Stereological Quantification of Plaques and Tangles in Neocortex from Alzheimer's Disease Patients

We estimated by stereological methods the neocortical volume occupied by plaques and tangles in females dying with severe Alzheimer's disease (AD), age-matched female subjects with severe vascular dementia (VaD), and normal control brains. Stereological investigations include a uniform sampling of the tissue in the whole of neocortex and its subdivisions. Resultant volume estimates provide information about the overall burden of these two pathological changes and their volume fractions and allow for correlational studies between the pathological changes and factors such as the total neocortical neuronal cell numbers, dementia test scores, and age. We estimated the volume of plaques and tangles in the entire neocortex and frontal-, temporal-, parietal-, and occipital cortex in nine female AD brains, four female patients dying with VaD, and six neurologically normal female control brains using point-counting in uniform samples of neocortex. The volume occupied by plaques comprised approximately 1% of neocortex, while the neocortical tangles made up approximately 0.1% of neocortex of AD patients but were scarcely present in the other study groups. The individual tangle and plaque volumes did not correlate to the ultimate dementia score of the AD subjects, despite correlating with reduced neocortical volume. In neocortex of AD patients, the burden of plaques and tangles is much higher than that in patients with severe vascular dementia or normal older women but only occupy a small fraction of the neocortical volume.