If the ICP is chronically elevated, the cerebrospinal fluid will accumulate within the enlarged optic nerve and cause the optic disc to be raised and bulge into the retina. The combination of a widened ONSD along with optic disc edema is known as papilledema.
On ocular ultrasound, papilledema presents with an ONSD > 5 mm and an optic nerve disc bulging of more than 0.6 mm. This differs from an acute elevation in ICP which only shows an ONSD > 5 mm on ultrasound.
Papilledema can be caused by brain masses, hydrocephalus, stroke or idiopathic intracranial hypertension/pseudotumor cerebri. The presence of unilateral papilledema can signal rare etiologies such as optic neuritis.