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

Management of Suspected Meningoencephalitis

Start intravenous acyclovir immediately along with empiric antibiotics (ceftriaxone and vancomycin) until bacterial meningitis and HSV encephalitis are definitively excluded. 1

Critical Clinical Context

This presentation is a medical emergency requiring immediate dual therapy because:

• Lymphocytic pleocytosis with low glucose does NOT exclude bacterial meningitis - partially treated bacterial meningitis, tuberculous meningitis, and listeriosis all present with identical CSF profiles 2, 1
• The combination of seizure, decreased level of consciousness, recent viral prodrome, and CSF lymphocytosis is classic for HSV encephalitis, which requires treatment within 6 hours to prevent mortality rates of 70% (untreated) versus 20-30% (treated) 1
• HSV encephalitis presents with normal or minimally abnormal CSF in 5-10% of cases, so even "clear" CSF does not exclude this diagnosis 2, 1

Immediate Treatment Protocol

Start Both Therapies Simultaneously

Acyclovir 500 mg/m² IV every 8 hours (or 10 mg/kg IV every 8 hours in adults) must be initiated immediately 1, 3

Ceftriaxone 2g IV every 12 hours PLUS vancomycin 15-20 mg/kg IV every 8-12 hours to cover bacterial pathogens 1

• Delays beyond 48 hours in treating HSV encephalitis significantly worsen outcomes 1
• Continue acyclovir for 14-21 days if HSV is confirmed 1
• Discontinue antibiotics once bacterial cultures are negative at 48-72 hours and clinical course supports viral etiology 1

Why Not Corticosteroids Alone?

Corticosteroids are NOT indicated as first-line therapy in this presentation 4

• They are reserved for confirmed bacterial meningitis (given before or with first antibiotic dose) or specific immune-mediated conditions after infectious causes are excluded 4, 5
• Starting corticosteroids without antimicrobial coverage in this scenario could be catastrophic if bacterial meningitis is present 4

Essential Diagnostic Workup

Send CSF immediately for:

• PCR for HSV-1, HSV-2, VZV, and enteroviruses (identifies 90% of viral CNS infections) 2, 1
• Bacterial culture and Gram stain 1
• CSF lactate (levels <2 mmol/L effectively rule out bacterial disease) 2, 1

Obtain brain MRI with and without contrast to identify temporal lobe enhancement (HSV encephalitis) or basilar meningeal enhancement (TB/fungal meningitis) 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 falsely negative early in disease course 2, 1

Critical Pitfalls to Avoid

Never assume lymphocytic CSF means "just viral" - bacterial meningitis with lymphocytic predominance occurs in 32% of cases when CSF WBC is <1,000/mm³, particularly with Streptococcus pneumoniae, Listeria, and partially treated meningitis 6, 7

Never delay acyclovir waiting for PCR results - the clinical presentation (decreased LOC, seizure, recent viral illness) warrants immediate empiric treatment regardless of CSF findings 1, 3

Low CSF glucose is a red flag - while viral meningitis typically maintains normal glucose, the low glucose in this case increases concern for bacterial (including TB and Listeria), HSV-2 in immunocompromised patients, or fungal etiologies 4, 8

Monitoring Strategy

• Ensure adequate hydration to prevent acyclovir-induced crystalluria and nephrotoxicity 1
• Monitor renal function daily while on acyclovir 1
• Reassess antibiotic need at 48-72 hours based on culture results and clinical trajectory 1