P4‐332: Regional brain stiffness changes across the Alzheimer's disease spectrum

Abstract

Several imaging and biofliud biomarkers exist to measure various disease processes associated with AD. However, the field is still in need of novel disease biomarkers. Magnetic resonance elastography (MRE) is a noninvasive technique to measure tissue stiffness, akin to manual palpation. Our objective was to investigate the effect of AD on regional brain stiffness. We examined 48 subjects with brain MRE including 16 PIB-negative cognitively normal controls (CN-), 16 PIB-positive controls (CN+), 8 PIB-positive subjects with mild cognitive impairment (MCI) and 8 PIB-positive subjects with AD (groups were age-matched, p=0.19). Group-wise difference in stiffness was most prominent in the frontal lobes (p=0.015, Kruskal-Wallis) and a statistical trend was observed in the parietal lobes (p=0.090). Stiffness did not differ by group in the temporal lobes, occipital lobes or the pre- and post-central gyri. Based on these results, a summary ROI composed of the frontal and parietal lobes but excluding the sensory/motor areas was generated. ROC analysis indicates 90% accuracy for discriminating AD and CN subjects, as compared to 87.5% for normalized hippocampal volumes. Figure 1 shows a plot of stiffness for each subject within each of the 4 clinical groups. The groups are arranged from left to right in order of increasing “ADness.” The groups have significantly different relationships with PIB (p=0.0004, ANCOVA), and stiffness significantly correlates with PIB in the MCI group (p=0.011, Spearman rank correlation).