IC–P–017: Different patterns of gray and white matter atrophy in Alzheimer's disease and subtypes of frontotemproal lobar dementia

angiopathy, CAA) is major cause of hemorrhagic stroke and a likely contributor to vascular cognitive impairment. Research in CAA has been hampered by the inability to detect vascular -amyloid in living subjects. Objective: To evaluate PET imaging with the -amyloid-binding compound Pittsburgh Compound B (PIB) as a potential noninvasive method for detection of CAA. Methods: We performed PIB-PET imaging on 5 subjects (mean age 71.4 8.8) diagnosed with probable CAA according to the Boston criteria based on brain biopsy (n 3) or multiple strictly lobar bleeds (n 2). All 5 CAA subjects were nondemented (Mini-Mental State Exam 27 or Blessed Information-Memory-Concentration Scale 3). PIB-PET images were acquired over 60 minutes following injection of 10-15 mCi PIB. Results were compared with 16 older (mean age 74.7 7.3) cognitively normal controls (NC) and 9 subjects with probable Alzheimer’s disease (AD). Specific PIB binding was calculated using the Logan graphical analysis method, yielding a distribution volume ratio (DVR) with cerebellar grey matter as reference. DVRs were calculated in an aggregated cortical (bilateral superior frontal, anterior cingulate, parietal, and precuneus cortex) region-of-interest (ROI) and a bilateral occipital ROI. Results: PIB retention was significantly elevated in CAA relative to NC (DVR mean SD 1.25 0.07 versus 1.03 0.10, p 0.0005 for aggregated cortical ROI; 1.25 0.09 versus 1.10 0.12, p 0.02 for occipital ROI). PIB retention in the CAA subjects was significantly lower than AD in the aggregated cortical ROI (DVR for AD subjects 1.40 0.15, p 0.03) but not in the occipital ROI (1.34 0.17 in AD, p 0.2). Inspection of the pattern of PIB retention among CAA subjects suggested relatively strong specific binding in occipital cortex, consistent with the known predilection of CAA pathology for this region. Conclusions: Increased PIB retention in nondemented CAA subjects relative to similar aged controls suggests that PIB-PET imaging can detect cerebrovascular -amyloid. The data also raise the possibility that PIB-PET may identify a pattern of occipital predominance characteristic of CAA.