Comparative study on neuropsychological tests for typical Alzheimer's disease, frontal variant of Alzheimer's disease and behavioral variant of frontotemporal dementia

Abstract

Objective To compare the neuropsychological features and other clinical and imaging characteristics among patients with typical Alzheimer's disease (TAD), frontal variant Alzheimer's disease (fvAD) and behavioral variant frontotemporal dementia (bvFTD). Methods Neuropsychological scales were used to evaluate the cognitive function and neuropsychiatric symptoms of nine patients with fvAD, 30 patients with bvFTD and 32 patients with typical AD (TAD). The apolipoprotein E (ApoE) e4 allele and brain imaging techniques, including the magnetic resonance imaging (MRI), 11C-Pittsburgh compound B positron emission tomography (PIB-PET), and 18F-deoxyglucose positron emission tomography (FDG-PET), were used for the differential diagnosis of fvAD and bvFTD. Results There were no significant differences in general cognitive function or daily activity in patients among the three groups.However, the cognitive subscale scores of Montreal Cognitive Assessment (MoCA) scale, including visual acuity and executive function, delayed recall, and orientation, were significantly different among the groups (Z=7.891, P=0.035; Z=7.412, P=0.031; Z=6.437, P=0.043, respectively). The clock drawing test (CDT) score of TAD group was higher than that in the bvFTD and fvAD groups (Z=8.673, P=0.020), while the neuropsychological questionnaire (NPI) scores of the bvFTD and fvAD groups were higher than those of the TAD group (Z=7.577, P=0.023). Meanwhile, the incidences of agitation, disinhibition and abnormal behavior of NPI in the bvFTD and fvAD groups were higher than those in the TAD group (χ2=11.139, P=0.004; χ2=6.481, P=0.039; χ2=6.812, P=0.033, respectively). The frequencies of the ApoE e4 allele were 44.4% in the fvAD group and 33.3% in the bvFTD group, which were not significant different from that in the TAD group (40.6%). Furthermore, patients in the fvAD group were associated with decreased regional cerebral glucose metabolism and amyloid deposition in the temporal-parietal cortex evaluated by FDG-PET and PIB-PET. Conclusions Neuropsychological evaluation is valuable for the differential diagnosis of TAD, fvAD and bvFTD.The frequencies of the ApoEe4 allele are similar among the three groups.FDG-PET and PIB-PET imaging plays an important role in the diagnosis of variant types of Alzheimer's disease. Key words: Alzheimer disease; Frontal lobe; Dementia; Neuropsychological tests; Apolipoprotein E4; Positron-emission tomography