A characterization of cardiac-induced noise in R2 * maps of the brain

PURPOSE

Cardiac pulsation increases the noise level in brain maps of the transverse relaxation rate R2 *. Cardiac-induced noise is challenging to mitigate during the acquisition of R2 * mapping data because its characteristics are unknown. In this work, we aim to characterize cardiac-induced noise in brain maps of the MRI parameter R2 *.

METHODS

We designed a sampling strategy to acquire multi-echo 3D data in 12 intervals of the cardiac cycle, monitored with a fingertip pulse-oximeter. We measured the amplitude of cardiac-induced noise in this data and assessed the effect of cardiac pulsation on R2 * maps computed across echoes. The area of k-space that contains most of the cardiac-induced noise in R2 * maps was then identified. Based on these characteristics, we introduced a tentative sampling strategy that aims to mitigate cardiac-induced noise in R2 * maps of the brain.

RESULTS

In inferior brain regions, cardiac pulsation accounts for R2 * variations of up to 3 s-1 across the cardiac cycle (i.e., ∼35% of the overall variability). Cardiac-induced fluctuations occur throughout the cardiac cycle, with a reduced intensity during the first quarter of the cycle. A total of 50% to 60% of the overall cardiac-induced noise is localized near the k-space center (k < 0.074 mm-1 ). The tentative cardiac noise mitigation strategy reduced the variability of R2 * maps across repetitions by 11% in the brainstem and 6% across the whole brain.

CONCLUSION

We provide a characterization of cardiac-induced noise in brain R2 * maps that can be used as a basis for the design of mitigation strategies during data acquisition.

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.

Iron in multiple sclerosis - Neuropathology, immunology, and real-world considerations

Iron is an essential element involved in a multitude of bodily processes. It is tightly regulated, as elevated deposition in tissues is associated with diseases such as multiple sclerosis (MS). Iron accumulation in the central nervous system (CNS) of MS patients is linked to neurotoxicity through mechanisms including oxidative stress, glutamate excitotoxicity, misfolding of proteins, and ferroptosis. In the past decade, the combination of MRI and histopathology has enhanced our understanding of iron deposition in MS pathophysiology, including in the pro-inflammatory and neurotoxicity of iron-laden rims of chronic active lesions. In this regard, iron accumulation may not only have an impact on different CNS-resident cells but may also promote the innate and adaptive immune dysfunctions in MS. Although there are discordant results, most studies indicate lower levels of iron but higher amounts of the iron storage molecule ferritin in the circulation of people with MS. Considering the importance of iron, there is a need for evidence-guided recommendation for dietary intake in people living with MS. Potential novel therapeutic approaches include the regulation of iron levels using next generation iron chelators, as well as therapies to interfere with toxic consequences of iron overload including antioxidants in MS.

High serum neurofilament light chain levels correlate with brain atrophy and physical disability in multiple sclerosis

BACKGROUND AND PURPOSE

Serum neurofilament light chain (sNfL) is a promising biomarker of neuroaxonal damage in persons with multiple sclerosis (pwMS). In cross-sectional studies, sNfL has been associated with disease activity and brain magnetic resonance imaging (MRI) changes; however, it is still unclear to what extent in particular high sNfL levels impact on subsequent disease evolution.

METHODS

sNfL was quantified by an ultrasensitive single molecule array (Simoa) in 199 pwMS (median age = 34.2 years, 64.3% female) and 49 controls. All pwMS underwent 3-T MRI to assess global and compartmental normalized brain volumes, T2-lesion load, and cortical mean thickness. Follow-up data and serum samples were available in 144 pwMS (median follow-up time = 3.8 years). Linear and binary logistic models were used to estimate the independent contribution of sNfL for changes in MRI and Expanded Disability Status Scale (EDSS). Age-corrected sNfL z-scores from a normative database of healthy controls were used for sensitivity analyses.

RESULTS

High sNfL levels at baseline were associated with atrophy measures of the whole brain (standardized beta coefficient βj = -0.352, p < 0.001), white matter (βj = -0.229, p = 0.007), thalamus (βj = -0.372, p = 0.004), and putamen (βj = -1.687, p = 0.012). pwMS with high levels of sNfL at baseline and follow-up had a greater risk of EDSS worsening (p = 0.007).

CONCLUSIONS

Already single time point elevation of sNfL has a distinct effect on brain volume changes over a short-term period, and repeated high levels of sNfL indicate accumulating physical disability. Serial assessment of sNfL may provide added value in the clinical management of pwMS.

Iron deposition in multiple sclerosis: overall load or distribution alteration?

Background

Though abnormal iron deposition has been reported in specific brain regions in multiple sclerosis (MS), no data exist about whether the overall quantity of iron in the brain is altered or not. We aimed to determine whether the noted aberrant iron deposition in MS brains was a problem of overall load or regional distribution in a cohort of MS patients.

Methods

An experienced neuroradiologist, a radiology software engineer, and four neurologists analysed data from quantitative susceptibility maps reconstructed from 3-T magnetic resonance brain images of 30 MS patients and 15 age- and sex-matched healthy controls. Global brain iron load was calculated, and the regional iron concentrations were assessed in 1,000 regions of interest placed in MS lesions in different locations, normal appearing white matter, thalami, and basal ganglia.

Results

Global brain iron load was comparable between patients and controls after adjustment for volume (p = 0.660), whereas the regional iron concentrations were significantly different in patients than in control (p ≤ 0.031). There was no significant correlation between global iron load and clinical parameters, whereas regional iron concentrations correlated with patients’ age, disease duration, and disability grade (p ≤ 0.039).

Conclusions

The aberrant iron deposition noted in MS seems to be a problem of regional distribution rather than an altered global brain iron load.

Supplementary Information

The online version contains supplementary material available at 10.1186/s41747-022-00279-9.

Brain iron assessment in patients with First-episode schizophrenia using quantitative susceptibility mapping

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Patients with first-episode schizophrenia had significantly decreased QSM values in the bilateral substantia nigra, left red nucleus and left thalamus.

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Patients with first-episode schizophrenia had significantly increased regional volumes in the bilateral putamen and bilateral substantia nigra.

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QSM provides superior sensitivity over R₂* mapping in the evaluation of schizophrenia-related iron alterations.

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QSM values in regions that showed intergroup differences did not exhibited significant correlations with PANSS scores.

Purpose

Decreased serum ferritin level was recently found in schizophrenia. Whether the brain iron concentration in schizophrenia exists abnormality is of research significance. Quantitative susceptibility mapping (QSM) was used in this study to assess brain iron changes in the grey matter nuclei of patients with first-episode schizophrenia.

