New Insights into Cerebrovascular Pathophysiology and Hypertension

Despite advances in acute management and prevention of cerebrovascular disease, stroke and vascular cognitive impairment together remain the world’s leading cause of death and neurological disability. Hypertension and its consequences are associated with over 50% of ischaemic and 70% of haemorrhagic strokes but despite good control of blood pressure there remains a 10% risk of recurrent cerebrovascular events and there is no proven strategy to prevent vascular cognitive impairment. Hypertension evolves over the life-span, from predominant sympathetically-driven hypertension with elevated mean blood pressure (BP) in early and mid-life to a late-life phenotype of increasing systolic and falling diastolic pressures, associated with increased arterial stiffness and aortic pulsatility. This pattern may partially explain both the increasing incidence of stroke in younger adults as well as late-onset, chronic cerebrovascular injury associated with concurrent systolic hypertension and historic midlife diastolic hypertension. With increasing arterial stiffness and autonomic dysfunction, blood pressure variability increases, independently predicting the risk of ischaemic and intracerebral haemorrhage, and is potentially modifiable beyond control of mean blood pressure. However, the interaction between hypertension and control of cerebral blood flow remains poorly understood. Cerebral small vessel disease is associated with increased pulsatility in large cerebral vessels and reduced reactivity to carbon dioxide, both of which are being targeted in early-phase clinical trials. Cerebral arterial pulsatility is mainly dependent upon increased transmission of aortic pulsatility via stiff vessels to the brain whilst cerebrovascular reactivity reflects endothelial dysfunction. In contrast, although cerebral autoregulation is critical to adapt cerebral tone to blood pressure fluctuations to maintain cerebral blood flow, its role as a modifiable risk factor for cerebrovascular disease is uncertain. New insights into hypertension-associated cerebrovascular pathophysiology may provide key targets to prevent chronic cerebrovascular disease, acute events and vascular cognitive impairment.