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Neuropathological correlates of psychotic phenomena in confirmed Alzheimer's disease
Background:
The prevalence of psychotic phenomena in confirmed Alzheimer's disease (AD) and their potential neuropathological correlates have rarely been the subject of prospective investigation.
Method:
Psychopathological disturbances were recorded prospectively according to the Geriatric Mental State Schedule and the CAMDEX: The frequency of these phenomena and neuropathological changes were examined in 56 patients with definite AD.
Results:
Hallucinations had been documented in 13 patients, paranoid delusions in 9 and delusional misidentification (e.g. the Capgras-type and the 'phantom boarder' symptoms) in 14 patients. Misidentifications were associated with lower neurone counts in the area CA1 of the hippocampus. Delusions and hallucinations were observed in patients with less severe cell loss in the parahippocampal gyrus and with lower cell counts in the dorsal raphe nucleus. A decrease of neurones in the locus coeruleus in a subset of depressed patients with AD had been reported earlier. Delusions and delusional misidentification were common in 5 patients with basal ganglia mineralisation, but there was no statistically significant association of these symptoms with the presence of Lewy bodies in the brainstem and neocortex of our patient sample.
Conclusions:
These findings are compatible with the view that morphological changes in certain brain areas may promote the development of psychotic phenomena in AD. AD may offer a model for the understanding of pathomechanisms underlying the development of psychopathological disturbances in other psychoses with more discrete neuropathological changes.