White matter alterations in cognitively normal apoE ε2 carriers: Insight into Alzheimer resistance?

Abstract

BACKGROUND AND PURPOSE: The basis for decreased vulnerability to AD among apoE ε2 carriers is unknown. The purpose of this study was to use diffusion tensor imaging to detect possible differences in white matter integrity between cognitively normal elderly apoE ε2 carriers and apoE ε3/ε3 controls. MATERIALS AND METHODS: Thirty-nine cognitively normal elderly individuals (19 heterozygous carriers of the apoE ε2 allele, 20 apoE ε3/ε3 subjects as controls) underwent diffusion tensor MR imaging on a 4T scanner. Fractional anisotropy, MD, and axial and radial diffusivity were compared using a ROI approach. In addition, an exploratory whole-brain analysis of fractional anisotropy between the 2 groups was undertaken using TBSS. RESULTS: apoE ε2 carriers had higher FA in the posterior cingulate white matter (P = .01) and anterior corpus callosum (P = .005) than apoE ε3/ε3 controls, secondary to lower radial diffusivity. No significant differences in the FA of the posterior corpus callosum, anterior cingulate white matter, or parahippocampal white matter were seen. Whole-brain TBSS analysis detected regions of higher FA in the apoE ε2 group in the superior longitudinal fasciculus, right thalamus, and the bilateral anterior limbs of the internal capsule, in addition to the posterior cingulum and corpus callosum (P