Methods

The local ethics committee approved the study, and all subjects gave written informed consent. Thirty patients with first-episode schizophrenia and 30 age and gender-matched healthy controls were included in this study. QSM and effective transverse relaxation rate (R₂*) maps were reconstructed from a three-dimensional multi-echo gradient-echo sequence. The inter-group differences of regional QSM values, R₂* values and volumes were calculated in the grey matter nuclei, including bilateral caudate nucleus, putamen, globus pallidus, substantia nigra, red nucleus, and thalamus. The diagnostic performance of QSM and R₂* was evaluated using receiver operating characteristic curve. The correlations between regional iron variations and clinical PANSS (Positive and Negative Syndrome Scale) scores were assessed using partial correlation analysis.

Results

Compared to healthy controls, patients with first-episode schizophrenia had significantly decreased QSM values (less paramagnetic) in the bilateral substantia nigra, left red nucleus and left thalamus (p < 0.05, FDR correction). QSM proved more sensitive than R₂* regarding inter-group differences. The highest diagnostic performance for first-episode schizophrenia was observed in QSM value of the left substantia nigra (area under the curve, AUC = 0.718, p = 0.004). Regional volumes of bilateral putamen and bilateral substantia nigra were increased (p < 0.05, FDR correction) in first-episode schizophrenia. However, both QSM and R₂* values did not show significant correlations with PANSS scores (p > 0.05).

Conclusion

This study reveals decreased iron concentration in grey matter nuclei of patients with first-episode schizophrenia. QSM provides superior sensitivity over R₂* in the evaluation of schizophrenia-related brain iron changes. It demonstrated that QSM may be a potential biomarker for further understanding the pathophysiological mechanism of first-episode schizophrenia.

Positivity of oligoclonal bands in the cerebrospinal fluid predisposed to metabolic changes and rearrangement of inhibitory/excitatory neurotransmitters in subcortical brain structures in multiple sclerosis

BACKGROUND

The latest diagnostic criteria for multiple sclerosis (MS) have revitalized the role of oligoclonal bands synthesis in the cerebrospinal fluid (CSF-OCB). This study identifies predictors of CSF-OCB-positivity among in vivo metabolic markers in the subcortical gray/white matter in MS patients after their first episode (CIS) and in patients with relapsing-remitting course (RRMS).

METHODS

The study enrolled 13 CIS and 23 RRMS patients. Metabolism was evaluated using Mescher-Garwood-edited proton-magnetic resonance spectroscopy on a 3T MR scanner. In addition to N-acetyl-aspartate (tNAA), myoinositol (mIns), and choline- and creatine compounds (tCho, tCr) were also evaluated γ-aminobutyric acid (GABA) and glutamate-glutamine (Glx) ratios.

RESULTS

CSF-OCB-positivity was found in 76.9% of CIS and 78.2% of RRMS patients. GABA and Glx ratios in putamen and corpus callosum strongly determined CSF-OCB-positive CIS patients. Other essential predictors of CSF-OCB-positive CIS were mIns and Glx ratios in the putamen, and tCho/tNAA in the corpus callosum. In RRMS, GABA ratios in the right thalamus and Glx ratios in the left hippocampus strongly predicted CSF-OCB-positive patients. tCho/tNAA and tNAA/tCr in the left hippocampus were also identified as essential predictors of CSF-OCB-positive RRMS patients.

CONCLUSION

This is the first in vivo evidence of GABA-Glx rearrangement in CSF-OCB-positive patients since its early stages of MS.

Novel insights into ferroptosis: Implications for age-related diseases

Rapid increase in aging populations is an urgent problem because older adults are more likely to suffer from disabilities and age-related diseases (ARDs), burdening healthcare systems and society in general. ARDs are characterized by the progressive deterioration of tissues and organs over time, eventually leading to tissue and organ failure. To date, there are no effective interventions to prevent the progression of ARDs. Hence, there is an urgent need for new treatment strategies. Ferroptosis, an iron-dependent cell death, is linked to normal development and homeostasis. Accumulating evidence, however, has highlighted crucial roles for ferroptosis in ARDs, including neurodegenerative and cardiovascular diseases. In this review, we a) summarize initiation, regulatory mechanisms, and molecular signaling pathways involved in ferroptosis, b) discuss the direct and indirect involvement of the activation and/or inhibition of ferroptosis in the pathogenesis of some important diseases, and c) highlight therapeutic targets relevant for ARDs.

In vivo imaging of chronic active lesions in multiple sclerosis

New clinical activity in multiple sclerosis (MS) is often accompanied by acute inflammation which subsides. However, there is growing evidence that a substantial proportion of lesions remain active well beyond the acute phase. Chronic active lesions are most frequently found in progressive MS and are characterised by a border of inflammation associated with iron-enriched cells, leading to ongoing tissue injury. Identifying imaging markers for chronic active lesions in vivo are thus a major research goal. We reviewed the literature on imaging of chronic active lesion in MS, focussing on ‘slowly expanding lesions’ (SELs), detected by volumetric longitudinal magnetic resonance imaging (MRI) and ‘rim-positive’ lesions, identified by susceptibility iron-sensitive MRI. Both SELs and rim-positive lesions have been found to be prognostically relevant to future disability. Little is known about the co-occurrence of rims around SELs and their inter-relationship with other emerging techniques such as dynamic contrast enhancement (DCE) and positron emission tomography (PET).

Simultaneous time of flight-MRA and T2* imaging for cerebrovascular MRI

PURPOSE

3D multi-echo gradient-recalled echo (ME-GRE) can simultaneously generate time-of-flight magnetic resonance angiography (pTOF) in addition to T2*-based susceptibility-weighted images (SWI). We assessed the clinical performance of pTOF generated from a 3D ME-GRE acquisition compared with conventional TOF-MRA (cTOF).

METHODS

Eighty consecutive children were retrospectively identified who obtained 3D ME-GRE alongside cTOF. Two blinded readers independently assessed pTOF derived from 3D ME-GRE and compared them with cTOF. A 5-point Likert scale was used to rank lesion conspicuity and to assess for diagnostic confidence.

RESULTS

Across 80 pediatric neurovascular pathologies, a similar number of lesions were reported on pTOF and cTOF (43-40%, respectively, p > 0.05). Rating of lesion conspicuity was higher with cTOF (4.5 ± 1.0) as compared with pTOF (4.0 ± 0.7), but this was not significantly different (p = 0.06). Diagnostic confidence was rated higher with cTOF (4.8 ± 0.5) than that of pTOF (3.7 ± 0.6; p < 0.001). Overall, the inter-rater agreement between two readers for lesion count on pTOF was classified as almost perfect (κ = 0.98, 96% CI 0.8-1.0).

