Intracranial pressure physiology, monitoring and individualized management in the acute brain injured patient.

Acute brain injury (ABI), including traumatic brain injury, ischemic and hemorrhagic stroke, is associated with high morbidity and mortality, which is driven not only by the primary brain injury, but also by the development of secondary cerebral insults. Among these, raised intracranial pressure (ICP) plays a central pathophysiological role, acting both as a consequence and a driver of ongoing brain injury through mechanical deformation and cerebral ischemia. Although invasive intracranial pressure (ICP) monitoring has a longstanding and ongoing role in neurocritical care management, the interpretation and clinical use of ICP remain controversial. Traditional management strategies rely on fixed ICP thresholds (e.g., > 22 mmHg) to trigger a standardized stepwise escalation of therapy; however, growing clinical evidence indicates that tolerance to ICP elevation varies widely across patients, disease entities, and physiological contexts. This review summarizes the physiological determinants of ICP, including intracranial compliance, cerebrospinal fluid dynamics, cerebral blood volume, and systemic factors, and describes the mechanisms underlying intracranial hypertension. We discuss limitations of using fixed ICP thresholds and highlight emerging concepts, such as ICP burden, waveform morphology, cerebral autoregulation, and functional brain monitoring, as tools to individualize ICP interpretation. The role of invasive and noninvasive ICP monitoring (nICP) modalities is reviewed, emphasizing the complementary value of nICP in guiding decision-making when invasive monitoring is unavailable or contraindicated. Particular attention is given to the integration of ICP within multimodal neuromonitoring frameworks assessing cerebral perfusion, oxygenation, and metabolism. Finally, we explore future perspectives, including the potential of artificial intelligence-based approaches to analyse complex neuromonitoring data, predict secondary insults, and move toward actionable, patientspecific therapeutic strategies. Collectively, these advances support a shift from a uniform, threshold-driven approach toward individualized, physiology-informed management of intracranial hypertension.