Elevated Intracranial Pressure

Overview

An elevated intracranial pressure (ICP) is caused by an increase in the volume of components within the skull e.g. brain tissue, CSF, blood, tumours etc. The pressure increases due to there being a limited ability to expand with additional volume due to the rigidity of the overlying skull.

A normal ICP in adults is 7-15 mmHg when lying down.

Cerebral perfusion pressure (CPP) is a measure of oxygen delivery to the brain calculated using mean arterial pressure – ICP.

Causes

• Intracranial bleeds and haemorrhagic stroke:
  • Extradural haematoma
  • Subdural haematoma
  • Subarachnoid haemorrhage
  • Intraparenchymal haemorrhage
  • Intraventricular haemorrhage
• Brain infections and abscesses
• Brain tumours
• Hydrocephalus
• Oedema secondary to trauma/infarctions/tumours
• Cerebral venous sinus thrombosis
• Idiopathic intracranial hypertension

Presentation

Headaches, papilloedema, and vomiting together are highly suggestive of a raised ICP. Features are:

• Headaches – worrying features are:
  • Nocturnal headaches
  • Worse on coughing
  • Worse on head movements
  • Associated with altered mental status
  • The headache starts on waking
• Change in mental state:
  • Lethargy
  • Irritability
  • Slowness
• Vomiting:
  • Due to pressure on the vomiting centre in the medulla oblongata
  • This may occur without nausea
• Pupil abnormalities e.g. irregularity/dilation
• Papilloedema – seen as blurred optic disc margins on fundoscopy
• Retinal haemorrhages can be seen in later stages
• CN III or CN VI palsies
• The Cushing reflex may be seen and is pre-terminal and indicates imminent brain herniation. It is characterised by a triad of:
  • Hypertension
  • Bradycardia and widened pulse pressure
  • Irregular breathing
• Problems relating to the location of mass/lesion:
  • Frontal lobe lesions – personality changes and disinhibition
  • Parietal lobe lesions – dysarthria

Investigations

• Urgent neuroimaging:
  • Immediate CT head – may show the underlying lesion
  • MRI head – may show underlying lesion
• Intracranial pressure monitoring – can be diagnostic or guide treatment
  • Not routinely indicated if mild-moderate head injury

Never perform a lumbar puncture in a patient who is suspected to have raised intracranial pressure without specialist supervision – this can cause cerebral herniation.

Management

Overview

The underlying cause must be managed. Initial measures include:

• Elevate the head to 30º
• IV mannitol or hypertonic saline
• Controlled hyperventilation
  • Induces vasoconstriction due to less CO2 and can reduce ICP but carries risk of cerebral hypoperfusion
• Give antipyretics e.g. paracetamol if needed
• Manage seizures
• CSF drainage – methods are:
  • Intracranial pressure monitoring – the intraventricular monitor can drain some CSF
  • Repeated lumbar punctures, particularly for idiopathic intracranial hypertension
  • Ventriculoperitoneal shunting, particularly for hydrocephalus
• In some severe cases, craniectomy is considered