NO GLOBAL NEOCORTICAL NERVE-CELL LOSS IN BRAINS FROM PATIENTS WITH SENILE DEMENTIA OF ALZHEIMERS 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 A lzheimer's type (SDAT) were compared with similar estimates in 10 cogn itively 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) w ith a coefficient of variation (CV = SD/mean) = 0.14, whereas mean tot al 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 numbe r 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 unti l shortly before death. The SDAT patients showed a rather consistent r eduction in cortical volume by 14%, an atrophy that was solely due to a reduced cortical thickness. In addition, all had multiple neocortica l plaques (Bielschowsky silver stain).