Figure 1. Hypertension, stroke and dementia.

Hypertension has a key role in two major brain pathologies: stroke and dementia. Stroke can result from occlusion of a major cerebral artery (ischemic stroke) or rupture of intracerebral arterioles (hemorrhage). Hypertension also causes rupture of berry aneurysms of the circle of Willis leading to bleeding into the subarachnoid space (subarachnoid hemorrhage). Ischemia can lead to hemorrhage by rupture of ischemic vessels or extravasation of blood from leaky blood vessels. Conversely, hemorrhage can lead to ischemia by compressing the surrounding areas and reducing local blood flow. Vascular cognitive impairment (VCI) is caused by occlusion of small arterioles in the subcortical white matter, which interrupt neural connections subserving cognition and memory (Chui, 2007). A single stroke can lead to dementia by interrupting circuits involved in memory and cognition, such as the midline thalamus (strategic infarct dementia; SID). Multiple strokes can cause dementia by producing cumulative brain damage (multi infarct dementia; MID). Hypertension is a risk factor for Alzheimer’s disease (AD), a progressive dementia caused by accumulation of amyloid-β (Staessen et al., 2007). While vascular dementia and AD were traditionally considered separate entities, recent evidence suggests that they share common and interacting pathogenic factors (Iadecola, 2004).