Quantitative electroencephalographic correlates of psychosis in Alzheimer disease.

Objective: We hypothesized that the distinctive neurobiology of Alzheimer disease (AD) with psychosis would be reflected in more severe abnormalities in frontal and temporal regions on quantitative electroencephalography (QEEG).

Background: Patients with AD and psychosis have more rapid cognitive decline and greater pathologic involvement of frontal and temporal cortex than AD patients without psychotic features.

Method: We evaluated brain function using QEEG in a group of 44 patients who had a diagnosis of probable or possible AD. All patients were administered the Mini-Mental State Examination and the Neuropsychiatric Inventory to assess psychiatric symptoms, including the presence of hallucinations and delusions. Absolute and relative power in patients with and without psychosis were compared to determine if there were regional or global QEEG differences in these two groups.

Results: Patients with psychosis showed greater overall absolute and relative delta power but no regional predominance of slowing compared with those without psychosis. Those with psychosis had a concomitant decrease in relative alpha power. These differences remained after adjustment for different dementia severity in the two groups.

Conclusions: This finding suggests more severe brain dysfunction in patients with psychosis than in those with similar levels of cognitive impairment but without psychosis. The QEEG abnormalities were not regionally specific and involved all areas assessed.