Contents · 12 sections
In a nutshell. Meningitis is inflammation of the arachnoid and pia mater. The classic triad (fever, nuchal rigidity, altered mental status) is present in < 50%; most commonly 2 out of 4 (+ headache). The key is CSF: bacterial — neutrophilic pleocytosis > 1000, ↓↓ glucose, ↑↑ protein; viral — lymphocytic 10–500, normal glucose; TB — lymphocytic + ↓ glucose + ↑ protein. Empirical antibiotic therapy for suspected bacterial meningitis — ceftriaxone 2 g IV bid + vancomycin (+ ampicillin if > 50 years and immunocompromised); dexamethasone 10 mg IV qid 10–20 min before the 1st dose of antibiotics. Vaccines: pneumococcal, H. influenzae b, meningococcal A/C/W/Y and B.
1. Etiology
Bacterial
- Adults aged 16–50 years: Streptococcus pneumoniae, Neisseria meningitidis.
- > 50 years and immunocompromised: + Listeria monocytogenes.
- Children aged 2 months – 16 years: S. pneumoniae, N. meningitidis, H. influenzae b (if unimmunized).
- Neonates (< 1 month): Streptococcus agalactiae (Group B), E. coli, L. monocytogenes.
- Post-neurosurgery / TBI: S. aureus, S. epidermidis, Gram(-) rods (P. aeruginosa).
Viral meningitis
- Enteroviruses (Coxsackie, ECHO) — 80%.
- HSV-2 (meningitis), HSV-1 (encephalitis).
- VZV, HSV, CMV, EBV, HIV (acute), mumps, tick-borne encephalitis.
Other
- Tuberculous meningitis: Mycobacterium tuberculosis.
- Cryptococcal: Cryptococcus neoformans (HIV, immunosuppression).
- Lyme disease, syphilis, amebic meningoencephalitis.
2. Clinical presentation
- Classic triad (fever + nuchal rigidity + altered mental status) — < 50% of cases.
- ≥ 2 of 4 symptoms (+ headache) — 95% of bacterial meningitis.
- Meningeal signs: nuchal rigidity, Kernig's and Brudzinski's signs.
- Petechial/purpuric rash — meningococcemia (medical emergency!).
- Focal neurological deficits, seizures, altered mental status — poor prognostic signs.
- In neonates: apathy, poor feeding, vomiting, bulging fontanelle, seizures.
- In the elderly: fewer meningeal signs, more confusion.
3. Workup
- Blood cultures — prior to starting antibiotics (do not delay antibiotic therapy!).
- Lumbar puncture: CSF for biochemistry, cell count, microbiology, PCR.
- Measurement of CSF opening pressure (elevated in bacterial meningitis).
- CT prior to LP if: altered mental status, focal neurological deficits, seizures, immunosuppression, recent TBI.
- Laboratory tests: CBC, biochemistry, C-reactive protein, procalcitonin, coagulation panel.
- CSF PCR (HSV, VZV, enteroviruses) — high sensitivity.
- Latex agglutination / antigens (S. pneumoniae, N. meningitidis, H. influenzae) — if prior antibiotic therapy was given.
4. CSF analysis — differential diagnosis
| Parameter | Normal | Bacterial | Viral meningitis | TB | Crypto |
|---|---|---|---|---|---|
| Opening pressure (mm H₂O) | 100–180 | ↑↑ (> 250) | N or ↑ | ↑ | ↑↑ |
| Color | Clear | Turbid | Clear | Opalescent | Clear |
| Cell count (×10⁶/L) | < 5 | 1000–10,000, neutrophilic | 10–500, lymphocytic | 100–500, lymphocytic | 20–500, lymphocytic |
| Protein (g/L) | 0,15–0,45 | > 1 | N / ↑ | ↑↑ | ↑ |
| Glucose (mmol/L) | 2,5–4,4 | ↓↓ (< 2) | N | ↓ | ↓ |
| Lactate (mmol/L) | < 2,1 | > 3,5 | N | ↑ | ↑ |
| CSF/blood glucose ratio | > 0,6 | < 0,4 | > 0,5 | < 0,5 | < 0,5 |
5. Empirical antibiotic therapy
| Age / Context | Diagram |
|---|---|
| < 1 month | Ampicillin + cefotaxime (or gentamicin) |
| 1 month – 50 years | Ceftriaxone 2 g bid + vancomycin 15–20 mg/kg bid-tid |
| > 50 years, immunocompromised | + ampicillin 2 g q4h (Listeria) |
| Nosocomial / post-neurosurgery | Vancomycin + meropenem or cefepime |
| Beta-lactam allergy | Vancomycin + moxifloxacin + co-trimoxazole (Listeria) |
Administration: as early as possible after CSF and blood culture collection (do not delay antibiotic therapy!). Critically important — within the first 30 minutes of hospitalization if suspected.
