Identification of pure subcortical vascular dementia using 11C-Pittsburgh compound B

Background: Subcortical vascular dementia (SVaD) is considered the most common type of vascular dementia and often follows a slowly progressive course, simulating Alzheimer disease (AD). Whether the progressive cognitive decline is associated with pure SVaD or concomitant AD remains unknown. The purpose of this study was to determine what proportion of patients with SVaD lack abnormal amyloid imaging, and to examine differences in the clinical or MRI features between subjects with SVaD with cortical amyloid deposition and those without. Methods: We measured brain amyloid deposition using 11C-Pittsburgh compound B (PiB) PET in 45 patients (men: women = 19:26; mean age 74.2 ± 7.6 years) with SVaD. They all met DSM-IV criteria for vascular dementia and had severe white matter high signal intensities without territorial infarction or macrohemorrhage on MRI. Results: Thirty-one (68.9%) of 45 patients with SVaD were negative for cortical PiB binding. There was significant difference between 11C-PiB-positive and 11C-PiB-negative groups in terms of age (79.5 vs 71.9 years), Mini-Mental State Examination score (18.6 vs 22.6), the number of lacunes (3.9 vs 9.0), and the visual rating scale of hippocampal atrophy (3.1 vs 2.3). The neuropsychological assessments revealed that patients with 11C-PiB-negative SVaD performed better on the delayed recall of both the verbal and visual memory test than did those with 11C-PiB-positive scan. Conclusion: SVaD without abnormal amyloid imaging was more common than expected. Patients with SVaD with and without abnormal amyloid imaging differed in clinical and MRI features, although there was considerable overlap.