Magnetic resonance techniques for the in vivo assessment of multiple sclerosis pathology: Consensus report of the white matter study group

[Consensus recommendations on regional interdisciplinary standardization of MRI diagnostics for multiple sclerosis in the metropolitan area of Essen]

Magnetic resonance imaging (MRI) is of exceptional importance in the diagnostics and monitoring of multiple sclerosis (MS); however, a close interdisciplinary cooperation between neurologists in private practice, (neuro)radiological practices, hospitals or specialized MS centers is only rarely established. In particular, there is a lack of standardized MRI protocols for image acquisition as well as established quality parameters, which guarantee the comparability of MRI records; however, this is a fundamental prerequisite for an effective application of MRI in the treatment of MS patients, e.g., for making the diagnosis or treatment monitoring. To address these challenges a group of neurologists and (neuro)radiologists developed a consensus proposal for standardization of image acquisition, interpretation and transmission of results and for improvement in interdisciplinary cooperation. This pilot project in the metropolitan area of Essen used a modified Delphi process and was based on the most up to date scientific knowledge. The recommendation takes the medical, economic, temporal and practical aspects of MRI in MS into consideration. The model of interdisciplinary cooperation between radiologists and neurologists with the aim of a regional standardization of MRI could serve as an example for other regions of Germany in order to optimize MRI for MS.

Synthesis and bioactivity evaluation of a myelin-specific contrast agent for magnetic resonance imaging of myelination in central nervous system

Demyelination exists in many neurological diseases of nervous system, such as stroke. Currently, magnetic resonance imaging (MRI) has been the main tool for diagnosing and monitoring the myelin related diseases. However, the conventional MRI unable to distinguish demyelinating lesions from other inflammatory lesions. To address this problem, we have designed and prepared a myelin specific magnetic resonance contrast agent, Gd-DTDAS, which was based myelin specific moiety MeDAS^g and Gd-DTPA^h. In this work, we verified the specificity and sensitivity of Gd-DTDAS to myelin. Moreover, we investigated the specific binding ability of Gd-DTDAS to myelin sheath in the MCAO miceⁱ models. The in vivo imaging results showed that Gd-DTDAS can bind to the undamaged myelin sheath in the BBB disruption areas, and in turn reduce the relaxation time. The fluorescence images also showed significant fluorescence in the brain right infarct area of the MCAO model mice with administration of Gd-DTDAS. The above results confirmed that Gd-DTDAS could be preferentially distributed in areas with high myelination and can detect focally induced demyelination.

Improving Detection of Multiple Sclerosis Lesions in the Posterior Fossa Using an Optimized 3D-FLAIR Sequence at 3T

BACKGROUND AND PURPOSE

There is no consensus regarding the best MR imaging sequence for detecting MS lesions. The aim of our study was to assess the diagnostic value of optimized 3D-FLAIR in the detection of infratentorial MS lesions compared with an axial T2-weighted imaging, a 3D-FLAIR with factory settings, and a 3D double inversion recovery sequence.

MATERIALS AND METHODS

In this prospective study, 27 patients with confirmed MS were included. Two radiologists blinded to clinical data independently read the following sequences: axial T2WI, 3D double inversion recovery, standard 3D-FLAIR with factory settings, and optimized 3D-FLAIR. The main judgment criterion was the overall number of high-signal-intensity lesions in the posterior fossa; secondary objectives were the assessment of the reading confidence and the measurement of the contrast. A nonparametric Wilcoxon test was used to compare the MR images.

RESULTS

Twenty-two patients had at least 1 lesion in the posterior fossa. The optimized FLAIR sequence detected significantly more posterior fossa lesions than any other sequence: 7.5 versus 5.8, 4.8, and 4.1 (P values of .04, .03, and .03) with the T2WI, the double inversion recovery, and the standard FLAIR, respectively. The reading confidence index was significantly higher with the optimized FLAIR, and the contrast was significantly higher with the optimized FLAIR than with the standard FLAIR and the double inversion recovery.