CONCLUSIONS

In this study, TOF-MRA simultaneously generated in addition to SWI from 3D MR-GRE can serve as a diagnostic adjunct, particularly for proximal vessel disease and when conventional TOF-MRA images are absent.

The Role of Iron Metabolism in Fatigue, Depression, and Quality of Life in Multiple Sclerosis Patients

Multiple sclerosis (MS) is a chronic inflammatory disease of autoimmune origin for which there is currently no available cure. In the course of MS, next to neurological disorders, patients often present with chronic fatigue syndrome and depressive disorders, which impact on their daily function and quality of life. The aim of study was to analyse the relationship between serum parameters of iron metabolism and the severity of fatigue, depressive symptoms, and quality of life in MS patients.

METHODS

The study sample consisted of 90 people with a diagnosis of multiple sclerosis, age range 19-67 years, whose functional status evaluated using the Expanded Disability Status Scale in 90% of the participants did not exceed 3.5 points. Venous blood samples were collected for blood cell count determination and for the purposes of obtaining serum analysed for the concentrations of iron, ferritin, transferrin, transferrin saturation, unsaturated iron binding capacity (UIBC), and total iron binding capacity (TIBC). The participants were also evaluated according to the Fatigue Severity Scale, Beck Depression Inventory, and Functional Assessment of Multiple Sclerosis.

RESULTS

Ferritin levels were significantly correlated with the severity of depressive symptoms (r = -0.22; p = 0.04) and quality of life assessment (r = 0.22; p = 0.04) in the MS patients. Moreover, the severity of fatigue and depressive symptoms was significantly linked to a deterioration in quality of life.

CONCLUSIONS

Ferritin deficiency in MS patients is associated with an exacerbation of depressive disorders and a decline in quality of life. Symptoms of fatigue in MS patients are inversely proportional to mood and quality of life.

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.

Serum hepcidin levels in multiple sclerosis

Background

Brain iron accumulation is associated with multiple sclerosis (MS). Hepcidin is the master regulator of iron homeostasis and distribution. Dysregulation of hepcidin is a feature of different chronic inflammatory diseases but has not been investigated in MS so far.

Objective

The aim of this study was to determine serum hepcidin levels of MS patients and healthy volunteers serving as controls and to investigate possible relations between hepcidin levels, disease activity and disease course.

Methods

In a cross-sectional design, we measured serum hepcidin levels in 71 MS patients and 16 healthy controls (HC). MS patients were sub-grouped in active relapsing–remitting MS (aRRMS), inactive (i)RRMS, active progressive MS (aPMS) and inactive (i)PMS. Blood parameters were measured by standard laboratory methods.

Results

Median hepcidin levels were 26.9 ng/ml (confidence interval (CI) 22.8; 30.9) in MS and 17.3 ng/ml (CI 12.8; 23.4) in HC with significant age and sex effects. Hepcidin correlates were in line with hepcidin as an indicator of iron stores. After correction for age and sex, hepcidin was neither associated with MS subgroups nor degree of disability and occurrence of relapses.

Conclusions

Serum hepcidin levels are not associated with disease activity and disease course in MS.

Multiparameter MRI quantification of microstructural tissue alterations in multiple sclerosis

Objectives

Conventional MRI is not sensitive to many pathological processes underpinning multiple sclerosis (MS) ongoing in normal appearing brain tissue (NABT). Quantitative MRI (qMRI) and a multiparameter mapping (MPM) protocol are used to simultaneously quantify magnetization transfer (MT) saturation, transverse relaxation rate R2* (1/T2*) and longitudinal relaxation rate R1 (1/T1), and assess differences in NABT microstructure between MS patients and healthy controls (HC).

Methods

This prospective cross-sectional study involves 36 MS patients (21 females, 15 males; age range 22–63 years; 15 relapsing-remitting MS - RRMS; 21 primary or secondary progressive MS - PMS) and 36 age-matched HC (20 females, 16 males); age range 21–61 years). The qMRI maps are computed and segmented in lesions and 3 normal appearing cerebral tissue classes: normal appearing cortical grey matter (NACGM), normal appearing deep grey matter (NADGM), normal appearing white matter (NAWM). Individual median values are extracted for each tissue class and MR parameter. MANOVAs and stepwise regressions assess differences between patients and HC.

Results

MS patients are characterized by a decrease in MT, R2* and R1 within NACGM (p < .0001) and NAWM (p < .0001). In NADGM, MT decreases (p < .0001) but R2* and R1 remain normal. These observations tend to be more pronounced in PMS. Quantitative MRI parameters are independent predictors of clinical status: EDSS is significantly related to R1 in NACGM and R2* in NADGM; the latter also predicts motor score. Cognitive score is best predicted by MT parameter within lesions.

Conclusions

Multiparametric data of brain microstructure concord with the literature, predict clinical performance and suggest a diffuse reduction in myelin and/or iron content within NABT of MS patients.

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We revisit microstructural alterations of NABT in MS patients by simultaneously quantifying three MRI parameters.

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Data suggest reduction of MT/R2*/R1 in NABT of MS patients, suggesting a reduction in myelin and/or iron content.

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Quantitative MRI parameters in NABT are independent predictors of clinical status.

Iron deposition quantification: Applications in the brain and liver

Iron has long been implicated in many neurological and other organ diseases. It is known that over and above the normal increases in iron with age, in certain diseases there is an excessive iron accumulation in the brain and liver. MRI is a noninvasive means by which to image the various structures in the brain in three dimensions and quantify iron over the volume of the object of interest. The quantification of iron can provide information about the severity of iron-related diseases as well as quantify changes in iron for patient follow-up and treatment monitoring. This article provides an overview of current MRI-based methods for iron quantification, specifically for the brain and liver, including: signal intensity ratio, R₂ , R2*, R2', phase, susceptibility weighted imaging and quantitative susceptibility mapping (QSM). Although there are numerous approaches to measuring iron, R₂ and R2* are currently preferred methods in imaging the liver and QSM has become the preferred approach for imaging iron in the brain.

LEVEL OF EVIDENCE

5 Technical Efficacy: Stage 5 J. Magn. Reson. Imaging 2018. J. MAGN. RESON. IMAGING 2018;48:301-317.

Magnetic Resonance Imaging in Multiple Sclerosis

Since its technical development in the early 1980s, magnetic resonance imaging (MRI) has quickly been adopted as an essential tool in supporting the diagnosis, longitudinal monitoring, evaluation of therapeutic response, and scientific investigations in multiple sclerosis (MS). The clinical usage of MRI has increased in parallel with technical innovations in the technique itself; the widespread adoption of clinically routine MRI at 1.5T has allowed sensitive qualitative and quantitative assessments of macroscopic central nervous system (CNS) inflammatory demyelinating lesions and tissue atrophy. However, conventional MRI lesion measures lack specificity for the underlying MS pathology and only weakly correlate with clinical status. Higher field strength units and newer, advanced MRI techniques offer increased sensitivity and specificity in the detection of disease activity and disease severity. This review summarizes the current status and future prospects regarding the role of MRI in the characterization of MS-related brain and spinal cord involvement.

