Background

We recently showed that 7T MRI leptomeningeal enhancement (LME) is common in relapsing-remitting multiple sclerosis (RRMS) and is related to gray matter (cortical/thalamic) and white matter (WMLs) lesions.

Objectives

To investigate the dynamics of LME longitudinal change and relationship to subsequent lesion accumulation using 7T MRI.

Methods

25 RRMS subjects [age 44.5±11.2 years (mean±SD), 68% women, Expanded Disability Status Scale (EDSS) 2.0±1.5, 92% on disease-modifying therapy-DMT] and 12 healthy controls (HC) underwent brain 3D MP2RAGE and FLAIR 7T MRI with 0.7 mm³ voxels at baseline and ~1 year. Gadolinium-enhanced 3D-FLAIR was evaluated for LME. WMLs, cortical lesions (CLs) and thalamic lesions (TLs) were expert-quantified. Wilcoxon rank-sum, two-sample t-tests and Spearman’s correlations were investigated.

Results

LME was found in 17/25 (68%) RRMS subjects at baseline and 18/25 (72%) at follow-up vs. a single stable focus in 1/12 HC (8.3%). In the RRMS group, 42 LME foci [mean 2.5±1.1 (range 1-5) per LME+ subject] were identified at baseline versus 48 foci [2.7±1.2 (1-5)] at follow-up. LME foci number at follow-up was unchanged in 18 (72%) RRMS subjects, increased in 6 (24%), decreased in 1 (4%). All 6 subjects with increased LME foci were on treatment [glatiramer acetate, interferon-β (2), rituximab, ocrelizumab, fingolimod]. The subject with LME resolution was treated with ocrelizumab. LME+ subjects had an on-study increase in volume of WMLs (baseline 11.0±14.4 vs. follow-up 12.6±16.3 ml, p<0.001), CLs (0.85±1.2 vs. 1.0±1.4 ml, p=0.002) and TLs (0.103±0.093 vs. 0.117±0.099 ml, p=0.005), whereas LME- subjects had an increase only in WML volume (2.7±2.3 vs. 3.3±2.6 ml, p=0.023). Baseline LME foci number correlated with 1-year change in CL (r=0.36, p=0.078) and WML (r=0.50, p=0.010) volumes. Minimal EDSS change over 1 year was noted. We used these data as the basis for a sample size calculation for a hypothetical trial of a putative therapy that would reduce the rate of MRI lesion accrual by 80% over 1 year. For a single-arm study with 1-year run-in on standard therapy and 1 year on new treatment to achieve 80% power, sample sizes of n=46, n=56 and n=79 were calculated for CL volume, TL volume and LME foci number, respectively.

Conclusions

The evolution of cerebral LME may be a dynamic process in the short term in RRMS, providing a monitoring tool, with about one quarter of patients showing new foci at one year. LME may pose a risk for the subsequent development of new lesions in widespread brain regions, implicating meningeal involvement as a marker or mediator of increased disease severity.

Abstract

Background: Multiple sclerosis is characterized by both neuroinflammation and accelerated brain atrophy. These two processes can be quantified by MRI, are at least partially independent, and have different underlying pathological mechanisms. MicroRNA (miRNA) have previously shown strong ties to various neurological disease processes, and have potential as biomarkers in MS.

Objectives: To classify and immunologically characterize persons with MS based on serum miRNA profiles in conjunction with MRI phenotypes, as defined by relative burden of cerebral T2-hyperintense lesion volume (T2LV) and brain parenchymal fraction (BPF).

Methods: Cerebral T2LV and BPF were retrospectively quantified from 1.5T MRI, and used to define the following MRI phenotypes. Type I: low T2LV, low atrophy; type II: high T2LV, low atrophy; type III: low T2LV, high atrophy; type IV: high T2LV, high atrophy, in a large cross-sectional cohort (n = 1,088) and a subset with 5-year longitudinal follow-up (n = 153). Serum miRNAs were assessed on a third MS cohort with 2-year MRI phenotype stability (n = 98). A proportional odds logistic regression model was used to determine significant associations been MRI features and miRNA expression.

Results: One-third of the patients showed dissociation between lesion burden and atrophy severity as defined by MRI phenotypes II or III. At 5-year follow-up, all phenotypes showed increased atrophy (p < 0.001), disproportionally in type II (BPF −2.28%). Only type IV experienced significantly worse neurological disability scores. Types I and II had a 5-year MRI phenotype conversion rate of 33% and 46%, whereas III and IV had >90% stability. Type II switched primarily to IV (91%); type I switched primarily to II (47%) or III (37%). Baseline higher age (p = 0.006) and lower BPF (p < 0.001) predicted 5-year phenotype conversion. MicroRNA analysis revealed sixteen miRNA differentially expressed (p < 0.05, uncorrected) between the four phenotypes. Each phenotype demonstrated a distinct miRNA signature. Biological interpretation of these miRNA suggest a role for blood-brain barrier pathology. miR-22-3p, miR-361-5p, and miR-345-5p were the most valid differentiators.

Conclusions: MRI-defined MS phenotypes show high conversion rates characterized by relentless brain atrophy with or without ongoing inflammation, and results support the partial independence of these two features. Differentially expressed serum microRNA for the MRI phenotypes implicates the blood-brain barrier as an important mechanism determining pathological course. MicroRNA are promising as biomarkers in MS but require significant further verification and methodological standardization.