Introduction Apolipoprotein E (APOE) ε4 allele is a known risk factor for the development of cognitive impairment. APOE ε4 carriers have been reported as having lower hippocampal volume in Alzheimer’s disease, mild cognitive impairment, and in healthy cohorts,1 but this is not well investigated in stroke. Here, we compared the regional volume in the medial temporal lobe in ischaemic stroke survivors, with and without the ε4 allele, three (time point 1, t1) and twelve (t2) months after stroke.
Methods 21 APOE ε4 carriers and 21 non-carriers, matched for lesion size and location and for neurological impairment as measured by NIHSS, were sampled from the CANVAS study, a longitudinal imaging study in stroke survivors.2 A mixed-effect linear model was used to analyse the effect of the ε4 allele on hippocampal, entorhinal, and para-hippocampal volumes, adjusting for age, sex, years of education, and total intracranial volume. Volumes were estimated using the longitudinal stream in FreeSurfer 5.3.
Results The left hippocampal (pt1=0.038, pt2=0.040) and entorhinal (pt1=0.044, pt2=0.038) volumes were significantly lower in the ε4-carrier group at each time point. The right entorhinal (pt1=pt2=0.002) and para-hippocampal (pt1=0.018, pt2=0.020) volumes were also significantly lower in the ε4-carrier group, but there was no difference in the right hippocampal volume (pt1=pt2=0.055) between the two groups. The group-time interaction was significant for the left para-hippocampal cortex (p=0.019): ε4 non-carriers showed a significant volume increase (p=0.018) between t1 and t2.
Conclusion These findings suggest that stroke survivors who carry the APOE-ε4 allele will experience greater atrophy in the medial temporal lobe in the twelve months following their stroke.
References 1. Manning EN, et al. e4 Is Associated with Disproportionate Progressive Hippocampal Atrophy in AD. PLoS ONE2014;9(5):e97608.
2. Brodtmann A, et al. Charting cognitive and volumetric trajectories after stroke: Protocol for the Cognition And Neocortical Volume After Stroke (CANVAS) study. Int J Stroke2014;9(6):824–828.
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