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.

Thalamic Iron Differentiates Primary-Progressive and Relapsing-Remitting Multiple Sclerosis

BACKGROUND AND PURPOSE

Potential differences between primary progressive and relapsing remitting multiple sclerosis are the subject of ongoing controversial discussions. The aim of this work was to determine whether and how primary-progressive and relapsing-remitting multiple sclerosis subtypes differ regarding conventional MR imaging parameters, cerebral iron deposits, and their association with clinical status.

MATERIALS AND METHODS

We analyzed 24 patients with primary-progressive MS, 80 with relapsing-remitting MS, and 20 healthy controls with 1.5T MR imaging for assessment of the conventional quantitative parameters: T2 lesion load, T1 lesion load, brain parenchymal fraction, and corpus callosum volume. Quantitative susceptibility mapping was performed to estimate iron concentration in the deep gray matter.

RESULTS

Decreased susceptibility within the thalamus in relapsing-remitting MS compared with primary-progressive MS was the only significant MR imaging difference between these MS subtypes. In the relapsing-remitting MS subgroup, the Expanded Disability Status Scale score was positively associated with conventional parameters reflecting white matter lesions and brain atrophy and with iron in the putamen and caudate nucleus. A positive association with putaminal iron and the Expanded Disability Status Scale score was found in primary-progressive MS.

CONCLUSIONS

Susceptibility in the thalamus might provide additional support for the differentiation between primary-progressive and relapsing-remitting MS. That the Expanded Disability Status Scale score was associated with conventional MR imaging parameters and iron concentrations in several deep gray matter regions in relapsing-remitting MS, while only a weak association with putaminal iron was observed in primary-progressive MS suggests different driving forces of disability in these MS subtypes.

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.

Cognitive Implications of Deep Gray Matter Iron in Multiple Sclerosis

BACKGROUND AND PURPOSE

Deep gray matter iron accumulation is increasingly recognized in association with multiple sclerosis and can be measured in vivo with MR imaging. The cognitive implications of this pathology are not well-understood, especially vis-à-vis deep gray matter atrophy. Our aim was to investigate the relationships between cognition and deep gray matter iron in MS by using 2 MR imaging-based iron-susceptibility measures.

MATERIALS AND METHODS

Forty patients with multiple sclerosis (relapsing-remitting, n = 16; progressive, n = 24) and 27 healthy controls were imaged at 4.7T by using the transverse relaxation rate and quantitative susceptibility mapping. The transverse relaxation rate and quantitative susceptibility mapping values and volumes (atrophy) of the caudate, putamen, globus pallidus, and thalamus were determined by multiatlas segmentation. Cognition was assessed with the Brief Repeatable Battery of Neuropsychological Tests. Relationships between cognition and deep gray matter iron were examined by hierarchic regressions.

RESULTS

Compared with controls, patients showed reduced memory (P < .001) and processing speed (P = .02) and smaller putamen (P < .001), globus pallidus (P = .002), and thalamic volumes (P < .001). Quantitative susceptibility mapping values were increased in patients compared with controls in the putamen (P = .003) and globus pallidus (P = .003). In patients only, thalamus (P < .001) and putamen (P = .04) volumes were related to cognitive performance. After we controlled for volume effects, quantitative susceptibility mapping values in the globus pallidus (P = .03; trend for transverse relaxation rate, P = .10) were still related to cognition.

CONCLUSIONS

Quantitative susceptibility mapping was more sensitive compared with the transverse relaxation rate in detecting deep gray matter iron accumulation in the current multiple sclerosis cohort. Atrophy and iron accumulation in deep gray matter both have negative but separable relationships to cognition in multiple sclerosis.

New rapid, accurate T2 quantification detects pathology in normal-appearing brain regions of relapsing-remitting MS patients

Introduction

Quantitative T₂ mapping may provide an objective biomarker for occult nervous tissue pathology in relapsing-remitting multiple sclerosis (RRMS). We applied a novel echo modulation curve (EMC) algorithm to identify T₂ changes in normal-appearing brain regions of subjects with RRMS (N = 27) compared to age-matched controls (N = 38).

Methods

The EMC algorithm uses Bloch simulations to model T₂ decay curves in multi-spin-echo MRI sequences, independent of scanner, and scan-settings. T₂ values were extracted from normal-appearing white and gray matter brain regions using both expert manual regions-of-interest and user-independent FreeSurfer segmentation.

Results

Compared to conventional exponential T₂ modeling, EMC fitting provided more accurate estimations of T₂ with less variance across scans, MRI systems, and healthy individuals. Thalamic T₂ was increased 8.5% in RRMS subjects (p < 0.001) and could be used to discriminate RRMS from healthy controls well (AUC = 0.913). Manual segmentation detected both statistically significant increases (corpus callosum & temporal stem) and decreases (posterior limb internal capsule) in T₂ associated with RRMS diagnosis (all p < 0.05). In healthy controls, we also observed statistically significant T₂ differences for different white and gray matter structures.

Conclusions

The EMC algorithm precisely characterizes T₂ values, and is able to detect subtle T₂ changes in normal-appearing brain regions of RRMS patients. These presumably capture both axon and myelin changes from inflammation and neurodegeneration. Further, T₂ variations between different brain regions of healthy controls may correlate with distinct nervous tissue environments that differ from one another at a mesoscopic length-scale.

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EMC technique provides accurate and scanner-invariant T₂ mapping in MS subjects.

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Thalamus T₂ differences distinguish relapsing-remitting MS subjects from controls.

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Normal-appearing brain regions demonstrate T₂ changes in MS patients compared to controls.

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T₂ values reflect anatomic and function-specific differences in healthy controls.

Iron Mapping in Multiple Sclerosis

Increased iron deposition in cerebral deep gray matter has been considered a global marker for neurodegeneration in multiple sclerosis (MS); it scales with disease duration and severity. Iron accumulation in white matter and MS lesions might be more directly related to disease activity and has been discussed as a contributor to the inflammatory and neurodegenerative cascade. New insights into iron and MS are expected from MR imaging. We discuss findings from MR iron mapping proposed. Because of the confounding magnetic properties of myelin, iron mapping in white matter remains an unresolved issue.

