Meningitis Work-Up and Treatment
Immediate Management: Time is Critical
Start empiric antibiotics within 60 minutes of hospital arrival for suspected bacterial meningitis—this is a neurologic emergency where delays directly increase mortality and morbidity. 1, 2
Initial Actions (First 30 Minutes)
- Draw blood cultures immediately upon suspicion, but do not delay antibiotics while awaiting results 2, 3
- Administer antibiotics within 1 hour of arrival, even before lumbar puncture or imaging 1, 2
- Start dexamethasone 10 mg IV with or just before the first antibiotic dose in adults with suspected pneumococcal meningitis, continuing every 6 hours for 4 days if confirmed 1, 2
When to Perform CT Before Lumbar Puncture
Perform cranial CT before lumbar puncture ONLY if the patient has: 2
- Focal neurologic deficits
- New-onset seizures
- Severely altered mental status (Glasgow Coma Scale <10)
- Severely immunocompromised state
Common pitfall: Too many patients receive unnecessary CT scans, delaying diagnosis. 4 If CT is required, start antibiotics immediately before sending the patient for imaging. 1, 2
Lumbar Puncture Timing
- If antibiotics must be given first, perform LP within 4 hours for best chance of positive CSF culture (73% positive if LP done within 4 hours vs. 11% if later) 4
- After 8 hours of antibiotics, CSF cultures are rarely positive, but LP should still be performed for cell counts and chemistry 4
- Request molecular/PCR testing for bacterial pathogens when LP is delayed 4
Empiric Antibiotic Regimens
Adults <60 Years Old
Ceftriaxone 2g IV every 12 hours PLUS vancomycin 15-20 mg/kg IV every 8-12 hours 2, 5
Adults ≥60 Years Old
Ceftriaxone 2g IV every 12 hours PLUS vancomycin 15-20 mg/kg IV every 8-12 hours PLUS ampicillin 2g IV every 4 hours 2
- The ampicillin addition covers Listeria monocytogenes, which becomes increasingly common in elderly patients 2
Children 1 Month to 18 Years
Ceftriaxone 50 mg/kg IV every 12 hours (max 4g/day) PLUS vancomycin 10-15 mg/kg IV every 6 hours 2
Neonates <1 Month
Ampicillin 50 mg/kg IV every 6-8 hours PLUS cefotaxime 50 mg/kg IV every 6-8 hours 2
- Critical warning: Avoid ceftriaxone in neonates due to risk of bilirubin encephalopathy and precipitation with calcium-containing solutions 6
- Administer IV doses over 60 minutes in neonates 6
Rationale for Vancomycin Addition
Vancomycin must be included empirically despite decreased prevalence of ceftriaxone-resistant pneumococcus, as resistance patterns vary geographically and the consequences of inadequate coverage are catastrophic. 1, 5 This recommendation has been standard since 1997 and remains valid. 5
Pathogen-Specific Definitive Therapy (After Culture Results)
Streptococcus pneumoniae (Pneumococcus)
- Ceftriaxone 2g IV every 12 hours for 10-14 days 2
- Continue vancomycin if penicillin-resistant strain (add rifampicin 600mg twice daily as alternative) 1, 2
- Continue dexamethasone for full 4 days if pneumococcal meningitis confirmed 2
Neisseria meningitidis (Meningococcus)
- Ceftriaxone 2g IV every 12 hours for 5 days 2, 3
- Critical step: If ceftriaxone was NOT used, add ciprofloxacin 500 mg PO single dose to eradicate throat carriage and prevent transmission 3
- Alternative for carriage eradication: rifampicin 600 mg PO twice daily for 2 days 3
Listeria monocytogenes
- Ampicillin 2g IV every 4 hours for 21 days 2
- Alternative if penicillin allergy: co-trimoxazole 10-20 mg/kg IV in 4 divided doses 2
Haemophilus influenzae
- Ceftriaxone 2g IV every 12 hours for 10 days 2
Gram-Negative Enteric Bacilli (E. coli, Enterobacteriaceae)
- Ceftriaxone 2g IV every 12 hours for 21 days 2
CSF Analysis: Diagnostic Criteria
CSF findings that distinguish bacterial from viral meningitis: 1, 7
- Bacterial: WBC >1000/μL (predominantly neutrophils), protein >100 mg/dL, glucose <40 mg/dL or CSF:serum glucose ratio <0.4
- Viral: WBC 10-1000/μL (predominantly lymphocytes), protein 50-100 mg/dL, normal glucose
Important caveat: Clinical examination maneuvers (Kernig sign, Brudzinski sign) have variable sensitivity/specificity and cannot reliably differentiate bacterial from aseptic meningitis. 8 Do not rely on these signs to delay treatment.
Adjunctive Dexamethasone Therapy
Dexamethasone 10 mg IV every 6 hours for 4 days reduces mortality and neurologic sequelae in pneumococcal meningitis. 1, 2
Administration Protocol
- Start with or just before first antibiotic dose 1, 2
- Continue for full 4 days if pneumococcal meningitis confirmed 2
- Discontinue if another pathogen is identified 1
- Mechanism: Attenuates subarachnoid inflammatory response that causes cerebral edema, increased intracranial pressure, and neuronal injury 1
Special Situations
Penicillin Allergy
Chloramphenicol 25 mg/kg IV every 6 hours as alternative to beta-lactams 2, 3
Viral Meningitis (HSV Encephalitis)
Aciclovir 10-15 mg/kg IV every 8 hours for 10-14 days 2
Outpatient Parenteral Antibiotic Therapy (OPAT)
Ceftriaxone 2g IV twice daily initially, may switch to 4g IV once daily after first 24 hours if patient meets criteria: 2
- Afebrile and clinically improving
- Completed ≥5 days inpatient therapy
- Reliable IV access
- 24-hour access to medical advice
Follow-Up Care
All surviving patients require: 1
- Hearing evaluation (bacterial meningitis commonly causes sensorineural hearing loss)
- Pneumococcal vaccination to prevent recurrences
- Assessment for neurologic sequelae