Incidental MRI anomalies suggestive of multiple sclerosis: the radiologically isolated syndrome.

BACKGROUND The discovery and broad application of MRI in medicine has led to an increased awareness in the number of patients with incidental white matter pathology in the CNS. Routinely encountered in clinical practice, the natural history or evolution of such individuals with respect to their risk of developing multiple sclerosis (MS) is unclear. OBJECTIVE To investigate the natural history of patients who exhibit incidental imaging findings highly suggestive of MS pathology. METHODS Detailed clinical and radiologic data were obtained from asymptomatic patients with MRI anomalies suggestive of MS. RESULTS The cohort consisted of 41 female and 3 male subjects (median age = 38.5, range: 16.2-67.1). Clinical evaluations were performed in 44 patients at the time of initial imaging; longitudinal clinical follow-up occurred for 30 patients, and longitudinal MRI data were acquired for 41 patients. Neurologic examination at the time of the initial MRI scans was normal in nearly all cases. While radiologic progression was identified in 59% of cases, only 10 patients converted to either clinically isolated syndrome or definite MS. The presence of contrast-enhancing lesions on the initial MRI was predictive of dissemination in time on repeat imaging of the brain (hazard ratio [HR] = 3.4, 95% confidence interval [1.3, 8.7], p = 0.01). CONCLUSION Individuals with MRI anomalies highly suggestive of demyelinating pathology, not better accounted for by another disease process, are very likely to experience subsequent radiologic or clinical events related to multiple sclerosis. Additional studies will be necessary to fully define this risk.