Prognostic value of free light chains lambda and kappa in early multiple sclerosis

Background:

Cerebrospinal fluid (CSF) immunoglobulin free light chains (FLC) have been suggested as quantitative alternative to oligoclonal bands (OCB) in the diagnosis of multiple sclerosis (MS). However, little is known on their role in predicting clinical and paraclinical disease progression, particularly in early stages.

Objective:

To assess the prognostic value of FLC in OCB-positive patients with clinically isolated syndrome (CIS) suggestive of MS and early MS.

Methods:

We determined FLC kappa (KFLC) and lambda (LFLC) in CSF and serum by nephelometry in 61 patients (CIS ( n = 48), relapsing-remitting multiple sclerosis ( n = 13)) and 60 non-inflammatory neurological controls. Median clinical follow-up time in CIS was 4.8 years (interquartile range (IQR), 1.5–6.5 years). Patients underwent 3T magnetic resonance imaging (MRI) at baseline and follow-up (median time interval, 2.2 years; IQR, 1.0–3.7 years) to determine T2 lesion load (T2LL) and percent brain volume change (PBVC).

Results:

CSF FLC were significantly increased in CIS/MS compared to controls (all p < 0.001). A lower KFLC/LFLC CSF ratio was associated with CIS-clinically definite multiple sclerosis (CDMS) conversion (hazard ratio (HR) = 2.89; 95% confidence interval (CI) = 1.17–7.14; p < 0.05). No correlations were found for FLC variables with T2LL or PBVC.

Conclusion:

Our study confirms increased intrathecal synthesis of FLC in CIS/MS which supports their diagnostic contribution. The KFLC/LFLC CSF ratio appears to have a prognostic value in CIS beyond OCB.

Multiple Sclerosis - A Vascular Etiology?

From the earliest pathological studies the perivenular localization of the demyelination in multiple sclerosis (MS) has been observed. It has recently been suggested that obstructions to venous flow or inadequate venous valves in the great veins in the neck, thorax and abdomen can cause damaging backflow into the cerebral and spinal cord circulations. Paolo Zamboni and colleagues have demonstrated abnormal venous circulation in some multiple sclerosis patients using non-invasive sonography and invasive venography. Furthermore, they have obtained apparent clinical improvement or stabilization by endovascular ballooning of points of obstruction in the great veins in some, at least temporarily. If non-invasive observations by others validate their initial observations of a significantly increased prevalence of venous obstructions in MS then trials of angioplasty/stenting would be justified in selected cases in view of the biological plausibility of the concept.

Cerebrospinal fluid lipocalin 2 in patients with clinically isolated syndromes and early multiple sclerosis

Background:

Lipocalin 2 (LCN2) may be involved in the immunopathogenesis of multiple sclerosis (MS) and might further impact on iron homoeostasis. Brain iron accumulates in MS; however, the association to iron-related proteins is still unsolved.

Objective:

To investigate cerebrospinal fluid (CSF) and serum LCN2, transferrin (Trf) and ferritin in early MS in relation to disease evolution and longitudinal brain iron accumulation.

Methods:

We analysed CSF and serum LCN2 by enzyme-linked immunosorbent assay (ELISA) and Trf and ferritin by nephelometry in 55 patients (45 clinically isolated syndrome (CIS), 10 MS, median clinical follow-up 4.8 years) and 63 controls. In patients, we assessed sub-cortical grey matter iron by 3T magnetic resonance imaging (MRI) R2* relaxometry (median imaging follow-up 2.2 years).

Results:

Compared to controls serum ( p < 0.01), CSF ( p < 0.001) LCN2 and CSF Trf ( p < 0.001) levels were reduced in the patients. CSF LCN2 correlated with CSF Trf ( r = 0.5, p < 0.001). In clinically stable patients, CSF LCN2 levels correlated with basal ganglia iron accumulation ( r = 0.5, p < 0.05). In CIS, higher CSF LCN2 levels were associated with conversion to clinically definite MS ( p < 0.05).

Conclusion:

We demonstrate altered LCN2 regulation in early MS and provide first evidence for this to be possibly linked to both clinical MS activity and iron accumulation in the basal ganglia.

Differences in iron and manganese concentration may confound the measurement of myelin from R1 and R2 relaxation rates in studies of dysmyelination

A model of dysmyelination, the Long Evans Shaker (les) rat, was used to study the contribution of myelin to MR tissue properties in white matter. A large region of white matter was identified in the deep cerebellum and was used for measurements of the MR relaxation rate constants, R1  = 1/T1 and R2  = 1/T2 , at 7 T. In this study, R1 of the les deep cerebellar white matter was found to be 0.55 ± 0.08 s (-1) and R2 was found to be 15 ± 1 s(-1) , revealing significantly lower R1 and R2 in les white matter relative to wild-type (wt: R1  = 0.69 ± 0.05 s(-1) and R2  = 18 ± 1 s(-1) ). These deviated from the expected ΔR1 and ΔR2 values, given a complete lack of myelin in the les white matter, derived from the literature using values of myelin relaxivity, and we suspect that metals could play a significant role. The absolute concentrations of the paramagnetic transition metals iron (Fe) and manganese (Mn) were measured by a micro-synchrotron radiation X-ray fluorescence (μSRXRF) technique, with significantly greater Fe and Mn in les white matter than in wt (in units of μg [metal]/g [wet weight tissue]: les: Fe concentration,19 ± 1; Mn concentration, 0.71 ± 0.04; wt: Fe concentration,10 ± 1; Mn concentration, 0.47 ± 0.04). These changes in Fe and Mn could explain the deviations in R1 and R2 from the expected values in white matter. Although it was found that the influence of myelin still dominates R1 and R2 in wt rats, there were non-negligible changes in the contribution of the metals to relaxation. Although there are already problems with the estimation of myelin from R1 and R2 changes in disease models with pathology that also affects the relaxation rate constants, this study points to a specific pitfall in the estimation of changes in myelin in diseases or models with disrupted concentrations of paramagnetic transition metals. Copyright © 2016 John Wiley & Sons, Ltd.

