Disease course after clinically isolated syndrome in children versus adults: a prospective cohort study.

BACKGROUND AND PURPOSE: Clinically isolated syndrome (CIS) is a first demyelinating event of the central nervous system and can be a single event. After CIS, a chronic disease course with ongoing inflammation and relapses might occur, resulting in a diagnosis of multiple sclerosis (MS). As yet, there has been no prospective exploration of whether children and adults with CIS have the same disease course. METHODS: Patients with CIS, whose age ranged from 1 to 50 years, were prospectively followed. We divided the patients into three different age groups, i.e. 1-10, 11-17 and 18-50 years old. Demographic data, disease course, time to MS diagnosis and annualized relapse rates (ARRs) were compared among these groups. RESULTS: We included 383 patients with CIS, of whom 218 (56.9%) were diagnosed with MS. Children of between 11 and 17 years old had the highest rate of MS conversion (83.5% vs. 50.0% in the other age groups together, P < 0.01) and the shortest time to MS diagnosis [median time 2.6 months (interquartile range, 0.6-6.0) vs. 8.2 months (interquartile range, 1.9-28.2) in the other age groups together, P < 0.01). ARRs corrected for follow-up were higher in children of <18 years old than in adults of ≥18 years old with MS (mean ARR, 0.65 vs. 0.43, P < 0.01). CONCLUSION: Children with CIS tend to have a more inflammatory disease course appearing from higher ARRs in all children and the highest rate of MS conversion in 11-17-year-old children. This supports early initiation of disease-modifying therapy in children, perhaps even at the first event in children at high risk for MS in line with clinical practice in adults.