Objectives: To investigate the rate of progression from probable to clinically definite multiple sclerosis (MS) and to define patients who had rapidly (within 1 year) progressed to a definite diagnosis.
Design: A 7-year prospective study.
Patients: A group of 163 patients experiencing their first episode of neurologic symptoms suggestive of MS. All patients had brain magnetic resonance imaging that demonstrated at least 3 demyelinating lesions at onset.
Results: Within the follow-up period (mean, 42 months; range, 13-84 months), 136 patients (83.4%) had an additional relapse and were thus defined as having clinically definite MS, whereas 27 patients (16.6%) were defined as having clinically probable MS. Most of the 136 patients with clinically definite MS (57.6%, 94 patients) experienced the additional relapse within 1 year. Demographic and clinical parameters at presentation were analyzed to identify variables predictive of rapid progression (within 1 year) to clinical definite MS. Motor involvement at onset was the only clinical parameter associated with rapid progression to a definite diagnosis. Survival curves demonstrated that polysymptomatic involvement and higher Extended Disability Status Scale score at presentation correlated with rapid progression to definite diagnosis.
Conclusion: Most patients with a diagnosis of probable MS and positive brain magnetic resonance imaging will progress rapidly to clinically definite MS.