6. Targeted therapy
- S. pneumoniae — ceftriaxone 2 g × 2 ± vancomycin for penicillin resistance, 10–14 days.
- N. meningitidis — ceftriaxone or benzylpenicillin 4 million IU × 6, 7 days.
- H. influenzae b — ceftriaxone, 7–10 days.
- L. monocytogenes — ampicillin + gentamicin, 21 days.
- S. agalactiae — ampicillin + gentamicin, 14–21 days.
- S. aureus MSSA — cefazolin/nafcillin; MRSA — vancomycin ± linezolid.
- P. aeruginosa — ceftazidime or cefepime + aminoglycoside.
- TB — isoniazid + rifampicin + pyrazinamide + ethambutol for 2 months → isoniazid + rifampicin for 10 months + dexamethasone according to a tapering schedule for 6–8 weeks.
- Cryptococcal — amphotericin B + flucytosine for 2 weeks → fluconazole.
- HSV — acyclovir 10 mg/kg × 3 IV, 14–21 days.
7. Dexamethasone
- 10 mg IV × 4/day 10–20 min before the 1st antibiotic dose or simultaneously.
- Continued for 4 days if S. pneumoniae is confirmed.
- Reduces mortality and neurological complications (hearing loss) in pneumococcal meningitis.
- Discontinued if pneumococcus is ruled out and in case of viral etiology.
8. Viral meningitis
- Enteroviral: symptomatic treatment, favorable prognosis.
- HSV-2 meningitis: frequently recurring — acyclovir for severe disease.
- VZV: acyclovir 10 mg/kg × 3 IV.
- In case of encephalitis (focal signs, seizures, MRI) — empirical acyclovir until HSV is ruled out.
9. Complications
- Brain edema, intracranial hypertension, herniation.
- Septic shock, DIC (meningococcemia).
- SIADH.
- Hydrocephalus (TB, post-infectious).
- Subdural effusion, empyema.
- Ventriculitis.
- Hearing loss — up to 30% in children after pneumococcal meningitis.
- Epilepsy, cognitive impairment.
- Waterhouse-Friderichsen syndrome (adrenal insufficiency) in meningococcemia.
10. Prevention
- Vaccination: pneumococcal (PCV13, PPSV23), H. influenzae b, meningococcal A/C/W/Y + B (Bexsero/Trumenba).
- Chemoprophylaxis for close contacts of meningococcal disease: rifampicin 600 mg × 2/day for 2 days, ciprofloxacin 500 mg single dose, ceftriaxone 250 mg IM.
- Close contacts of H. influenzae b: rifampicin for 4 days.
- Patient isolation for the first 24 hours of antibiotic therapy in meningococcal disease.
11. Prognosis
- Bacterial meningitis: overall mortality 10–20%; pneumococcal — up to 30%.
- Poor prognostic factors: older age, impaired consciousness, tachycardia, pneumococcal etiology, antibiotic delay > 3 h.
- Viral — favorable; usually self-limiting within 7–10 days.
- Tuberculous meningitis: mortality 20–50%; complications — hydrocephalus, cranial nerve palsy, stroke.
12. FAQ
Is CT necessary before LP?
Yes in case of: altered consciousness, focal neurological signs, seizures, immunosuppression, age > 60 years, recent TBI. In other cases — LP without delay.
Can antibiotics be started before LP?
Yes — in case of any delay with LP (waiting for CT, transport), empirical antibiotic therapy is initiated after blood cultures. CSF culture sensitivity decreases, but antigens and PCR remain detectable.
How to differentiate meningitis from encephalitis?
Meningitis — signs of meningeal irritation (nuchal rigidity, headache); encephalitis — signs of parenchymal involvement (altered consciousness, focal neurological signs, seizures). Often — meningoencephalitis.
What is meningococcemia without meningitis?
A septic form of meningococcal infection with petechial rash, shock, and DIC without meningeal involvement. Mortality > 40%.
Is the meningococcal B vaccine safe?
Bexsero and Trumenba are well tolerated, cause fever in infants. Recommended for adolescents, college dorm residents, military personnel, patients with asplenia and complement deficiencies.
See also: Normal CSF · Sepsis · Antibiotics · Tuberculosis · Neurology Catalog