Variabilities in the distribution of neurofibrillary tangles in the anterior parahippocampal gyrus at initial stages of Alzheimer's disease.

The entorhinal region is located in the ventromedial surface of the temporal lobe on the parahippocampal gyrus. Occurrence of early argyrophilic neurofibrillary tangles was investigated in brain sections of the left and right entorhinal region of 9 individuals of both sexes between the age of 26 to 54 years. Parasagittal serial sections at 100 microns were performed to include the very anterior part of the entorhinal region. An advanced silver method was used for staining neurofibrillary changes. The neurofibrillary tangles were counted via light microscopy, marked on the sections and staged as proposed by Braak and Braak. In 1 case we found a left-right difference by 1 stage (right: stage I, left: stage II). The tangle distribution in another case exhibited several neurofibrillary tangles only in the very anterior part of the entorhinal cortex on both sides (stage 0). In 3 cases some neurofibrillary tangles occurred in the very anterior part of the right entorhinal region, while a few are present in more posterior parts (stage I). The corresponding left hemisphere showed the same anterior-posterior distribution pattern as on the right in only 1 of these cases. In the remaining 4 cases, no neurofibrillary changes were visible. In conclusion, the very anterior part of the entorhinal region is among the earliest sites for development of neurofibrillary tangles. Distribution of early Alzheimer-related neurofibrillary changes in the entorhinal region displays variabilities in the anterior-posterior direction as well as in a left-right comparison.