[Neuropathological study on progression of the limbic degeneration in senile dementia of Alzheimer type].

Neuropathological study on the limbic lesion of 33 autopsy cases with senile dementia of Alzheimer type (SDAT) showed as follows. 1) The entorhinal cortex was more atrophied than the hippocampus. 2) Neuronal loss was found in the 2nd and 3rd layers of the entorhinal cortex, irrespective of the different numbers of senile plaques and neurofibrillary tangles (NFTs). 3) Fibrillary gliosis occurred in the stratum lacunosum of the hippocampus, irrespective of the different degrees of neuronal loss in the stratum pyramidale of the hippocampus. 4) The prosubiculum showed gliosis disproportional to neuronal loss. 5) The degree of fibrillary gliosis in the stratum lacunosum of the hippocampus and in the prosubiculum was proportional to that of the entorhinal cortical degeneration. 6) The shape of the hippocampus of the cases with SDAT was different from that in the cases with anoxic encephalopathy in which neuronal loss in the CA1 occurred primarily: 7) Distribution pattern of the lesion in the hippocampus of SDAT cases was almost the same as that found in the cases with infarct in the collateral sulcus involving the entorhinal cortex. It is assumed that the hippocampal atrophy is a primary degeneration attributable to appearance of senile plaques and NFTs. However, our present observations and previous report (Neurosci Lett 184: 141-144 1995) suggest that degeneration of the entorhinal cortex and its efferent fibres (perforant pathway) plays a considerable part of role in development of the hippocampal atrophy. The present study could contribute to understanding of progression of the limbic lesion in SDAT.