# Papilledema and Idiopathic Intracranial Hypertension

## Papilledema

### Definition

Papilledema is optic disc swelling caused specifically by elevated intracranial pressure. By definition, it is bilateral, though the degree of swelling may be asymmetric between the two eyes. It must be distinguished from other causes of disc edema, including pseudopapilledema, optic neuritis, anterior ischemic optic neuropathy, and compressive optic neuropathy.

### Pathophysiology

Elevated intracranial pressure is transmitted through the cerebrospinal fluid that surrounds the optic nerve within its sheath. At the lamina cribrosa, the elevated pressure causes stasis of axoplasmic flow within the ganglion cell axons. These axons swell at the disc, producing the visible disc edema. Venous congestion and capillary leakage contribute to the swelling.

### Clinical Features by Stage

Papilledema progresses through recognizable stages. In the early phase, the disc margins blur (beginning nasally), the disc becomes hyperemic, spontaneous venous pulsations are lost, and peripapillary nerve fiber layer haze appears. In established papilledema, the disc is visibly elevated, vessels are obscured at the disc margin, and peripapillary hemorrhages, cotton-wool spots, hard exudates, and choroidal folds (Paton lines) develop. Chronic papilledema produces a grey-white disc appearance as the hemorrhages and exudates resolve, and optociliary shunt vessels and drusen-like deposits may form. Atrophic papilledema represents the end stage, with a pale disc, loss of the retinal nerve fiber layer, attenuated vessels, and permanent vision loss.

### Symptoms

Transient visual obscurations -- brief episodes of vision loss lasting seconds, typically triggered by posture changes -- are pathognomonic for elevated intracranial pressure. Headache is common, often positional, worse in the morning, and exacerbated by Valsalva maneuvers. Pulsatile tinnitus is frequently reported. Diplopia may occur from a sixth cranial nerve palsy, which is a false localizing sign of elevated ICP -- the long intracranial course of the abducens nerve makes it vulnerable to compression from diffusely elevated pressure. Visual acuity is characteristically preserved until late in the disease course; visual field loss occurs well before central acuity is affected.

### Visual Field Changes

The earliest and most common visual field abnormality is an enlarged blind spot. As the condition progresses, generalized constriction, inferior nasal field loss, and arcuate defects develop. Central vision is lost only in severe, prolonged papilledema, and its presence indicates that urgent intervention is needed.

<image>Fundus photographs showing progressive stages of papilledema from early disc margin blurring through established papilledema with hemorrhages and exudates to chronic papilledema with pallor and shunt vessels</image>

## Pseudopapilledema

### Causes

The most common cause of pseudopapilledema is optic disc drusen -- calcified deposits within the optic nerve head that produce disc elevation mimicking true edema. Other causes include tilted discs, crowded discs with small cups, hyperopic discs, myelinated nerve fibers, and Bergmeister papilla remnants.

### Distinguishing Features (vs. True Papilledema)

Several features help differentiate pseudopapilledema from true papilledema. Optic disc drusen demonstrate autofluorescence on fundus photography and appear as calcified bodies on B-scan ultrasonography. Importantly, disc drusen do not cause vessel obscuration at the disc margin. Spontaneous venous pulsations, present in approximately 80% of normal individuals, are typically preserved in pseudopapilledema. Peripapillary hemorrhages and exudates are absent. OCT may show elevated RNFL measurements but without associated fluid, and enhanced depth imaging OCT can directly visualize drusen as hyperreflective deposits within the optic nerve head.

## Idiopathic Intracranial Hypertension (IIH)

### Diagnostic Criteria (Modified Dandy Criteria)

The diagnosis of IIH requires five criteria to be met: signs and symptoms of elevated intracranial pressure (papilledema, headache, transient visual obscurations, sixth nerve palsy), no localizing neurological signs other than sixth nerve palsy, normal neuroimaging on MRI with MR venography to exclude a mass lesion, hydrocephalus, or venous sinus thrombosis, elevated opening pressure on lumbar puncture exceeding 25 cmH2O in adults or 28 cmH2O in children, and normal CSF composition.

### Epidemiology

IIH predominantly affects obese women of childbearing age, with a female predominance of approximately 20:1. The incidence is increasing in parallel with rising obesity rates. Although the typical patient is a young obese woman, IIH can occur in men and children, where the clinical presentation and demographic profile differ.

### Risk Factors and Associations

Obesity, defined as a BMI above 30, is the strongest risk factor, and recent weight gain is particularly significant. Several medications are associated with IIH, including tetracyclines (doxycycline and minocycline), vitamin A and retinoids, growth hormone, and lithium. Endocrine disorders including hypothyroidism, hyperthyroidism, Addison disease, and hypoparathyroidism are recognized associations. Obstructive sleep apnea and iron deficiency anemia are additional risk factors.

### MRI Findings in IIH

Characteristic MRI findings include an empty or partially empty sella turcica from pituitary compression, flattening of the posterior sclera from elevated perioptic pressure, distension of the perioptic subarachnoid space, enhancement of the prelaminar optic nerve, and bilateral transverse venous sinus stenosis, which may be either a cause or a consequence of elevated ICP.

### Treatment

#### Weight Loss

Weight loss is the most important long-term intervention for IIH. A reduction of just 5 to 10% of body weight can significantly decrease intracranial pressure. The IIH Treatment Trial demonstrated that diet-induced weight loss is beneficial. Bariatric surgery is considered for patients with morbid obesity and refractory IIH who have not responded to dietary measures.

