A 35-year-old man with chronic headaches and papilloedema on fundoscopy is found to have elevated intracranial pressure (ICP) on lumbar puncture (opening pressure 35 cm H₂O). Visual acuity is preserved, there is no eye pain, and the optic disc margins are blurred bilaterally with venous engorgement. No demyelinating lesions are seen on brain MRI. What is the drug of choice for acute management of this condition?

Explanation

## Clinical Diagnosis: Papilloedema (Elevated ICP) ### Key Distinguishing Features **Key Point:** Papilloedema presents with **preserved vision + no eye pain + bilateral disc swelling + elevated ICP**, distinguishing it from papillitis (optic neuritis), which causes vision loss and RAPD. ### Pathophysiology Papilloedema results from elevated intracranial pressure transmitted along the optic nerve sheath, causing axoplasmic flow obstruction and disc swelling. It is a sign of raised ICP, not a primary inflammatory demyelinating disease. ### First-Line Treatment **High-Yield:** **Oral acetazolamide** is the first-line pharmacological agent for managing papilloedema secondary to idiopathic intracranial hypertension (IIH) and other causes of raised ICP. **Clinical Pearl:** Acetazolamide reduces cerebrospinal fluid (CSF) production by inhibiting carbonic anhydrase in the choroid plexus, thereby lowering ICP. Typical dose is 500 mg–1 g daily in divided doses, titrated to effect. ### Mechanism of Action Acetazolamide inhibits carbonic anhydrase in the choroid plexus epithelium, reducing HCO₃^−^ secretion and decreasing CSF production by ~50%, thereby reducing ICP. ### Comparison: Papilloedema vs Papillitis | Feature | Papilloedema | Papillitis (Optic Neuritis) | |---------|--------------|-----------------------------| | **Vision** | Preserved initially | Loss (sudden, unilateral) | | **Pain** | None | Eye pain on movement | | **RAPD** | Absent | Present | | **Bilaterality** | Bilateral | Unilateral | | **ICP** | Elevated | Normal | | **CSF findings** | Elevated opening pressure | Normal | | **First-line drug** | Acetazolamide | IV methylprednisolone | **Mnemonic:** **ACE** = **A**cetazolamide for **C**erebrospinal fluid reduction in **E**levated ICP ### Adjunctive Measures - Weight loss (if obese) - Sodium restriction - Diuretics (furosemide) in refractory cases - Optic nerve sheath fenestration or lumboperitoneal shunt if vision-threatening despite medical therapy **Warning:** Do not confuse papilloedema (ICP-related) with papillitis (demyelinating). Using acetazolamide for optic neuritis delays appropriate immunosuppressive therapy and risks permanent vision loss.