Apolipoprotein E epsilon4 is associated with atrophy of the amygdala in Alzheimer's disease

Although the ApoE ϵ4 allele is well-established as the most important genetic risk factor for Alzheimer's disease (AD), the effects of this allele on regional brain atrophy in AD patients remain controversial. We performed MRI-based volumetric measurements of the hippocampus and amygdala (normalized to intracranial volume) in 32 ϵ4+ AD patients, 23 ϵ4− AD patients, and 42 cognitively normal elderly control subjects. Analysis of covariance revealed that amygdaloid volume was significantly smaller (19.2%) in ApoE ϵ4+ than ϵ4− AD patients, controlling for disease severity (F=10.62; d.f.=1,52; p=0.002; ANCOVA). Alternatively, when ApoE ϵ4 dose was considered, this effect appeared to accrue from a difference between the 0ϵ4 and each of the other two AD groups, with no significant difference between the 1ϵ4 and 2ϵ4 AD groups. Hippocampal volumes and asymmetry indices for hippocampus and amygdala did not differ between ϵ4 carriers and noncarriers. These results suggest accelerated atrophy of the amygdala in AD in association with ApoE ϵ4 and provide further evidence for regionally specific effects of this allele.