#### Medical Therapy

Acetazolamide is the first-line pharmacotherapy. It is a carbonic anhydrase inhibitor that reduces CSF production. The IIH Treatment Trial showed that acetazolamide combined with diet was superior to diet alone for visual field improvement. The starting dose is 500 mg twice daily, titrated up to 2 to 4 grams per day as tolerated. Side effects include paresthesias, dysgeusia (metallic taste), metabolic acidosis, fatigue, kidney stones, and hypokalemia. It is relatively contraindicated in patients with sulfa allergy.

Topiramate is a second-line option that has the additional benefit of promoting weight loss and possesses carbonic anhydrase inhibitor activity; its side effects include cognitive dysfunction, kidney stones, and paresthesias. Furosemide may be used as an adjunctive diuretic with modest ICP-reducing effect. Serial lumbar punctures provide temporary ICP relief but are not a viable long-term strategy due to discomfort and infection risk.

#### Surgical Options (for Vision-Threatening IIH)

Optic nerve sheath fenestration (ONSF) is performed via a medial orbital approach, with incisions made in the optic nerve sheath to allow CSF drainage. It directly addresses optic nerve compression and is preferred when papilledema with progressive visual field loss is the primary concern and headache is adequately controlled. Bilateral procedures may be needed. ONSF does not always relieve headache.

CSF shunting, either ventriculoperitoneal or lumboperitoneal, reduces ICP and often relieves both papilledema and headache. However, shunts have a high revision rate of 40 to 60% within two years, and complications include shunt obstruction, infection, overdrainage, and Chiari herniation.

Venous sinus stenting is an emerging technique for patients with significant transverse sinus stenosis and an elevated pressure gradient across the stenosis. It can reduce ICP and improve papilledema, with a growing evidence base supporting its efficacy. Complications include stent thrombosis, vessel perforation, and restenosis.

<image>MRI findings in idiopathic intracranial hypertension showing empty sella turcica, flattening of the posterior globe, distended perioptic subarachnoid space, and bilateral transverse sinus stenosis</image>

## Monitoring and Follow-Up

### Visual Function Assessment

Humphrey visual field testing (24-2 or 30-2) is the most objective measure of visual function in papilledema and is the critical monitoring tool. Serial OCT measurements of RNFL thickness track structural damage to the optic nerve. Dilated fundus examination with papilledema grading using the Frisen scale documents the clinical severity. Visual acuity may remain normal until late in the disease and should not be relied upon as the sole measure of visual function.

### Frisen Scale for Papilledema Grading

The Frisen scale grades papilledema from 0 to 5. Grade 0 is normal. Grade 1 shows minimal blurring of the nasal, temporal, or superior disc borders. Grade 2 has a circumferential halo of elevation. Grade 3 demonstrates obliteration of one or more major vessel segments at the disc margin. Grade 4 shows total obliteration of all vessels on the disc. Grade 5 presents as a dome-shaped protrusion with obliteration of all visible vessels.

| Frisen Grade | Description | Key Finding |
|---|---|---|
| 0 | Normal | No disc edema |
| 1 | Early | Minimal blurring of nasal/temporal/superior borders |
| 2 | Mild | Circumferential halo of elevation |
| 3 | Moderate | Obliteration of 1+ major vessel segments at disc margin |
| 4 | Severe | Total obliteration of all vessels on the disc |
| 5 | Atrophic | Dome-shaped protrusion; obliteration of all visible vessels |

## Clinical Pearls

Papilledema by definition is bilateral disc swelling from elevated intracranial pressure; unilateral disc edema is not papilledema and should prompt investigation for optic neuritis, anterior ischemic optic neuropathy, or a compressive lesion. Visual acuity is preserved until late in papilledema, making visual field testing the critical monitoring tool -- clinicians must not be falsely reassured by good Snellen acuity. Neuroimaging with both MRI and MR venography must always be obtained before lumbar puncture to exclude a mass lesion and venous sinus thrombosis. Weight loss is the cornerstone of long-term IIH management. Acetazolamide should be started at a low dose and titrated upward, with patients warned about the common side effects of paresthesias and fatigue. Fulminant IIH with rapid vision loss over days is a surgical emergency requiring urgent optic nerve sheath fenestration or shunt placement -- there is no time to wait for acetazolamide to take effect. Transient visual obscurations indicate elevated ICP but do not themselves predict permanent visual loss. The medication history must always be reviewed for tetracyclines, vitamin A, and retinoids. The presence of spontaneous venous pulsations at the optic disc suggests that ICP is likely below 20 cmH2O, but their absence is nonspecific, as they are absent in 20% of the normal population.

## References

- Wall M, et al. Effect of acetazolamide on visual function in patients with idiopathic intracranial hypertension and mild visual loss (IIHTT). JAMA. 2014;311(16):1641-1651.
- Friedman DI, et al. Revised diagnostic criteria for the pseudotumor cerebri syndrome in adults and children. Neurology. 2013;81(13):1159-1165.
- Mollan SP, et al. Idiopathic intracranial hypertension: consensus guidelines on management. J Neurol Neurosurg Psychiatry. 2018;89(10):1088-1100.
- American Academy of Ophthalmology. Basic and Clinical Science Course, Section 5: Neuro-Ophthalmology.