A 35-year-old man is referred to ophthalmology by his neurologist for fundoscopic evaluation. He has a 6-week history of progressive headaches, morning nausea, and recently developed blurred vision. Neuroimaging revealed a posterior fossa mass compressing the fourth ventricle. On examination, visual acuity is 6/6 bilaterally with normal pupillary responses. Fundoscopy shows bilateral disc swelling with blurred margins, obscuration of vessels at the disc edge, and absent spontaneous venous pulsations. There is no pain on eye movement. What is the most likely optic nerve head finding?

Explanation

## Clinical Diagnosis: Papilloedema from Raised Intracranial Pressure ### Key Distinguishing Features **Key Point:** Papilloedema is a sign of raised intracranial pressure (ICP), characterised by **bilateral disc swelling, obscured vessels, absent spontaneous venous pulsations, and preserved vision initially**. ### Pathophysiology of Papilloedema 1. Space-occupying lesion (posterior fossa mass) → obstruction of CSF flow 2. Elevated ICP → impaired axoplasmic flow in optic nerve 3. Accumulation of axoplasmic debris → disc swelling 4. **Bilateral involvement** (both optic nerves affected equally) 5. Progressive if untreated → optic atrophy and vision loss ### Comparison: Papilloedema vs Papillitis | Feature | Papilloedema | Papillitis (Optic Neuritis) | |---------|--------------|-----------------------------| | **Onset** | Gradual (days to weeks) | Acute (hours to 24 hrs) | | **Laterality** | **Bilateral** | **Unilateral** | | **Vision loss** | Late/absent initially | Early, marked | | **Pain** | Absent | Present (pain on eye movement) | | **RAPD** | Absent | Present (unilateral) | | **Disc swelling** | Hyperaemia, blurred margins, obscured vessels | Hyperaemia, blurred margins, flame haemorrhages | | **Spontaneous venous pulsations** | Absent | Present | | **Associated symptoms** | Headache, nausea, transient visual obscurations | Demyelinating disease history | | **Aetiology** | Raised ICP (mass, hydrocephalus, pseudotumour) | Demyelination (MS, NMO) | **High-Yield:** The **absence of pain on eye movement** and **bilateral disc swelling** in a patient with imaging evidence of a mass and raised ICP strongly favour papilloedema over optic neuritis. ### Clinical Features of Papilloedema (Frisén Scale) **Mnemonic: SWOLLEN DISC = Swelling (bilateral), Wiped-out margins, Obscured vessels, Layered appearance, Loss of spontaneous pulsations, Enlarged blind spot, Disc hyperaemia, Indistinct nasal border** 1. **Early papilloedema:** Blurring of nasal disc margin, obscuration of vessels at disc edge 2. **Established papilloedema:** Complete obscuration of disc margins, elevation of disc (0.5–2 diopters), hyperaemia 3. **Chronic papilloedema:** Gliosis, optociliary shunt vessels, hard exudates (macular star), peripapillary haemorrhages 4. **Atrophic papilloedema:** Optic atrophy with persistent disc elevation ("waxy pallor") **Clinical Pearl:** Absence of spontaneous venous pulsations is a sensitive sign of raised ICP but not specific (absent in 20% of normal individuals). Obliteration of spontaneous pulsations (previously present) is more specific. ### Why This Patient Has Papilloedema, Not Papillitis - **Bilateral disc swelling** rules out papillitis (unilateral) - **No pain on eye movement** excludes optic neuritis - **Preserved visual acuity (6/6)** is typical of early papilloedema; papillitis causes acute severe loss - **No RAPD** indicates bilateral, symmetric involvement (papilloedema); RAPD is pathognomonic for unilateral optic nerve disease - **Imaging evidence of mass with raised ICP** is the direct cause of papilloedema - **Gradual onset** (6 weeks) fits papilloedema; papillitis is acute ### Management Implications ```mermaid flowchart TD A[Papilloedema confirmed]:::outcome --> B[Treat underlying cause]:::action B --> C{Space-occupying lesion?}:::decision C -->|Yes| D[Neurosurgical intervention]:::action C -->|No| E[Medical management]:::action E --> F[Acetazolamide, fluid restriction]:::action D --> G[Monitor disc appearance & VF]:::action G --> H{Vision threatened?}:::decision H -->|Yes| I[Urgent intervention]:::urgent H -->|No| J[Follow-up imaging & ophthalmology]:::action ``` [cite:Harrison 21e Ch 379; Kline & Bajandas Neuro-Ophthalmology]