Papilledema is the swelling of the optic nerve as it enters the back of the eye due to raised intracranial pressure. Fluid surrounding the brain is constantly produced and reabsorbed, maintaining just enough intracranial pressure to help protect the brain if there is blunt head trauma.
When you have a headache or unexplained nausea and vomiting, your doctor will look into your eye with an ophthalmoscope. This handheld instrument shines a bright light into your eye. Changes in the appearance of the optic nerve and the blood vessels that pass through it can be seen through the ophthalmoscope and might be related to the source of your symptoms.
The anatomy of the optic nerve makes it a sensitive marker for problems inside the brain. This nerve is a thick cord that connects the back of each eyeball and its retina to the brain. In its short span between the brain and the eye, the optic nerve's whole surface is bathed in cerebral spinal fluid. This fluid protects the nerve from sudden movement. However, even slight increases in the pressure of this fluid, from swelling of the brain, can compress the optic nerve around its whole circumference in a "choking" manner. When this nerve is exposed to high pressure, or when it develops inflammation on its own, it can bulge into the back wall of the eyeball, causing papilledema.
Doctors have commonly used the term to describe the appearance independent of the underlying cause. The term papilledema ideally should be reserved for swelling of the nerve head when the swelling is caused by elevated intracranial pressure. Other conditions can have a similar appearance to papilledema caused by high intracranial pressure.
Some important causes of increased pressure from cerebral spinal fluid and papilledema are brain tumors and brain infections, such as a brain abscess, meningitis or encephalitis. A significant proportion of people who are diagnosed with brain tumors have some evidence of papilledema. A pressure increase resulting from bleeding or from very high blood pressure also can cause papilledema.
One condition can cause increased pressure in the cerebral spinal fluid without associated swelling of the brain or ventricles. This condition, called pseudotumor cerebri or benign intracranial hypertension, is caused when the body makes too much spinal fluid. It is more common in women who are obese and of childbearing age. The condition seems to be triggered at times that the body is adjusting to hormone changes, such as pregnancy, the start of birth control pills, the first menstrual period, or menopause.