Neurofibrillary tangles, granulovacuolar degeneration, and neuron loss in Down Syndrome: quantitative comparison with Alzheimer dementia.

The degree of neurofibrillary tangle formation, granulovascuolar degeneration, and nerve cell loss was quantified in serial sections of the hippocampal formation from the brains of 5 adults dying with Down syndrome (monogolism). These morphometric results were compared with values obtained from a series of mentally normal elderly patients reported previously. Granulovacuolar change appeared to be related as much to patient age as to the existence of monogolism. By contrast, the number of Alzheimer neurofibrillary tangles and loss of pyramidal neurons from the hippocampus exceeded levels found in considerably older subjects and fell into the same range of severity as was noted in 8 patients with Alzheimer dementia. The neuron population in the hippocampus of Down syndrome patients may be only half the expected normal number for their decade. These quantitative similarities stimulate the search for a common pathogenetic mechanism underlying cerebral changes in monogolism and senile dementia of the Alzheimer type.