CONCLUSIONS

An optimized 3D-FLAIR sequence improved posterior fossa lesion detection in patients with MS.

[Standartization of MRI studies in multiple sclerosis]

The use of magnetic resonance imaging (MRI) in patients with multiple sclerosis has markedly increased in recent years. The main task of the MRI studies after the diagnosis of multiple sclerosis is to assess the dynamics of MRI for determining disease progression and monitoring the efficacy of therapy. In this regard, it is very important to obtain the most identical baseline and follow-up MRI that is possible when a single standard protocol is used. This article presents the protocol of brain MRI and spinal cord MRI and interpretation of MRI studies in patients with multiple sclerosis.

Suppression of acute experimental allergic encephalomyelitis with a small molecule inhibitor of α4 integrin

Purpose: To determine the efficacy of a small molecule inhibitor of α4 integrin (CT301) at reversing the clinical, pathological and MR- detectable deficits associated with the acute phase of experimental allergic encephalomyelitis (EAE). Materials and methods: EAE was induced in 36 female Hartley guinea pigs, and the treatment period was from day 11 to day 17 post-immunization. Animals received either saline (n=12), anti-α4 integrin antibody (AN100226m; n=12) or CT301 (n=12). T2-weighted fast spin echo and T1-weighted pre- and post-contrast scans were performed at the beginning (day 11) and end (day 18) of the treatment period, and scored for cerebral inflammation and gadolinium enhancement. T1-weighted images were further analyzed to quantify this enhancement as a measure of blood-brain barrier integrity. Dissected CNS was evaluated for inflammation and demyelination. Results: CT301 successfully reversed two clinical indicators of disease over the course of the treatment period. These animals showed decreased T2-weighted abnormalities, as well as a reduction in gadolinium leakage on T1-weighted images. Meningeal and perivascular inflammation was decreased by anti-α4 integrin treatments. Conclusion: CT301 effectively reverses the clinical, pathological and MR-detectable deficits of acute EAE, and may therefore be a promising therapeutic agent in multiple sclerosis (MS).

Design, Synthesis, and Evaluation of Fluorinated Radioligands for Myelin Imaging

Myelination is one of the fundamental processes in vertebrates. A major challenge is to quantitatively image myelin distribution in the central nervous system. For this reason, we designed and synthesized a series of fluorinated radioligands that can be radiolabeled as radiotracers for positron emission tomography (PET) imaging of myelin. These newly developed radioligands readily penetrate the blood-brain barrier and selectively bind to myelin membranes in the white matter region. Structure-activity relationship studies of such ligands suggested that optimal permeability could be achieved with calculated lipophilicty in the range of 3-4. After radiolabeling with fluorine-18, the brain uptake and retention of each radioligand were determined by microPET/CT imaging studies. These pharmacokinetic studies led us to identify a lead compound ([(18)F]FMeDAS, 32) with promising in vivo binding properties, which was subsequently validated by ex vivo autoradiography.

Evidence-based guidelines: MAGNIMS consensus guidelines on the use of MRI in multiple sclerosis-clinical implementation in the diagnostic process

The clinical use of MRI in patients with multiple sclerosis (MS) has advanced markedly over the past few years. Technical improvements and continuously emerging data from clinical trials and observational studies have contributed to the enhanced performance of this tool for achieving a prompt diagnosis in patients with MS. The aim of this article is to provide guidelines for the implementation of MRI of the brain and spinal cord in the diagnosis of patients who are suspected of having MS. These guidelines are based on an extensive review of the recent literature, as well as on the personal experience of the members of the MAGNIMS (Magnetic Resonance Imaging in MS) network. We address the indications, timing, coverage, reporting and interpretation of MRI studies in patients with suspected MS. Our recommendations are intended to help radiologists and neurologists standardize and optimize the use of MRI in clinical practice for the diagnosis of MS.

