Basal nucleus of Meynert. A neuropathological study in Alzheimer's disease, simple senile dementia, Pick's disease and Huntington's chorea.

The basal nucleus of Meynert (bnM) was examined in 9 patients with Alzheimer's disease--4 presenile and 5 senile cases--in 3 patients with simple senile dementia, 5 with Pick's disease, 5 with Huntington's chorea and 5 non-demented controls. The histopathological study was followed by a quantitative analysis of the magnocellular population of neurons and by the determination of their nucleolar volume. In Alzheimer's disease there was a neuronal loss ranging from 44 to 76%, which was negatively correlated with both the age at onset and age at death of the patients. Numerous surviving cells showed neurofibrillary tangles, and in 3 cases senile plaques were present. The nucleolar volume of the large neurons was significantly reduced and the percentage reduction correlated with the percentage loss of cells. In contrast, the bnM was relatively unaffected in the other disorders considered. The involvement of bnM in Alzheimer's disease confirms the previous neuropathological observations, providing further evidence that it constitutes a constant anatomical feature of this disorder. The extent of the damage is age-dependent. The sparing of the bnM in simple senile dementia suggests that it may be a different nosological entity from late onset Alzheimer's disease and this may constitute a simple criterion for distinguishing between the two forms of dementia on an anatomical basis.