Imaging the tip of the iceberg: visualization of cortical lesions in multiple sclerosis

Multicenter Evaluation of AI-generated DIR and PSIR for Cortical and Juxtacortical Multiple Sclerosis Lesion Detection

Background Cortical multiple sclerosis lesions are clinically relevant but inconspicuous at conventional clinical MRI. Double inversion recovery (DIR) and phase-sensitive inversion recovery (PSIR) are more sensitive but often unavailable. In the past 2 years, artificial intelligence (AI) was used to generate DIR and PSIR from standard clinical sequences (eg, T1-weighted, T2-weighted, and fluid-attenuated inversion-recovery sequences), but multicenter validation is crucial for further implementation. Purpose To evaluate cortical and juxtacortical multiple sclerosis lesion detection for diagnostic and disease monitoring purposes on AI-generated DIR and PSIR images compared with MRI-acquired DIR and PSIR images in a multicenter setting. Materials and Methods Generative adversarial networks were used to generate AI-based DIR (n = 50) and PSIR (n = 43) images. The number of detected lesions between AI-generated images and MRI-acquired (reference) images was compared by randomized blinded scoring by seven readers (all with >10 years of experience in lesion assessment). Reliability was expressed as the intraclass correlation coefficient (ICC). Differences in lesion subtype were determined using Wilcoxon signed-rank tests. Results MRI scans of 202 patients with multiple sclerosis (mean age, 46 years ± 11 [SD]; 127 women) were retrospectively collected from seven centers (February 2020 to January 2021). In total, 1154 lesions were detected on AI-generated DIR images versus 855 on MRI-acquired DIR images (mean difference per reader, 35.0% ± 22.8; P < .001). On AI-generated PSIR images, 803 lesions were detected versus 814 on MRI-acquired PSIR images (98.9% ± 19.4; P = .87). Reliability was good for both DIR (ICC, 0.81) and PSIR (ICC, 0.75) across centers. Regionally, more juxtacortical lesions were detected on AI-generated DIR images than on MRI-acquired DIR images (495 [42.9%] vs 338 [39.5%]; P < .001). On AI-generated PSIR images, fewer juxtacortical lesions were detected than on MRI-acquired PSIR images (232 [28.9%] vs 282 [34.6%]; P = .02). Conclusion Artificial intelligence-generated double inversion-recovery and phase-sensitive inversion-recovery images performed well compared with their MRI-acquired counterparts and can be considered reliable in a multicenter setting, with good between-reader and between-center interpretative agreement. Published under a CC BY 4.0 license. Supplemental material is available for this article. See also the editorial by Zivadinov and Dwyer in this issue.

Cortical lesions at diagnosis predict long-term cognitive impairment in multiple sclerosis: A 20-year study

BACKGROUND AND PURPOSE

Although cognitive impairment (CI) is frequent in multiple sclerosis (MS) patients, few studies (and with conflicting results) have evaluated early predictors of CI in the long term. We aimed at determining associations between early clinical/neuroradiological variables with reference to CI after 20 years of MS.

METHODS

We investigated in 170 MS patients the relationship between clinical/magnetic resonance imaging (MRI) data at diagnosis and cognitive status almost 20 years after MS onset. Among others, number and volume of both white matter lesions (WMLs) and cortical lesions (CLs) were evaluated at diagnosis and after 2 years. All MS patients were followed over time and underwent a comprehensive neuropsychological assessment at the end of study. Advanced statistical methods (unsupervised cluster analysis and random forest model) were conducted.

RESULTS

CI patients showed higher focal cortical pathology at diagnosis compared to cognitively normal subjects (p < 0.001). Volumes of both WMLs and CLs emerged as the MRI metrics most associated with long-term CI. Moreover, number of CLs (especially ≥3) was also strongly associated with long-term CI (≥3 CLs: odds ratio [OR] = 3.7, 95% confidence interval = 1.8-7.5, p < 0.001), more than number of WMLs; the optimal cutoff of three CLs (area under the curve = 0.67, specificity = 75%, sensitivity = 55%) was estimated according to the risk of developing CI.

CONCLUSIONS

These results highlight the impact of considering both white and gray matter focal damage from early MS stages. Given the low predictive value of WML number and the poor clinical applicability of lesion volume estimation in the daily clinical context, the evaluation of number of CLs could represent a reliable prognostic marker of CI.

Brain functional connectivity analysis in patients with relapsing-remitting multiple sclerosis: A graph theory approach of EEG resting state

Multiple sclerosis (MS) is an autoimmune disease related to the central nervous system (CNS). This study aims to investigate the effects of MS on the brain's functional connectivity network using the electroencephalogram (EEG) resting-state signals and graph theory approach. Resting-state eyes-closed EEG signals were recorded from 20 patients with relapsing-remitting MS (RRMS) and 18 healthy cases. In this study, the prime objective is to calculate the connectivity between EEG channels to assess the differences in brain functional network global features. The results demonstrated lower cortical activity in the alpha frequency bands and higher activity for the gamma frequency bands in patients with RRMS compared to the healthy group. In this study, graph metric calculations revealed a significant difference in the diameter of the functional brain network based on the directed transfer function (DTF) measure between the two groups, indicating a higher diameter in RRMS cases for the alpha frequency band. A higher diameter for the functional brain network in MS cases can result from anatomical damage. In addition, considerable differences between the networks' global efficiency and transitivity based on the imaginary part of the coherence (iCoh) measure were observed, indicating higher global efficiency and transitivity in the delta, theta, and beta frequency bands for RRMS cases, which can be related to the compensatory functional reaction from the brain. This study indicated that in RRMS cases, some of the global characteristics of the brain's functional network, such as diameter and global efficiency, change and can be illustrated even in the resting-state condition when the brain is not under cognitive load.

Artificial double inversion recovery images can substitute conventionally acquired images: an MRI-histology study

Cortical multiple sclerosis lesions are disease-specific, yet inconspicuous on magnetic resonance images (MRI). Double inversion recovery (DIR) images are sensitive, but often unavailable in clinical routine and clinical trials. Artificially generated images can mitigate this issue, but lack histopathological validation. In this work, artificial DIR images were generated from postmortem 3D-T1 and proton-density (PD)/T2 or 3D-T1 and 3D fluid-inversion recovery (FLAIR) images, using a generative adversarial network. All sequences were scored for cortical lesions, blinded to histopathology. Subsequently, tissue samples were stained for proteolipid protein (myelin) and scored for cortical lesions type I-IV (leukocortical, intracortical, subpial and cortex-spanning, respectively). Histopathological scorings were then (unblinded) compared to MRI using linear mixed models. Images from 38 patients (26 female, mean age 64.3 ± 10.7) were included. A total of 142 cortical lesions were detected, predominantly subpial. Histopathology-blinded/unblinded sensitivity was 13.4/35.2% for artificial DIR generated from T1-PD/T2, 14.1/41.5% for artificial DIR from T1-FLAIR, 17.6/49.3% for conventional DIR and 10.6/34.5% for 3D-T1. When blinded to histopathology, there were no differences; with histopathological feedback at hand, conventional DIR and artificial DIR from T1-FLAIR outperformed the other sequences. Differences between histopathology-blinded/unblinded sensitivity could be minified through adjustment of the scoring criteria. In conclusion, artificial DIR images, particularly generated from T1-FLAIR could potentially substitute conventional DIR images when these are unavailable.

Imaging cortical multiple sclerosis lesions with ultra-high field MRI

BACKGROUND

Cortical lesions are abundant in multiple sclerosis (MS), yet difficult to visualize in vivo. Ultra-high field (UHF) MRI at 7 T and above provides technological advances suited to optimize the detection of cortical lesions in MS.

