Course of the illness and prognosis of multiple sclerosis .1. The natural course of the illness

This review summarizes the natural history of multiple sclerosis (MS) in terms of disease type, survival, relapse rate and recovery as well as disability. The course of MS is highly variable and individually difficult to predict. In epidemiological studies, the most common type of MS is the relapsing-remitting form. However, after 10-15 years of disease duration, 30-40% of patients will develop chronic progressive MS. Survival of all MS patients is only mildly affected, but markedly decreased in severely disabled patients mainly due to secondary complications. Suicide is more frequent in MS patients than in normals, especially within the first 5 years of the disease. The mean relapse rate ranges from approximately 0.5 to 0.8 relapses per year and decreases with time. Most patients will recover from relapses within 4 weeks. 50% of patients will require some form of walking aid within 15-18 years from onset. 20-40% of patients have ,,benign'' MS, i.e. no or only mild disability after 10 years of MS.