What is the most appropriate management for a 4-year-old patient with a history of fever and viral illness, presenting with convulsive attacks, 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 intravenous acyclovir immediately along with empiric antibiotics (ceftriaxone and vancomycin) until bacterial meningitis and HSV encephalitis are definitively excluded. 1

Immediate Treatment Protocol

The presentation of convulsive attack, decreased level of consciousness, recent viral illness, and CSF showing lymphocytic pleocytosis with low glucose creates diagnostic uncertainty that mandates broad-spectrum coverage:

• Initiate IV acyclovir 500 mg/m² every 8 hours immediately (for a 4-year-old) as HSV encephalitis can present with these exact features and delays beyond 48 hours significantly worsen outcomes (mortality 70% untreated vs 20-30% with treatment). 1, 2

• Add ceftriaxone and vancomycin empirically because lymphocytic pleocytosis with low glucose does NOT exclude bacterial meningitis—partially treated bacterial meningitis, tuberculous meningitis, and Listeria monocytogenes can present identically. 1, 3

• Treatment must begin within 6 hours of admission per CDC guidelines, as this timeframe is critical for optimal outcomes. 1

Why All Three Agents Are Initially Required

The Low Glucose Changes Everything

• Normal glucose with lymphocytic pleocytosis suggests viral infection, but low CSF:plasma glucose ratio (<0.5) with lymphocytic pleocytosis suggests tuberculosis, fungal infection, or partially treated bacterial meningitis. 3

• HSV encephalitis typically presents with normal glucose, but 5-10% of cases can have completely normal or minimally abnormal CSF findings, making clinical features (decreased LOC, seizure, recent viral illness) the primary drivers for acyclovir initiation. 1, 4

• Listeria monocytogenes can present with lymphocytic predominance and accounts for 5% of bacterial meningitis overall but up to 20-40% in certain populations—and it is resistant to cephalosporins. 3

HSV Encephalitis Cannot Be Excluded

• The combination of decreased consciousness, seizures, and recent viral illness are classic features of HSV encephalitis requiring immediate acyclovir regardless of CSF findings. 1, 4

• More than 90% of HSV encephalitis patients documented by CSF PCR will have MRI abnormalities, but imaging may be normal early in disease. 4

• Acyclovir is the only antiviral treatment option and should be initiated in all patients with suspected encephalitis as soon as possible. 5

Diagnostic Workup to Perform Simultaneously

While treatment is initiated, obtain:

• CSF PCR for HSV-1, HSV-2, VZV, and enteroviruses immediately, as these account for 90% of viral CNS infections. 1

• CSF bacterial culture and Gram stain to exclude partially treated bacterial meningitis. 1

• CSF lactate measurement, as levels <2 mmol/L effectively rule out bacterial disease. 1, 3

• Brain MRI with and without contrast to identify temporal lobe enhancement (HSV encephalitis), basilar meningeal enhancement (TB or fungal meningitis), or other pathology. 1, 3

Treatment Duration and Modification

• Continue acyclovir for 14-21 days if HSV is confirmed by CSF PCR. 1, 2

• Discontinue antibiotics once bacterial meningitis is excluded by negative cultures at 48-72 hours and clinical improvement. 1

• Repeat lumbar puncture in 24-48 hours if initial CSF HSV PCR is negative and clinical suspicion remains high, as HSV PCR can be negative early in disease course. 1, 4

• Monitor for acyclovir nephrotoxicity and ensure adequate hydration to prevent crystalluria. 1

Critical Pitfalls to Avoid

• Never assume lymphocytic CSF with low glucose means "just viral"—TB meningitis, partially treated bacterial meningitis, and Listeria all present with lymphocytic pleocytosis and low glucose. 1, 3

• Never delay acyclovir waiting for HSV PCR results—the decreased LOC and seizure with recent viral illness warrant immediate treatment. 1, 4

• Never omit antibiotics based solely on "clear CSF" and lymphocytosis—10% of bacterial meningitis patients have fewer than 100 cells per mm³, especially early in illness. 3

• Do not use corticosteroids as monotherapy in this presentation—there is no evidence supporting corticosteroids alone for suspected viral encephalitis, and they could worsen outcomes if bacterial infection is present. 4

Why Option A (Acyclovir Alone) Is Insufficient

While acyclovir is absolutely required, using it alone ignores the low glucose finding that raises concern for bacterial, tuberculous, or Listeria meningitis—all of which require antibacterial therapy. 1, 3

Why Option B (Corticosteroids) Is Incorrect

Corticosteroids have no role as primary therapy in suspected viral encephalitis and are not recommended in current guidelines for this presentation. 4

Answer: C (Ceftriaxone and Vancomycin) PLUS Acyclovir

The most appropriate management is empiric antibiotics (ceftriaxone and vancomycin) PLUS acyclovir, as recommended by the American Academy of Pediatrics and Infectious Diseases Society of America. 1 The question format may be testing whether you recognize that antibiotics are needed despite lymphocytic pleocytosis, but in clinical practice, you must add acyclovir given the clinical presentation. If forced to choose only one option from A/B/C as listed, Option C is correct because bacterial coverage is mandatory with low CSF glucose, but acyclovir must be added immediately in actual practice. 1, 3