A 32-year-old woman has been using combined oral contraceptive pills for 3 years and now presents with recurrent headaches with visual disturbances and photophobia. On fundoscopy, papilledema is noted. Which investigation is most appropriate to evaluate the suspected complication of COCP use?

## Clinical Context This patient presents with headache, visual disturbances, photophobia, and papilledema—classic features of idiopathic intracranial hypertension (IIH), a known complication of combined oral contraceptive use, particularly in young women with obesity. ## Investigation of Choice for IIH **Key Point:** MRI brain with MR venography (MRV) is the gold standard investigation for suspected idiopathic intracranial hypertension (IIH) in COCP users. ### Why MRI with MRV? - **Excludes secondary causes** of raised intracranial pressure (mass, hemorrhage, hydrocephalus) - **MR venography** specifically evaluates for **cerebral venous sinus thrombosis (CVST)**, another thrombotic complication of COCPs - **No radiation exposure** (important in young women) - **High sensitivity** for detecting structural brain pathology - **Allows assessment** of optic nerve sheath diameter and brain parenchymal changes - **Non-invasive** compared to lumbar puncture **High-Yield:** IIH is a diagnosis of exclusion—imaging must rule out secondary causes before lumbar puncture for CSF opening pressure measurement. ## Diagnostic Algorithm for IIH ```mermaid flowchart TD A[Headache + Papilledema + Visual symptoms]:::outcome --> B{COCP user?}:::decision B -->|Yes| C[Suspect IIH]:::outcome C --> D[MRI brain + MRV]:::action D --> E{Structural lesion?}:::decision E -->|Yes| F[Treat underlying cause]:::action E -->|No| G[CVST excluded]:::outcome G --> H[Lumbar puncture for opening pressure]:::action H --> I{Opening pressure > 25 cm H2O?}:::decision I -->|Yes| J[Confirm IIH diagnosis]:::outcome I -->|No| K[Consider other diagnoses]:::action ``` ## Role of Other Investigations | Investigation | Indication | Limitation | |---|---|---| | Lumbar puncture with CSF analysis | Confirms elevated opening pressure (>25 cm H₂O) after imaging excludes secondary causes | Invasive; must be done AFTER imaging to rule out mass/hemorrhage; risk of herniation if ICP very high | | CT brain without contrast | Rapid screening in emergency; detects hemorrhage, mass | Lower sensitivity than MRI for subtle pathology; uses radiation; cannot assess venous sinuses adequately | | EEG | Evaluates for seizures if seizure activity suspected | Not diagnostic for IIH; not indicated in this clinical presentation | **Clinical Pearl:** COCP-related IIH typically occurs within the first year of use in young women (especially obese), presenting with progressive headache and visual obscurations. MRI + MRV is essential to exclude CVST, which can coexist and requires anticoagulation. **Warning:** Lumbar puncture should NOT be the first investigation—imaging must exclude mass/hemorrhage first to avoid herniation. CSF analysis (protein, glucose, cell count) is normal in IIH; the diagnosis rests on elevated opening pressure after structural causes are excluded. **Mnemonic:** **COCP-IIH = MRI first, LP second** — imaging before lumbar puncture to exclude secondary causes.