Optimizing the use of radiologist seed points for improved multiple sclerosis lesion segmentation

Many current methods for multiple sclerosis (MS) lesion segmentation require radiologist seed points as input, but do not necessarily allow the expert to work in an intuitive or efficient way. Ironically, most methods also assume that the points are placed optimally. This paper examines how seed points can be processed with intuitive heuristics, which provide improved segmentation accuracy while facilitating quick and natural point placement. Using a large set of MRIs from an MS clinical trial, two radiologists are asked to seed the lesions while unaware that the points would be fed into a classifier, based on Parzen windows, that automatically delineates each marked lesion. To evaluate the impact of the new heuristics, an interactive region-growing method is used to provide ground truth and the Dice coefficient (DC) and Spearman’s rank correlation are used as the primary measures of agreement. A stratified analysis is performed to determine the effect on scans with low-, medium-, and high lesion loads. Compared to the unenhanced classifier, the heuristics dramatically improve the DC (+32.91 pt.) and correlation (+0.50) for the scans with low lesion loads, and also improve the DC (+14.55 pt.) and correlation (+0.15) for the scans with medium lesion loads, while having aminimal effect for the scans with high lesion loads, which are already segmented accurately by Parzen windows.With the heuristics, the DC is close to 80% and the correlation is above 0.9 for all three load categories.

The association between cognitive function and white matter lesion location in older adults: a systematic review

Background

Maintaining cognitive function is essential for healthy aging and to function autonomously within society. White matter lesions (WMLs) are associated with reduced cognitive function in older adults. However, whether their anatomical location moderates these associations is not well-established. This review systematically evaluates peer-reviewed evidence on the role of anatomical location in the association between WMLs and cognitive function.

Methods

In accordance with the preferred reporting items for systematic reviews and meta-analysis (PRISMA) statement, databases of EMBASE, PUBMED, MEDLINE, and CINAHL, and reference lists of selected papers were searched. We limited our search results to adults aged 60 years and older, and studies published in the English language from 2000 to 2011. Studies that investigated the association between cognitive function and WML location were included. Two independent reviewers extracted: 1) study characteristics including sample size, sample characteristic, and study design; 2) WML outcomes including WML location, WML quantification method (scoring or volume measurement), strength of the MRI magnet in Tesla, and MRI sequence used for WML detection; and 3) cognitive function outcomes including cognitive tests for two cognitive domains of memory and executive function/processing speed.

Results

Of the 14 studies included, seven compared the association of subcortical versus periventricular WMLs with cognitive function. Seven other studies investigated the association between WMLs in specific brain regions (e.g., frontal, parietal lobes) and cognitive function. Overall, the results show that a greater number of studies have found an association between periventricular WMLs and executive function/processing speed, than subcortical WMLs. However, whether WMLs in different brain regions have a differential effect on cognitive function remains unclear.

Conclusions

Evidence suggests that periventricular WMLs may have a significant negative impact on cognitive abilities of older adults. This finding may be influenced by study heterogeneity in: 1) MRI sequences, WML quantification methods, and neuropsychological batteries; 2) modifying effect of cardiovascular risk factors; and 3) quality of studies and lack of sample size calculation.

Iron deposition in the precentral grey matter in patients with multiple sclerosis: a quantitative study using susceptibility-weighted imaging

PURPOSE

Several studies suggest that iron deposition may play a role in multiple sclerosis (MS) pathology. Three-dimensional (3D) enhanced T2*-weighted angiography (ESWAN) at 3T was used to quantify iron deposition in the precentral grey matter in MS and its relationship with disease duration, atrophy and Expanded Disability Status Scale (EDSS) scores.

