Content of delusional thoughts in Alzheimer's disease and assessment of content-specific brain dysfunctions with BEHAVE-AD-FW and SPECT

Background: A consensus on the brain dysfunction(s) underlying the delusions of Alzheimer's Dementia (AD) remains to be achieved. The aim of the present study was to test the hypothesis that content-based categorization of delusional ideas manifests as dysfunction of category-specific brain regions. Methods: Fifty-nine consecutive first-visit AD outpatients underwent Single Photon Emission Computed Tomography (SPECT), Mini-Mental State Examination, and Behavioral Pathology in Alzheimer's Disease Frequency-Weighted Severity scale (BEHAVE-AD-FW) to assess cerebral blood flow (CBF), cognitive function, and delusion, respectively. SPECT images were analyzed by SPM5. Results: CBF decreased at the temporal poles and right inferior temporal gyrus in delusion of theft, at the temporal poles in suspiciousness/paranoia, at the right parahippocampal gyrus and insula in abandonment, and at the right amygdala in Residence is not home. Conclusions: Our findings offer a perspective on the discrete categories of the pathological thoughts of AD patients that have previously been lumped together as delusions. Dysfunction of the temporal poles may be associated with a socioemotional deterioration that may include pathological suspiciousness. Delusion of theft may be a manifestation of socioemotional deterioration and poor insight. Emotional factors may be essential for delusions of abandonment and not home.