Delirium and persistent dyskinesia induced by a lithium-neuroleptic interaction.

We report the case of a bipolar patient developing severe delirium and extrapyramidal signs shortly after initiation of a lithium-neuroleptic combination therapy. Clinical presentation, EEG changes and lithium plasma levels showed a close correlation. The delirium was reversible when all drugs were stopped; however, dyskinesia was found to be persistent after a period of 6 months. This rare syndrome is difficult to differentiate from lithium intoxication and neuroleptic malignant syndrome. Given the additional use of valproate and biperiden in this patient, valproate encephalopathy and anticholinergic delirium are further differential diagnoses. To avoid this serious pharmacodynamic drug interaction, patients should be closely monitored when lithium-neuroleptic comedication is started.