Quantitative changes in cerebral cortical microvasculature in ageing and dementia.

Brains were obtained postmortem from 25 mentally normal patients aged 26 to 96 years and from 3 patients with Alzheimer's disease. Although the number of pyramidal nerve cells within frontal and temporal cortex decreased significantly with age, measures of capillary density correlated only weakly with age. Stronger correlations, however, were noted between measures of capillary density and number of pyramidal cells, irrespective of age or disease. Capillary measures did not differ in 6 of the mentally normal patients who showed a few plaques and tangles in their cortex from those of 6 other patients of similar age who did not show such changes. It is concluded that the extent of the capillary network in the cerebral cortex alters to match the number and activity of functioning nerve cells; changes in quantity of capillary occurring with age or Alzheimer's disease may, therefore, secondarily reflect a primary loss of nerve cells and do not form, per se, part of the degenerative process.