Recurrent delusional ideas due to left caudate head infarction, without dementia.

Herein we report the case of a 77-year-old, right-handed man, without dementia, who had a cerebral infarction in the left caudate head that manifested recurrent delusional ideas. He experienced three episodes of delusional ideas; the first two occurred after loss of consciousness and the third after delirium at night. MRI findings of left caudate head infarction were the same for all three episodes. An unstable cerebral perfusion may have caused problems in the cerebral network between the caudate head and cerebral cortex. Decreased cerebral blood flow in the frontal lobe was noted particularly in the second and third episodes, supporting the neurological background of disinhibition of emotional behaviour. Antipsychotic drugs and a small dose of risperidone were effective in controlling the patient's delusional ideas.