[Etiology of parkinsonism. A verification of Poskanzer's and Schwab's hypothesis].

It was the purpose of this work to verify the hypothesis of Poskanzer and Schwab according to which nearly all cases of parkinsonism are consequences of clinical and subclinical lethargic encephalitis in the years 1917-1926. The investigated material included 495 patients with parkinsonism treated at the neurological hospital departments in Warsaw in the years 1967-1976 and 263 patients living in the City of Warsaw and treated as outpatients or inpatients in the years 1972-1976. The control group comprised patients with amyotrophic lateral sclerosis treated in the Warsaw hospitals in the years 1967-1976. The correlation between the mean age at the time of disease onset and the calendar year of disease onset was studied in different groups of patients. The indices of disease prevalence, first visits and mortality were calculated in the group of patients living in the City of Warsaw. Low values of correlation indices and persistence of approximately unchanged indices of first visits and mortality in the years 1972-1976 failed to confirm the hypothesis of Poskanzer and Schwab.