Cerebral emboli in the genesis of dementia

Alzheimer's disease (AD) and vascular dementia (VaD) are the two commonest forms of dementia, with evidence of a considerable overlap between them. Vascular risk factors are important in the genesis of both dementias but underlying mechanisms need further exploration. In this respect, asymptomatic spontaneous cerebral emboli (SCE) may be of interest. Such emboli are common in patients at risk of stroke, for example those with symptomatic or severe carotid artery disease, and predict the future risk of strokes. Here we summarise our research which shows that asymptomatic SCE may be involved in the aetiology, symptomatology and progression of both AD and VaD. In just 1 h of transcranial Doppler (TCD) monitoring SCE were detected in 40% of AD and 37% of VaD patients compared to 15% and 14% of their respective controls. The odds ratio for SCE was 2.70 (1.18-6.21) for AD and 5.36 (1.24-23.18) for VaD, adjusted for cardiovascular risk factors. The presence of SCE was associated with the concurrent presence of clinically relevant depressive symptoms and the future rapid rates of decline in cognition and daily function. SCE may represent a potentially treatable target to slow and possibly prevent dementia, both AD and VaD.