[Extrapyramidal syndrome induced by chemical substances].

Extrapyramidal signs are frequently observed in toxic diseases due to environmental and industrial chemical substances. The predominant manifestations are Parkinsonism and less frequently tremor. Parkinsonism has been described among the toxic diseases due to carbon monoxide, hydrogen sulfide, and hydrogen cyanide. In these diseases, Parkinsonism used to appear in the recovery stage from coma in the severe cases. This was also true in methyl alcohol poisoning. The extrapyramidal signs are usually symmetrical. Akinesia and rigidity are main features. Tremor is absent or mild. Levodopa and the other antiparkinsonian drugs are not so effective. Brain CT studies have revealed symmetrical low density areas in the globus pallidus and putamen. On the other hand, postural tremor is main neurological findings in the poisonings by inorganic mercury and tetraethyl lead. In general, tremor in the toxic disease is reported to be self-limited.