The psychotic phenomenon in probable Alzheimer's disease: A positron emission tomography study

Positron emission tomography was used to examine the mechanisms of the psyc hotic phenomenon in Alzheimer's disease (AD). Data from 2 patients with del usions and 2 with hallucinations were compared with those of 5 AD patients without psychosis. The patients with paranoid delusions had diminished rela tive regional cerebral blood flow (rel-CBF) in the left dorsolateral prefro ntal and left medial temporal cortices. The patients with visual hallucinat ions showed diminished rel-CBF in the right parietal, left medial temporal, and left dorsolateral prefrontal cortices. These findings support the hypo thesis that a frontal-temporal abnormality is associated with paranoid delu sions in AD. By contrast, visual hallucinations are associated with parieta l as well as frontal and temporal lobe dysfunction. In these patients, a le ft prefrontal-temporal cortex dysfunction appears to be a common denominato r for the development of the psychotic phenomenon in AD.