No global neocortical nerve cell loss in brains from patients with senile dementia of Alzheimer's type.

Precise estimates of total neuron numbers in neocortices of 11 women, mean age 82.6 years (range 79-88) with severe senile dementia of the Alzheimer's type (SDAT) were compared with similar estimates in 10 cognitively normal women of comparable mean age (84.1 years; range 74-92). The total mean nerve cell number in the SDAT group was 16.9 x 10(9) with a coefficient of variation (CV = SD/mean) = 0.14, whereas mean total neuron number in the control group was 18.1 x 10(9), CV = 0.18. In a material of this size the reduction of 6% in neocortical cell number in the SDATs is neither statistically nor biologically significant. Nevertheless, all patients with SDAT were severely demented, having a mean score of 5.6 on a 1-7-scale of dementia. This contrasts with the nondemented individuals who had lived an independent life at home until shortly before death. The SDAT patients showed a rather consistent reduction in cortical volume by 14%, an atrophy that was solely due to a reduced cortical thickness. In addition, all had multiple neocortical plaques (Bielschowsky silver stain).