

The prognostic utility of MRI in clinically isolated syndrome: a literature review

For patients presenting with clinically isolated syndrome, the treating clinician needs to advise the patient on the probability of conversion to clinically definite multiple sclerosis. MR imaging may give useful prognostic information, and there is large body of literature pertaining to the use of MR imaging in assessing patients presenting with clinically isolated syndrome. This literature review evaluates the accuracy of MR imaging in predicting which patients with clinically isolated syndrome will go on to develop long-term disease and/or disability. New and emerging MR imaging technologies and their applicability to patients with clinically isolated syndrome are also considered.

Hemoglobin as a source of iron overload in multiple sclerosis: does multiple sclerosis share risk factors with vascular disorders?

Although iron is known to be essential for the normal development and health of the central nervous system, abnormal iron deposits are found in and around multiple sclerosis (MS) lesions that themselves are closely associated with the cerebral vasculature. However, the origin of this excess iron is unknown, and it is not clear whether this is one of the primary causative events in the pathogenesis of MS, or simply another consequence of the long-lasting inflammatory conditions. Here, applying a systems biology approach, we propose an additional way for understanding the neurodegenerative component of the disease caused by chronic subclinical extravasation of hemoglobin, in combination with multiple other factors including, but not limited to, dysfunction of different cellular protective mechanisms against extracellular hemoglobin reactivity and oxidative stress. Moreover, such considerations could also shed light on and explain the higher susceptibility of MS patients to a wide range of cardiovascular disorders.

Determinants of iron accumulation in deep grey matter of multiple sclerosis patients

BACKGROUND

Iron accumulation in deep grey matter (GM) structures is a consistent finding in multiple sclerosis (MS) patients. This study focused on the identification of independent determinants of iron accumulation using R2* mapping.

SUBJECTS AND METHODS

Ninety-seven MS patients and 81 healthy controls were included in this multicentre study. R2* mapping was performed on 3T MRI systems. R2*in deep GM was corrected for age and was related to disease duration, disability, T2 lesion load and brain volume.

RESULTS

Compared to controls, R2* was increased in all deep GM regions of MS patients except the globus pallidus and the substantia nigra. R2* increase was most pronounced in the progressive stage of the disease and independently predicted by disease duration and disability. Reduced cortical volume was not associated with iron accumulation in the deep GM with the exception of the substantia nigra and the red nucleus. In lesions, R2* was inversely correlated with disease duration and higher total lesion load.

CONCLUSION

Iron accumulation in deep GM of MS patients is most strongly and independently associated with duration and severity of the disease. Additional associations between cortical GM atrophy and deep GM iron accumulation appear to exist in a region specific manner.

Iron chelation and multiple sclerosis

Histochemical and MRI studies have demonstrated that MS (multiple sclerosis) patients have abnormal deposition of iron in both gray and white matter structures. Data is emerging indicating that this iron could partake in pathogenesis by various mechanisms, e.g., promoting the production of reactive oxygen species and enhancing the production of proinflammatory cytokines. Iron chelation therapy could be a viable strategy to block iron-related pathological events or it can confer cellular protection by stabilizing hypoxia inducible factor 1α, a transcription factor that normally responds to hypoxic conditions. Iron chelation has been shown to protect against disease progression and/or limit iron accumulation in some neurological disorders or their experimental models. Data from studies that administered a chelator to animals with experimental autoimmune encephalomyelitis, a model of MS, support the rationale for examining this treatment approach in MS. Preliminary clinical studies have been performed in MS patients using deferoxamine. Although some side effects were observed, the large majority of patients were able to tolerate the arduous administration regimen, i.e., 6-8 h of subcutaneous infusion, and all side effects resolved upon discontinuation of treatment. Importantly, these preliminary studies did not identify a disqualifying event for this experimental approach. More recently developed chelators, deferasirox and deferiprone, are more desirable for possible use in MS given their oral administration, and importantly, deferiprone can cross the blood-brain barrier. However, experiences from other conditions indicate that the potential for adverse events during chelation therapy necessitates close patient monitoring and a carefully considered administration regimen.

