Radiologically isolated syndrome and multiple sclerosis

Background: Incidental white matter lesions (WML) are increasingly seen on brain magnetic resonance imaging (MRI) in clinical practice. Demyelination consistent with MS is seen in 0.1-0.7% of the population as evident by autopsy and MRI studies. The term radiologically isolated syndrome (RIS) was coined to define a subgroup of patients with demyelinating lesions highly suggestive of multiple sclerosis (MS). The Okuda criteria for diagnosing RIS help in stratifying the risk of conversion to MS but RIS is still not considered a distinct MS phenotype.

Methods: The authors reviewed the current literature on diagnostic criteria, natural history and treatment indications in RIS, to assess the challenges faced in diagnosing and treating such patients in clinical practice.

Results: Typically, one-third of patients convert to clinically definite MS within 5 years, with some progressing directly into primary progressive MS (PPMS). The main risk factors for conversion are: age < 37 years, male gender and presence of spinal cord lesions. Patients with RIS have evidence of early axonal loss, brain atrophy, cognitive deficits, increased anxiety and depression, and subclinical inflammatory disease.

Conclusion: Patients with RIS at high risk of clinical conversion might be considered for treatment, although this is still a controversial issue. Prospective follow-up of RIS patients by an MS specialist is recommended.