Post-encephalitic parkinsonism: clinical features and experimental model

Post-encephalitic parkinsonism has been well documented by now. Recently, an Indian group reported some post-encephalitic parkinsonism patients that resembled Japanese encephalitis cases with bilateral substantia nigra lesions that were detected by MRI. Post-encephalitis parkinsonism has been described following Coxsackie B virus, influenza A, poliovirus and measles virus infections. The possible involvement of virus infection has also been supported by experimental animal models. We have demonstrated pathological and to a certain extent clinical features consistent with Parkinson's disease following infection of rats with Japanese encephalitis virus (JEV). We evaluated new treatments with Parkinson's disease using this model. It was reported that tremor primarily involving the fingers, tongue and eyelids, muscle rigidity and masked face as the clinical features by JEV. Recently brainstem lesions produced by West Nile virus, which is a flavivirus like JEV, were documented by MRI. In the future, post-encephalitic parkinsonism may be found elsewhere in the world. In adult Fischer rats sacrificed 12 weeks after infection with JEV at the age of 13 days, neuronal loss with gliosis was confined mainly to the zona compacta of the bilateral substantia nigra, without lesions in the cerebral cortex and cerebellum. Furthermore, the most severe lesions were in the central part of zona compacta; the lateral cell groups were less affected. Thus, the distribution of the pathologic lesions in infected rats resembled those found in Parkinson's disease. JEV-infected rats showed marked bradykinesia. Significant behavioral improvement was observed upon administration of L-DOPA and monoamine oxidase (MAO) inhibitor. The findings suggest that JEV infection of rats under the conditions described may serve as a model of virus induced Parkinson's disease.