Gray matters in multiple sclerosis: cognitive impairment and structural MRI

Multiple sclerosis (MS) is an immune-mediated disease affecting central nervous system (CNS). Although MS is classically considered a white matter (WM) disease, the involvement of gray matter (GM) in the pathogenic process has been confirmed by pathology studies and MRI studies. Impairment of cognitive domains such as memory, mental processing speed, attention, and executive function can occur from the early stage of the disease and tends to worsen over time, despite stable physical symptoms. WM demyelination is moderately correlated with CI, suggesting that probably WM abnormalities alone cannot fully explain the extent of clinical symptoms in MS, including CI. Several MRI techniques have shown the involvement of GM in MS and the association between GM damage, physical disability, and CI. The aim of this review is to provide an overview of CI and GM damage assessed by structural brain MRI.

Iron accumulation in multiple sclerosis: an early pathogenic event

Iron has been shown to accumulate in deep gray matter structures in many forms of multiple sclerosis (MS), but detecting its presence early in the disease course (e.g., clinically isolated syndrome [CIS]) has been less clear. Here, we review a recent study where MRI scanning at 7 T together with susceptibility mapping was performed to assess iron deposition in CIS and control subjects. Susceptibility indicative of iron deposition was found to be increased in the globus pallidus, caudate, putamen and pulvinar of CIS patients compared with controls. The findings suggest that iron deposition is a pathological change that occurs early in the development of MS. Identifying the mechanisms of iron accumulation and determining whether iron promotes pathogenesis in MS are important areas of future research.

Increased deep gray matter iron is present in clinically isolated syndromes

OBJECTIVE

Abnormal iron accumulation in MS has been known for decades, however it remains to be established whether iron reflects a cause or epiphenomenon of pathology. The objective of the present study is to determine if iron is increased in the brains of patients with clinically isolated syndromes (CIS) suggestive of early MS.

METHODS

Twenty-two patients with a CIS and 16 age- and sex-matched controls underwent 3T MRI studies. Differences in R2*, a metric of iron concentration, were assessed for all voxels throughout the brain. Similar clusters of significant differences were grouped, wherein mean R2* was regressed against a number of parameters, including extended disability status scale (EDSS), age, disease duration, and internal jugular vein (IJV) cross-sectional area (CSA), as measured from magnetic resonance time-of-flight venograms.

RESULTS

Patients had significantly increased R2* in globus pallidus, thalamus, right pulvinar, and cortical areas. Thalamic R2* correlated positively with EDSS. Decreased white matter R2* was detected at various positions in the patient group average. No correlations were found between any changes in R2* and IJV CSA.

INTERPRETATION

Iron is increased in CIS in deep gray matter, suggesting this iron accumulation, well-known in definite MS, occurs early in the disease course. Increases in thalamic iron are associated with worsened clinical status. Decreased white matter R2* may be interpreted as diffuse damage to normal appearing white matter, not often reported in CIS. Observations do not support a role for venous abnormalities in either iron accumulation or white matter damage.

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.

Brain iron accumulation in aging and neurodegenerative disorders

Over the decades, various studies have established an association between accumulation of iron and both aging and neurodegenerative disorders such as Alzheimer's disease and Parkinson's disease. Excess levels of iron can lead to increased oxidative stress through Fenton chemistry, and depletion of iron can similarly have deleterious effects. In addition, metal ions are known to be involved in both Alzheimer's disease and Parkinson's disease protein aggregation. Metal ion chelators have been extensively investigated in preclinical models, and may prove to be appropriate for modulating brain iron levels in age-related neurodegenerative disorders. Investigating age-related iron deposition is vital, and can possibly aid in determining at-risk groups and diagnosing neurodegenerative diseases at an early stage. Novel imaging methods have enabled researchers to examine iron deposition in vivo, and offer a noninvasive method of monitoring the progression of accumulation, and possible therapeutic effects of chelating compounds.

