Future Brain and Spinal Cord Volumetric Imaging in the Clinic for Monitoring Treatment Response in MS

Central intra-lesional iron deposits as a possible novel imaging marker at 7 Tesla MRI in Susac Syndrome - an exploratory study

BACKGROUND

Susac syndrome (SuS) is a rare autoimmune disease that leads to hearing impairment, visual field deficits, and encephalopathy due to an occlusion of precapillary arterioles in the brain, retina, and inner ear. Given the potentially disastrous outcome and difficulties in distinguishing SuS from its differential diagnoses, such as multiple sclerosis (MS), our exploratory study aimed at identifying potential new SuS-specific neuroimaging markers.

METHODS

Seven patients with a definite diagnosis of SuS underwent magnetic resonance imaging (MRI) at 7 Tesla (7T), including T2* weighted and quantitative susceptibility mapping (QSM) sequences. T2 weighted hyperintense lesions were analyzed with regard to number, volume, localization, central vein sign, T1 hypointensity, and focal iron deposits in the center of SuS lesions ("iron dots"). Seven T MRI datasets from the same institute, comprising 75 patients with, among others, MS, served as controls.

RESULTS

The "iron dot" sign was present in 71.4% (5/7) of the SuS patients, compared to 0% in our control cohort. Thus, sensitivity was 71.4% and specificity 100%. A central vein sign was only incidentally detected.

CONCLUSION

We are the first to demonstrate this type of "iron dot" lesions on highly resolving 7T T2*w and QSM images in vivo as a promising neuroimaging marker of SuS, corroborating previous histopathological ex vivo findings.

Natalizumab Treatment for Relapsing Multiple Sclerosis Stabilises Normal-Appearing White Matter Microstructure: A One-Year Prospective Ultra-High-Field Quantitative Imaging Study

(1) Background: Natalizumab dramatically reduces relapses and MRI inflammatory activity (new lesions and enhancing lesions) in multiple sclerosis (MS). Chemical exchange saturation transfer (CEST) MRI can explore brain tissue in vivo with high resolution and sensitivity. We investigated if natalizumab can prevent microstructural tissue damage progression measured with MRI at ultra-high field (7 Tesla) over the first year of treatment. (2) Methods: In this one-year prospective longitudinal study, patients with active relapsing-remitting MS were assessed clinically and scanned at ultra-high-field MRI at the time of their first natalizumab infusion, at 6 and 12 months, with quantitative imaging aimed to detect microstructural changes in the normal-appearing white matter (NAWM), including sequences sensitive to magnetisation transfer (MT) effects from amide proton transfer (MTRAPT) and the nuclear Overhauser effect (MTRNOE). (3) Results: 12 patients were recruited, and 10 patients completed the study. The difference in the T1 relaxation times at month 6 and month 12 of natalizumab treatment was not significant, suggesting the lack of accumulation of tissue damage, while improvements were seen in MTR (MTRAPT and MTRNOE measures) at month 12, suggesting a tissue repair effect. This paralleled the expected lack of clinical and radiological worsening of conventional MRI measures of disease activity (new lesions or gadolinium-enhancing lesions). (4) Conclusion: Natalizumab prevents microstructural brain damage and has effects suggesting an improved white matter microstructure measured at ultra-high field during the first year of treatment.

Brain atrophy measurement over a MRI scanner change in multiple sclerosis

BACKGROUND

A change in MRI hardware impacts brain volume measurements. The aim of this study was to use MRI data from multiple sclerosis (MS) patients and healthy control subjects (HCs) to statistically model how to adjust brain atrophy measures in MS patients after a major scanner upgrade.

METHODS

We scanned 20 MS patients and 26 HCs before and three months after a major scanner upgrade (1.5 T Siemens Healthineers Magnetom Avanto to 3 T Siemens Healthineers Skyra Fit). The patient group also underwent standardized serial MRIs before and after the scanner change. Percentage whole brain volume changes (PBVC) measured by Structural Image Evaluation using Normalization of Atrophy (SIENA) in the HCs was used to estimate a corrective term based on a linear model. The factor was internally validated in HCs, and then applied to the MS group.

