IC-P3-207: Decreased activation in the left medial parietal lobe in presymptomatic FAD mutation carriers in fMRI during an unrelated word pair memory task

2 and Lesion Explorer 3 WMH segmentation was performed, with VichowRobin perivascular spaces excluded. To appreciate the 3-dimensional anatomy of WMH, PV-WMH was defined as any hyperintensity touching the ventricles in 3D, the remaining discrete WMSH were defined as DWWMH. Hypointense components within PV-WMH and DW-WMH of cerebrospinal fluid intensity on T1-based segmentation were considered to represent cystic necrosis. Volumetrics were obtained. Hypointense lesion volumes were expressed as percentage of WMH. Results: Mean percentage of hypointensities were as follows: periventricular (AD 2.2%, NC 0.37%); deep white (AD 2.16%, NC 1.6%), with the PV between group difference approaching significance (p .07). Total PV-WMH and DW-WMH volumes was significantly correlated in NC (r .62, p .019) but not in AD (r .32, p .24). However, DW and PV hypointensities did not show correlation (NC: r -.05, p .87; AD: r .24, p .39). Conclusions: The higher percentage of implied cystic necrosis in the PV distribution, and the differences in DW and PV correlations in AD and NC, suggests a different underlying pathology occurring in the periventricular regions of AD patients. It is recommended that future studies examining WMH should include PV and DW delineations as well as an additional T1-based hypointense segmentation to account for these lesions.