Characterizing active and inactive brown adipose tissue in adult humans using PET-CT and MR imaging

Activated brown adipose tissue (BAT) plays an important role in thermogenesis and whole body metabolism in mammals. Positron emission tomography (PET)-computed tomography (CT) imaging has identified depots of BAT in adult humans, igniting scientific interest. The purpose of this study is to characterize both active and inactive supraclavicular BAT in adults and compare the values to those of subcutaneous white adipose tissue (WAT). We obtained [(18)F]fluorodeoxyglucose ([(18)F]FDG) PET-CT and magnetic resonance imaging (MRI) scans of 25 healthy adults. Unlike [(18)F]FDG PET, which can detect only active BAT, MRI is capable of detecting both active and inactive BAT. The MRI-derived fat signal fraction (FSF) of active BAT was significantly lower than that of inactive BAT (means ± SD; 60.2 ± 7.6 vs. 62.4 ± 6.8%, respectively). This change in tissue morphology was also reflected as a significant increase in Hounsfield units (HU; -69.4 ± 11.5 vs. -74.5 ± 9.7 HU, respectively). Additionally, the CT HU, MRI FSF, and MRI R2* values are significantly different between BAT and WAT, regardless of the activation status of BAT. To the best of our knowledge, this is the first study to quantify PET-CT and MRI FSF measurements and utilize a semiautomated algorithm to identify inactive and active BAT in the same adult subjects. Our findings support the use of these metrics to characterize and distinguish between BAT and WAT and lay the foundation for future MRI analysis with the hope that some day MRI-based delineation of BAT can stand on its own.

Magnetic Susceptibility from Quantitative Susceptibility Mapping Can Differentiate New Enhancing from Nonenhancing Multiple Sclerosis Lesions without Gadolinium Injection

BACKGROUND AND PURPOSE

Magnetic susceptibility values of multiple sclerosis lesions increase as they change from gadolinium-enhancing to nonenhancing. Can susceptibility values measured on quantitative susceptibility mapping without gadolinium injection be used to identify the status of lesion enhancement in surveillance MR imaging used to monitor patients with MS?

MATERIALS AND METHODS

In patients who had prior MR imaging and quantitative susceptibility mapping in a current MR imaging, new T2-weighted lesions were evaluated for enhancement on conventional T1-weighted imaging with gadolinium, and their susceptibility values were measured on quantitative susceptibility mapping. Receiver operating characteristic analysis was used to assess the diagnostic accuracy of using quantitative susceptibility mapping in distinguishing new gadolinium-enhancing from new nonenhancing lesions. A generalized estimating equation was used to assess differences in susceptibility values among lesion types.

RESULTS

In 54 patients, we identified 86 of 133 new lesions that were gadolinium-enhancing and had relative susceptibility values significantly lower than those of nonenhancing lesions (β = -17.2; 95% CI, -20.2 to -14.2; P < .0001). Using susceptibility values to discriminate enhancing from nonenhancing lesions, we performed receiver operating characteristic analysis and found that the area under the curve was 0.95 (95% CI, 0.92-0.99). Sensitivity was measured at 88.4%, and specificity, at 91.5%, with a cutoff value of 11.2 parts per billion for quantitative susceptibility mapping-measured susceptibility.

CONCLUSIONS

During routine MR imaging monitoring to detect new MS lesion activity, quantitative susceptibility mapping can be used without gadolinium injection for accurate identification of the BBB leakage status in new T2WI lesions.

Longitudinal change in magnetic susceptibility of new enhanced multiple sclerosis (MS) lesions measured on serial quantitative susceptibility mapping (QSM)

PURPOSE

To measure the longitudinal change in multiple sclerosis (MS) lesion susceptibility using quantitative susceptibility mapping (QSM).

MATERIALS AND METHODS

The study was approved by our Institutional Review Board. Longitudinal changes in quantitative susceptibility values of new enhanced-with-Gd MS lesions were measured at baseline magnetic resonance imaging (MRI) and on a follow-up MRI in 29 patients within 2 years using a 3D multiple echo gradient echo sequence on a 3T scanner. Paired t-test and the generalized estimating equations (GEE) model was used to analyze the longitudinal change.

RESULTS

Lesion susceptibility values relative to normal-appearing white matter (NAWM) changed from 3.61 ± 6.11 ppb when enhanced-with-Gd at the baseline MRI to 20.42 ± 10.23 ppb when not-enhanced-with-Gd at the follow-up MRI (P < 0.001).

CONCLUSION

MS lesion susceptibility value increases significantly as the lesion evolves from enhanced-with-Gd to not-enhanced-with-Gd, serving as a disease biomarker. J. Magn. Reson. Imaging 2016;44:426-432.

Iron in Multiple Sclerosis and Its Noninvasive Imaging with Quantitative Susceptibility Mapping

Iron is considered to play a key role in the development and progression of Multiple Sclerosis (MS). In particular, iron that accumulates in myeloid cells after the blood-brain barrier (BBB) seals may contribute to chronic inflammation, oxidative stress and eventually neurodegeneration. Magnetic resonance imaging (MRI) is a well-established tool for the non-invasive study of MS. In recent years, an advanced MRI method, quantitative susceptibility mapping (QSM), has made it possible to study brain iron through in vivo imaging. Moreover, immunohistochemical investigations have helped defining the lesional and cellular distribution of iron in MS brain tissue. Imaging studies in MS patients and of brain tissue combined with histological studies have provided important insights into the role of iron in inflammation and neurodegeneration in MS.

Iron in Multiple Sclerosis and Its Noninvasive Imaging with Quantitative Susceptibility Mapping

Iron is considered to play a key role in the development and progression of Multiple Sclerosis (MS). In particular, iron that accumulates in myeloid cells after the blood-brain barrier (BBB) seals may contribute to chronic inflammation, oxidative stress and eventually neurodegeneration. Magnetic resonance imaging (MRI) is a well-established tool for the non-invasive study of MS. In recent years, an advanced MRI method, quantitative susceptibility mapping (QSM), has made it possible to study brain iron through in vivo imaging. Moreover, immunohistochemical investigations have helped defining the lesional and cellular distribution of iron in MS brain tissue. Imaging studies in MS patients and of brain tissue combined with histological studies have provided important insights into the role of iron in inflammation and neurodegeneration in MS.

Multiple sclerosis

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

Multicenter R2* mapping in the healthy brain

PURPOSE

The R2* relaxation rate constant has been suggested as a sensitive measure for iron accumulation. The aim of this multi-center study was to assess the inter-scanner and inter-subject variability of R2* mapping and to investigate the relationship between brain volume and R2* in specific structures.

METHODS

R2* mapping was performed in 81 healthy subjects in seven centers using different 3 T systems. R2* was calculated from a dual-echo gradient echo sequence and was assessed in several deep gray matter structures. The inter-scanner and inter-subject variability of R2* was calculated by means of the coefficient of variation before and after correcting for age.

RESULTS

Significant center effects were seen in some regions which get lost after age correction. The coefficient of variation for the inter-center variability was much lower (<5.6%) than for the intra-subject variability (6.7%-11.7%). R2* in the putamen and red nucleus scaled with cortical volume while R2* in the globus pallidus and the substantia nigra was negatively associated with white matter volume.

