Severity of dementia in Alzheimer disease and neurofibrillary tangles in multiple brain regions

We studied the relationship of numbers of neurofibrillary tangles (NFTs) in selected cortical and subcortical sites to the duration of clinical disease and severity of dementia. Sixteen patients with a clinical diagnosis of "probable" Alzheimer disease were screened with standardized neuropsychological instruments to estimate the severity of dementia. Tissues were obtained at autopsy from the subiculum, four neocortical areas, and the nucleus basalis of Meynert: NFT counts were assessed with the thioflavin S stain. Overall, the subiculum showed the most NFTs, followed by visual association and premotor cortices, primary cortex (motor and visual), and the nucleus basalis. NFT counts were significantly positively correlated with the duration of disease in the nucleus basalis and less strongly in the motor cortex. Neuropsychological impairment was significantly correlated with NFT counts only in the nucleus basalis. In turn, counts in the nucleus basalis were reliably correlated with those in all other brain regions except the subiculum. Counts in the subiculum showed no correlation with any other area. Numbers of NFTs within functionally related sites, the primary motor and premotor cortices or primary and visual association cortices, were significantly or near-significantly correlated, whereas motor and visual cortical counts showed no intercorrelation. Our results indicate that although there is less NFT accumulation in the nucleus basalis than in many other brain regions, counts in this structure bear a close relationship to disease severity and duration and to NFT accumulation in other regions.