New diagnostic criteria for multiple sclerosis - Application in first demyelinating episode

Background: Recently developed diagnostic criteria for MS (McDonald criteria) indicate that in patients with a single demyelinating episode (clinically isolated syndromes [CIS]), evidence for dissemination in space and time, essential for diagnosis, may be provided by MRI. Objective: To assess the usefulness of these new criteria in patients with CIS suggestive of MS. Methods: A total of 139 patients with CIS followed for a median of 3 years under-went brain MRI within 3 months of their first attack and again 12 months later. The number and location of lesions at baseline, the development of new lesions at follow-up, and the results of CSF examination (which, if positive, requires fewer MR abnormalities for diagnosis) were analyzed. The new McDonald criteria (incorporating MRI) were compared to the existing Poser diagnostic criteria and their accuracy was evaluated. Results: At 12 months, 11% had clinically definite MS according to the Poser criteria compared to 37% with the McDonald criteria. Eighty percent of patients fulfilling these new criteria developed a second clinical episode within a mean follow-up of 49 months. The new criteria showed a sensitivity of 74%, specificity of 86%, and accuracy of 80% in predicting conversion to clinically definite MS. Conclusion: One year after symptom onset, more than three times as many patients with CIS were diagnosed with MS using new diagnostic criteria incorporating MRI results compared to older criteria. However, the proposed MRI criteria require further prospective studies to optimize sensitivity and specificity.