Temporal lobe asymmetry in patients with Alzheimer's disease with delusions

Objective - To test the hypothesis that delusions are associated with asymmetric involvement of the temporal lobe regions in Alzheimer's disease. Methods - Temporal lobe atrophy was assessed with a linear measure of width of the temporal horn (WTH) taken from CT films. Temporal asymmetry was computed as the right/left (R/L) ratio of the WTH in 22 non-delusional and 19 delusional patients with Alzheimer's disease. Delusional patients had paranoid delusions (of theft, jealousy, persecution). None of the patients had misidentifications or other delusions of non-paranoid content. Results - The R/L ratio indicated symmetric temporal horn size in the nondelusional (mean 1.05 (SD 0.20), and right greater than left temporal horn in the delusional patients. (mean 1.30, (SD 0.46); t = 2.27, df = 39, p = 0.03). When patients were stratified into three groups according to the R/L ratio, 47% of the delusional (9/19) and 14% of the non-delusional patients (3/21; χ² = 5.6, df = 1, p = 0.02) showed right markedly greater than left WTH. Conclusions - Predominantly right involvement of the medial temporal lobe might be a determinant of paranoid delusions in the mild stages of Alzheimer's disease.