Risk factors and mechanisms of post-stroke dementia.

Stroke significantly increases the risk of dementia in subjects aged 55 yea rs or more. Twenty to 25p. 100 of patients are demented 5 years after a str oke. Age and supratentorial location of the vascular lesion are risk factor s for post-stroke dementia. Volume, left side of the lesion, large middle c erebral artery infarction, lesions of the frontal lobe, second stroke, diab etes, aphasia, clinical features expressing the severity of the stroke even t in the acute phase, mitral valve prolapse, atrial fibrillation, depressio n, concomitant hypoxic / ischemic disorders, and white matter changes have also been found as predictors of dementia. There are many different mechani sms of vascular pathology that may lead to dementia: ischemic or hemorrhagi c lesions, large vessel disease including multi-infarct and strategic singl e infarct, small-vessel disease including lacunes and white matter changes, hypoperfusion... Post-stroke dementia may not be due only to vascular lesi on. Some post-stroke dementias have a progressive onset and course. The cog nitive decline may pre-exist to the stroke, even when a dementia is not dia gnosed. This suggests a degenerative process. Alzheimer's disease is freque nt in ages when the majority of strokes occur. Alzheimer's and vascular dis eases share common risk factors such as age, APOE4, hypertension, and smoki ng. Patients with low MMS scores and AD patients are at risk for stroke. Mo reover, white matter changes are associated with stroke and Alzheimer's dis ease and may contribute to the cognitive decline, Many post-stroke dementia s could be multifactorial. Even when vascular lesions and degenerative chan ges (mainly Alzheimer changes) are not severe enough, on their own, to be t he cause of dementia, their summation may reduce the preclinical stage of t he degenerative process.