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
• CPP = mean arterial pressure - ICP

Causes

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

PC

• headache

• vomiting

• reduced levels of consciousness

• papilloedema

• Cushing's triad

  • widening pulse pressure
  • bradycardia
  • irregular breathing

  *Systolic hypertension occurs as a reflex to maintain cerebral perfusion pressure in the presence of raised intracranial pressure.