A 5-year-old child in Mumbai presents with fever, headache, and photophobia for 3 days. CSF shows lymphocytic pleocytosis (120 cells/μL, 90% lymphocytes), normal glucose (45 mg/dL, serum 80 mg/dL), and elevated protein (60 mg/dL). Viral PCR is positive for enterovirus. Regarding viral meningitis, all of the following statements are correct EXCEPT:

Explanation

## Viral Meningitis: Distinguishing Features ### Correct Answer Analysis **CSF glucose and protein patterns:** The statement is INCORRECT because it describes the CSF profile typical of **bacterial meningitis**, not viral meningitis. **Viral meningitis CSF profile:** - Glucose: **Normal or mildly low** (typically > 40% of serum glucose) - Protein: **Mildly to moderately elevated** (40–100 mg/dL, rarely > 100) - Cell count: 10–1000 cells/μL, predominantly **lymphocytes** **Bacterial meningitis CSF profile:** - Glucose: **Very low** (< 40% of serum glucose) - Protein: **Markedly elevated** (> 100 mg/dL, often 200–500) - Cell count: 100–10,000+ cells/μL, predominantly **PMNs** ### Comparative CSF Analysis Table | Parameter | Viral Meningitis | Bacterial Meningitis | |-----------|------------------|---------------------| | **Cell count** | 10–1000/μL | 100–10,000+/μL | | **Cell type** | Lymphocytes (early PMN possible) | PMNs (predominant) | | **Glucose** | Normal or mildly ↓ (> 40% serum) | Markedly ↓ (< 40% serum) | | **Protein** | 40–100 mg/dL | > 100 mg/dL (often 200–500) | | **Gram stain** | Negative | Positive (60–90% cases) | | **Culture** | Negative | Positive (70–90% cases) | ### Why the Other Options Are Correct **Option 0 — Enteroviruses as leading cause:** - Account for 80–90% of viral meningitis cases - Include coxsackieviruses, echoviruses, and enterovirus 71 - Seasonal peaks in summer and autumn **Option 2 — Excellent prognosis:** - Most patients recover completely without antimicrobial therapy - No specific antiviral needed for enteroviral meningitis - Mortality < 1%; neurological sequelae rare **Option 3 — Mollaret meningitis:** - Recurrent aseptic meningitis caused by HSV-2 (rarely HSV-1) - Characterized by self-limited episodes of fever, headache, and meningeal signs - CSF shows lymphocytic pleocytosis with characteristic "LE cells" (monocytes with phagocytosed RBCs) - Can recur over months to years; eventually resolves spontaneously ### High-Yield Clinical Pearls **Key Point:** The **CSF glucose-to-serum glucose ratio** is the most discriminating parameter: **< 0.4 (or < 40%)** strongly suggests bacterial meningitis; **> 0.4** favors viral meningitis. **Clinical Pearl:** In a child with lymphocytic CSF pleocytosis and normal/mildly low glucose, viral meningitis is likely. Do NOT give empiric antibiotics if the CSF profile is clearly viral and the patient is clinically stable. However, if bacterial meningitis cannot be excluded clinically, empiric antibiotics should be started immediately. **Mnemonic — CSF Patterns: "LUMP vs. BUMP"** - **LUMP** = **L**ymphocytes, **U**sually normal glucose, **M**ild protein, **P**ositive viral PCR (Viral) - **BUMP** = **B**acteria, **U**sually low glucose, **M**arkedly high protein, **P**ositive culture (Bacterial) ### Diagnostic Algorithm ```mermaid flowchart TD A[Acute meningitis suspected]:::outcome --> B[Perform LP immediately]:::action B --> C{CSF cell count & type?}:::decision C -->|PMNs predominant| D{Glucose < 40% serum?}:::decision C -->|Lymphocytes predominant| E{Glucose normal/mildly low?}:::decision D -->|Yes| F[Bacterial meningitis]:::outcome D -->|No| G[Atypical/partially treated]:::outcome E -->|Yes| H[Viral meningitis likely]:::outcome E -->|No| I[Consider TB, fungal, carcinomatous]:::outcome F --> J[Empiric antibiotics + dexamethasone]:::action H --> K[Supportive care, viral PCR]:::action ``` [cite:Harrison 21e Ch 297] [cite:Robbins 10e Ch 7]