The emergence of multiple sclerosis, 1870-1950: a puzzle of historical epidemiology.

In 1868, Jean-Martin Charcot identified multiple sclerosis (MS) as a distinct nosological entity. By 1870, American neurologists became aware of the "new" disease and began to diagnose cases in the United States. For the next 50 years, however, American physicians thought it was a rare condition. From 1920 to 1950, this perception changed dramatically; by 1950, neurologists considered it among the most common neurological diseases in America. The increasing prevalence of MS between 1920 and 1950 can largely be explained as an effect of an increase in the number of trained neurologists, urbanization, a changed ecology of disease, and altered concepts of gender and disease. Physicians recognized MS more frequently because over time there were more neurologists who had the skills necessary to make the difficult diagnosis, and because patients were more likely to be seen by a trained neurologist. Significant numbers of patients with MS had been misdiagnosed with other diseases such as hysteria and neurosyphilis; over time, they were increasingly diagnosed correctly.