PURPOSE

To provide a narrative and quantitative systematic review of the literature on UHF MRI of cortical lesions in MS.

METHODS

A systematic search of all literature on UHF MRI of cortical lesions in MS published before September 2020. Quantitative outcome measures included cortical lesion numbers reported using 3 T and 7 T MRI and between 7 T MRI sequences, along with sensitivity of UHF MRI towards cortical lesions verified by histopathology.

RESULTS

7 T MRI detected on average 52 ± 26% (mean ± 95% confidence interval) more cortical lesions than the best performing image contrast at 3 T, with the largest increase in type II-IV intracortical lesion detection. Across all studies, the mean cortical lesion number was 17 ± 6 per patient. In progressive MS cohorts, approximately four times more cortical lesions were reported than in CIS/early RRMS, and RRMS. Yet, there was no difference in lesion type ratio between these MS subtypes. Furthermore, superiority of one MRI sequence over another could not be established from available data. Post-mortem lesion detection with UHF MRI agreed only modestly with pathological examinations. Mean pro- and retrospective sensitivity was 33 ± 6% and 71 ± 10%, respectively, with the highest sensitivity towards type I and type IV lesions.

CONCLUSION

UHF MRI improves cortical lesion detection in MS considerably compared to 3 T MRI, particularly for type II-IV lesions. Despite modest sensitivity, 7 T MRI is still capable of visualizing all aspects of cortical lesion pathology and could potentially aid clinicians in diagnosing and monitoring MS, and progressive MS in particular. However, standardization of acquisition and segmentation protocols is needed.

Artificial double inversion recovery images for (juxta)cortical lesion visualization in multiple sclerosis

Background:

Cortical lesions are highly inconspicuous on magnetic resonance imaging (MRI). Double inversion recovery (DIR) has a higher sensitivity than conventional clinical sequences (i.e. T1, T2, FLAIR) but is difficult to acquire, leading to overseen cortical lesions in clinical care and clinical trials.

Objective:

To evaluate the usability of artificially generated DIR (aDIR) images for cortical lesion detection compared to conventionally acquired DIR (cDIR).

Methods:

The dataset consisted of 3D-T1 and 2D-proton density (PD) T2 images of 73 patients (49RR, 20SP, 4PP) at 1.5 T. Using a 4:1 train:test-ratio, a fully convolutional neural network was trained to predict 3D-aDIR from 3D-T1 and 2D-PD/T2 images. Randomized blind scoring of the test set was used to determine detection reliability, precision and recall.

Results:

A total of 626 vs 696 cortical lesions were detected on 15 aDIR vs cDIR images (intraclass correlation coefficient (ICC) = 0.92). Compared to cDIR, precision and recall were 0.84 ± 0.06 and 0.76 ± 0.09, respectively. The frontal and temporal lobes showed the largest differences in discernibility.

Conclusion:

Cortical lesions can be detected with good reliability on artificial DIR. The technique has potential to broaden the availability of DIR in clinical care and provides the opportunity of ex post facto implementation of cortical lesions imaging in existing clinical trial data.

Histopathology-validated recommendations for cortical lesion imaging in multiple sclerosis

Cortical demyelinating lesions are clinically important in multiple sclerosis, but notoriously difficult to visualize with MRI. At clinical field strengths, double inversion recovery MRI is most sensitive, but still only detects 18% of all histopathologically validated cortical lesions. More recently, phase-sensitive inversion recovery was suggested to have a higher sensitivity than double inversion recovery, although this claim was not histopathologically validated. Therefore, this retrospective study aimed to provide clarity on this matter by identifying which MRI sequence best detects histopathologically-validated cortical lesions at clinical field strength, by comparing sensitivity and specificity of the thus far most commonly used MRI sequences, which are T₂, fluid-attenuated inversion recovery (FLAIR), double inversion recovery and phase-sensitive inversion recovery. Post-mortem MRI was performed on non-fixed coronal hemispheric brain slices of 23 patients with progressive multiple sclerosis directly after autopsy, at 3 T, using T₁ and proton-density/T₂-weighted, as well as FLAIR, double inversion recovery and phase-sensitive inversion recovery sequences. A total of 93 cortical tissue blocks were sampled from these slices. Blinded to histopathology, all MRI sequences were consensus scored for cortical lesions. Subsequently, tissue samples were stained for proteolipid protein (myelin) and scored for cortical lesion types I–IV (mixed grey matter/white matter, intracortical, subpial and cortex-spanning lesions, respectively). MRI scores were compared to histopathological scores to calculate sensitivity and specificity per sequence. Next, a retrospective (unblinded) scoring was performed to explore maximum scoring potential per sequence. Histopathologically, 224 cortical lesions were detected, of which the majority were subpial. In a mixed model, sensitivity of T₁, proton-density/T₂, FLAIR, double inversion recovery and phase-sensitive inversion recovery was 8.9%, 5.4%, 5.4%, 22.8% and 23.7%, respectively (20, 12, 12, 51 and 53 cortical lesions). Specificity of the prospective scoring was 80.0%, 75.0%, 80.0%, 91.1% and 88.3%. Sensitivity and specificity did not significantly differ between double inversion recovery and phase-sensitive inversion recovery, while phase-sensitive inversion recovery identified more lesions than double inversion recovery upon retrospective analysis (126 versus 95; P < 0.001). We conclude that, at 3 T, double inversion recovery and phase-sensitive inversion recovery sequences outperform conventional sequences T₁, proton-density/T₂ and FLAIR. While their overall sensitivity does not exceed 25%, double inversion recovery and phase-sensitive inversion recovery are highly pathologically specific when using existing scoring criteria and their use is recommended for optimal cortical lesion assessment in multiple sclerosis.

The relevance of multiple sclerosis cortical lesions on cortical thinning and their clinical impact as assessed by 7.0-T MRI

OBJECTIVE

This study aimed to investigate at 7.0-T MRI a) the role of multiple sclerosis (MS) cortical lesions in cortical tissue loss b) their relation to neurological disability.

METHODS

In 76 relapsing remitting and 26 secondary progressive MS patients (N = 102) and 56 healthy subjects 7.0-T T₂^*-weighted images were acquired for lesion segmentation; 3.0-T T₁-weighted structural scans for cortical surface reconstruction/cortical thickness estimation. Patients were dichotomized based on the median cortical lesion volume in low and high cortical lesion load groups that differed by age, MS phenotype and degree of neurological disability. Group differences in cortical thickness were tested on reconstructed cortical surface. Patients were evaluated clinically by means of the Expanded Disability Status Scale (EDSS).

RESULTS

Cortical lesions were detected in 96% of patients. White matter lesion load was greater in the high than in the low cortical lesion load MS group (p = 0.01). Both MS groups disclosed clusters (prevalently parietal) of cortical thinning relative to healthy subjects, though these regions did not show the highest cortical lesion density, which predominantly involved frontal regions. Cortical thickness decreased on average by 0.37 mm, (p = 0.002) in MS patients for each unit standard deviation change in white matter lesion volume. The odds of having a higher EDSS were associated with cortical lesion volume (1.78, p = 0.01) and disease duration (1.15, p < 0.001).

CONCLUSION

Cortical thinning in MS is not directly related to cortical lesion load but rather with white matter lesion volume. Neurological disability in MS is better explained by cortical lesion volume assessment.

