Restriction spectrum imaging of white matter and its relation to neurological disability in multiple sclerosis.

BACKGROUND: Restriction spectrum imaging (RSI) is a recently introduced magnetic resonance imaging diffusion technique. The utility of RSI in multiple sclerosis (MS) is unknown. OBJECTIVE: To investigate the association between RSI-derived parameters and neurological disability in MS. METHODS: Seventy-seven relapsing-remitting MS patients were scanned with RSI on a 3-T scanner. RSI-derived parameters: fast and slow apparent diffusion coefficient (sADC), fractional anisotropy, restricted fractional anisotropy, neurite density (ND), cellularity, extracellular water fraction, and free water fraction, were obtained in white matter lesions (WML) and normal appearing white matter (NAWM). Patients were divided into three groups according to their expanded disability status scale (EDSS): with minimal, low, and substantial disability (<2.5, 2.5-3, and >3, respectively). Group comparisons and correlation analyses were performed. RESULTS: All tested RSI-derived parameters differed between WML and NAWM ( p < 0.001 for all pairwise comparisons). The sADC in WML showed largest difference across disability subgroups (analysis of variance (ANOVA): F = 5.1, η2 = 0.12, p = 0.008). ND in NAWM showed strongest correlation with disability (ϱ = -0.39, p < 0.001). CONCLUSION: The strongest correlation with EDSS of ND obtained in NAWM indicates that processes outside lesions are important for disability in MS. Our study suggests that RSI-derived parameters may help understand the "clinico-radiological paradox" and improve disease monitoring in MS.

Prevalence of multiple sclerosis among immigrants in Norway.

BACKGROUND: Multiple sclerosis (MS) prevalence is unevenly distributed worldwide. Immigration to Norway from countries with a lower MS prevalence is increasing. The aim of this study was to investigate MS prevalence in different immigrant populations in Norway and evaluate the effect of migrating from low- to high-risk regions of MS. METHOD: First- and second-generation immigrants from the largest immigrant populations were identified from the 2012 Norwegian prevalence study. Prevalence of MS in different ethnic groups was compared using the standardized prevalence ratio (SPR). RESULTS: European and North-American immigrants had the highest prevalence of MS, whereas African and Asian immigrants had the lowest. The prevalence of first-generation Iranian immigrants was not significantly different from the total Norwegian population (SPR 0.70, 95% CI: 0.46-1.03). Second-generation immigrants from Pakistan (SPR 1.62, 95% CI: 0.88-2.76) had a strong increase in prevalence compared to the first generation (SPR 0.13, 95% CI: 0.05-0.28). CONCLUSION: MS prevalence among immigrants in Norway in general reflects the uneven distribution worldwide. The sharp increase in prevalence in immigrants seen in one generation suggests strong environmental factors affecting the MS risk in Norway.