Delusions in AD are associated with a normal pattern of asymmetry in the temporal and frontal lobes

Objective. To assess whether delusional Alzeimer's disease (AD) patients have a specific pattern of regional brain atrophy. Methods. Temporal lobe and frontal lobe atrophy were assessed with linear measures (radial width of the temporal horn, rWTH, and Frontal Index, FI) taken from CT films. Temporal and frontal asymmetries were computed as right/left (R/L) ratio of the rWTH and Fl in 22 nondelusional and 19 delusional AD patients with mild dementia (Mini-Mental State Exam of 22±3, range 18 to 27), and in 29 nondemented elderly controls. Thirteen (68%) of the delusional patients had isolated theft delusions, and 6 (32%) had theft associated with another paranoid delusion (of jealousy or persecution). None of the patients had misidentifications or other delusions of non-paranoid content. Results. AD patients without delusions had symmetrical enlargement of both temporal (8.1±3.9 vs 8.5±4.5) and frontal horns (35.8±4.8 vs 35.9±4.6). In contrast, AD with delusions showed temporal horns larger to the right (9.1±3.3 vs 7.7±3.1, P=.06) and the frontal horn to the left (35.7±4.3 vs 37.5±4.2, P=.02). This different pattern was confirmed with a gender-adjusted, repeated-measures ANOVA model (interaction term between asymmetry and group: F _1.38=5.5, P=.03). The atrophic pattern of delusional AD patients was similar to that of controls (right and left rWTH: 2.9±1.4 vs 2.4±1.3; P=0.02; right and left FI 31.8±6.1 vs 33.5±4.3, P=0.06). Conclusions. AD patients with delusions are characterized by a pattern of frontal and temporal asymmetry similar to that of normal, nondemented individuals. The data suggest that in mild AD the absence of delusions rather than their presence might be an abnormal phenomenon. A delusional reaction to memory impairment might be an indicator of preserved "psychic reactivity.".