METHODS

We recruited 33 patients with diagnosis of clinically definite MS and 31 age- and sex-matched healthy controls who underwent conventional brain MRI, 3D-ESWAN and 3D T1sequences. We obtained the mean phase values (MPVs) of the precentral grey matter on ESWAN-filtered phase images and volume of the precentral gyrus on 3D T1 images. We investigated the correlation between precentral grey matter MPVs, precentral gyrus volume, disease duration and EDSS scores of MS patients and healthy controls.

RESULTS

The precentral grey matter MPVs in MS patients and controls were 1870.83 ± 56.61 and 1899.22 ± 51.73 respectively and had significant difference in the MS group vs. the control group (t=-2.09, P=0.04). There was significant negative correlation between precentral grey matter MPVs and disease duration (r=-0.365, P=0.03). No correlation was found between MPVs and EDSS scores. Mean precentral gyrus volume in MS patients was 4368.55 ± 867.78 whereas in controls was 5701.00 ± 1184.03 with significant difference between volume of the precentral gyrus in MS patients compared to healthy controls (t=-5.167, P<0.001). There was a positive correlation between MPVs and precentral gyrus volume (r=0.291, P=0.020).

CONCLUSIONS

Our study demonstrated that quantitative assessment of abnormal iron deposition in the precentral grey matter in MS patients can be measured using 3D-ESWAN.

Improving the clinical correlation of multiple sclerosis black hole volume change by paired-scan analysis

The change in T 1-hypointense lesion ("black hole") volume is an important marker of pathological progression in multiple sclerosis (MS). Black hole boundaries often have low contrast and are difficult to determine accurately and most (semi-)automated segmentation methods first compute the T 2-hyperintense lesions, which are a superset of the black holes and are typically more distinct, to form a search space for the T 1w lesions. Two main potential sources of measurement noise in longitudinal black hole volume computation are partial volume and variability in the T 2w lesion segmentation. A paired analysis approach is proposed herein that uses registration to equalize partial volume and lesion mask processing to combine T 2w lesion segmentations across time. The scans of 247 MS patients are used to compare a selected black hole computation method with an enhanced version incorporating paired analysis, using rank correlation to a clinical variable (MS functional composite) as the primary outcome measure. The comparison is done at nine different levels of intensity as a previous study suggests that darker black holes may yield stronger correlations. The results demonstrate that paired analysis can strongly improve longitudinal correlation (from -0.148 to -0.303 in this sample) and may produce segmentations that are more sensitive to clinically relevant changes.

Optimized double inversion recovery for reduction of T₁ weighting in fluid-attenuated inversion recovery

Fluid-attenuated inversion recovery (FLAIR) is a routinely used technique in clinical practice to detect long T(2) lesions by suppressing the cerebrospinal fluid. Concerns remain, however, that the inversion pulse in FLAIR imparts T(1) weighting that can decrease the detectability and mischaracterize some lesions. Hence, FLAIR is usually acquired in conjunction with a standard T(2) to guard against these concerns. Recently, double inversion recovery (DIR) preparations have highlighted certain types of lesions by suppressing both cerebrospinal fluid and white matter but produce even stronger T(1) contrast than FLAIR. This work shows that the inversion times in a DIR sequence can be optimized to minimize unwanted T(1) weighting, enabling the acquisition of cerebrospinal fluid-suppressed images with pure T(2) weighting. This technique is referred to as T(1) -nulled DIR. The theory to determine the optimized inversion times is discussed and the results are shown by simulations, normal volunteer studies, and multiple sclerosis patient studies. T(1) -nulled DIR provides equivalent or superior contrast between gray and white matters as well as white matter and multiple sclerosis lesion at the same repetition time. Multiple sclerosis lesions appeared sharper on T(1) -nulled DIR compared to FLAIR. T(1) -nulled DIR has the potential to replace the combination of standard T(2) and FLAIR acquisitions in many clinical protocols.

