Some morphometric observations on the brains of patients with Down's syndrome: their relationship to age and dementia.

The number of senile plaques (SP) and neurofibrillary tangles (NFT) and the number and nucleolar volume of nerve cells have been estimated in certain cortical and subcortical regions in 22 patients with Down's syndrome (DS) and have been related to the patients' age and to the presence and severity of dementia. Elderly (i.e. over 50 years of age) patients showed increased densities of SP and NFT and significant reductions in number and nucleolar volume of nerve cells, when compared with patients under 50 years of age, though the extent of these changes was, in general, no greater in the non-demented elderly group than that in the demented elderly group. Of the younger, nondemented group, those patients with a limited formation of SP and NFT in their brains showed a similar number and nucleolar volume of nerve cells, as those completely devoid of SP and NFT. It is concluded that in DS, formation of SP and NFT predate any significant atrophy and loss of nerve cells and that it is only after the age of 50 years that gross atrophy and loss of neurones occurs, though the extent of this process seemingly does not predict the onset, nor the progress, of dementia.