Imaging Correlates of the Smoldering Multiple Sclerosis Plaque

Chronic multiple sclerosis (MS) lesions are characterized by an inactive center and either a rim of activated microglia and macrophages filled with myelin (active) or a paucity of infiltrating lymphocytes, macrophages, and microglia (inactive). Active, smoldering plaques are thought to contribute to ongoing demyelination, axon loss, and disease progression. Investigators analyzed slowly expanding lesions (SELs) using imaging data from the phase III research supporting approval of ocrelizumab for treatment of relapsing-remitting (RR) and primary-progressive (PP) MS. More than 2300 patients were studied, including 1334 with relapsing and 555 with progressive disease. SELs were identified based on T1- and T2-weighted MRI sequences, where there…