A 38-year-old woman presents with sudden-onset severe headache, neck stiffness, and fever. On examination, she is photophobic and has a positive Kernig sign. You suspect acute bacterial meningitis. What is the most appropriate next step in management?

Explanation

## Clinical Context Acute bacterial meningitis is a medical emergency with high mortality if treatment is delayed. The key principle is that **time to antibiotics is more critical than time to imaging** in suspected meningitis. ## Management Algorithm ```mermaid flowchart TD A[Suspected acute bacterial meningitis]:::outcome --> B{Signs of raised ICP<br/>or focal neuro deficit?}:::decision B -->|No| C[Start empirical antibiotics<br/>+ dexamethasone immediately]:::action B -->|Yes| D[CT head first to rule out<br/>mass/herniation risk]:::action C --> E[Perform LP after antibiotics started]:::action D --> F{Contraindication to LP?}:::decision F -->|No| E F -->|Yes| G[Blood cultures + imaging<br/>Skip LP if high risk]:::action E --> H[CSF analysis + culture]:::outcome ``` ## Key Point: **Empirical antibiotics should NOT be delayed for imaging or LP in suspected meningitis.** Every hour of delay increases mortality and morbidity. ## High-Yield: The correct sequence is: 1. **Clinical diagnosis** (history + examination) 2. **Immediate empirical therapy** (3rd-generation cephalosporin + vancomycin + dexamethasone) 3. **Blood cultures** (before antibiotics if possible, but do not delay antibiotics) 4. **Imaging** (CT head only if signs of raised ICP, focal deficit, or immunocompromise) 5. **Lumbar puncture** (after antibiotics; CSF sterilization occurs within 30 minutes but cultures may still grow) ## Clinical Pearl: Dexamethasone (10 mg IV) given with or just before the first dose of antibiotics reduces mortality and morbidity in bacterial meningitis, particularly in pneumococcal disease. It should be given **before or with** the first antibiotic dose, not after. ## Warning: **Do NOT delay antibiotics waiting for CT or LP.** This is a common exam trap. Imaging is only indicated if there are specific contraindications to LP (papilledema, focal neurological signs, immunocompromise, recent head trauma). ## Why Imaging May Be Needed: - Papilledema or signs of raised intracranial pressure - Focal neurological deficits - Immunocompromised state (risk of opportunistic infection mimicking meningitis) - Immunosuppression (HIV with CD4 <100) In this straightforward case with no mention of focal signs or immunocompromise, imaging is **not a prerequisite** — antibiotics take priority. [cite:Harrison 21e Ch 381]