Transitional progressive multiple sclerosis: a clinical and imaging study.

OBJECTIVE To study the prevalence and the natural course of transitional progressive multiple sclerosis (TPMS). This clinical form is defined by a progressive course beginning many years after an isolated bout. METHODS 214 consecutive outpatients with definite or probable multiple sclerosis were studied. The prevalence of TPMS was established. Patients with TPMS were compared with patients with other progressive forms of multiple sclerosis according to the clinical course. A prospective one year follow up study was performed in a subgroup of patients to compare progression of the disease using clinical indices and MRI. RESULTS In this clinical population of 214 outpatients with multiple sclerosis, 55 had secondary progressive multiple sclerosis (SPMS), 38 primary progressive multiple sclerosis (PPMS), and 12 TPMS. Retrospective analysis of the clinical data of these patients shows that TPMS is very similar to SPMS at the beginning of the disease (age at onset, time before progression, clinical symptoms at onset, progression index). In addition a cohort of patients was prospectively followed up clinically and by MRI for one year. CONCLUSIONS The results did not show any significant differences between the three forms during this follow up. However, all data showed a concordant trend suggesting that at this progressive stage, TPMS is closer to PPMS in terms of progression of disability and new MRI lesions.