Relevance of hypointense brain MRI lesions for long-term worsening of clinical disability in relapsing multiple sclerosis

Background: The accrual of brain focal pathology is considered a good substrate of disability in relapsing-remitting multiple sclerosis (RRMS). However, knowledge on long-term lesion evolution and its relationship with disability progression is poor. Objective: The objective of this paper is to evaluate in RRMS the long-term clinical relevance of brain lesion evolution. Methods: In 58 RRMS patients we acquired, using the same scanner and protocol, brain magnetic resonance imaging (MRI) at baseline and 100.5 years later. MRI data were correlated with disability changes as measured by the Expanded Disability Status Scale (EDSS). Results: The annualized 10-year lesion volume (LV) growth was +0.25 +/- 0.5 cm(3) (+6.7 +/- 8.7%) for T2-weighted (T2-W) lesions and +0.20 +/- 0.31 cm(3) (+11.5 +/- 12.3%) for T1-weighted (T1-W) lesions. The univariate analysis showed moderate correlations between baseline MRI measures and EDSS at 10 years (p < 0.001). Also, 10-year EDSS worsening correlated with LV growth and the number of new/enlarging lesions measured over the same period (p < 0.005). In the stepwise multiple regression analysis, EDSS worsening over 10 years was best correlated with the combination of baseline T1-W lesion count and increasing T1-W LV (R = 0.61, p < 0.001). Conclusion: In RRMS patients, long-term brain lesion accrual is associated with worsening in clinical disability. This is particularly true for hypointense, destructive lesions.