An Instrumental Study of the Relationship Between Extrapyramidal Signs and Psychosis in Alzheimer's Disease

Neurobehavioral disturbances often coexist with extrapyramidal signs (EPS) in patients with Alzheimer's disease (AD). In the present study, we examined the relationships between delusions and hallucinations and EPS by using standard observer ratings and sensitive electromyographic (EMG) measures in 52 patients with probable AD. On the basis of observer ratings, 36.5% of the patients exhibited psychotic features and 63.5% exhibited parkinsonism. Severity of clinically rated parkinsonism and the EMG measure of bradykinesia were significantly correlated with severity of neurobehavioral disturbances in this sample. The association between parkinsonism and delusions and hallucinations suggests a subcortical mechanism in the etiopathology of psychosis in AD.