Parallels between neuroleptic effects and lethargic encephalitis: the production of dyskinesias and cognitive disorders.

A retrospective examination of lethargic encephalitis finds many parallels with neuroleptic effects. The encephalitis, like the neuroleptics, produced an acute continuum of cognitive disorders from emotional indifference through apathy and onto a rousable stupor. It also produced similar acute dyskinesias, including akinesia, akathisia, dystonia, oculogyric crises, and tremors. The encephalitis also caused similar chronic effects, including dementia and psychosis, and somewhat different persistent dyskinesias. The chronic motor and cognitive disorders, like those associated with the neuroleptics, were often delayed in onset. An acute, severe episode of lethargic encephalitis also finds a parallel in the neuroleptic malignant syndrome. These parallels are probably due to a common site of action in the basal ganglia. They provide a model for understanding many neuroleptic effects and alert us to the probability of persistent cognitive deficits, including dementia, from neuroleptic treatment.