In #RadiologicallyIsolatedSyndrome, greater paramagnetic rim lesion burden on MRI was associated with increased risk and earlier development of clinical MultipleSclerosis.

Question Are paramagnetic rim lesions (PRLs) and central vein sign–positive white matter lesions (CVS+L) associated with developing clinical symptoms of multiple sclerosis (MS) in people with radiologically isolated syndrome (RIS)?

Findings In this cohort of 36 people with RIS, a higher PRL count was associated with a shorter time to developing clinical symptoms of MS and was an independent predictor of symptom onset; these findings were validated in an independent cohort of 43 people with RIS.

Meaning Results show that PRLs may have prognostic utility for risk stratification and help guide treatment decisions in people with RIS, the earliest detectable stage of MS.