Changes in nerve cells of the nucleus basalis of Meynert in Alzheimer's disease and their relationship to ageing and to the accumulation of lipofuscin pigment.

The number of nerve cells in the nucleus basalis of Meynert in normally aged persons is reduced by 30% by 90 years of age and cytoplasmic RNA content and nucleolar volume by about 20%. In Alzheimer's disease the changes are greatly exacerbated, with the cell number being depleted by a further 60% and cytoplasmic RNA content and nucleolar volume by an extra 35%. Moreover, younger patients with Alzheimer's disease show a much greater difference from controls of the same age than do older patients; indeed, by 90 years of age the levels of these changes are similar in Alzheimer's disease and in old age alone. Lipofuscin content is increased to a similar extent with age in both Alzheimer's disease and control patients and was associated with loss of cytoplasmic RNA content and nucleolar volume in both groups. It is suggested that mechanisms which result in the accumulation of this pigment during life also lower the capability of cells of the nucleus basalis of Meynert to withstand disease pathogens, leading to a certain degree of change in old age alone and one which in other persons may be compounded by secondary factors giving the extreme degeneration of Alzheimer's disease.