A myelin-specific contrast agent for magnetic resonance imaging of myelination

Myelination is one of the most fundamental biological processes in the development of vertebrate nervous systems. Abnormal or disrupted myelination occurs in many acquired or inherited neurodegenerative diseases, including multiple sclerosis (MS) and various leukodystrophies. To date, magnetic resonance imaging (MRI) has been the primary tool for diagnosing and monitoring the progression of MS and related diseases; however, any change in signal intensity of conventional MRI reflects a change only in tissue water content, which is a nonspecific measure of the overall changes in macroscopic tissue injury. Thus, the use of MRI as a primary measure of disease activity was shown to be disassociated from the clinical outcome due to the lack of specificity for myelination. In order to increase the MRI specificity for myelin pathologies, we designed and synthesized the first Gd-based T(1) MR contrast agent (MIC) that binds to myelin with high specificity. In this Communication, we demonstrate that MIC localizes in brain regions in proportion to the extent of myelination. In addition, MIC possesses promising MR contrast properties, which allow for direct detection of myelin distribution through T(1) mapping in the mouse brain.

IL-1R signaling within the central nervous system regulates CXCL12 expression at the blood-brain barrier and disease severity during experimental autoimmune encephalomyelitis

Multiple sclerosis (MS) is an autoimmune disease of the CNS characterized by disruption of the blood-brain barrier (BBB). This breach in CNS immune privilege allows undeterred trafficking of myelin-specific lymphocytes into the CNS where they induce demyelination. Although the mechanism of BBB compromise is not known, the chemokine CXCL12 has been implicated as a molecular component of the BBB whose pattern of expression is specifically altered during MS and which correlates with disease severity. The inflammatory cytokine IL-1beta has recently been shown to contribute not only to BBB permeability but also to the development of IL-17-driven autoimmune responses. Using experimental autoimmune encephalomyelitis, the rodent model of MS, we demonstrate that IL-1beta mediates pathologic relocation of CXCL12 during the induction phase of the disease, before the development of BBB disruption. We also show that CD4, CD8, and, surprisingly gammadelta T cells are all sources of IL-1beta. In addition, gammadelta T cells are also targets of this cytokine, contributing to IL-1beta-mediated production of IL-17. Finally, we show that the level of CNS IL-1R determines the clinical severity of experimental autoimmune encephalomyelitis. These data suggest that T cell-derived IL-1beta contributes to loss of immune privilege during CNS autoimmunity via pathologic alteration in the expression of CXCL12 at the BBB.

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

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

Molecular probes for imaging myelinated white matter in CNS

Abnormalities and changes in myelination in the brain are seen in many neurodegenerative disorders such as multiple sclerosis (MS). Direct detection and quantification of myelin content in vivo is desired to facilitate diagnosis and therapeutic treatments of myelin-related diseases. The imaging studies require use of myelin-imaging agents that readily enter the brain and selectively bind to myelinated regions. For this purpose, we have systematically evaluated a series of stilbene derivatives as myelin imaging agents. Spectrophotometry-based and radioligand-based binding assays showed that these stilbene derivatives exhibited relatively high myelin-binding affinities. In vitro myelin staining exhibited that the compounds selectively stained intact myelinated regions in wild type mouse brain. In situ tissue staining demonstrated that the compounds readily entered the mouse brain and selectively labeled myelinated white matter regions. These studies suggested that these stilbene derivatives can be used as myelin-imaging probes to monitor myelin pathology in vivo.

Quantifying subclinical central nervous lesions in primary antiphospholipid syndrome: the role of magnetization transfer imaging

PURPOSE

To define the role of magnetization transfer imaging (MTI) in detecting subclinical central nervous system (CNS) lesions in primary antiphospholipid syndrome (PAPS).

MATERIALS AND METHODS

Ten non-CNS PAPS patients were compared to 10 CNS PAPS patients and 10 age- and sex-matched controls. All PAPS patients met Sapporo criteria. All subjects underwent conventional MRI and complementary MTI analysis to compose histograms. CNS viability was determined according to the magnetization transfer ratio (MTR) by mean pixel intensity (MPI) and the mean peak height (MPH). Volumetric cerebral measurements were assessed by brain parenchyma factor (BPF) and total/cerebral volume.

