Slowly Expanding Lesions Differentiate Pediatric Multiple Sclerosis from Myelin Oligodendrocyte Glycoprotein Antibody Disease

Slowly expanding lesions (SELs) in adults with multiple sclerosis (MS) indicate a progressive pathological process. Whether SELs are present in pediatric‐onset MS (POMS) or myelin oligodendrocyte glycoprotein antibody‐associated disease (MOGAD) is unknown. We studied 19 children with POMS and 14 with MOGAD (median age 14.3 and 9.4 years, respectively) recruited to the Canadian Pediatric Demyelinating Disease Study with: (1) ≥3 research scans 12 months apart; and (2) ≥1 T2‐lesions on the earliest scan. A total of 70 SELs from 16 POMS participants and 1 SEL in the MOGAD group were detected. SELs are an early feature of POMS and essentially not a feature of MOGAD. ANN NEUROL 2024;96:1086–1091