Papilloedema

Overview

Papilloedema is swelling of the optic disc secondary to raised intracranial pressure (ICP) - always bilateral, always significant, always demands urgent evaluation.

Pathophysiology

Raised ICP → increased pressure in perineural CSF sheath → obstruction of axoplasmic flow at the lamina cribrosa → axoplasm accumulates → disc swells. Both eyes affected simultaneously because the same CSF pressure surrounds both optic nerves.

Presentation

•Visual obscurations - brief (seconds) transient greying/blackout, provoked by posture change or Valsalva; hallmark visual symptom of raised ICP

•Headache - worse lying flat, coughing, straining; may wake from sleep

•Pulsatile tinnitus - whooshing/heartbeat sound; particularly associated with IIH

•Diplopia - horizontal, due to CN VI palsy (false localising sign - nerve compressed over petrous ridge by raised ICP)

•Visual field loss - enlarged blind spot earliest; progresses to inferior nasal loss, concentric constriction, tunnel vision

•Reduced visual acuity - late feature; indicates established optic nerve damage

🎯

Preserved visual acuity with bilateral disc swelling strongly favours papilloedema over optic neuritis - a classic exam discriminator.

Investigations

🥇 First-line

•MRI brain with gadolinium (preferred) or CT head - exclude space-occupying lesion, hydrocephalus, venous sinus thrombosis BEFORE LP (avoid coning); MRI shows IIH features (empty sella, flattened posterior globes, tortuous optic nerve sheaths)

•MRV or CT venography - exclude cerebral venous sinus thrombosis (especially young women on COCP/thrombophilia)

•Visual field testing (automated perimetry) - enlarged blind spot earliest change; essential for monitoring

•OCT of optic nerve - quantifies RNFL thickness; monitors swelling and detects atrophy

•Blood pressure - exclude malignant hypertension immediately

🏆 Gold standard

•Lumbar puncture with opening pressure measurement - opening pressure >25 cmH₂O (lateral decubitus, legs extended) confirms raised ICP; send CSF for cell count, protein, glucose, culture

Differential diagnosis

Key differentials of disc swelling

Feature	Papilloedema	Optic neuritis	Pseudopapilloedema (drusen)
Laterality	Bilateral	Unilateral (usually)	Bilateral
Visual acuity	Preserved early	Reduced early	Normal
Pain	Headache (ICP)	Pain on eye movement	None
ICP	Raised	Normal	Normal

Management

Treat the underlying cause. Neurosurgical referral for SOL/hydrocephalus; anticoagulation for cerebral venous sinus thrombosis; antihypertensives for malignant hypertension. Ophthalmology review mandatory for all.

IIH-specific management:

🥇 First-line

•Weight loss (target 5-10% body weight) - single most effective intervention; reduces ICP; refer to structured weight management

•Acetazolamide 250-500 mg twice daily (titrated) - carbonic anhydrase inhibitor, reduces CSF production; side effects: paraesthesia, fatigue, kidney stones; contraindicated in sulphonamide allergy

•Therapeutic LP - rapid ICP reduction, immediate symptom relief; may be repeated; used when symptoms severe or vision threatened

🥈 Second-line

•Topiramate - alternative carbonic anhydrase inhibitor; also promotes weight loss; useful if acetazolamide not tolerated

•Furosemide - adjunct diuretic; less evidence

🥉 Third-line

•Optic nerve sheath fenestration (ONSF) - primarily protects vision; less effect on headache; for rapidly deteriorating vision

•CSF diversion (VP or LP shunt) - refractory IIH with severe headache or vision loss

•Cerebral venous sinus stenting - specialist centres; for IIH associated with venous sinus stenosis

🚨

Rapidly declining visual acuity or visual fields in IIH is a sight-threatening emergency - arrange same-day ophthalmology review and consider urgent therapeutic LP or surgical referral. Do not wait for outpatient follow-up.

Complications

•Permanent visual loss - irreversible axonal death from chronic compression; presents as optic atrophy (disc pallor)

•Chronic atrophic papilloedema - pale, less swollen disc but significantly impaired vision; can be mistaken for improvement

•Severe visual field constriction - tunnel vision; may occur despite preserved central acuity until late

•CN VI palsy - resolves once ICP controlled

Risk factors (IIH)

Idiopathic intracranial hypertension (IIH) is the most common cause in clinical practice.

IIH risk factors

Female sex - ~15x more common in women

Obesity - strongest modifiable risk factor

Childbearing age - peak 20-45 years

Tetracyclines (doxycycline/minocycline)

Vitamin A/retinoids (isotretinoin)

Corticosteroid withdrawal

COCP

Lithium, growth hormone

Thrombophilia - risk of cerebral venous sinus thrombosis

Fundoscopy findings

•Early - loss of spontaneous venous pulsation (SVP; first sign), blurring of superior/inferior disc margins, disc hyperaemia

•Established - disc elevation, loss of physiological cup, peripapillary flame haemorrhages, cotton-wool spots

•Chronic - disc pallor (optic atrophy) - established damage, demands urgent intervention

⚠️

A paradoxically pale, less swollen disc in a patient with known raised ICP does NOT mean improvement - it may signal chronic atrophic papilloedema, where optic atrophy is replacing oedema. Visual fields and OCT are essential to distinguish.