RESULTS

Mean PBVC during the scanner change was higher in MS than HCs (-4.1 ± 0.8 % versus -3.4 ± 0.6 %). A fixed corrective term of 3.4 (95% confidence interval: 3.13-3.67)% was estimated based on the observed average changes in HCs. Age and gender did not have a significant influence on this corrective term. After adjustment, a linear mixed effects model showed that the brain atrophy measures in MS during the scanner upgrade were not anymore associated with the scanner type (old vs new scanner; p = 0.29).

CONCLUSION

A scanner change affects brain atrophy measures in longitudinal cohorts. The inclusion of a corrective term based on changes observed in HCs helps to adjust for the known and unknown factors associated with a scanner upgrade on a group level.

An Update on the Measurement of Motor Cerebellar Dysfunction in Multiple Sclerosis

Multiple sclerosis (MS) is a progressive disease that often affects the cerebellum. It is characterised by demyelination, inflammation, and neurodegeneration within the central nervous system. Damage to the cerebellum in MS is associated with increased disability and decreased quality of life. Symptoms include gait and balance problems, motor speech disorder, upper limb dysfunction, and oculomotor difficulties. Monitoring symptoms is crucial for effective management of MS. A combination of clinical, neuroimaging, and task-based measures is generally used to diagnose and monitor MS. This paper reviews the present and new tools used by clinicians and researchers to assess cerebellar impairment in people with MS (pwMS). It also describes recent advances in digital and home-based monitoring for people with MS.

The Use, Standardization, and Interpretation of Brain Imaging Data in Clinical Trials of Neurodegenerative Disorders

Imaging biomarkers play a wide-ranging role in clinical trials for neurological disorders. This includes selecting the appropriate trial participants, establishing target engagement and mechanism-related pharmacodynamic effect, monitoring safety, and providing evidence of disease modification. In the early stages of clinical drug development, evidence of target engagement and/or downstream pharmacodynamic effect-especially with a clear relationship to dose-can provide confidence that the therapeutic candidate should be advanced to larger and more expensive trials, and can inform the selection of the dose(s) to be further tested, i.e., to "de-risk" the drug development program. In these later-phase trials, evidence that the therapeutic candidate is altering disease-related biomarkers can provide important evidence that the clinical benefit of the compound (if observed) is grounded in meaningful biological changes. The interpretation of disease-related imaging markers, and comparability across different trials and imaging tools, is greatly improved when standardized outcome measures are defined. This standardization should not impinge on scientific advances in the imaging tools per se but provides a common language in which the results generated by these tools are expressed. PET markers of pathological protein aggregates and structural imaging of brain atrophy are common disease-related elements across many neurological disorders. However, PET tracers for pathologies beyond amyloid β and tau are needed, and the interpretability of structural imaging can be enhanced by some simple considerations to guard against the possible confound of pseudo-atrophy. Learnings from much-studied conditions such as Alzheimer's disease and multiple sclerosis will be beneficial as the field embraces rarer diseases.

Assessment of Racial/Ethnic Disparities in Volumetric MRI Correlates of Clinical Disability in Multiple Sclerosis: A Preliminary Study

BACKGROUND AND PURPOSE

Although global and regional brain volume has been established as a relevant measure to define and predict multiple sclerosis (MS) severity, characterization of specific trends by race/ethnicity is currently lacking. We aim to (1) characterize racial disparities in disability-specific patterns of brain MRI volumetric measures between Hispanic and Caucasian individuals with MS and (2) explore the relevance of these measures as predictors of clinical disability progression.

METHODS

Brain MRI scans from 94 Hispanic and 94 age- and gender-matched Caucasian MS patients were analyzed using automatic and manual segmentation techniques. Select global and regional volume measures were correlated to Expanded Disability Status Scale (EDSS) scores at baseline and subsequent follow-up visits.

