A 52-year-old man is referred to the eye clinic by his neurologist for fundoscopic examination. He presented 3 weeks ago with progressive headaches, morning vomiting, and recent-onset horizontal diplopia. On examination, both optic discs are swollen with blurred margins and hyperaemia. The swelling is bilateral and symmetrical. Visual acuity is 6/6 in both eyes. Colour vision is normal. There is no pain on eye movement. Fundoscopy also shows obscuration of vessels at the disc margin and peripapillary retinal folds (Paton's lines). Intraocular pressure is 16 mmHg. What is the most likely diagnosis?

Explanation

## Clinical Diagnosis: Papilloedema from Raised Intracranial Pressure ### Key Distinguishing Features **Key Point:** Papilloedema is optic disc swelling due to raised intracranial pressure (ICP). It is **bilateral, painless, and preserves visual acuity until late stages**. ### Clinical Presentation Analysis This patient presents with: 1. **Bilateral, symmetrical optic disc swelling** — hallmark of papilloedema 2. **Preserved visual acuity** (6/6 in both eyes) — papilloedema does not cause early visual loss 3. **Normal colour vision** — preserved in papilloedema 4. **Absence of pain on eye movement** — rules out optic neuritis 5. **Signs of raised ICP**: progressive headaches, morning vomiting, horizontal diplopia (CN VI palsy from transtentorial herniation) 6. **Fundoscopic findings of papilloedema**: - Blurred disc margins (initially temporal, then circumferential) - Hyperaemia of disc - Obscuration of vessels at disc margin - **Paton's lines** (peripapillary retinal folds) — pathognomonic for papilloedema 7. **Normal IOP** (16 mmHg) — excludes glaucoma ### Papilloedema vs Papillitis Comparison | Feature | Papilloedema | Papillitis (Optic Neuritis) | |---------|--------------|-----------------------------| | **Onset** | Insidious (days to weeks) | **Acute (hours to 2–3 days)** | | **Bilaterality** | **Bilateral, symmetrical** ✓ | Usually unilateral | | **Visual acuity** | **Preserved initially** ✓ | Early, marked loss | | **Pain on eye movement** | **Absent** ✓ | Present | | **Colour vision** | **Normal** ✓ | Defective | | **Associated ICP signs** | **Headache, vomiting, CN palsies** ✓ | Absent | | **Paton's lines** | **Present** ✓ | Absent | | **Fundus pattern** | Bilateral, circumferential swelling | Often polar or segmental | | **MRI optic nerve** | Normal or atrophic | T2 hyperintensity | **High-Yield:** **Paton's lines** (peripapillary retinal folds) are virtually pathognomonic for papilloedema and indicate chronic, severe raised ICP. ### Clinical Pearl **Clinical Pearl:** The combination of **progressive headache + morning vomiting + horizontal diplopia (CN VI palsy) + bilateral optic disc swelling** is classic for intracranial mass or hydrocephalus causing raised ICP. Horizontal diplopia from CN VI palsy is a "false localizing sign" — CN VI is stretched as the brainstem herniates downward, not because of a pontine lesion. ### Mnemonic: PAPILLOEDEMA Signs **Mnemonic:** **SWOLLEN DISC** = **S**welling bilateral, **W**ell-preserved acuity, **O**bscured vessels at margin, **L**ate visual loss, **L**oss of spontaneous venous pulsation, **E**arly hyperaemia, **N**o pain, **D**isc hyperaemia, **I**CP raised, **S**ymmetrical, **C**ircumferential blur ### Stages of Papilloedema (Frisén Scale) 1. **Stage 0**: Normal disc 2. **Stage 1**: Temporal disc blurring (earliest sign) 3. **Stage 2**: Complete circumferential blurring 4. **Stage 3**: Obscuration of major vessels at disc 5. **Stage 4**: Complete obscuration of vessels; Paton's lines visible 6. **Stage 5**: Optic atrophy (chronic papilloedema) ### Causes of Raised ICP (Differential) - Space-occupying lesion (tumour, abscess, haematoma) - Hydrocephalus (obstruction of CSF flow) - Cerebral oedema (trauma, infection, metabolic) - Venous sinus thrombosis - Idiopathic intracranial hypertension (IIH) ### Management 1. **Urgent neuroimaging**: CT/MRI brain to identify cause 2. **Lumbar puncture** (if imaging normal): measure opening pressure; send CSF for analysis 3. **Treatment of underlying cause**: neurosurgical intervention if mass/hydrocephalus 4. **Serial fundoscopy** to monitor disc changes 5. **Visual field testing** (perimetry) to detect early visual loss