Raised Intracranial Pressure
Raised intracranial pressure is a dangerous final pathway in which increased volume within the fixed skull reduces cerebral perfusion and may cause herniation; the cause, visual risk and speed of neurological deterioration determine the emergency pathway.
Definition
Raised intracranial pressure is a dangerous increase in pressure or pressure gradient within the cranial cavity, usually because brain, blood, CSF or oedema volume has increased or CSF or venous drainage is impaired. It is a final common pathway of multiple conditions and can reduce cerebral perfusion, impair vision or cause brain herniation.
First principles
The Monro–Kellie relationship explains delayed decompensation
The adult skull contains brain, blood and cerebrospinal fluid in a constrained space. Extra volume from a tumour, haemorrhage, oedema, obstructed CSF or venous congestion is initially buffered by moving CSF and reducing venous blood volume. Once those buffers are exhausted, a small additional volume can cause a steep pressure rise, reduce cerebral perfusion and produce herniation.
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