Slowly Expanding Lesions May Contribute to Disease Progression in Multiple Sclerosis

Slowly expanding brain lesions (SELs) are multiple sclerosis (MS) demyelinating plaques with ongoing destruction at the edge. Pathological studies show that the edges of these chronically active lesions have a rim of lymphocytes, macrophages, and activated microglia. SELs have a decreasing T1 signal within existing lesions over time, suggestive of ongoing axonal injury. In this study, investigators evaluated SELs in 555 patients with primary progressive MS as part of the manufacturer-sponsored phase 3 ORATORIO clinical trial evaluating ocrelizumab versus placebo.

Within existing lesions, nonenhancing T1 hypointensity volume increased in both treatment groups. Ocrelizumab-treated patients had very few new T2 lesions, and their overall lesion …