Gray Matter Matters: A Longitudinal Magnetic Resonance Voxel-Based Morphometry Study of Primary Progressive Multiple Sclerosis

Background: Multiple Sclerosis (MS) lesions in white matter (WM) are easily detected with conventional MRI which induce inflammation thereby generating contrast. WM lesions do not consistently explain the extent of clinical disability, cognitive impairment, or the source of an exacerbation. Gray matter (GM) structures including the cerebral cortex and various deep nuclei are known to be affected early in Primary Progressive Multiple Sclerosis (PPMS) and drive disease progression, disability, fatigue, and cognitive dysfunction. However, little is known about how rapidly GM lesions develop and accumulate over time.

Objective: The purpose of this study is to analyze the degree and rate of progression in 25 patients with PPMS using voxel-based automated volumetric quantitation.

Methods: This is a retrospective single-center study which includes a cohort of 25 patients with PPMS scanned utilizing NeuroQuant® 3 dimensional voxel-based morphometry (3D VBM) automated analysis and database and restudied after a period of ~1 year (11–14 months). Comparisons with normative data were acquired for whole brain, forebrain parenchyma, cortical GM, hippocampus, thalamus, superior and inferior lateral ventricles. GM volume changes were correlated with their clinical motor and cognitive scores using Extended Disability Status Scales (EDSS) and Montreal Cognitive Assessments (MoCA).

Results: Steep reductions occurred in cerebral cortical GM and deep GM nuclei volumes which correlated with each patient's clinical and cognitive impairment. The median observed percentile volume losses were statistically significant compared with the 50th percentile for each GM component. Longitudinal assessments of an unselected sample of one dozen patients involved in the PPMS study showed prominent losses occurring mainly in cortical GM and hippocampus which were reflected in their EDSS and MoCA. The longitudinal results were compared with a similar sample of patients having Relapsing MS (RMS) whose GM values were largely in normal range, annualized volume GM changes were much less, while WM hyperintensities were in abnormal range in half the unselected cases.

Conclusions: Knowledge of the degree and rapidity with which cortical atrophy and deep GM volume loss develops clarifies the source of progressive cognitive and clinical decline in PPMS.

Cortical projection neurons as a therapeutic target in multiple sclerosis

INTRODUCTION

Multiple sclerosis (MS) is a chronic inflammatory-demyelinating disease of the central nervous system associated with lesions of the cortical gray matter and subcortical white matter. Recently, cortical lesions have become a major focus of research because cortical pathology and neuronal damage are critical determinants of irreversible clinical progression. Recent transcriptomic studies point toward cell type-specific changes in cortical neurons in MS with a selective vulnerability of excitatory projection neuron subtypes.

AREAS COVERED

We discuss the cortical mapping and the molecular properties of excitatory projection neurons and their role in MS lesion pathology while placing an emphasis on their subtype-specific transcriptomic changes and levels of vulnerability. We also examine the latest magnetic resonance imaging techniques to study cortical MS pathology as a key tool for monitoring disease progression and treatment efficacy. Finally, we consider possible therapeutic avenues and novel strategies to protect excitatory cortical projection neurons. Literature search methodology: PubMed articles from 2000-2020.

EXPERT OPINION

Excitatory cortical projection neurons are an emerging therapeutic target in the treatment of progressive MS. Understanding neuron subtype-specific molecular pathologies and their exact spatial mapping will help establish starting points for the development of novel cell type-specific therapies and biomarkers in MS.

Pathologic correlates of the magnetization transfer ratio in multiple sclerosis

OBJECTIVE

To identify pathologic correlates of magnetization transfer ratio (MTR) in multiple sclerosis (MS) in an MRI-pathology study.

METHODS

We acquired MTR maps at 3T from 16 fixed MS brains and 4 controls, and immunostained 100 tissue blocks for neuronal neurofilaments, myelin (SMI94), tissue macrophages (CD68), microglia (IBA1), B-lymphocytes, T-lymphocytes, cytotoxic T-lymphocytes, astrocytes (glial fibrillary acidic protein), and mitochondrial damage (COX4, VDAC). We defined regions of interest in lesions, normal-appearing white matter (NAWM), and cortical normal-appearing gray matter (NAGM). Associations between MTR and immunostaining intensities were explored using linear mixed-effects models (with cassettes nested within patients) and interaction terms (for differences between regions of interest and between cases and controls); a multivariate linear mixed-effects model identified the best pathologic correlates of MTR.

RESULTS

MTR was the lowest in white matter (WM) lesions (23.4 ± 9.4%) and the highest in NAWM (38.1 ± 8.7%). In MS brains, lower MTR was associated with lower immunostaining intensity for myelin (coefficient 0.31; 95% confidence interval [CI] 0.07-0.55), macrophages (coefficient 0.03; 95% CI 0.01-0.07), and astrocytes (coefficient 0.51; 95% CI 0.02-1.00), and with greater mitochondrial damage (coefficient 0.31; 95% CI 0.07-0.55). Based on interaction terms, MTR was more strongly associated with myelin in WM (coefficient 1.58; 95% CI 1.09-2.08) and gray matter (GM) lesions (coefficient 0.66; 95% CI 0.13-1.20), and with macrophages (coefficient 1.40; 95% CI 0.56-2.25), astrocytes (coefficient 2.66; 95% CI 1.31-4.01), and mitochondrial damage (coefficient -12.59; 95% CI -23.16 to -2.02) in MS brains than controls. In the multivariate model, myelin immunostaining intensity was the best correlate of MTR (coefficient 0.31; 95% CI 0.09-0.52; p = 0.004).

CONCLUSIONS

Myelin was the strongest correlate of MTR, especially in WM and cortical GM lesions, but additional correlates should be kept in mind when designing and interpreting MTR observational and experimental studies in MS.

Voxel-based analysis of gray matter relaxation rates shows different correlation patterns for cognitive impairment and physical disability in relapsing-remitting multiple sclerosis

BACKGROUND

Regional analyses of markers of microstructural gray matter (GM) changes, including relaxation rates, have shown inconsistent correlations with physical and cognitive impairment in MS.

OBJECTIVE

To assess voxelwise the correlation of the R1 and R2 relaxation rates with the physical and cognitive impairment in MS.

METHODS

GM R1 and R2 relaxation rate maps were obtained in 241 relapsing-remitting MS patients by relaxometric segmentation of MRI studies. Correlations with the Expanded Disability Status Scale (EDSS) and the percentage of impaired cognitive test (Brief Repeatable Battery and Stroop Test, available in 186 patients) were assessed voxelwise, including voxel GM content as nuisance covariate to remove the effect of atrophy on the correlations.

RESULTS

Extensive clusters of inverse correlation between EDSS and R2 were detected throughout the brain, while inverse correlations with R1 were mostly limited to perirolandic and supramarginal cortices. Cognitive impairment correlated negatively with R1, and to a lesser extent with R2, in the middle frontal, mesial temporal, midcingulate and medial parieto-occipital cortices.

CONCLUSION

In relapsing-remitting MS patients, GM microstructural changes correlate diffusely with physical disability, independent of atrophy, with a preferential role of the sensorimotor cortices. Neuronal damage in the limbic system and dorsolateral prefrontal cortices correlates with cognitive dysfunction.

