Differentiation of vascular dementia from AD on neuropsychological tests

Background: The concept of vascular dementia (VaD) is currently in a state of evolution. Memory impairment is emphasized as a primary criterion, reflecting the influence of AD on the concept of dementia. We have systematically reviewed whether the nature of neuropsychological dysfunction is distinct in AD and VaD, and whether similar defining criteria for the concept of dementia in both disorders can be supported. Methods: We searched five bibliographic databases (Medline, Biological Abstracts, EMBASE, PsychINFO, PsychLIT) for research articles in which VaD and AD had been compared using neuropsychological tests and that met criteria for scientific merit. Results: Of the 45 studies, 18 were excluded because of inadequacies, and the remaining 27 were analyzed. There were a number of similarities of dysfunction between VaD and AD. However, when matched for age, education, and severity of dementia, VaD patients had relatively superior function in verbal long-term memory and more impairment in frontal executive functioning compared with AD patients. Interpretation of the results is Limited by uncertainty in diagnostic criteria for VaD, possible inclusion bias due to use of clinical diagnosis alone, possible overlap of AD and VaD, and the methodologic shortcomings of some studies. Conclusions: The neuropsychological differentiation of VaD from AD was consistent with the different neuroimaging findings in the two disorders, and argues for differential criteria for the definition of the syndromes. The simple application of Alzheimer's dementia criteria,to VaD, with the inclusion of cerebrovascular disease etiology, may not be sufficient to capture the uniqueness of VaD.