Hypertension, blood-brain barrier disruption and changes in intracranial pressure.

Intracranial pressure (ICP) is pressure within the cranium, between 5 and 15 mmHg in a normal brain, and is influenced by the dynamic balance between brain tissue, cerebrospinal fluid (CSF) and cerebral blood volume. ICP is vital for cerebral health, impacting outcomes in various neurological conditions. Disruptions, such as cerebral haemorrhage, hydrocephalus and malignant hypertension, can lead to elevated ICP, a dangerous condition known as intracranial hypertension (IH). Systemic hypertension significantly impacts cerebral health by causing microvascular damage, dysfunction of the blood-brain barrier (BBB) and impairment of intracranial compliance (ICC). This increases the risk of IH), cerebral ischaemia, neuroinflammation and lacunar infarction, further worsening neurological dysfunction. This review describes the complex relationship between hypertension and ICP regulation, focusing on the mechanisms underlying ICP and ICC adjustments in hypertensive conditions and emphasizing the role of BBB integrity and cerebral blood flow (CBF) dynamics. It discusses how the sympathetic output might change the regulation of CBF and the maintenance of ICP, highlighting how hypertensive conditions can impair this mechanism, increasing the risk of cerebral ischaemia. The neurovascular unit, including astrocytes and microglia, plays a significant role in this process, contributing to IH in hypertensive patients. Understanding the effects of hypertension on ICP and ICC could lead to therapies aimed at preserving BBB integrity, reducing inflammation and improving cerebral compliance, potentially preventing brain dysfunction and reducing stroke risk in hypertensive patients. This review underscores the need for early detection and intervention to mitigate the severe consequences of uncontrolled hypertension on cerebral health.