Quantitative Imaging of White and Gray Matter Remyelination in the Cuprizone Demyelination Model Using the Macromolecular Proton Fraction

Macromolecular proton fraction (MPF) has been established as a quantitative clinically-targeted MRI myelin biomarker based on recent demyelination studies. This study aimed to assess the capability of MPF to quantify remyelination using the murine cuprizone-induced reversible demyelination model. MPF was measured in vivo using the fast single-point method in three animal groups (control, cuprizone-induced demyelination, and remyelination after cuprizone withdrawal) and compared to quantitative immunohistochemistry for myelin basic protein (MBP), myelinating oligodendrocytes (CNP-positive cells), and oligodendrocyte precursor cells (OPC, NG2-positive cells) in the corpus callosum, caudate putamen, hippocampus, and cortex. In the demyelination group, MPF, MBP-stained area, and oligodendrocyte count were significantly reduced, while OPC count was significantly increased as compared to both control and remyelination groups in all anatomic structures (p < 0.05). All variables were similar in the control and remyelination groups. MPF and MBP-stained area strongly correlated in each anatomic structure (Pearson’s correlation coefficients, r = 0.80–0.90, p < 0.001). MPF and MBP correlated positively with oligodendrocyte count (r = 0.70–0.84, p < 0.01 for MPF; r = 0.81–0.92, p < 0.001 for MBP) and negatively with OPC count (r = −0.69–−0.77, p < 0.01 for MPF; r = −0.72–−0.89, p < 0.01 for MBP). This study provides immunohistological validation of fast MPF mapping as a non-invasive tool for quantitative assessment of de- and remyelination in white and gray matter and indicates the feasibility of using MPF as a surrogate marker of reparative processes in demyelinating diseases.

Inflammatory intrathecal profiles and cortical damage in multiple sclerosis

OBJECTIVE

Gray matter (GM) damage and meningeal inflammation have been associated with early disease onset and a more aggressive disease course in multiple sclerosis (MS), but can these changes be identified in the patient early in the disease course?

METHODS

To identify possible biomarkers linking meningeal inflammation, GM damage, and disease severity, gene and protein expression were analyzed in meninges and cerebrospinal fluid (CSF) from 27 postmortem secondary progressive MS and 14 control cases. Combined cytokine/chemokine CSF profiling and 3T magnetic resonance imaging (MRI) were performed at diagnosis in 2 independent cohorts of MS patients (35 and 38 subjects) and in 26 non-MS patients.

RESULTS

Increased expression of proinflammatory cytokines (IFNγ, TNF, IL2, and IL22) and molecules related to sustained B-cell activity and lymphoid-neogenesis (CXCL13, CXCL10, LTα, IL6, and IL10) was detected in the meninges and CSF of postmortem MS cases with high levels of meningeal inflammation and GM demyelination. Similar proinflammatory patterns, including increased levels of CXCL13, TNF, IFNγ, CXCL12, IL6, IL8, and IL10, together with high levels of BAFF, APRIL, LIGHT, TWEAK, sTNFR1, sCD163, MMP2, and pentraxin III, were detected in the CSF of MS patients with higher levels of GM damage at diagnosis.

INTERPRETATION

A common pattern of intrathecal (meninges and CSF) inflammatory profile strongly correlates with increased cortical pathology, both at the time of diagnosis and at death. These results suggest a role for detailed CSF analysis combined with MRI as a prognostic marker for more aggressive MS. Ann Neurol 2018 Ann Neurol 2018;83:739-755.

MRI of cortical lesions and its use in studying their role in MS pathogenesis and disease course

Cortical grey matter (GM) demyelination is present from the earliest stages of multiple sclerosis (MS) and is associated with physical deficits and cognitive impairment. In particular, the rate of disability progression in MS, both in the relapsing and progressive phases, appears to be strictly associated with degenerative GM demyelination and diffuse cortical atrophy. In the last decade, several histopathological studies and advanced radiological methodologies have contributed to better identify the exact involvement/load of cortical pathology in MS, even if the specific inflammatory features and the precise cell and molecular mechanisms of GM demyelination and neurodegeneration in MS remain still not fully understood. It has been proposed that a combined neuropathology, imaging and molecular approach may help to define a more detailed characterization and precise assessment of the heterogeneous features of GM injury and inflammation in MS. This, in turn, will possibly identify specific imaging and biohumoral (cerebrospinal fluid/serum) correlates of cortical pathology that may have an important role in predicting and monitor the disease evolution.

MRI in multiple sclerosis: what is changing?

PURPOSE OF REVIEW

To summarize recent findings from the application of MRI in the diagnostic work-up of patients with suspected multiple sclerosis (MS), and to review the insights into disease pathophysiology and the utility of MRI for monitoring treatment response.

RECENT FINDINGS

New evidence from the application of MRI in patients with clinically isolated syndromes has guided the 2017 revision of the McDonald criteria for MS diagnosis, which has simplified their clinical use while preserving accuracy. Other MRI measures (e.g., cortical lesions and central vein signs) may improve diagnostic specificity, but their assessment still needs to be standardized, and their reliability confirmed. Novel MRI techniques are providing fundamental insights into the pathological substrates of the disease and are helping to give a better understanding of its clinical manifestations. Combined clinical-MRI measures of disease activity and progression, together with the use of clinically relevant MRI measures (e.g., brain atrophy) might improve treatment monitoring, but these are still not ready for the clinical setting.

SUMMARY

Advances in MRI technology are improving the diagnostic work-up and monitoring of MS, even in the earliest phases of the disease, and are providing MRI measures that are more specific and sensitive to disease pathological substrates.

Gadolinium and Multiple Sclerosis: Vessels, Barriers of the Brain, and Glymphatics

The pathogenesis of multiple sclerosis is characterized by a cascade of pathobiologic events, ranging from focal lymphocytic infiltration and microglia activation to demyelination and axonal degeneration. MS has several of the hallmarks of an inflammatory autoimmune disorder, including breakdown of the BBB. Gadolinium-enhanced MR imaging is currently the reference standard to detect active inflammatory lesions in MS. Knowledge of the patterns and mechanisms of contrast enhancement is vital to limit the radiologic differential diagnosis in the staging and evaluation of MS lesion activity. The aim of this review was the following: 1) to outline the pathophysiology of the effect of lymphocyte-driven inflammation in MS, 2) to describe the effects of gadolinium on the BBB and glymphatic system, and 3) to describe gadolinium enhancement patterns and artifacts that can mimic lesions in MS.

The effect of fingolimod on focal and diffuse grey matter damage in active MS patients

INTRODUCTION

The mechanism of action of fingolimod within the central nervous system and its efficacy in reducing/preventing both focal and diffuse grey matter (GM) damage in active multiple sclerosis (MS) are not completely understood.

METHODS

In this longitudinal, 2-year prospective, phase IV, single-blind study, 40 MS patients treated with fingolimod and 39 untreated age, gender, and disability-matched MS patients were enrolled. Each patient underwent a neurological examination every 6 months and a 3T MRI at the beginning of the treatment and after 24 months. The accumulation of new cortical lesions (CLs) and the progression of regional GM atrophy were compared between the two groups.

RESULTS

At the end of the study (T24), the percentage of patients with new CLs (13.5 vs. 89%, p < 0.001) and the percentage of GM volume change was lower in the treated group (p < 0.001). The regional analysis revealed that the treated group had also less volume loss in thalamus, caudatus, globus pallidus, cingulate cortex, and hippocampus (p < 0.001), as well as in, cerebellum, superior frontal gyrus, and insular-long gyrus (p < 0.05). Patients with no evidence of disease activity were 60% in the treated group and 10% in the untreated group (p < 0.001).

CONCLUSIONS

These results suggest a possible protective effect of fingolimod on focal and diffuse GM damage.

Correlation between cortical lesions and cognitive impairment in multiple sclerosis

OBJECTIVES

Gray matter (GM) damage is well known as a fundamental aspect of multiple sclerosis (MS). Above all, cortical lesions (CLs) burden, detectable at MRI with double inversion recovery (DIR) sequences, has been demonstrated to correlate with cognitive impairment (CI). The aim of this study was to investigate the role of CLs number in predicting CI in a cohort of patients with MS in a clinical practice setting.

