## Clinical Diagnosis: Viral Meningoencephalitis in Dengue — Empirical HSV Coverage Required This patient is in the **resorption phase** of dengue (defervescence, rising platelets, falling haematocrit) and has developed **neurological complications** — severe headache and neck stiffness with a CSF profile consistent with viral meningoencephalitis. ### CSF Analysis Interpretation | Parameter | Finding | Interpretation | |-----------|---------|----------------| | **Cell count** | 120/μL, 90% lymphocytes | Viral meningitis/encephalitis pattern | | **Protein** | 80 mg/dL | Mildly elevated (viral range) | | **Glucose** | 55 mg/dL (serum 110) | CSF:serum ratio ~0.5; borderline low, seen in viral encephalitis | | **Gram stain** | Negative | Bacterial meningitis unlikely | ## Why Empirical Aciclovir is the Most Appropriate Next Step **High-Yield:** In any patient presenting with **viral meningoencephalitis** (lymphocytic pleocytosis, elevated protein, negative Gram stain), **Herpes Simplex Encephalitis (HSE)** must be empirically covered until excluded. This is a cardinal principle in infectious disease management. - **HSE** is the most common cause of fatal sporadic encephalitis worldwide. It carries a mortality of >70% if untreated and ~20–30% even with treatment (Harrison's Principles of Internal Medicine, 21e, Ch. 133). - The **clinical presentation** — severe headache, neck stiffness, CSF lymphocytic pleocytosis — is indistinguishable from dengue meningoencephalitis on clinical grounds alone. - **Dengue RT-PCR on CSF** is the gold standard to confirm CNS dengue, but results take time. Waiting for confirmation before starting aciclovir is dangerous if HSE is the true diagnosis. - **EEG** is appropriate to assess for subclinical seizures or temporal lobe involvement (characteristic of HSE). - **Fluid management:** The patient is haemodynamically stable in the resorption phase with good urine output (1.2 mL/kg/hr) — current fluid management (maintenance/restriction) is appropriate and should be continued; aggressive resuscitation is not indicated. ## Management Algorithm ``` Viral encephalitis suspected ↓ Empirical IV Aciclovir (10 mg/kg q8h) IMMEDIATELY ↓ Send CSF for HSV PCR + Dengue RT-PCR ↓ EEG to assess for seizure activity ↓ Continue supportive care; fluid restriction to prevent cerebral oedema ↓ Taper aciclovir only when HSV PCR returns NEGATIVE ``` ## Why Other Options Are Incorrect - **Option B (IVIG + aggressive fluids):** IVIG has no evidence base in dengue meningoencephalitis. Fluid resuscitation at 5–7 mL/kg/hr is for dengue shock phase, not the resorption phase — it risks fluid overload and cerebral oedema. - **Option C (Ceftriaxone + vancomycin + MRI):** Bacterial meningitis is effectively excluded by negative Gram stain, lymphocytic (not neutrophilic) pleocytosis, and clinical dengue context. Empirical antibiotics are not indicated. - **Option D (Repeat LP + dengue RT-PCR alone):** While dengue RT-PCR on CSF is appropriate, **withholding aciclovir** while awaiting results is dangerous — HSE cannot be excluded clinically and must be covered empirically. **Clinical Pearl:** The standard of care for viral encephalitis of unknown aetiology is **empirical aciclovir until HSV PCR is negative**, regardless of the suspected underlying cause (Harrison 21e; Mandell, Douglas & Bennett's Principles of Infectious Diseases, 9e). Dengue meningoencephalitis is a diagnosis of exclusion in this context. [cite: Harrison's Principles of Internal Medicine 21e Ch. 133 & Ch. 189; Mandell Douglas Bennett 9e Ch. 89]
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