NEURONAL LOSS CORRELATES WITH BUT EXCEEDS NEUROFIBRILLARY TANGLES IN ALZHEIMERS-DISEASE

To assess the relationship between dementia, neuronal loss, and neurop athological findings in Alzheimer's disease (AD), we counted the numbe r of neurons, senile plaques, and neurofibrillary tangles in a high-or der association cortex. We studied the superior temporal sulcus of 34 individuals with AD and 17 nondemented control subjects, using statist ically unbiased, stereological counting techniques. The number of supe rior temporal sulcus neurons in nondemented control subjects was stabl e across the sixth to ninth decades. In AD, more than 50% of the neuro ns were lost Both neuronal loss and neurofibrillary tangles increased in parallel with the duration and severity of illness, but the amount of neuronal loss exceeded by manyfold the amount of neurofibrillary ta ngles accumulated. In contrast to the correlation between neurofibrill ary tangles and neuronal loss, the number of senile plaques and the pe rcentage of the superior temporal sulcus that was covered by A beta (a myloid burden) were not related to neuronal loss, number of neurofibri llary tangles, or duration of disease. Neither the amount nor the rate of neuronal loss in the superior temporal sulcus in AD correlated wit h apolipoprotein E genotype. These data suggest that neuronal loss in association areas such as the superior temporal sulcus contributes dir ectly to cognitive impairment in AD.