In the nucleus basalis of Meynert (NBM) we studied the presence of early cytoskeletal alterations as shown by the antibody Alz-50 in ApoE-typed patients. Using an image analysis system, the area covered by Alz-50 staining and the percentage of neurons stained by Alz-50 were determined. There were no significant differences in the area covered by Alz-50 or in the proportion of Alz-50-stained neurons in the nucleus basalis of Meynert of Alzheimer's disease (AD) patients with one or two ApoE epsilon4 alleles as compared with those without any ApoE e4 allele. However, there was a significant sex difference in Alz-50 staining: female Alzheimer's disease patients showed more severe early cytoskeletal alterations than males. We also found a significant relationship between the number of Alz-50-stained neurons and the severity of dementia.