RESULTS

MTR histograms analysis revealed that MPI was significantly different among groups (P < 0.0001). Non-CNS PAPS had a higher MPI than CNS PAPS (30.5 +/- 1.01 vs. 25.1 +/- 3.17 percent unit (pu); P < 0.05) although lower than controls (30.5 +/- 1.01 vs. 31.20 +/- 0.50 pu; P < 0.05). MPH in non-CNS PAPS (5.57 +/- 0.20% (1/pu)) was similar to controls (5.63 +/- 0.20% (1/pu), P > 0.05) and higher than CNS PAPS (4.71 +/- 0.30% (1/pu), P < 0.05). A higher peak location (PL) was also observed in the CNS PAPS group in comparison with the other groups (P < 0.0001). In addition, a lower BPF was found in non-CNS PAPS compared to controls (0.80 +/- 0.03 vs. 0.84 +/- 0.02 units; P < 0.05) but similar to CNS PAPS (0.80 +/- 0.03 vs. 0.79 +/- 0.05 units; P > 0.05).

CONCLUSION

Our findings suggest that non-CNS PAPS patients have subclinical cerebral damage. The long-termclinical relevance of MTI analysis in these patients needs to be defined by prospective studies.

Clinically benign multiple sclerosis despite large T2 lesion load: can we explain this paradox?

Magnetic resonance imaging (MRI) techniques such as magnetization transfer imaging and magnetic resonance spectroscopy (MRS) may reveal otherwise undetectable tissue damage in multiple sclerosis (MS) and can serve to explain more severe disability than expected from conventional MRI. That an inverse situation may exist where non-conventional quantitative MRI and MRS metrics would indicate less abnormality than expected from T2 lesion load to explain preserved clinical functioning was hypothesized. Quantitative MRI and MRS were obtained in 13 consecutive patients with clinically benign MS (BMS; mean age 44 +/- 9 years) despite large T 2 lesion load and in 15 patients with secondary progressive MS (SPMS; mean age 47 +/- 6 years) matched for disease duration. The magnetization transfer ratio (MTR), magnetization transfer rate (kfor), brain parenchymal fraction (BPF) and brain metabolite concentrations from proton MRS were determined. BMS patients were significantly less disabled than their SPMS counterparts (mean expanded disability status score: 2.1 +/- 1.1 versus 6.2 +/- 1.1; P < 0.001) and had an even somewhat higher mean T2 lesion load (41.2 +/- 27.1 versus 27.9 +/- 24.8 cm3; P = 0.19). Normal appearing brain tissue histogram metrics for MTR and kfor, mean MTR and kfor of MS lesions and mean BPF were similar in BMS and SPMS patients. Levels of N-acetyl-aspartate, choline and myoinositol were comparable between groups. This study thus failed to explain the preservation of function in our BMS patients with large T2 lesion load by a higher morphologic or metabolic integrity of the brain parenchyma. Functional compensation must come from other mechanisms such as brain plasticity.

MRI to monitor treatment efficacy in multiple sclerosis

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

Update on multiple sclerosis

In this article the basic features of the focal MR imaging lesions and the underlying pathology are reviewed. Next, the diffuse pathology in the normal-appearing white and gray matter as revealed by conventional and quantitative MR imaging techniques is discussed, including reference to how the focal and diffuse pathology may be in part linked through axonal-neuronal degeneration. The MR imaging criteria incorporated for the first time into formal clinical diagnostic criteria for multiple sclerosis are next discussed. Finally, a discussion is provided as to how MR imaging is used in monitoring subclinical disease either before or subsequent to initiation of treatment, in identifying aggressive subclinical disease, and in monitoring treatment.

