Astrogliosis in von Economo's and postencephalitic Parkinson's diseases supports probable viral etiology.

A marked generalized astrogliosis was observed in the frontal and temporal white matter from a case of von Economo's disease and another of postencephalitic Parkinson's disease, which areas were otherwise devoid of any other demonstrable microscopic lesions. No similar astrocytic reaction of any severity was observed in the same areas in a number of other brain diseases or controls, except when other kinds of lesions were present in the same section, with reactive astrocytes being present within the primary or defining lesion or immediately close by. The marked astrogliosis in von Economo's and postencephalitic Parkinson's diseases in areas "distant" from the primary lesions seeming to indicate extensive pathological involvement, added to the strong qualitative and quantitative similarity of this reaction to that observed in concurrently studied cases of encephalitides caused by the human immunodeficiency virus, lend further factual support to the hypothesis of a viral etiology, albeit unspecified, in both von Economo's and postencephalitic Parkinson's diseases.