MATERIALS AND METHODS

Thirty consecutive patients with MS presenting CLs (CL+) at high-field (3.0 T) MRI 3D-DIR sequences and an even group of MS patients without CLs (CL-) as a control, were investigated with the Rao Brief Repeatable Battery of Neuropsychological Tests (BRB), Version A. Total and lobar CLs number were computed in CL+ patients.

RESULTS

Among the sixty patients with MS enrolled, forty-seven (78.3%) had a relapsing-remitting course, while thirteen (21.7%) a progressive one, eleven secondary progressive, and two primary progressive. Compared to CL-, CL+ patients had a greater proportion of progressive forms (p = .03). The most affected region was the frontal lobe (73.3% of patients), followed by temporal and parietal ones (both 60.0%). Multivariate (logistic regression) analysis revealed a significant correlation between total CLs number and the presence of mild cognitive impairment defined as pathologic score in at least one BRB test (p = .04); it was also correlated with deficit at PASAT 3 (p = .05) and Stroop Test (p = .02).

CONCLUSIONS

We confirmed CLs number, evaluated with a technique quite commonly available in clinical practice, as a predictive factor of CI in patients with MS, in order to improve the diagnosis and management of CI and monitor potential neuroprotective effects of therapies.

The cortical damage, early relapses, and onset of the progressive phase in multiple sclerosis

OBJECTIVE

To investigate the relationship among cortical radiologic changes, the number of early relapses (ERs), and the long-term course of multiple sclerosis (MS).

METHODS

In this cohort study, we assessed the number of cortical lesions (CLs) and white matter (WM) lesions and the cortical thickness (Cth) at clinical onset and after 7.9 mean years among 219 patients with relapsing remitting (RR) MS with 1 (Low-ER), 2 (Mid-ER), and ≥3 (High-ER) ERs during the first 2 years. Kaplan-Meier and Cox regression analyses investigated early factors influencing the risk of secondary progressive (SP) MS.

RESULTS

Fifty-nine patients (27%) converted to SPMS in 6.1 mean years. A larger number of CLs at onset predicted a higher risk of SPMS (hazard ratio [HR] 2.16, 4.79, and 12.3 for 2, 5, and 7 CLs, respectively, p < 0.001) and shorter latency to progression. The High-ER compared to the Low-ER and Mid-ER groups had a larger volume of WM lesions and CLs at onset, accrued more CLs, experienced more severe cortical atrophy over time, and entered the SP phase more rapidly. In the multivariate model, older age at onset (HR 1.97, p < 0.001), a larger baseline CL (HR 2.21, p = 0.005) and WM lesion (HR 1.32, p = 0.03) volume, early changes of global Cth (HR 1.36, p = 0.03), and ≥3 ERs (HR 6.08, p < 0.001) independently predicted a higher probability of SP.

CONCLUSIONS

Extensive cortical damage at onset is associated with florid inflammatory clinical activity and predisposes to a rapid occurrence of the progressive phase. Age at onset, the number of early attacks, and the extent of baseline focal cortical damage can identify groups at high risk of progression who may benefit from more active therapy.

Postmortem magnetic resonance imaging

This chapter provides a brief overview of studies that combine postmortem magnetic resonance imaging (MRI) and histopathology. We touch upon the logistics of setting up a protocol that limits unwanted postmortem delays and explain how combining postmortem MRI and histopathology can elucidate the histologic substrate of signal changes that appear on MRI. This is demonstrated by exemplary studies in multiple sclerosis, and includes various histopathologic techniques and a wide range of conventional and advanced MRI sequences at various field strengths. We cover topics such as how to visualize white-matter pathology and repair with conventional and advanced MRI sequences, describe the history of visualizing pathology of the gray matter (with newly developed MRI and immunohistopathology techniques), and how advanced methods have aided research in other neurologic diseases. We conclude with several suggestions for future development, such as bridging the gap between postmortem and in vivo research and the importance of collecting non-neurological control tissue.

Resolving the clinico-radiological paradox in multiple sclerosis

Understanding the clinico-radiological paradox is important in the search for more sensitive and specific surrogates of relapses and disability progression (such that they can be used to inform treatment choices in individual people with multiple sclerosis) and to gain a better understanding of the pathophysiological basis of disability in multiple sclerosis (to identify and assess key therapeutic targets). In this brief review, we will consider themes and issues underlying the clinico-radiological paradox and recent advances in its resolution.

Neuropsychology of Multiple Sclerosis: Looking Back and Moving Forward

The neuropsychological aspects of multiple sclerosis (MS) have evolved over the past three decades. What was once thought to be a rare occurrence, cognitive dysfunction is now viewed as one of the most disabling symptoms of the disease, with devastating effects on patients' quality of life. This selective review will highlight major innovations and scientific discoveries in the areas of neuropathology, neuroimaging, diagnosis, and treatment that pertain to our understanding of the neuropsychological aspects of MS. Specifically, we focus on the recent discovery that MS produces pathogical lesions of gray matter (GM) that have consequences for cognitive functions. Methods for imaging these GM lesions in MS are discussed along with multimodal imaging studies that integrate structural and functional imaging methods to provide a better understanding of the relationship between cognitive test performance and functional reserve. Innovations in the screening and comprehensive assessment of cognitive disorders are presented along with recent research that examines cognitive dysfunction in pediatric MS. Results of innovative outcome studies in cognitive rehabilitation are discussed. Finally, we highlight trends for potential future innovations over the next decade. (JINS, 2017, 23, 832-842).

Heterogeneity of Cortical Lesion Susceptibility Mapping in Multiple Sclerosis

BACKGROUND AND PURPOSE

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

MATERIALS AND METHODS

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

RESULTS

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

CONCLUSIONS

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

MRI Analysis of White Matter Myelin Water Content in Multiple Sclerosis: A Novel Approach Applied to Finding Correlates of Cortical Thinning

A novel lesion-mask free method based on a gamma mixture model was applied to myelin water fraction (MWF) maps to estimate the association between cortical thickness and myelin content, and how it differs between relapsing-remitting (RRMS) and secondary-progressive multiple sclerosis (SPMS) groups (135 and 23 patients, respectively). It was compared to an approach based on lesion masks. The gamma mixture distribution of whole brain, white matter (WM) MWF was characterized with three variables: the mode (most frequent value) m₁ of the gamma component shown to relate to lesion, the mode m₂ of the component shown to be associated with normal appearing (NA) WM, and the mixing ratio (λ) between the two distributions. The lesion-mask approach relied on the mean MWF within lesion and within NAWM. A multivariate regression analysis was carried out to find the best predictors of cortical thickness for each group and for each approach. The gamma-mixture method was shown to outperform the lesion-mask approach in terms of adjusted R², both for the RRMS and SPMS groups. The predictors of the final gamma-mixture models were found to be m₁ (β = 1.56, p < 0.005), λ (β = −0.30, p < 0.0005) and age (β = −0.0031, p < 0.005) for the RRMS group (adjusted R² = 0.16), and m₂ (β = 4.72, p < 0.0005) for the SPMS group (adjusted R² = 0.45). Further, a DICE coefficient analysis demonstrated that the lesion mask had more overlap to an ROI associated with m₁, than to an ROI associated with m₂ (p < 0.00001), and vice versa for the NAWM mask (p < 0.00001). These results suggest that during the relapsing phase, focal WM damage is associated with cortical thinning, yet in SPMS patients, global WM deterioration has a much stronger influence on secondary degeneration. Through these findings, we demonstrate the potential contribution of myelin loss on neuronal degeneration at different disease stages and the usefulness of our statistical reduction technique which is not affected by the typical bias associated with approaches based on lesion masks.

