Inobvious stroke: a cause of delirium and dementia

Six hundred and sixty-one patients with stroke, confirmed by CT scan or at autopsy, were reviewed in order to evaluate the frequency of presentation with altered mental state. Nineteen patients (3%) had presented with delirium, an organic delusional state, the acute onset of dementia, or mania, mimicking psychiatric illness. All had focal cerebrovascular lesions which were usually, but not invariably, right sided. None had a previous history of cognitive impairment, psychiatric disease, drug abuse, or alcohol excess. Neurological signs were absent or mild and transient, and therefore easily missed. Post-mortem examinations in four patients showed localised cerebral infarctions with no evidence of multiple lesions, Alzheimer's disease, or metabolic encephalopathies. The possible causative factors are discussed and the evidence of asymmetrical cerebral representation of emotion, and for a relationship with epilepsy, is reviewed.