Leopold Ordenstein: on paralysis agitans and multiple sclerosis.

In 1868 the German Leopold Ordenstein (1835-1902) published in Paris a doctoral thesis in French language under the patronage of Jean-Martin Charcot (1825-1893). For the first time, multiple sclerosis and Parkinson's disease were clearly recognized as different clinical entities, based on clinical and pathological data. Ordenstein's work represents today a fundamental and often credited, yet still widely unknown, contribution to the history of these two diseases. The present paper delivers a synopsis of this key document. In addition, the life and work of Leopold Ordenstein will be reviewed.