CONCLUSION

R2* is a robust and reproducible measure in a multicenter setting provided that a standardized MRI protocol is used. The relationship between iron concentration in deep gray matter and volume of specific brain compartments needs further investigation.

Quantitative assessment of brain iron by R2* relaxometry in patients with cervical dystonia

BACKGROUND

The pathophysiology of cervical dystonia is poorly understood. Increased brain iron deposition has been described in different movement disorders. Our aim was to investigate brain iron content in patients with cervical dystonia, using R2* relaxation rate, a validated MRI marker of brain iron level.

METHODS

Twelve female patients with primary focal cervical dystonia (mean age: 45.4 ± 8.0 years) and 12 age-matched healthy female subjects (mean age: 45.0 ± 8.0 years) underwent 3T MRI to obtain regional R2* relaxation rates of the thalamus, caudate nucleus, putamen, and globus pallidus (GP). Regions of interest were delineated automatically on T1-weighted MRIs.

RESULTS

R2* values in the putamen were positively correlated with age. Patients with cervical dystonia showed elevated R2* values in the GP.

CONCLUSIONS

This pilot study provides the first quantitative support for increased brain iron deposition in cervical dystonia. Further studies are needed to explore the implications of this finding.

Dynamics of brain iron levels in multiple sclerosis: A longitudinal 3T MRI study

OBJECTIVE

We investigated longitudinal changes in iron concentration in the subcortical gray matter (caudate nucleus, globus pallidus, putamen, thalamus) of patients with clinically isolated syndrome (CIS) and definite multiple sclerosis (MS) and their relation to clinical and other morphologic variables.

METHODS

We followed 144 patients (76 CIS; median Expanded Disability Status Scale [EDSS] 1.0 [interquartile range (IQR) 0.0-2.0]; 68 MS; median EDSS 2.0 [IQR 1.0-3.3]) clinically and with 3T MRI over a median period of 2.9 (IQR 1.3-4.0) years. Iron concentration was determined by R2* relaxometry at baseline and last follow-up.

RESULTS

At baseline, subcortical gray matter iron deposition was higher in MS compared to CIS. In CIS, R2* rates increased in the globus pallidus (p < 0.001), putamen (p < 0.001), and caudate nucleus (p < 0.001), whereas R2* rates in the thalamus decreased (p < 0.05). In MS, R2* rates increased in the putamen (p < 0.05), remained stable in the globus pallidus and caudate nucleus, and decreased in the thalamus (p < 0.01). Changes in R2* relaxation rates were unrelated to changes in the volume of respective structures, of T2 lesion load, and of disability.

CONCLUSIONS

Iron accumulation in the basal ganglia is more pronounced in the early than later phases of the disease and occurs independent from other morphologic brain changes. Short-term changes in iron concentration are not associated with disease activity or changes in disability.

Correlation of Brain Atrophy, Disability, and Spinal Cord Atrophy in a Murine Model of Multiple Sclerosis

BACKGROUND

Disability progression in multiple sclerosis (MS) remains incompletely understood. Unlike lesional measures, central nervous system atrophy has a strong correlation with disability. Theiler's murine encephalomyelitis virus infection in SJL/J mice is an established model of progressive MS. We utilized in vivo MRI to quantify brain and spinal cord atrophy in this model and analyzed the temporal relationship between atrophy and disability.

METHODS

Infected and control mice were followed for 12 months. Disability was assessed periodically using rotarod assay. Volumetric MRI datasets were acquired at 7 Tesla. Ventricular volume and C4-5 spinal cord cross-sectional area measurements were performed using Analyze 10.

RESULTS

At 3 months, brain atrophy reached statistical significance (P = .005). In contrast, disability did not differ until 4 months post-infection (P = .0005). Cord atrophy reached significance by 9 months (P = 0.009). By 12 months, brain atrophy resulted in 111.8% increased ventricular volume (P = .00003), while spinal cord cross-sectional area was 25.6% reduced (P = .001) among cases.

CONCLUSIONS

Our results suggest that significant brain atrophy precedes and predicts the development of disability, while spinal cord atrophy occurs late and correlates with severe disability. The observed temporal relationship establishes a framework for mechanisms of disability progression and enables further investigations of their underlying substrate.

Predictive value of different conventional and non-conventional MRI-parameters for specific domains of cognitive function in multiple sclerosis

Objective

While many studies correlated cognitive function with changes in brain morphology in multiple sclerosis (MS), few of them used a multi-parametric approach in a single dataset so far. We thus here assessed the predictive value of different conventional and quantitative MRI-parameters both for overall and domain-specific cognitive performance in MS patients from a single center.

Methods

69 patients (17 clinically isolated syndrome, 47 relapsing–remitting MS, 5 secondary-progressive MS) underwent the “Brief Repeatable Battery of Neuropsychological Tests” assessing overall cognition, cognitive efficiency and memory function as well as MRI at 3 Tesla to obtain T2-lesion load (T2-LL), normalized brain volume (global brain volume loss), normalized cortical volume (NCV), normalized thalamic volume (NTV), normalized hippocampal volume (NHV), normalized caudate nuclei volume (NCNV), basal ganglia R2* values (iron deposition) and magnetization transfer ratios (MTRs) for cortex and normal appearing brain tissue (NABT).

Results

Regression models including clinical, demographic variables and MRI-parameters explained 22–27% of variance of overall cognition, 17–26% of cognitive efficiency and 22–23% of memory. NCV, T2-LL and MTR of NABT were the strongest predictors of overall cognitive function. Cognitive efficiency was best predicted by NCV, T2-LL and iron deposition in the basal ganglia. NTV was the strongest predictor for memory function and NHV was particularly related to memory function.

Conclusions

The predictive value of distinct MRI-parameters differs for specific domains of cognitive function, with a greater impact of cortical volume, focal and diffuse white matter abnormalities on overall cognitive function, an additional role of basal ganglia iron deposition on cognitive efficiency, and thalamic and hippocampal volume on memory function. This suggests the usefulness of using multiparametric MRI to assess (micro)structural correlates of different cognitive constructs.

•

The predictive value of MRI-parameters for cognition was assessed in 69 MS-patients.

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Cortical volume and focal white matter lesions predict overall cognitive function.

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T2-lesion load is a strong predictor for cognition (overall and specific domains).

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Cortical volume and basal ganglia iron deposition predict cognitive efficiency.

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Thalamic volume, MTR of NABT and hippocampal volume predict memory function.

