Cerebral oedema

This is an excess of brain water. It often develops around an intrinsic lesion within the brain tissue e g. a tumour or an abscess, or in relation to trauma or ischaemic brain damage.

Cerebral oedema may complicate a variety of conditions, for example:

• acute hepatic failure
• benign intracranial hypertension
• Reye's syndrome
• excess fluid infusion in a dehydrated/hypernatraemic patient
• rarely in diabetic ketoacidosis

High altitude cerebral oedema may result from an abrupt increase in cerebral blood flow at 3500 - 4000 m upwards.

Different forms of cerebral oedema are described:

• vasogenic:
  • caused by excessive protein rich fluid leakage into the extracellular space through damaged capillaries
  • particularly affects the white matter
  • treated with systemic corticosteroids
    
    
• cytotoxic:
  • damage is intracellular, within the neurones and glia
    
    
• interstitial:
  • CSF leaks into the extracellular space e.g. non-communicating hydrocephalus

Cerebral oedema appears as a hypodense area on CT scans.