Imaging of CNS myelin by positron-emission tomography

Promoting myelin repair is one of the most promising therapeutic avenues in the field of myelin disorders. In future clinical trials, evaluation of remyelination will require a reliable and quantifiable myelin marker to be used as a surrogate marker. To date, MRI assessment lacks specificity for evaluating the level of remyelination within the brain. Here, we describe 1,4-bis(p-aminostyryl)-2-methoxy benzene (BMB), a synthesized fluorescent molecule, that binds selectively to myelin both ex vivo and in vivo. The binding of BMB to myelin allows the detection of demyelinating lesions in an experimental autoimmune encephalitis model of demyelination and allows a mean for quantifying myelin loss in dysmyelinating mutants. In multiple sclerosis brain, different levels of BMB binding differentiated remyelination in shadow plaques from either demyelinated lesions or normal-appearing white matter. After systemic injection, BMB crosses the blood-brain barrier and binds to myelin in a dose-dependent and reversible manner. Finally, we provide evidence that (11)C-radiolabeled BMB can be used in vivo to image CNS myelin by positron-emission tomography in baboon. Our results provide a perspective for developing a brain myelin imaging technique by positron-emission tomography.

Imaging of inflammatory lesions at 3.0 Tesla in patients with clinically isolated syndromes suggestive of multiple sclerosis: a comparison of fluid-attenuated inversion recovery with T2 turbo spin-echo

The aims of this study were to determine and compare the sensitivity of T2 turbo spin-echo (T2 TSE) and fluid-attenuated inversion recovery (FLAIR) sequences at 3.0 T in the detection of inflammatory lesions in patients with clinically isolated syndromes suggestive of multiple sclerosis. Forty-nine patients were examined with a 3.0 T MRI system using 5 mm axial sections of T2 TSE (2:19 min), FLAIR (4:00 min) and pre- and postcontrast T1 spin-echo sequences (3:37 min). Brain lesions were counted and categorized according to their anatomic location. Patients were classified according to Barkhof MRI criteria for FLAIR and T2 TSE sequences. The FLAIR sequence detected more lesions in every anatomic region except for the infratentorial region. The higher sensitivity was significant for the total number of lesions (p<0.01), the juxtacortical (p<0.01), and the periventricular (p=0.01) region. A 9% increase of infratentorial lesions using the T2 TSE sequence was not significant. The higher sensitivity using the FLAIR sequence resulted in one additional MRI criterion in nine patients, whereas the better detection of infratentorial lesions using the T2 TSE sequence resulted in additional MRI criteria in three patients. In conclusion, FLAIR provides the highest sensitivity when compared with the T2 TSE, although T2 TSE still has a diagnostic relevance in terms of MRI criteria classification.

Magnetic resonance imaging advances in multiple sclerosis

Magnetic resonance imaging (MRI) has become a core component of clinical management and scientific research in multiple sclerosis (MS), providing essential information about tissue structure and function. MRI is now the most important laboratory diagnostic and longitudinal monitoring technology. A number of conventional MRI techniques, which include T2-weighted, T1-weighted, and gadolinium-enhanced imaging, are used to identify overt lesions and quantify tissue atrophy. MRI is highly sensitive in detecting brain and spinal cord involvement in MS and can visualize multifocal lesions, occult disease, and macroscopic atrophy. Advanced MRI techniques, such as magnetization transfer imaging, spectroscopy, diffusion-weighted imaging, and functional MRI, have added to our understanding of the pathogenesis of the disease. The precise role of these newer imaging approaches continues to be defined. In this supplement to the Journal of Neuroimaging, the authors review the role of conventional and advanced MRI techniques in detecting tissue changes in MS, diagnosing and monitoring patients, and charting the progression of disease in new and established patients.

