Brain lesion location and clinical status 20 years after a diagnosis of clinically isolated syndrome suggestive of multiple sclerosis

Background/Objectives: The objective of this study was to investigate associations between the spatial distribution of brain lesions and clinical outcomes in a cohort of people followed up 20 years after presentation with a clinically isolated syndrome (CIS) suggestive of multiple sclerosis (MS). Methods: Brain lesion probability maps (LPMs) of T1 and T2 lesions were generated from 74 people who underwent magnetic resonance imaging (MRI) and clinical assessment a mean of 19.9 years following a CIS. One-tailed t-test statistics were used to compare LPMs between the following groups: clinically definite (CD) MS and those who remained with CIS, with an abnormal MRI; people with MS and an Expanded Disability Status Scale (EDSS) <= 3 and > 3; people with relapsing-remitting (RR) and secondary progressive (SP) MS. The probability of each voxel being lesional was analysed adjusting for age and gender using a multiple linear regression model. Results: People with CDMS were significantly more likely than those with CIS and abnormal scan 20 years after onset to have T1 and T2 lesions in the corona radiata, optic radiation, and splenium of the corpus callosum (periventricularly) and T2 lesions in the right fronto-occipital fasciculus. People with MS EDSS > 3, compared with those with EDSS <= 3, were more likely to have optic radiation and left internal capsule T2 lesions. No significant difference in lesion distribution was noted between RRMS and SPMS. Conclusion: This work demonstrates that lesion location characteristics are associated with CDMS and disability after long-term follow-up following a CIS. The lack of lesion spatial distribution differences between RRMS and SPMS suggests focal pathology affects similar regions in both subgroups.