Visualizing iron in multiple sclerosis

Magnetic resonance imaging (MRI) protocols that are designed to be sensitive to iron typically take advantage of (1) iron effects on the relaxation of water protons and/or (2) iron-induced local magnetic field susceptibility changes. Increasing evidence sustains the notion that imaging iron in brain of patients with multiple sclerosis (MS) may add some specificity toward the identification of the disease pathology. The present review summarizes currently reported in vivo and post mortem MRI evidence of (1) iron detection in white matter and gray matter of MS brains, (2) pathological and physiological correlates of iron as disclosed by imaging and (3) relations between iron accumulation and disease progression as measured by clinical metrics.

The thalamus and multiple sclerosis: modern views on pathologic, imaging, and clinical aspects

The paired thalamic nuclei are gray matter (GM) structures on both sides of the third ventricle that play major roles in cortical activation, relaying sensory information to the higher cortical centers that influence cognition. Multiple sclerosis (MS) is an immune-mediated disease of the human CNS that affects both the white matter (WM) and GM. A number of clinical observations as well as recent neuropathologic and neuroimaging studies have clearly demonstrated extensive involvement of the thalamus, basal ganglia, and neocortex in patients with MS. Modern MRI techniques permit visualization of GM lesions and measurement of atrophy. These contemporary methods have fundamentally altered our understanding of the pathophysiologic nature of MS. Evidence confirms the contention that GM injury can be detected in the earliest phases of MS, and that iron deposition and atrophy of deep gray nuclei are closely related to the magnitude of inflammation. Extensive involvement of GM, and particularly of the thalamus, is associated with a wide range of clinical manifestations including cognitive decline, motor deficits, fatigue, painful syndromes, and ocular motility disturbances in patients with MS. In this review, we characterize the neuropathologic, neuroimaging, and clinical features of thalamic involvement in MS. Further, we underscore the contention that neuropathologic and neuroimaging correlative investigations of thalamic derangements in MS may elucidate not heretofore considered pathobiological underpinnings germane to understanding the ontogeny, magnitude, and progression of the disease process.

Quantitative susceptibility mapping in multiple sclerosis

PURPOSE

To apply quantitative susceptibility mapping (QSM) in the basal ganglia of patients with multiple sclerosis (MS) and relate the findings to R2* mapping with regard to the sensitivity for clinical and morphologic measures of disease severity.

MATERIALS AND METHODS

The local ethics committee approved this study, and all subjects gave written informed consent. Sixty-eight patients (26 with clinically isolated syndrome, 42 with relapsing-remitting MS) and 23 control subjects underwent 3-T magnetic resonance (MR) imaging. Susceptibility and R2* maps were reconstructed from the same three-dimensional multiecho spoiled gradient-echo sequence. Mean susceptibilities and R2* rates were measured in the basal ganglia and were compared between different phenotypes of the disease (clinically isolated syndrome, MS) and the control subjects by using analysis of variance, and regressing analysis was used to identify independent predictors.

RESULTS

Compared with control subjects, patients with MS and clinically isolated syndrome had increased (more paramagnetic) magnetic susceptibilities in the basal ganglia. R2* mapping proved less sensitive than QSM regarding group differences. The strongest predictor of magnetic susceptibility was age. Susceptibilities were higher with increasing neurologic deficits (r = 0.34, P < .01) and lower with normalized volumes of gray matter (r = -0.35, P < .005) and the cortex (r = -0.35, P < .005).

CONCLUSION

QSM provides superior sensitivity over R2* mapping in the detection of MS-related tissue changes in the basal ganglia. With QSM but not with R2* mapping, changes were already observed in patients with clinically isolated syndrome, which suggests that QSM can serve as a sensitive measure at the earliest stage of the disease.