Cohort Study: One-Fourth of MS Relapses Occur Without MRI Activity, Highlighting ACES Phenomenon – JAMA Neurol

Study Design and Population: This multicenter observational cohort study examined 637 clinical relapse events in 608 patients with relapsing-remitting multiple sclerosis (RRMS) from the French MS registry, spanning January 2015 to June 2023. The study included relapses with brain and spinal cord MRI performed within 12-24 months before and 50 days after the event.

Main Findings: Approximately 26% of relapses were classified as acute clinical events with stable MRI (ACES), showing no new T2 or gadolinium-enhanced T1 lesions. ACES were more likely in patients on highly effective disease-modifying therapies (DMTs), with longer disease duration, or with fatigue. ACES were associated with increased rates of relapse, confirmed disability accrual, and progression to secondary progressive MS, though their MRI stability was unaffected by DMTs.

Implications for Practice: The study suggests that MRI alone may not fully capture disease activity in RRMS, highlighting the need for comprehensive clinical assessment in therapeutic decision-making and clinical trial designs.

Reference: Gavoille, A., Rollot, F., Casey, R., et al. (2024). Acute clinical events identified as relapses with stable magnetic resonance imaging in multiple sclerosis. JAMA Neurology, 81(8), 814-823. DOI: 10.1001/jamaneurol.2024.1961.