Can Stroke Cause Neurodegenerative Dementia?

Stroke and dementia have typically been housed in different taxonomies. They are considered to be exemplars of very different forms of brain injury: stroke as an acute vascular injury and dementia as a progressive degenerative disease. Yet there is definite overlap between the two conditions: stroke increases the likelihood of developing dementia. Recent work has confirmed that vascular risk factors such as diabetes and hypertension predispose to dementia. However, in the absence of any clear findings of a direct pathway from stroke to degenerative dementia, the separation has persisted. In this review, we summarize the evidence relating to whether stroke can initiate or promote degenerative dementia and, in particular, Alzheimer's disease. The evidence comes from autopsy studies, from brain imaging studies, from studies of patients with symptomatic stroke and from studies in CADASIL. A number of studies have demonstrated that stroke can lead to changes in brain volume and cognitive performance, although generally of a different profile to the atrophy and cognitive decline seen in Alzheimer's disease. Much of the evidence is circumstantial, and does little to support a claim that stroke triggers neurodegenerative dementia. The question, then, remains open. None of the studies reviewed included the necessary longitudinal follow-up of stroke patients incorporating cognitive assessment, imaging and pathology. Given the high prevalence and substantial burden of dementia, there is much to be gained from identifying prognostic markers and it remains an exciting idea that we might be able to identify a subgroup of stroke patients who are at high risk.