Postencephalitic parkinsonism is reported following infection with certain viruses such as Japanese B encephalitis virus, St Louis encephalitis virus, western equine encephalitis virus, eastern equine encephalitis virus, West Nile virus, Epstein-Barr virus, influenza A virus, and certain enteroviruses such as coxsackievirus B and echoviruses.1 These viruses affect the cortex, thalamus, brainstem, and spine, but preferential involvement of the substantia nigra (SN) has been reported.1,2 Postencephalitic parkinsonism with SN involvement has also been reported in cases of encephalitis lethargica (EL; von Economo disease),3,4 which occurred in epidemic form between 1915 and 1928. To our knowledge, although a viral etiology has long been suspected in EL, no infectious agent has ever been isolated.
Toledano M, Davies NWS. Enteroviral Postencephalitic Parkinsonism With Evidence of Impaired Presynaptic Dopaminergic Function. JAMA Neurol. 2016;73(8):1023-1025. doi:10.1001/jamaneurol.2016.1043