The purposes of the present study were to explore whether hippocampal atrophy exists in pure subcortical vascular dementia (SVaD) as defined by negative (11)C-Pittsburg compound-B (PiB(-)) positron emission tomography and to compare hippocampal volume and shape between PiB(-) SVaD and PiB positive (PiB(+)) Alzheimer's disease (AD) dementia. Hippocampal volume and shape were compared among 40 patients with PiB(-) SVaD, 34 with PiB(+) AD, and 21 elderly with normal cognitive function (NC). The normalized hippocampal volume of PiB(-) SVaD was significantly smaller than NC but larger than that of PiB(+) AD (NC > PiB(-) SVaD > PiB(+) AD). Both PiB(-) SVaD and PiB(+) AD patients had deflated shape changes in the cornus ammonis (CA) 1 and subiculum compared with NC. However, direct comparison between PiB(-) SVaD and PiB(+) AD demonstrated more inward deformity in the subiculum of the left hippocampus in PiB(+) AD. PiB(-) SVaD patients did have smaller hippocampal volumes and inward shape change on CA 1 and subiculum compared with NC, suggesting that cumulative ischemia without amyloid pathology could lead to hippocampal atrophy and shape changes.
Keywords: Alzheimer's disease; Hippocampus; PiB-PET; Vascular dementia.
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