The natural history of multiple sclerosis: update 1998

The definition of multiple sclerosis (MS) is problematic. MS is best appreciated as a series of syndromes with unique but overlapping clinical and pathological features. Each has a distinct prognosis. Prototypic MS is a relapsing-remitting disease that culminates in a secondarily progressive course in most patients. Several clinical and demographic features permit stratification of patients according to risk of advanced permanent disability. It will be critical to determine if currently available "long-term treatments" truly have an impact on the long-term course of MS.