Encephalitis in Etiology of Parkinsonism in Australia

THERE IS uncertainty as to the prevalence of parkinsonism and the relative importance of its three principal etiological varieties—idiopathic paralysis agitans, the postencephalitic, and the arteriopathic. Age-adjusted death rates for parkinsonism per 100,000 of population range from 0.5 (Mexico, Japan, Czechoslovakia) to 3.8 (Australia),1but variation in certification from country to country makes interpretation of these figures uncertain. The few figures available for prevalence of parkinsonism range from 30 per 100,000 (Canadian Sickness Survey),2through 65-70 (Sweden),3and 180 per 100,000 (USA),4to 660 per 100,000 (USA).5 As to the relative importance of the three major etiological types, we have elsewhere considered arteriosclerotic parkinsonism6and have suggested that on the evidence available cerebral arteriosclerosis is unlikely to be a major cause of typical parkinsonism featuring both rigidity and tremor. Here we propose to consider the possible role played by encephalitis in producing parkinsonism, with