PRL and primary progressive multiple sclerosis: The goal of this study was to assess for the first time the association between different types of QSM lesions (including PRL) and the presence of LMCE with clinical disability, global measures of structural tissue damage, gray matter atrophy (cortical and subcortical), global and regional cortical thickness as well as their interactions in a cohort of remitting (RR) MS and PPMS patients.