Myocardial T2* mapping: influence of noise on accuracy and precision

BACKGROUND

Pixel-wise, parametric T2* mapping is emerging as a means of automatic measurement of iron content in tissues. It enables quick, intuitive interpretation and provides the potential benefit of spatial context between tissues. However, pixel-wise mapping uses much lower SNR data to estimate T2* when compared to region-based mapping thereby decreasing both its accuracy and precision. In this study, the effects that noise has on the precision and accuracy of pixel-wise T2* mapping were investigated and techniques to mitigate those effects are proposed.

METHODS

To study precision across T2* mapping techniques, a pipeline to estimate the pixel-wise standard deviation (SD) of the T2* based on the fit residuals is proposed. For validation, a Monte-Carlo analysis was performed in which T2* phantoms were scanned N = 64 times, the true SD was measured and compared to the estimated SD. To improve accuracy and precision, the automatic truncation method for mitigating noise bias was extended to pixel-wise fitting by using an SNR scaled image reconstruction and truncating low SNR measurements. Finally, the precision and accuracy of non-linear regression with and without automatic truncation, were investigated using Monte-Carlo simulations.

RESULTS

Measured and estimated SD's were >99.9% correlated for non-linear regression with and without truncation. Non-linear regression with automatic truncation was shown to be the best mapping technique for improving accuracy and precision in low T2* and low SNR measurements.

CONCLUSIONS

A method for applying an automatic truncation method to pixel-wise T2* mapping that reduces T2* overestimation due to noise bias was proposed. A formulation for estimating pixel-wise standard deviation (SD) maps for T2* that can serve as a quality map for interpreting images and for comparison of imaging protocols was also proposed and validated.

A novel neuroferritinopathy mouse model (FTL 498InsTC) shows progressive brain iron dysregulation, morphological signs of early neurodegeneration and motor coordination deficits

Neuroferritinopathy is a rare genetic disease with a dominant autosomal transmission caused by mutations of the ferritin light chain gene (FTL). It belongs to Neurodegeneration with Brain Iron Accumulation, a group of disorders where iron dysregulation is tightly associated with neurodegeneration. We studied the 498–499InsTC mutation which causes the substitution of the last 9 amino acids and an elongation of extra 16 amino acids at the C-terminus of L-ferritin peptide. An analysis with cyclic voltammetry on the purified protein showed that this structural modification severely reduces the ability of the protein to store iron. In order to analyze the impact of the mutation in vivo, we generated mouse models for the some pathogenic human FTL gene in FVB and C57BL/6J strains.

Transgenic mice in the FVB background showed high accumulation of the mutated ferritin in brain where it correlated with increased iron deposition with age, as scored by magnetic resonance imaging. Notably, the accumulation of iron–ferritin bodies was accompanied by signs of oxidative damage. In the C57BL/6 background, both the expression of the mutant ferritin and the iron levels were lower than in the FVB strain. Nevertheless, also these mice showed oxidative alterations in the brain. Furthermore, post-natal hippocampal neurons obtained from these mice experienced a marked increased cell death in response to chronic iron overload and/or acute oxidative stress, in comparison to wild-type neurons. Ultrastructural analyses revealed an accumulation of lipofuscin granules associated with iron deposits, particularly enriched in the cerebellum and striatum of our transgenic mice. Finally, experimental subjects were tested throughout development and aging at 2-, 8- and 18-months for behavioral phenotype. Rotarod test revealed a progressive impaired motor coordination building up with age, FTL mutant old mice showing a shorter latency to fall from the apparatus, according to higher accumulation of iron aggregates in the striatum. Our data show that our 498–499InsTC mouse models recapitulate early pathological and clinical traits of the human neuroferritinopathy, thus providing a valuable model for the study of the disease. Finally, we propose a mechanistic model of lipofuscine formation that can account for the etiopathogenesis of human neuroferritinopathy.

•

We developed two new neuroferritinopathy mice models (NF).

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NF brains are characterized by iron/ferritin accumulation and oxidative damage.

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NF brains show granules of lipofuscine associated with iron.

•

A mechanism of lipofuscine formation is proposed.

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NF mice show impaired motor coordination increasing with age.

Iron in multiple sclerosis: roles in neurodegeneration and repair

MRI and histological studies have shown global alterations in iron levels in the brains of patients with multiple sclerosis (MS), including increases in the iron stored by macrophages and microglia. Excessive free iron can be toxic, and accumulation of iron in MS has generally been thought to be detrimental. However, iron maintains the integrity of oligodendrocytes and myelin, and facilitates their regeneration following injury. The extracellular matrix, a key regulator of remyelination, might also modulate iron levels. This Review highlights key histological and MRI studies that have investigated changes in iron distribution associated with MS. Potential sources of iron, as well as iron regulatory proteins and the detrimental roles of excessive iron within the CNS, are also discussed, with emphasis on the importance of iron within cells for oxidative metabolism, proliferation and differentiation of oligodendrocytes, and myelination. In light of the beneficial and detrimental properties of iron within the CNS, we present considerations for treatments that target iron in MS. Such treatments must balance trophic and toxic properties of iron, by providing sufficient iron levels for remyelination and repair while avoiding excesses that might overwhelm homeostatic mechanisms and contribute to damage.

Increase in the iron content of the substantia nigra and red nucleus in multiple sclerosis and clinically isolated syndrome: a 7 Tesla MRI study

PURPOSE

To study iron deposition in the substantia nigra (SN) and red nuclei (RN), in patients with clinically isolated syndrome (CIS) and relapsing remitting MS (RRMS) and healthy controls (HC).

MATERIALS AND METHODS

Iron deposition was assessed using susceptibility maps and T2*-w images acquired at high resolution MRI at 7 Tesla (T). Mean intensities were calculated within circular regions of interest in the SN (d/v, dorsal/ventral) and RN on high resolution T2*-w, quantitative susceptibility maps and their product for: RRMS, CIS and HC (N = 14, 21, 27, respectively).

RESULTS

Magnetic susceptibility was significantly greater in SNd and RN in RRMS compared with HC (P = 0.04 [0.001, 0.48] and P = 0.01 [0.005, 0.05]), with intermediate values for the CIS group. 1/T2*-w did not show significant inter-group differences (for SNv, SNd, RN, respectively: P = 0.5 [-0.352, 0976], P = 0.35 [-0.208, 0.778], P = 0.16 [-0.114, 0.885] for RRMS versus HC) and the T2*-susceptibility product maps showed the difference only for RN (P = 0.01, [0.009, 0.062]). Changes were independent of EDSS and disease duration.

CONCLUSION

MR changes consistent with iron accumulation occurring in the SN and RN of CIS patients can be identified using susceptibility mapping; this may provide an additional method of monitoring early MS development.

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.