Radiologically isolated syndrome (RIS) is the earliest documented stage in the disease continuum of multiple sclerosis (MS). It is discovered incidentally in individuals who are asymptomatic but have typical lesions in the brain or spinal cord suggestive of autoimmune inflammatory demyelination. The revised 2023 RIS criteria aim to secure an accurate and timely diagnosis due to the presence of imaging mimics. These criteria require having at least one T2-weighted hyperintense lesion in one of the four suggestive MS locations along with two of the following three features: spinal cord lesion, cerebrospinal fluid (CSF)-restricted oligoclonal bands, or new T2 or gadolinium-enhancing lesion observed on a subsequent magnetic resonance imaging (MRI) study. Once the diagnosis is confirmed, established risk factors, including age, lesion location and CSF, significantly improve prognostic stratification, which is crucial for immunoactive interventions. Recent clinical trials have shown that oral disease-modifying treatments can delay or prevent the first clinical event in RIS patients. Consulting with an MS team for each RIS case is strongly recommended to enhance care and disease surveillance. The revised 2024 McDonald criteria will classify individuals with additional CSF and advanced MRI biomarkers as having preclinical MS, highlighting the importance of vigilance in this area.
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