Cortical Gray Matter MR Imaging in Multiple Sclerosis

Several neuropathologic and imaging studies have consistently confirmed that multiple sclerosis affects both white (WM) and gray matter (GM) and that GM damage plays a key role in disability progression. However, differently from WM damage, the less inflammatory cell infiltration, the absence of significant blood-brain barrier damage, the low myelin density in upper cortical layers, as well as technical constraints, make the GM damage almost undetectable by means of conventional MR imaging.

The relevance of cortical lesions in patients with multiple sclerosis

BACKGROUND

Recent studies suggest that cortical lesions in multiple sclerosis (MS) substantially contribute to clinical disease severity. The present study aimed at investigating clinical, neuroanatomical, and cognitive correlates of these cortical lesions with a novel approach, i.e. by comparing two samples of relapsing-remitting multiple sclerosis (RRMS) patients, one group with and the other without cortical lesions.

METHODS

High-resolution structural MRI was acquired from 42 RRMS patients and 43 controls (HC). The patient group was dichotomized based on the presence versus absence of DIR-hyperintense cortex-involving lesions, resulting in a cortical lesion group (CL, n = 32) and a non-cortical lesion group (nCL, n =10). Cognitive functioning was assessed in all participants with a comprehensive neuropsychological battery, covering mnestic, executive, and attentional functions.

RESULTS

Highest densities of cortical lesions in the CL group were observed in the bilateral parahippocampal gyrus. Relative to HC, patients with cortical lesions - but not those without - showed significant global cortical thinning and mnestic deficits. The two patient groups did not differ from each other regarding demographic and basic disease characteristics such as EDSS scores.

CONCLUSION

The appearance of cortical lesions in MS patients is associated with cortical thinning as well as mnestic deficits, which might be key characteristics of a 'cortically dominant' MS subtype.

In vivo detection of connectivity between cortical and white matter lesions in early MS

BACKGROUND

The relationship between cortical lesions (CLs) and white matter lesions (WMLs) in multiple sclerosis (MS) is poorly understood. Pathological studies support a topographical association between CLs and underlying subcortical WMLs and suggest CLs may play a role in both disease initiation and progression. We hypothesized that cortical MS lesions are physically connected to white matter MS lesions via axonal connections.

OBJECTIVE

To assess the presence of CL-WML connectivity utilizing novel magnetic resonance imaging (MRI) methodology.

METHODS

In all, 28 relapsing-remitting MS patients and 25 controls received 3 T MRI scans, including double inversion recovery (DIR) for CL detection coupled with diffusion tensor imaging (DTI). CL and WML maps were created, and DTI was used to calculate inter-lesional connectivity and volumetric connectivity indices.

RESULTS

All patients showed inter-lesional WML connectivity (median 76% of WMLs connected to another WML; interquartile range (IQR), 58%-88%). On average, 52% of detected CLs per patient were connected to at least one WML (IQR, 42%-71%). Volumetric connectivity analysis showed significantly elevated cortical lesion ratios in MS patients (median, 2.3; IQR, 1.6-3.3) compared to null MS and healthy control datasets ( p < 0.001).

CONCLUSION

These findings provide strong evidence of inter-lesional connectivity between CLs and WMLs, supporting our hypothesis of intrinsic CL-WML connectivity.

Epilepsy in multiple sclerosis: The role of temporal lobe damage

Background:

Although temporal lobe pathology may explain some of the symptoms of multiple sclerosis (MS), its role in the pathogenesis of seizures has not been clarified yet.

Objectives:

To investigate the role of temporal lobe damage in MS patients suffering from epilepsy, by the application of advanced multimodal 3T magnetic resonance imaging (MRI) analysis.

Methods:

A total of 23 relapsing remitting MS patients who had epileptic seizures (RRMS/E) and 23 disease duration matched RRMS patients without any history of seizures were enrolled. Each patient underwent advanced 3T MRI protocol specifically conceived to evaluate grey matter (GM) damage. This includes grey matter lesions (GMLs) identification, evaluation of regional cortical thickness and indices derived from the Neurite Orientation Dispersion and Density Imaging model.

Results:

Regional analysis revealed that in RRMS/E, the regions most affected by GMLs were the hippocampus (14.2%), the lateral temporal lobe (13.5%), the cingulate (10.0%) and the insula (8.4%). Cortical thinning and alteration of diffusion metrics were observed in several regions of temporal lobe, in insular cortex and in cingulate gyrus of RRMS/E compared to RRMS ( p< 0.05 for all comparisons).

Conclusions:

Compared to RRMS, RRMS/E showed more severe damage of temporal lobe, which exceeds what would be expected on the basis of the global GM damage observed.

The substrate of increased cortical FA in MS: A 7T post-mortem MRI and histopathology study

Background:

Using diffusion tensor imaging (DTI), it was previously found that demyelinated gray matter (GM) lesions have increased fractional anisotropy (FA) when compared to normal-appearing gray matter (NAGM) in multiple sclerosis (MS). The biological substrate underlying this FA change is so far unclear; both neurodegenerative changes and microglial activation have been proposed as causal contributors.

Objective:

To test the proposed hypothesis that microglia activation is responsible for increased FA in cortical GM lesions.

Methods:

We investigated post-mortem cortical DTI changes in hemispheric, coronally cut sections and investigated the underlying histopathology using immunohistochemistry.

Results:

Overall, there were few activated microglia/macrophages, and no difference between GM lesions and NAGM was observed. However, cell density was increased in GM lesions compared to NAGM (309.67 ± standard deviation (SD) 124.44 vs 249.95 ± SD 56.75, p = 0.002).

Conclusion:

FA increase was not due to lesional and non-lesional differences in microglia activation and/or proliferation. We found an increase in general cellular density without a notable difference in cellular size, that is, tissue compaction, as a possible alternative explanation.

Assessment of cortical damage in early multiple sclerosis with quantitative T2 relaxometry

T2 relaxation time is a quantitative MRI in vivo surrogate of cerebral tissue damage in multiple sclerosis (MS) patients. Cortical T2 prolongation is a known feature in later disease stages, but has not been demonstrated in the cortical normal appearing gray matter (NAGM) in early MS. This study centers on the quantitative evaluation of the tissue parameter T2 in cortical NAGM in a collective of early MS and clinically isolated syndrome (CIS) patients, hypothesizing that T2 prolongation is already present at early disease stages and variable over space, in line with global and focal inflammatory processes in MS. Additionally, magnetization transfer ratio (MTR) mapping was performed for further characterization of the expected cortical T2 alteration. Quantitative T2 and MTR maps were acquired from 12 patients with CIS and early MS, and 12 matched healthy controls. The lesion-free part of the cortical volume was identified, and the mean T2 and MTR values and their standard deviations within the cortical volume were determined. For evaluation of spatial specificity, cortical lobar subregions were tested separately for differences of mean T2 and T2 standard deviation. We detected significantly prolonged T2 in cortical NAGM in patients. T2 prolongation was found across the whole cerebral cortex and in all individual lobar subregions. Significantly higher standard deviations across the respective region of interest were found for the whole cerebral cortex and all subregions, suggesting the occurrence of spatially inhomogeneous cortical damage in all regions studied. A trend was observed for MTR reduction and increased MTR variability across the whole cortex in the MS group, suggesting demyelination. In conclusion, our results suggest that cortical damage in early MS is evidenced by spatially inhomogeneous T2 prolongation which goes beyond demyelination. Iron deposition, which is known to decrease T2, seems less prominent.

