Neuroscience Clerkship at UH/VA
 

PAPILLEDEMA

 

By definition, papilledema is a swollen optic nerve head (papilla) resulting from increased intracranial pressure. As a rule, papilledema is bilateral and not associated with significant visual field loss or loss of central vision unless it continues untreated for weeks or months. The most common early visual field finding in papilledema is enlargement of the physiologic blind spots.

Early in papilledema, there is hyperemia of the disk. Subtle changes in the nerve fibers and vessels can be detected on slit lamp examination. Spontaneous venous pulsations are usually obliterated when the intracranial pressure rises above 200 mm water. As the papilledema worsens, the swelling then obscures the normal disc margins and the disc becomes elevated. Venous congestion develops and peripapillary hemorrhages then develop.

If the papilledema persists for months, the disc hyperemia slowly subsides, leaving a pale disc that loses its central cup.

Normal Optic Disk

Papilledema


 

Knowledge of anatomy is important in understanding papilledema. The subarachnoid space is continuous with the optic nerve sheath.


Thus, as the cerebrospinal fluid pressure increases, this same pressure is transmitted to the optic nerve sheath. This increased pressure on the optic nerve sheath then impedes axoplasmic flow, leading to the swelling of the nerve head

Above: Histopathology of papilledema (stasis of axoplasmic flow and intra-axonal edema in the area of the optic disc)

Above: Dural sheath enlargement of the optic nerves following chronic papilledema


Above: Variations in the appearance of papilledema.


It is important to note that not every swollen, or edematous, optic nerve is papilledema. The differential diagnosis of a swollen optic nerve is based on the "vital signs" of neuro-ophthalmology: visual acuity, visual field and the presence or absence of a relative afferent pupillary defect (RAPD).

For example, anterior ischemic optic neuropathy (AION) presents as sudden painless loss of vision in one eye associated with a swollen optic disc. Prominent field and acuity loss are present from the beginning. Although involvement of the other eye occurs in up to 40% of people over months or years, bilateral simultaneous AION is extremely unusual unless caused by vasculitic conditions (e.g., temporal arteritis). Anterior ischemic optic neuropathy of the non-arteritic type (NAION) almost never occurs before the age of 50 and is often associated with systemic risk factors for arteriosclerotic disease (e.g. hypertension, diabetes mellitus, hyperlipidemia).

Optic neuritis most often presents as subacute loss of vision in one eye over hours to days, commonly associated with mild to moderate pain on eye movement. Like AION, but unlike papilledema, loss of vision and visual field are prominent early signs of optic neuritis. Most cases of optic neuritis are associated with demyelinating disease (i.e., multiple sclerosis) and more often affect the retrobulbar optic nerve. Therefore, retrobulbar optic neuritis is by definition not associated with optic disc edema. However, anterior optic neuritis (aka, papillitis; neuroretinitis) does occur in some cases of demyelinating disease, but is also seen when the cause is infectious or infiltrating.