Papilloedema refers to swelling of the optic disc related to increased intracranial pressure.
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Terminology
Care must be taken to not use the term papilloedema for all causes of optic nerve head elevation. Although papilloedema literally means swelling of the optic disc (nerve head/papilla), in ophthalmological parlance, it is only one of many causes of optic disc oedema 8-10. Furthermore, it should also be distinguished from causes of pseudo-oedema from optic disc drusen 9.
Pathology
Aetiology
idiopathic intracranial hypertension (pseudotumour cerebri)
intracranial masses, e.g. primary CNS tumours (e.g. gliomas), cerebral metastases, cerebral abscesses
extra-axial fluid collection, e.g. subdural haemorrhages, subdural empyemas
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meningeal disease
Radiographic features
Ultrasound
Ultrasound can be used to detect optic disc elevation into the vitreous cavity.
The optic nerve sheath diameter posterior to the globe can also be measured 11.
CT and MRI
The CT and MRI appearance relates to the dural anatomy of the optic nerve, which is continuous with the subarachnoid space, thereby allowing increased intracranial pressure (ICP) to be transmitted to the optic disc. In most cases, the papilloedema is bilateral. However, it can be unilateral in Foster Kennedy syndrome and its pseudovariants.
With the advent of motion correction sequences or higher resolution 3D aquisitions, CSF in the dural sheath over the optic nerve is much more frequently seen, and caution should be shown when reporting this to avoid false positives 7. Flattening or bulging of the optic nerve head is probably a more specific sign 7.
Differential diagnosis
The differential for papilloedema includes other causes of optic disc oedema (e.g. optic neuropathy, hypertensive retinopathy, papillitis, and orbital tumours) as well as pseudoedema (pseodupapilledema) from optic disc drusen 2,3.