Phase-Sensitive Inversion-Recovery MRI Improves Longitudinal Cortical Lesion Detection in Progressive MS

Previous studies comparing phase sensitive inversion recovery (PSIR) to double inversion recovery (DIR) have demonstrated that use of PSIR improves cross-sectional in vivo detection of cortical lesions (CL) in multiple sclerosis. We studied the utility of PSIR in detection/characterization of accrual of CL over time in a 1-year longitudinal study in primary progressive multiple sclerosis (PPMS) compared to DIR. PSIR and DIR images were acquired with 3T magnetic resonance imaging (MRI) in 25 patients with PPMS and 19 healthy controls at baseline, and after 1 year in 20 patients with PPMS. CL were classified as intracortical, leucocortical or juxtacortical. Lesion counts and volumes were calculated for both time points from both sequences and compared. Correlations with measures of physical and cognitive disability were determined as well as new CL counts and volumes. Compared to DIR, PSIR led to detection of a higher number of CL involving a larger proportion of patients with PPMS both cross-sectionally (p = 0.006, 88%) and longitudinally (p = 0.007, 95%), and led to the reclassification of a third of CL seen on DIR at each time point. Interestingly, PSIR was more sensitive to new CL accumulation over time compared to DIR. PSIR is a promising technique to monitor cortical damage and disease progression in patients with PPMS over a short-term follow-up.

Increased cortical grey matter lesion detection in multiple sclerosis with 7 T MRI: a post-mortem verification study

The relevance of cortical grey matter pathology in multiple sclerosis has become increasingly recognized over the past decade. Unfortunately, a large part of cortical lesions remain undetected on magnetic resonance imaging using standard field strength. In vivo studies have shown improved detection by using higher magnetic field strengths up to 7 T. So far, a systematic histopathological verification of ultra-high field magnetic resonance imaging pulse sequences has been lacking. The aim of this study was to determine the sensitivity of 7 T versus 3 T magnetic resonance imaging pulse sequences for the detection of cortical multiple sclerosis lesions by directly comparing them to histopathology. We obtained hemispheric coronally cut brain sections of 19 patients with multiple sclerosis and four control subjects after rapid autopsy and formalin fixation, and scanned them using 3 T and 7 T magnetic resonance imaging systems. Pulse sequences included T1-weighted, T2-weighted, fluid attenuated inversion recovery, double inversion recovery and T2*. Cortical lesions (type I-IV) were scored on all sequences by an experienced rater blinded to histopathology and clinical data. Staining was performed with antibodies against proteolipid protein and scored by a second reader blinded to magnetic resonance imaging and clinical data. Subsequently, magnetic resonance imaging images were matched to histopathology and sensitivity of pulse sequences was calculated. Additionally, a second unblinded (retrospective) scoring of magnetic resonance images was performed. Regardless of pulse sequence, 7 T magnetic resonance imaging detected more cortical lesions than 3 T. Fluid attenuated inversion recovery (7 T) detected 225% more cortical lesions than 3 T fluid attenuated inversion recovery (Z = 2.22, P < 0.05) and 7 T T2* detected 200% more cortical lesions than 3 T T2* (Z = 2.05, P < 0.05). Sensitivity of 7 T magnetic resonance imaging was influenced by cortical lesion type: 100% for type I (T2), 11% for type II (FLAIR/T2), 32% for type III (T2*), and 68% for type IV (T2). We conclude that ultra-high field 7 T magnetic resonance imaging more than doubles detection of cortical multiple sclerosis lesions, compared to 3 T magnetic resonance imaging. Unfortunately, (subpial) cortical pathology remains more extensive than 7 T magnetic resonance imaging can reveal.

Perfusion reduction in the absence of structural differences in cognitively impaired versus unimpaired RRMS patients

BACKGROUND

Cognitive impairment affects 40%-68% of relapsing-remitting multiple sclerosis (RRMS) patients. Gray matter (GM) demyelination is complicit in cognitive impairment, yet cortical lesions are challenging to image clinically. We wanted to determine whether cortical cerebral blood flow (CBF), cerebral blood volume (CBV), and mean transit time (MTT) differences exist between cognitively impaired (CI) and unimpaired (NI) RRMS.

METHODS

Prospective study of healthy controls (n = 19), CI (n = 20), and NI (n = 19) undergoing magnetic resonance imaging (MRI) and cognitive testing <1 week apart. White matter (WM) T2 hyperintense lesions and T1 black holes were traced. General linear regression assessed the relationship between lobar WM volume and cortical and WM CBF, CBV, and MTT. Relationship between global and lobar cortical CBF, CBV, and MTT and cognitive impairment was tested using a generalized linear model. Adjusted Bonferroni p < 0.005 was considered significant.

RESULTS

No significant differences for age, gender, disease duration, and any fractional brain or lesion volume were demonstrated for RRMS subgroups. Expanded Disability Status Scale (EDSS) and Hospital Anxiety and Depression Scale-Depression (HADS-D) were higher in CI. Lobar cortical CBF and CBV were associated with cognitive impairment (p < 0.0001) after controlling for confounders. Cortical CBV accounted for 7.2% of cognitive impairment increasing to 8.7% with cortical CBF (p = 0.06), while WM and cortical CBF accounted for 8.2% of variance (p = 0.04).

CONCLUSION

Significant cortical CBF and CBV reduction was present in CI compared to NI in the absence of structural differences.

FLAIR2: A Combination of FLAIR and T2 for Improved MS Lesion Detection

BACKGROUND AND PURPOSE

FLAIR and double inversion recovery are important MR imaging scans for MS. The suppression of signal from CSF in FLAIR and the additional suppression of WM signal in double inversion recovery improve contrast between lesions, WM and GM, albeit at a reduced SNR. However, whether the acquisition of double inversion recovery is necessary is still debated. Here, we present an approach that allows obtaining CSF-suppressed images with improved contrast between lesions, WM and GM without strongly penalizing SNR.

MATERIALS AND METHODS

3D T2-weighted and 3D-FLAIR data acquired from September 2014 to April 2015 in healthy volunteers (23.4 ± 2.4 years of age; female/male ratio, 3:2) and patients (44.1 ± 14.0 years of age; female/male ratio, 4:5) with MS were coregistered and multiplied (FLAIR(2)). SNR and contrast-to-noise measurements were performed for focal lesions and GM and WM. Furthermore, data from 24 subjects with relapsing-remitting and progressive MS were analyzed retrospectively (52.7 ± 8.1 years of age; female/male ratio, 14:10).

RESULTS

The GM-WM contrast-to-noise ratio was by 133% higher in FLAIR(2) than in FLAIR and improved between lesions and WM by 31%, 93%, and 158% compared with T2, DIR, and FLAIR, respectively. Cortical and juxtacortical lesions were more conspicuous in FLAIR(2). Furthermore, the 3D nature of FLAIR(2) allowed reliable visualization of callosal and infratentorial lesions.

CONCLUSIONS

We present a simple approach for obtaining CSF suppression with an improved contrast-to-noise ratio compared with conventional FLAIR and double inversion recovery without the acquisition of additional data. FLAIR(2) can be computed retrospectively if T2 and FLAIR scans are available.

MRI criteria for the diagnosis of multiple sclerosis: MAGNIMS consensus guidelines

In patients presenting with a clinically isolated syndrome, MRI can support and substitute clinical information in the diagnosis of multiple sclerosis by showing disease dissemination in space and time and by helping to exclude disorders that can mimic multiple sclerosis. MRI criteria were first included in the diagnostic work-up for multiple sclerosis in 2001, and since then several modifications to the criteria have been proposed in an attempt to simplify lesion-count models for showing disease dissemination in space, change the timing of MRI scanning to show dissemination in time, and increase the value of spinal cord imaging. Since the last update of these criteria, new data on the use of MRI to establish dissemination in space and time have become available, and MRI technology has improved. State-of-the-art MRI findings in these patients were discussed in a MAGNIMS workshop, the goal of which was to provide an evidence-based and expert-opinion consensus on proposed modifications to MRI criteria for the diagnosis of multiple sclerosis.

