Chronic lithium neurotoxicity presenting as Parkinson's disease

A 71 year old man who had been on lithium for 9 years for mania presented with an encephalopathic illness which was almost certainly due to lithium intoxication. Having recovered from this acute episode (although he was left with some sequelae) he was recommenced on lithium for his manic symptoms with a careful control of his blood levels. After remaining fairly stable for 8 years he presented with features suggestive of Parkinsonism and was admitted to hospital for investigation. There was no history of taking additional medication such as antidepressants or antipsychotics. He died in hospital and a post-mortem examination confirmed the cause of death as acute myocardial infarction. However histological examination of the brain revealed neurological sequelae of chronic lithium intoxication. There was no evidence of degenerative condition such as Parkinsonism or Alzheimer's disease.