Some morphometric observations on the cerebral cortex and hippocampus in presenile Alzheimer's disease, senile dementia of Alzheimer type and Down's syndrome in middle age.

The frequency of senile plaques and neurofibrillary tangles and the number of pyramidal neurones and the volume of their nucleolus were measured in temporal cortex (middle temporal gyrus) and hippocampus (area h1) of 32 patients with Alzheimer's disease. Plaques and tangles were greatly increased in frequency in these patients while the pyramidal cell number was reduced (due to the effects of ageing plus disease) by a total of 78% in temporal cortex and 60% in hippocampus with nucleolar volume in surviving cells being reduced in total by 56% and 63%, respectively. These total losses did not correlate with patient age. However, when corrections for the effects of ageing alone were made on these total losses, the extent of pyramidal cell loss and decrease in nucleolar volume due solely to disease as well as the frequency of plaques and tangles were all found to correlate inversely with patient age for temporal cortex; in hippocampus only cell loss so related. The extent of nerve cell loss correlated with the reduction in nucleolar volume in temporal cortex but not in hippocampus. Correlations involving nerve cell loss and decreased nucleolar volume with plaque and tangle frequency were either weak or non-significant in both regions. The number of nerve cells and the volume of their nucleolus were less (when compared with age-matched control patients) in both temporal cortex and hippocampus, in the 6 middle aged patients with Down's syndrome, and match the corresponding values seen in 8 patients of similar age with Alzheimer's disease.