Ultra-high field MTR and qR2* differentiates subpial cortical lesions from normal-appearing gray matter in multiple sclerosis

BACKGROUND

Cortical gray matter (GM) demyelination is frequent and clinically relevant in multiple sclerosis (MS). Quantitative magnetic resonance imaging (qMRI) sequences such as magnetization transfer ratio (MTR) and quantitative R2* (qR2*) can capture pathological subtleties missed by conventional magnetic resonance imaging (MRI) sequences. Although differences in MTR and qR2* have been reported between lesional and non-lesional tissue, differences between lesion types or lesion types and myelin density matched normal-appearing gray matter (NAGM) have not been found or investigated.

OBJECTIVE

Identify quantitative differences in histopathologically verified GM lesion types and matched NAGM at ultra-high field strength.

METHODS

Using 7T post-mortem MRI, MRI lesions were marked on T2 images and co-registered to the calculated MTR and qR2* maps for further evaluation. In all, 15 brain slices were collected, containing a total of 74 cortical GM lesions and 45 areas of NAGM.

RESULTS

Intracortical lesions had lower MTR and qR2* values compared to NAGM. Type I lesions showed lower MTR than type III lesions. Type III lesions showed lower MTR than matched NAGM, and type I and IV lesions showed lower qR2* than matched NAGM.

CONCLUSION

qMRI at 7T can provide additional information on extent of cortical pathology, especially concerning subpial lesions. This may be relevant for monitoring disease progression and potential treatment effects.

Beyond focal cortical lesions in MS: An in vivo quantitative and spatial imaging study at 7T

OBJECTIVES

Using quantitative T2* 7-tesla (7T) MRI as a marker of demyelination and iron loss, we investigated, in patients with relapsing-remitting multiple sclerosis (RRMS) and secondary progressive multiple sclerosis (SPMS), spatial and tissue intrinsic characteristics of cortical lesion(s) (CL) types, and structural integrity of perilesional normal-appearing cortical gray matter (NACGM) as a function of distance from lesions.

METHODS

Patients with MS (18 RRMS, 11 SPMS), showing at least 2 CL, underwent 7T T2* imaging to obtain (1) magnitude images for segmenting focal intracortical lesion(s) (ICL) and leukocortical lesion(s) (LCL), and (2) cortical T2* maps. Anatomical scans were collected at 3T for cortical surface reconstruction using FreeSurfer. Seventeen age-matched healthy participants served as controls.

RESULTS

ICL were predominantly located in sulci of frontal, parietal, and cingulate cortex; LCL distribution was more random. In MS, T2* was higher in both ICL and LCL, indicating myelin and iron loss, than in NACGM (p < 0.00003) irrespective of CL subtype and MS phenotype. T2* was increased in perilesional cortex, tapering away from CL toward NACGM, the wider changes being for LCL in SPMS. NACGM T2* was higher in SPMS relative to RRMS (p = 0.006) and healthy cortex (p = 0.02).

CONCLUSIONS

CL had the same degree of demyelination and iron loss regardless of lesion subtype and disease stage. Cortical damage expanded beyond visible CL, close to lesions in RRMS, and more diffusely in SPMS. Evaluation of NACGM integrity, beyond focal CL, could represent a surrogate marker of MS progression.

Juxtacortical Lesions and Cortical Thinning in Multiple Sclerosis

BACKGROUND AND PURPOSE

The role of juxtacortical lesions in brain volume loss in multiple sclerosis has not been fully clarified. The aim of this study was to explore the role of juxtacortical lesions on cortical atrophy and to investigate whether the presence of juxtacortical lesions is related to local cortical thinning in the early stages of MS.

MATERIALS AND METHODS

A total of 131 patients with clinically isolated syndrome or with relapsing-remitting MS were scanned on a 3T system. Patients with clinically isolated syndrome were classified into 3 groups based on the presence and topography of brain lesions: no lesions (n = 24), only non-juxtacortical lesions (n = 33), and juxtacortical lesions and non-juxtacortical lesions (n = 34). Patients with relapsing-remitting MS were classified into 2 groups: only non-juxtacortical lesions (n = 10) and with non-juxtacortical lesions and juxtacortical lesions (n = 30). A juxtacortical lesion probability map was generated, and cortical thickness was measured by using FreeSurfer.

RESULTS

Juxtacortical lesion volume in relapsing-remitting MS was double that of patients with clinically isolated syndrome. The insula showed the highest density of juxtacortical lesions, followed by the temporal, parietal, frontal, and occipital lobes. Patients with relapsing-remitting MS with juxtacortical lesions showed significantly thinner cortices overall and in the parietal and temporal lobes compared with those with clinically isolated syndrome with normal brain MR imaging. The volume of subcortical structures (thalamus, pallidum, putamen, and accumbens) was significantly decreased in relapsing-remitting MS with juxtacortical lesions compared with clinically isolated syndrome with normal brain MR imaging. The spatial distribution of juxtacortical lesions was not found to overlap with areas of cortical thinning.

CONCLUSIONS

Cortical thinning and subcortical gray matter volume loss in patients with a clinically isolated syndrome or relapsing-remitting MS was related to the presence of juxtacortical lesions, though the cortical areas with the most marked thinning did not correspond to those with the largest number of juxtacortical lesions.

Detection and quantification of regional cortical gray matter damage in multiple sclerosis utilizing gradient echo MRI

Cortical gray matter (GM) damage is now widely recognized in multiple sclerosis (MS). The standard MRI does not reliably detect cortical GM lesions, although cortical volume loss can be measured. In this study, we demonstrate that the gradient echo MRI can reliably and quantitatively assess cortical GM damage in MS patients using standard clinical scanners. High resolution multi-gradient echo MRI was used for regional mapping of tissue-specific MRI signal transverse relaxation rate values (R2(*)) in 10 each relapsing-remitting, primary-progressive and secondary-progressive MS subjects. A voxel spread function method was used to correct artifacts induced by background field gradients. R2(*) values from healthy controls (HCs) of varying ages were obtained to establish baseline data and calculate ΔR2(*) values - age-adjusted differences between MS patients and HC. Thickness of cortical regions was also measured in all subjects. In cortical regions, ΔR2(*) values of MS patients were also adjusted for changes in cortical thickness. Symbol digit modalities (SDMT) and paced auditory serial addition (PASAT) neurocognitive tests, as well as Expanded Disability Status Score, 25-foot timed walk and nine-hole peg test results were also obtained on all MS subjects. We found that ΔR2(*) values were lower in multiple cortical GM and normal appearing white matter (NAWM) regions in MS compared with HC. ΔR2(*) values of global cortical GM and several specific cortical regions showed significant (p < 0.05) correlations with SDMT and PASAT scores, and showed better correlations than volumetric measures of the same regions. Neurological tests not focused on cognition (Expanded Disability Status Score, 25-foot timed walk and nine-hole peg tests) showed no correlation with cortical GM ΔR2(*) values. The technique presented here is robust and reproducible. It requires less than 10 min and can be implemented on any MRI scanner. Our results show that quantitative tissue-specific R2(*) values can serve as biomarkers of tissue injury due to MS in the brain, including the cerebral cortex, an area that has been difficult to evaluate using standard MRI.