Abstract
Three necropsied cases of chronic, sporadic brainstem encephalitis of unknown aetiology are presented. Since their outstanding symptoms were dementia and ataxia of a progressive nature, a noninflammatory disease of the central nervous system was suspected. Neuropathological studies showed chronic inflammatory changes mainly in the brainstem without the presence of inclusion bodies or viral particles. Compared to cases previously reported as brainstem encephalitis, the clinical and pathological findings observed in these cases have rather peculiar characteristics.