Profiles of neuropsychological impairment in autopsy-defined Alzheimer’s disease and cerebrovascular disease

Differentiating the cognitive effects of cerebrovascular disease, particularly small vessel disease, from those of Alzheimer’s disease is a difficult clinical challenge. An influentialmodel of how subcortical cerebrovascular disease causes cognitive dysfunction posits that damage to frontostriatal loops impairs frontal lobe function, leading to predominant impairment of executive function and secondary impairments of associated cognitive functions such as memory. Consistent with this, neuropsychological studies of clinically diagnosed patients have reported that individuals with vascular dementia do better on memory tests and worse on executive function tests com-pared with patients with Alzheimer’s disease.This observation has led to the suggestion that predominant cog-nitive executive dysfunction might serve as a useful diagnostic marker for vascular dementia.We sought to test this idea in a series of cases with autopsy-defined pathologies. Subjects were 62 autopsied cases from a prospec-tive study of vascular contributions to dementia. Using neuropathological features alone, 23 were diagnosed with Alzheimer’s disease (AD), 11 with cerebrovascular disease (CVD), 9 with both (mixed pathology) and 19 with normal elderly brain (NEB). Three psychometrically matched composite scales of different cognitive abilities were used: Verbal Memory, Nonverbal Memory and Executive Function. Analysis of group data showed that for Alzheimer’s disease memory scores were lower than Executive Function by nearly a standard deviation on average. In contrast, and contrary to the model, CVD was rather equally impaired on Executiv