Risk factors and neurodegenerative mechanisms in stroke related dementia.

Considerable evidence indicates that systemic vascular diseases are associated with neurodegenerative processes preceding cognitive decline and dementia. Conditions such as hypertension, diabetes, atrial fibrillation, ischemic heart disease, dyslipidaemia and obesity have propensity to induce strokes, which increase risk of dementia up to five-fold in the elderly. The link between vascular diseases and clinical Alzheimer's disease (AD) also exists but pathological confirmation has often been lacking. However, more than 30% of stroke survivors will develop dementia within two years. Transient ischaemic attacks and silent infarcts may unmask neurodegenerative processes characterized by primary pathologies such as those found in AD. Cerebral infarction and neurodegenerative pathologies are additive and accelerate dementia. Medial temporal atrophy is a strong predictor of dementia and also appears a feature in demented stroke survivors with minimal AD pathology. The atrophy is attributed to selective smaller cell volumes in the hippocampus and likely frontal lobe that may reflect loss of neuronal arborization and connectivity. Therapeutic strategies that maintain or restore functional morphology in surviving neurons could prevent further cognitive decline in post stroke and ageing related dementias.