Raised Intracranial Pressure

As the brain and ventricles are enclosed by a rigid skull, they have a limited ability to accommodate additional volume. Additional volume (e.g. haematoma, tumour, excessive CSF) will therefore lead to a rise in intracranial pressure (ICP).

Pathophysiology

• the normal ICP is 7-15 mmHg in adults in the supine position
• cerebral perfusion pressure (CPP) is the net pressure gradient causing cerebral blood flow to the brain

The CPP is tightly autoregulated to maximise cerebral perfusion. A sharp rise in CPP may result in a rising ICP, a fall in CPP may result in cerebral ischaemia. It may be calculated by the following equation:

• CPP = mean arterial pressure - ICP

Following trauma, the CPP has to be carefully controlled and the may require invasive monitoring of the ICP and MAP.

Causes

• idiopathic intracranial hypertension
• traumatic head injuries
• infection
  • meningitis
• tumours
• hydrocephalus

Features

• headache
• vomiting