The radiologically isolated syndrome: take action when the unexpected is uncovered?

The increasing diagnostic application of magnetic resonance imaging (MRI) in neurology has resulted in an increase in accidental disclosure of asymptomatic brain pathologies with potential clinical significance. Here, we discuss the incidental detection of multiple sclerosis (MS) typical central nervous system (CNS) lesions fulfilling MRI criteria for dissemination in space (radiologically isolated syndrome, RIS) and its diagnostic, prognostic and therapeutic implications. Three recent studies, including a total of 136 RIS cases which were followed for up to 10 years, indicate that a subgroup of such patients will develop MS. MRI-based dissemination in time (DIT) was determined in more than two-thirds and clinically isolated syndrome (CIS) occurred in almost one-third of the patients. Presence of Gadolinium (Gd)-enhancing lesions was identified as potential predictor for MRI-based DIT in one study, and pathological visual evoked potential (VEP) examinations at baseline and Gd-enhancement at the second MRI scan for CIS (clinical DIT) in another study. In the lack of established management guidelines, we propose a pragmatic diagnostic and therapeutic approach for patients with RIS. Individual concepts are required and both "wait" as well as "follow" strategies are justifiable. Further prospective studies are required to elucidate potential biomarkers for narrowing down the high-risk cohort and exploring further characteristics of this disease stage.