Papilloedema

Swelling of the optic nerve due to increased intracranial pressure

Aetiology

  • Caused by raised intracranial pressure
  • The ICP is the sum of the brain, blood and CSF
  • The sum must remain constant - increase in one variable will result in a decrease of one/both other variables (Monro-Kellie hypothesis) as cranium is rigid and cannot expand

Space-occupying lesion

  • When a mass expands within the skull, compensatory mechanisms initially maintain a normal intracranial pressure
  • Eventually further small increments in volume produce larger and larger increments in intracranial pressure
  • Further increases in volume cause blood vessels to be compressed, ultimately causing global brain ischaemia/swelling with herniation through foramen magnum, brainstem compression and death

Problems with cerebral blood flow

  • e.g. malignant hypertension - mechanism behind disc swelling poorly understood but may involve leakage and ischaemia of arterioles supplying optic disc, leading to swelling/haemorrhage around disc

Problems with CSF

  • Obstruction to CSF circulation e.g. due to congenital malformation
  • Overproduction of CSF e.g. due to a tumour
  • Inadequate absorption e.g. due to haemorrhage
Idiopathic intracranial hypertension
  • Common cause of bilateral disc swelling in young females
  • Mechanism of disc swelling not fully understood but theories suggest obstruction of CSF circulation or impairment of absorption

Pathophysiology

  • Optic nerve is extension of the brain (with meningeal sheaths)
  • Subarachnoid space around optic nerve is continuous with the subarachnoid space surrounding the brain
  • When intracranial pressure rises, this is transmitted to the subarachnoid space and then onto the optic nerve
  • This causes interruption of axoplasmic flow and venous congestion → swollen discs

Clinical presentation

  • Headache
  • Enlarged blind spot, blurring of vision, visual obscurations and loss of vision
  • N+V, especially if ICP rise is acute

Investigations

Fundoscopy

  • Disc swelling (blurring)
notion image

Management

  • Treat underlying cause

Complications

  • Chronic papilloedema can cause axon damage leading to optic atrophy → loss of visual function occurs and blindness may result