Distribution and morphology of brain stem plaques in Alzheimer's disease

The morphology, incidence and distribution of senile plaques in the brain stem were examined in 15 cases of Alzheimer's disease, using mainly the Methenamine-Bodian method. The plaques were found in all cases and were grouped into three types according to their morphology. They were not randomly scattered in the brain stem, but had a distribution common to all cases. There were numerous plaques in the periaqueductal gray, superior colliculus, fourth-ventricle floor and superior central nucleus. The plaques were also found less abundantly in the reticular formation, substantia nigra, pontine nucleus and inferior olivary nucleus. There was a tendency for certain plaque types to be associated with specific regions. In the familial cases, the plaques tended to occur even in the regions where they were rare in other cases. The capillaries with plaque-like degeneration were observed not infrequently in the brain stem. The distribution of plaques did not always coincide with that of neurofibrillary tangles.