Abstract
We review the etiological importance of the epidemic encephalitis for progressive supranuclear palsy (PSP) and addresses the question of whether the explosion of PSP literature in the mid-20th century reflects the appearance of a new disease. We examined 2,000 studies on Parkinson's disease from 1861 to 1963 and found PSP-like cases in the past, before the epidemic encephalitis era. It can be assumed that PSP is neither a new disease nor a variant of postencephalitic parkinsonism.