Update on Multiple Sclerosis

In this article the basic features of the focal MR imaging lesions and the underlying pathology are reviewed. Next, the diffuse pathology in the normal-appearing white and gray matter as revealed by conventional and quantitative MR imaging techniques is discussed, including reference to how the focal and diffuse pathology may be in part linked through axonal-neuronal degeneration. The MR imaging criteria incorporated for the first time into formal clinical diagnostic criteria for multiple sclerosis are next discussed. Finally, a discussion is provided as to how MR imaging is used in monitoring subclinical disease either before or subsequent to initiation of treatment, in identifying aggressive subclinical disease, and treatment of nonresponders.

The role of stress-response systems for the pathogenesis and progression of MS

Disease progression in multiple sclerosis (MS)--an inflammatory demyelinating and neurodegenerative disease with a presumed T-cell driven autoimmune origin--has long been hypothesized to be associated with stress. However, this notion has only recently been supported by prospective clinical studies. Several clinical and molecular studies in MS and its animal models have recently shown disruptions in the communication between the immune system and the two major stress response systems, the hypothalamo-pituitary-adrenal (HPA) axis and the autonomic nervous system. Insensitivity to glucocorticoid and beta-adrenergic modulation might be involved in overshooting inflammation in MS, whereas hyperactivity of the HPA axis has been linked to neurodegeneration and increased disability. Here, we integrate findings from molecular, cellular, experimental, clinical and epidemiological research to describe the involvement of stress response systems in MS pathogenesis and progression.

1H-MRS quantification of tNA and tCr in patients with multiple sclerosis: a meta-analytic review

Meta-analysis was performed on the results of 75 comparisons from the 30 peer-reviewed publications that used proton magnetic resonance spectroscopy (1H-MRS) or spectroscopic imaging to (i) quantify the mean concentrations of total creatine (tCr, found in neurons, astrocytes and oligodendrocytes), and/or total N-acetyl groups (tNA, found only in neurons), in the lesional and/or non-lesional white matter (WM) and/or the grey matter (GM) of patients with multiple sclerosis (MS) and (ii) compare these values with those in the homologous tissues of normal controls (NC). For mean [tNA] values, there was (i) a large-effect-sized overall decrease in patients' lesional WM relative to NC WM (25 comparisons), (ii) a medium-effect-sized overall decrease in patients' non-lesional WM relative to NC WM (36 comparisons) and (iii) a medium-effect-sized overall decrease in patients' GM relative to NC GM (14 comparisons). Patients' mean [tNA] values were sometimes statistically normal but were never statistically increased. For mean [tCr] values, there was (i) no statistically significant overall change in the patients' lesional WM relative to NC WM (24 comparisons), although statistically significant increases and decreases were sometimes found, (ii) a medium-effect-sized overall increase in patients' non-lesional WM relative to NC WM (33 comparisons) and (iii) no statistically significant overall change in patients' GM relative to NC GM (12 comparisons), although a significant decrease was found in one comparison. Of 41 comparisons with statistically significant changes, 38 combined in a way that would probably result in decreased mean [tNA]/[tCr] ratios such that (i) 66% had statistically decreased mean [tNA] and statistically unchanged mean [tCr] values, (ii) 13% had statistically decreased mean [tNA] and statistically increased mean [tCr] values and (iii) 21% had statistically unchanged mean [tNA] values and statistically increased mean [tCr] values. Of the 25 comparisons that came from studies that also analysed [tNA]/[tCr] ratios, the direction of change in mean [tNA] values and mean [tNA]/[tCr] ratios was concordant in 84%. In comparisons that quantified both [tNA] and [tCr], there was a similar amount of variability in both measures in each of the different tissue types studied, both in patients and NCs. Together, these results suggest that within-voxel tNA/tCr ratios can be interpreted as valid and accurate surrogate measures of 'cerebral tissue integrity'-with decreased tNA/tCr ratios indicating some combination of neuroaxonal disturbance, oligodendroglial disturbance, and astrocytic proliferation. These results also suggest that, although within-voxel tNA/tCr ratios are not perfect indicators of [tNA] content, they do represent a practical compromise to acquiring surrogate measures of within-voxel neuroaxonal integrity.