Distribution of cortical neurofibrillary tangles in progressive supranuclear palsy: a quantitative analysis of six cases.

Progressive supranuclear palsy is characterized neuropathologically by the presence of high densities of neurofibrillary tangles in several subcortical structures. In some cases, neurofibrillary tangles have also been described in the cerebral cortex. We performed a quantitative regional and laminar analysis of the distribution of these lesions in six cases of progressive supranuclear palsy. We observed that the neurofibrillary tangle distribution in the cerebral cortex was largely confined to the hippocampal formation. In particular, in all the cases neurofibrillary tangles were observed in the granule cell layer of the dentate gyrus. In the prefrontal and inferior temporal cortex, neurofibrillary tangles were predominantly distributed in layers II and III. In addition, there were moderate-to-high neurofibrillary tangle densities in the primary motor cortex. This localization pattern contrasts with the neurofibrillary tangle distribution observed in the cerebral cortex of Alzheimer's disease cases, where tangles are denser in layer V than in layer III, and where the primary motor cortex and the dentate gyrus are usually not involved. These results suggest that specific elements of the cortical circuitry might be differentially vulnerable in progressive supranuclear palsy as compared to Alzheimer's disease.