Paramagnetic Rim Lesions Predict Conversion to Clinical MS in Radiologically Isolated Syndrome

In a prospective multicenter cohort study published in JAMA Neurology, paramagnetic rim lesions (PRLs) detected on susceptibility-sensitive MRI in individuals with radiologically isolated syndrome (RIS) were associated with increased risk of developing clinical multiple sclerosis (MS). Across discovery and validation cohorts, higher PRL burden predicted shorter time to first clinical demyelinating event during longer-term follow-up, whereas total white matter lesion counts and central vein sign measures in the discovery cohort were not significantly different between those who converted to clinical MS and those who did not.

The multicenter observation cohort study included 79 adults with RIS recruited from 3 academic centers (36 in a discovery cohort; 43 in a validation cohort) who were followed prospectively with 3-T brain and spinal cord MRI and serial neurologic assessment. Median follow-up was 6.4 years in the discovery cohort and 4.4 years in the validation cohort. The primary outcome was development of clinical MS. The researchers utilized time-varying Cox regression and elastic net modeling to evaluate associations between baseline MRI features and symptom onset.

Key findings from the study include the following:

• In the discovery cohort, 9 of 36 participants (25%) developed MS; higher PRL count was associated with earlier symptom onset from 5 to 30 years after RIS diagnosis (hazard ratio [HR], 1.15; 95% CI, 1.05 to 1.26; P=.004).
• In the validation cohort, 9 of 43 participants (21%) developed MS; the association between PRL count and conversion to clinical MS was similar to the discovery cohort (HR, 1.51; 95% CI, 1.00 to 2.27; P=.04).
• In the discovery cohort, ≥4 PRLs predicted clinical MS (odds ratio [OR], 14.64; 95% CI, 2.00 to 207.23; P=.02), as did PRL count (OR, 1.15; 95% CI, 1.03 to 1.32; P=.02).
• In the validation cohort, presence of any PRL was associated with conversion (OR, 20.90; 95% CI, 2.35 to 533.30; P=.02).

Source:Lim TR, Suthiphosuwan S, Gaitán MI, et al. Paramagnetic Rim Lesions and Development of Clinical MS in Radiologically Isolated Syndrome. JAMA Neurol. Published online January 26, 2026. doi:10.1001/jamaneurol.2025.5394