RESULTS

Hispanic patients had a higher baseline median EDSS score (interquartile range [IQR], 2.0; [1.0-3.5]) compared to Caucasians (median [IQR], 1.0 [.0-2.0]) and an increased risk of requiring ambulatory assistance (hazard ratio [HR], 9.7; 95% confidence interval [CI], 2.8-32.5). Normalized thalamic volume was moderately associated with EDSS scores (r_s   = -.42,  P < .001 in Hispanics; r_s   = -.32, P  = .002 in Caucasians) and was the best predictor of sustained disability worsening in both racial groups in a time-to-event analysis.

CONCLUSIONS

The confounding impact of race on quantitative brain volume measures may affect the interpretation of outcome measures in MS clinical trials.

Visualizing the Central Nervous System: Imaging Tools for Multiple Sclerosis and Neuromyelitis Optica Spectrum Disorders

Multiple sclerosis (MS) and neuromyelitis optica spectrum disorders (NMOSD) are autoimmune central nervous system conditions with increasing incidence and prevalence. While MS is the most frequent inflammatory CNS disorder in young adults, NMOSD is a rare disease, that is pathogenetically distinct from MS, and accounts for approximately 1% of demyelinating disorders, with the relative proportion within the demyelinating CNS diseases varying widely among different races and regions. Most immunomodulatory drugs used in MS are inefficacious or even harmful in NMOSD, emphasizing the need for a timely and accurate diagnosis and distinction from MS. Despite distinct immunopathology and differences in disease course and severity there might be considerable overlap in clinical and imaging findings, posing a diagnostic challenge for managing neurologists. Differential diagnosis is facilitated by positive serology for AQP4-antibodies (AQP4-ab) in NMOSD, but might be difficult in seronegative cases. Imaging of the brain, optic nerve, retina and spinal cord is of paramount importance when managing patients with autoimmune CNS conditions. Once a diagnosis has been established, imaging techniques are often deployed at regular intervals over the disease course as surrogate measures for disease activity and progression and to surveil treatment effects. While the application of some imaging modalities for monitoring of disease course was established decades ago in MS, the situation is unclear in NMOSD where work on longitudinal imaging findings and their association with clinical disability is scant. Moreover, as long-term disability is mostly attack-related in NMOSD and does not stem from insidious progression as in MS, regular follow-up imaging might not be useful in the absence of clinical events. However, with accumulating evidence for covert tissue alteration in NMOSD and with the advent of approved immunotherapies the role of imaging in the management of NMOSD may be reconsidered. By contrast, MS management still faces the challenge of implementing imaging techniques that are capable of monitoring progressive tissue loss in clinical trials and cohort studies into treatment algorithms for individual patients. This article reviews the current status of imaging research in MS and NMOSD with an emphasis on emerging modalities that have the potential to be implemented in clinical practice.

Advances in oral immunomodulating therapies in relapsing multiple sclerosis

BACKGROUND

Oral treatment options for disease-modifying therapy in relapsing multiple sclerosis have substantially increased over the past decade with four approved oral compounds now available: fingolimod, dimethyl fumarate, teriflunomide, and cladribine. Although these immunomodulating therapies are all orally administered, and thus convenient for patients, they have different modes of action. These distinct mechanisms of action allow better adaption of treatments according to individual comorbidities and offer different mechanisms of treatment such as inhibition of immune cell trafficking versus immune cell depletion, thereby substantially expanding the available treatment options.

