Vascular cognitive impairment

Cerebrovascular disease is increasingly recognized as a common cause of cognitive impairment and dementia in later life either alone or in conjunction with other pathologies, most often Alzheimer disease (AD). Progress in the field has been limited by difficulties in terminology; for example, use of the term dementia necessitates the presence of memory impairment, which is the norm in AD, but not in cognitive disorders associated with cerebrovascular disease. The term vascular cognitive impairment (VCI) has been proposed as an umbrella term to recognize the broad spectrum of cognitive, and indeed behavioral, changes associated with vascular pathology. It is characterized by a specific cognitive profile with predominantly attentional and executive impairments together with particular noncognitive features (especially depression) and a relatively stable course, at least in clinical trial populations. Subtypes of VCI have been proposed based on clinical and pathologic differences, including cortical, subcortical, strategic infarct, hypoperfusion, hemorrhagic, and mixed (with AD) type. Diagnostic criteria are emerging but require refinement and validation, especially for mixed dementias. There remain fundamental gaps in our understanding of pathophysiology, predicting prognosis and outcome, and in therapeutics. Clinical trials to date, mainly in populations selected using currently accepted criteria for vascular dementia, have generally been disappointing. A relatively modest cognitive benefit of agents such as nimodipine, memantine, and cholinesterase inhibitors has been reported, although the clinical significance of these improvements remains to be established. Further studies, focusing on particular subtypes of VCI and involving subjects at earlier stages of the disease, are required. The aim of this article is to review the concept of VCI in terms of the evidence base surrounding diagnosis, clinical features, pathophysiology, and management and to make some recommendations regarding further research in the area. It begins with a discussion on the historical background, which is important to understand the different and somewhat confusing terminology that currently exists in the field.