A 35-year-old man with chronic headaches and gradual progressive vision loss over 3 months presents with bilateral disc swelling. Fundoscopy shows pale, elevated optic discs with blurred margins, venous obscuration at the disc, and retinal folds (Paton's lines). Visual acuity is normal. What is the most common cause of papilloedema in this patient?

## Papilloedema: Definition and Aetiology **Key Point:** Papilloedema is optic disc swelling due to raised intracranial pressure (ICP). It is NOT inflammation; the disc appears pale, swollen, and elevated. Vision is preserved until late stages. Bilateral presentation is typical. ## Most Common Cause **High-Yield:** Intracranial mass (brain tumour) is the most common cause of papilloedema worldwide. Space-occupying lesions obstruct cerebrospinal fluid (CSF) flow or cause mass effect, raising ICP and causing disc swelling. ## Distinguishing Features of Papilloedema vs Papillitis | Feature | Papilloedema | Papillitis | |---------|--------------|----------| | **Onset** | Insidious (weeks to months) | Acute (hours to days) | | **Pain on eye movement** | Absent | Present (90%) | | **Visual acuity** | Normal until late | Markedly reduced early | | **Disc appearance** | Pale, swollen, elevated | Hyperaemic, blurred | | **Exudates** | Late (hard exudates, cotton-wool spots) | Early peripapillary exudates | | **Venous changes** | Venous obscuration, venous pulsations lost | Minimal venous changes | | **Retinal folds** | Paton's lines (circumferential folds) | Absent | | **Bilateral** | Usually bilateral | Usually unilateral | | **Aetiology** | Raised ICP (tumour, IIH, CVST, hydrocephalus) | Inflammation (MS, TB, syphilis) | ## Clinical Features Supporting Papilloedema 1. **Insidious onset:** 3 months of gradual vision loss suggests chronic raised ICP, not acute inflammation. 2. **Bilateral disc swelling:** Papilloedema is bilateral; papillitis is usually unilateral. 3. **Normal visual acuity:** Early papilloedema preserves vision; papillitis causes acute VA loss. 4. **Pale, elevated discs with Paton's lines:** Pathognomonic for papilloedema from chronic raised ICP. 5. **Associated headache:** Classic symptom of raised ICP from mass lesion. **Clinical Pearl:** The combination of bilateral disc swelling + normal vision + Paton's lines + headache is diagnostic of papilloedema. The most common cause is an intracranial mass obstructing CSF flow or causing mass effect. ## Pathophysiology of Papilloedema ```mermaid flowchart TD A[Intracranial mass]:::outcome --> B[Obstruction of CSF flow<br/>or mass effect]:::action B --> C[Raised intracranial pressure]:::outcome C --> D[Increased pressure in optic nerve sheath]:::action D --> E[Axoplasmic flow impeded<br/>at lamina cribrosa]:::action E --> F[Accumulation of axoplasm<br/>in nerve head]:::action F --> G[Optic disc swelling<br/>Papilloedema]:::outcome ``` ## Differential Considerations - **Multiple sclerosis (option B):** Causes papillitis (inflammation), not papilloedema. Presents acutely with vision loss and pain on eye movement; disc is hyperaemic, not pale. Usually unilateral. - **Acute bacterial meningitis (option C):** Causes papilloedema via raised ICP, but onset is acute (hours) with fever, neck stiffness, and altered mental status. Papilloedema develops over days, not 3 months. - **Optic neuritis (option D):** Causes papillitis, not papilloedema. Acute vision loss, pain on eye movement, hyperaemic disc, usually unilateral. Not associated with chronic headache and gradual vision loss. **Mnemonic:** **ITCH** — Intracranial mass, Tumour, Chronic raised ICP, Headache → papilloedema. [cite:Neuro-Ophthalmology, Khurana 7e Ch 2; Harrison 21e Ch 428]