Prevalence of multiple sclerosis in the region of Osona, Catalonia, northern Spain.

To ascertain the prevalence of multiple sclerosis in the region of Osona in Catalonia, northern Spain, an intensive study was undertaken in a small population of 72,000 people over a period of five years, using many sources of information. Patients were classified according to the Poser criteria. Most of the patients presented with mild symptoms only and many had not seen a neurologist or attended a large hospital. The prevalence of definite and probable multiple sclerosis was 58 per 100,000. This is nine to 10 times higher than had been found previously in Catalonia and is a similar prevalence to that found in southern Spain, in Sicily, and in Greek speaking Cyprus.