RECENT DEVELOPMENTS

New sphingosine-1-phosphate receptor (S1PR) modulators with more specific S1PR target profiles and potentially better safety profiles compared with fingolimod were tested in patients with relapsing multiple sclerosis. For example, siponimod, which targets S1PR1 and S1PR5, was approved in March, 2019, by the US Food and Drug Administration for the treatment of relapsing multiple sclerosis including active secondary progressive multiple sclerosis. Ozanimod, another S1P receptor modulator in the approval stage that also targets S1PR1 and S1PR5, reduced relapse rates and MRI activity in two phase 3 trials of patients with relapsing multiple sclerosis. Blocking of matrix metalloproteinases or tyrosine kinases are novel modes of action in the treatment of relapsing multiple sclerosis, which are exhibited by minocycline and evobrutinib, respectively. Minocycline reduced conversion to multiple sclerosis in patients with a clinically isolated syndrome. Evobrutinib reduced MRI activity in a phase 2 trial, and a phase 3 trial is underway, in patients with relapsing multiple sclerosis. Diroximel fumarate is metabolised to monomethyl fumarate, the active metabolite of dimethyl fumarate, reduces circulating lymphocytes and modifies the activation profile of monocytes, and is being tested in this disease with the aim to improve gastrointestinal tolerability. The oral immunomodulator laquinimod did not reach the primary endpoint of reduction in confirmed disability progression in a phase 3 trial of patients with relapsing multiple sclerosis. In a phase 2 trial of patients with primary progressive multiple sclerosis, laquinimod also did not reach the primary endpoint of a reduction in brain volume loss, as a consequence the development of this drug will probably not be continued in multiple sclerosis. WHERE NEXT?: Several new oral compounds are in late-stage clinical development. With new modes of action introduced to the treatment of multiple sclerosis, the question of how to select and sequence different treatments in individual patients arises. Balancing risks with the expected efficacy of disease-modifying therapies will still be key for treatment selection. However, risks as well as efficacy can change when moving from the controlled clinical trial setting to clinical practice. Because some oral treatments, such as cladribine, have long-lasting effects on the immune system, the cumulative effects of sequential monotherapies can resemble the effects of a concurrent combination therapy. This treatment scheme might lead to higher efficacy but also to new safety concerns. These sequential treatments were largely excluded in phase 2 and 3 trials; therefore, monitoring both short-term and long-term effects of sequential disease-modifying therapies in phase 4 studies, cohort studies, and registries will be necessary.

Considerations for Mean Upper Cervical Cord Area Implementation in a Longitudinal MRI Setting: Methods, Interrater Reliability, and MRI Quality Control

BACKGROUND AND PURPOSE

Spinal cord atrophy is commonly measured from cerebral MRIs, including the upper cervical cord. However, rescan intraparticipant measures have not been investigated in healthy cohorts. This study investigated technical and rescan variability in the mean upper cervical cord area calculated from T1-weighted cerebral MRIs.

MATERIALS AND METHODS

In this retrospective study, 8 healthy participants were scanned and rescanned with non-distortion- and distortion-corrected MPRAGE sequences (11-50 sessions in 6-8 months), and 50 participants were scanned once with distortion-corrected MPRAGE sequences in the Day2day daily variability study. From another real-world observational cohort, we collected non-distortion-corrected MPRAGE scans from 27 healthy participants (annually for 2-4 years) and cross-sectionally from 77 participants. Statistical analyses included coefficient of variation, smallest real difference, intraclass correlation coefficient, Bland-Altman limits of agreement, and paired t tests.

RESULTS

Distortion- versus non-distortion-corrected MPRAGE-derived mean upper cervical cord areas were similar; however, a paired t test showed incomparability (t = 11.0, P = <.001). Higher variability was found in the mean upper cervical cord areas calculated from an automatic segmentation method. Interrater analysis yielded incomparable measures in the same participant scans (t = 4.5, P = <.001). Non-distortion-corrected mean upper cervical cord area measures were shown to be robust in real-world data (t = -1.04, P = .31). The main sources of variability were found to be artifacts from movement, head/neck positioning, and/or metal implants.

CONCLUSIONS

Technical variability in cord measures decreased using non-distortion-corrected MRIs, a semiautomatic segmentation approach, and 1 rater. Rescan variability was within ±4.4% for group mean upper cervical cord area when MR imaging quality criteria were met.

