Cell loss in the locus coeruleus in senile dementia of Alzheimer type.

Sample counts of the pigmented cells of the locus coeruleus (LC) were performed in 10 middle-aged and 15 old people considered to be intellectually well preserved and in 15 cases of senile dementia of Alzheimer type (SDAT). Evidence of a gradual loss of neurons from early middle to old age was found in the control group. In the cases of SDAT 7 counts were within the lower range for the controls but 8 had fewer neurons than any control recorded and the mean count for all the SDAT cases was significantly less than that of the older controls. Some evidence exists that the more severe cases of SDAT in terms of neocortical plaque formation have the greatest loss of LC neurons.