What is the most appropriate management for a patient with a history of fever and viral illness, presenting with convulsive attack, decreased level of consciousness (LOC), and cerebrospinal fluid (CSF) analysis showing lymphocytosis and low glucose?

Management of Suspected Viral Encephalitis with Lymphocytic CSF and Low Glucose

Start acyclovir immediately (10 mg/kg IV every 8 hours) for presumed HSV encephalitis, as this is the most critical treatable cause of viral encephalitis and delays in treatment significantly increase mortality and morbidity. 1, 2

Initial Empiric Treatment Approach

The clinical presentation—convulsive attack, decreased level of consciousness following a viral prodrome, with CSF showing lymphocytosis and low glucose—requires immediate empiric acyclovir therapy while awaiting definitive diagnostic results. 1

Why Acyclovir is the Priority (Option A)

• HSV encephalitis is the most important treatable viral encephalitis, with mortality rates of 59% in untreated patients versus 25% with acyclovir treatment. 2
• Acyclovir should be started immediately in all patients with suspected viral encephalitis, even before CSF PCR results are available, as delays worsen outcomes. 1
• The standard dose is 10 mg/kg IV every 8 hours for 14-21 days in confirmed cases. 1, 2
• Initial CSF PCR can be negative in 5-10% of HSV encephalitis cases, particularly if obtained early (<72 hours) or late in the illness, so treatment should not be withheld based on initial negative results. 1, 3

Why NOT Corticosteroids Alone (Option B)

• Corticosteroids should NOT be used routinely in HSV encephalitis while awaiting results of randomized controlled trials. 1
• Steroids may have a limited role under specialist supervision but only as adjunctive therapy, never as monotherapy. 1
• The inflammatory component of encephalitis does not justify steroid monotherapy when a treatable viral cause (HSV) must be covered. 1

Why NOT Ceftriaxone and Vancomycin Alone (Option C)

• The CSF profile argues against bacterial meningitis as the primary diagnosis: lymphocytic predominance (rather than neutrophilic), clear CSF, and normal protein are inconsistent with typical bacterial meningitis. 3
• Bacterial meningitis typically shows ≥2,000 WBCs/μL or ≥1,180 neutrophils/μL with low glucose, whereas viral infections show lymphocytic pleocytosis (5-1,000 cells/μL). 3
• However, if bacterial meningitis cannot be definitively excluded and there is diagnostic uncertainty, empiric antibiotics should be added to acyclovir, not used instead of it. 1

The Low Glucose Finding: A Critical Nuance

The low CSF glucose is unusual for typical viral encephalitis and raises important differential considerations:

• HSV encephalitis can occasionally present with low glucose, though this is not typical. 1
• Tuberculosis meningitis presents with lymphocytosis, low glucose, and elevated protein in a subacute pattern. 3
• Partially treated bacterial meningitis can show lymphocytic predominance with low glucose. 3
• Fungal or mycobacterial infections should be considered, especially in immunocompromised patients. 1

Practical Management Algorithm

1. Start acyclovir 10 mg/kg IV every 8 hours immediately upon suspicion of viral encephalitis. 1

2. Obtain comprehensive CSF testing including:

   • HSV-1, HSV-2, VZV, and enterovirus PCR (identifies 90% of viral encephalitis cases). 3
   • Bacterial culture and Gram stain. 3
   • Consider mycobacterial cultures and acid-fast bacillus staining given the low glucose. 3

3. Add empiric antibiotics (ceftriaxone and vancomycin) if:

   • Bacterial meningitis cannot be excluded with certainty. 1
   • The patient is severely ill or deteriorating. 1
   • There is any delay in obtaining or processing CSF results. 3

4. Obtain urgent MRI to look for temporal lobe involvement characteristic of HSV encephalitis. 1

5. Continue acyclovir for 14-21 days if HSV is confirmed, with repeat LP to confirm CSF is PCR-negative before stopping. 1

When to Stop Acyclovir

Acyclovir can be safely discontinued if: 1

• An alternative diagnosis is definitively established, OR
• HSV PCR is negative on two occasions 24-48 hours apart AND MRI is not characteristic for HSV encephalitis, OR
• HSV PCR is negative once >72 hours after symptom onset WITH unaltered consciousness, normal MRI (performed >72 hours after symptom onset), and CSF <5×10⁶/L

Critical Pitfalls to Avoid

• Never delay acyclovir while awaiting imaging or diagnostic results in suspected viral encephalitis—the mortality benefit is time-dependent. 1
• Do not stop acyclovir based on a single negative CSF PCR if clinical suspicion remains high; repeat LP at 24-48 hours. 1, 3
• Do not use corticosteroids as monotherapy in suspected viral encephalitis. 1
• The low glucose finding should prompt consideration of TB meningitis and fungal infections, but should not delay acyclovir initiation. 3
• If lumbar puncture is delayed for any reason, start empirical therapy immediately after obtaining blood cultures. 3