3D quantitative synthetic MRI-derived cortical thickness and subcortical brain volumes: Scan-rescan repeatability and comparison with conventional T1 -weighted images

Background

Previous quantitative synthetic MRI of the brain has been solely performed in 2D.

Purpose

To evaluate the feasibility of the recently developed sequence 3D‐QALAS for brain cortical thickness and volumetric analysis.

Study Type

Reproducibility/repeatability study.

Subjects

Twenty‐one healthy volunteers (35.6 ± 13.8 years).

Field Strength/Sequence

3D T₁‐weighted fast spoiled gradient recalled echo (FSPGR) sequence was performed once, and 3D‐QALAS sequence was performed twice with a 3T scanner.

Assessment

FreeSurfer and FIRST were used to measure cortical thickness and volume of subcortical structures, respectively. Agreement with FSPGR and scan–rescan repeatability were evaluated for 3D‐QALAS.

Statistical Tests

Percent relative difference and intraclass correlation coefficient (ICC) were used to assess reproducibility and scan–rescan repeatability of the 3D‐QALAS sequence‐derived measurements.

Results

Percent relative difference compared with FSPGR in cortical thickness of the whole cortex was 3.1%, and 89% of the regional areas showed less than 10% relative difference in cortical thickness. The mean ICC across all regions was 0.65, and 74% of the structures showed substantial to almost perfect agreement. For volumes of subcortical structures, the median percent relative differences were lower than 10% across all subcortical structures, except for the accumbens area, and all structures showed ICCs of substantial to almost perfect agreement. For the scan–rescan test, percent relative difference in cortical thickness of the whole cortex was 2.3%, and 97% of the regional areas showed less than 10% relative difference in cortical thickness. The mean ICC across all regions was 0.73, and 80% showed substantial to almost perfect agreement. For volumes of subcortical structures, relative differences were less than 10% across all subcortical structures except for the accumbens area, and all structures showed ICCs of substantial to almost perfect agreement.

Data Conclusion

3D‐QALAS could be reliably used for measuring cortical thickness and subcortical volumes in most brain regions.

Level of Evidence: 3

Technical Efficacy: Stage 1

J. Magn. Reson. Imaging 2019;50:1834–1842.

Quantitative 7T MRI does not detect occult brain damage in neuromyelitis optica

Objective

To investigate and compare occult damages in aquaporin-4 (AQP4)-rich periependymal regions in patients with neuromyelitis optica spectrum disorder (NMOSD) vs healthy controls (HCs) and patients with multiple sclerosis (MS) applying quantitative T1 mapping at 7 Tesla (T) in a cross-sectional study.

Methods

Eleven patients with NMOSD (median Expanded Disability Status Scale [EDSS] score 3.5, disease duration 9.3 years, age 43.7 years, and 11 female) seropositive for anti-AQP4 antibodies, 7 patients with MS (median EDSS score 1.5, disease duration 3.6, age 30.2 years, and 4 female), and 10 HCs underwent 7T MRI. The imaging protocol included T2*-weighted (w) imaging and an MP2RAGE sequence yielding 3D T1w images and quantitative T1 maps. We semiautomatically marked the lesion-free periependymal area around the cerebral aqueduct and the lateral, third, and fourth ventricles to finally measure and compare the T1 relaxation time within these areas.

Results

We did not observe any differences in the T1 relaxation time between patients with NMOSD and HCs (all p > 0.05). Contrarily, the T1 relaxation time was longer in patients with MS vs patients with NMOSD (lateral ventricle p = 0.056, third ventricle p = 0.173, fourth ventricle p = 0.016, and cerebral aqueduct p = 0.048) and vs HCs (third ventricle p = 0.027, fourth ventricle p = 0.013, lateral ventricle p = 0.043, and cerebral aqueduct p = 0.005).

Conclusion

Unlike in MS, we did not observe subtle T1 changes in lesion-free periependymal regions in NMOSD, which supports the hypothesis of a rather focal than diffuse brain pathology in NMOSD.