Meningitis

(Redirected from Viral meningitis)

Background

  • Inflammation of the meninges (membranes surrounding the brain and spinal cord)
  • Bacterial meningitis is a medical emergency — mortality 15-25% even with treatment; up to 50% untreated[1]
  • Time to antibiotics is the most critical intervention — every hour of delay increases mortality

Common Organisms by Age

  • Neonates (<1 month): Group B Streptococcus (GBS), E. coli, Listeria monocytogenes
  • Infants/Children (1 month - 18 years): Neisseria meningitidis, Streptococcus pneumoniae, Haemophilus influenzae type b (less common post-vaccination)
  • Adults (18-50): S. pneumoniae (most common), N. meningitidis
  • Adults >50, immunocompromised, alcoholics: S. pneumoniae, Listeria, gram-negative bacilli
  • Post-neurosurgical/VP shunt: Staphylococcus species, gram-negative bacilli

Viral Meningitis

  • Most common cause overall; enterovirus in majority
  • Generally self-limited; much better prognosis than bacterial

Clinical Features

  • Classic triad (headache, fever, neck stiffness): present in only ~44% of bacterial meningitis
  • At least 2 of 4 (headache, fever, neck stiffness, AMS) present in 95%[2]
  • Headache (87%), fever (77%), neck stiffness (83%)
  • Altered mental status (ranging from confusion to coma)
  • Photophobia
  • Kernig sign: pain with knee extension when hip is flexed (sensitivity ~5%)
  • Brudzinski sign: involuntary hip flexion with passive neck flexion (sensitivity ~5%)
  • Jolt accentuation: worsening headache with horizontal head rotation (better sensitivity than Kernig/Brudzinski)
  • Petechial/purpuric rash: highly suggestive of N. meningitidis (meningococcemia)
  • Neonates: irritability, poor feeding, bulging fontanelle, hypothermia or fever
  • Elderly: may present with only confusion without classic features

Differential Diagnosis

Template:Altered mental status and fever DDX

Evaluation

DO NOT DELAY ANTIBIOTICS FOR LP

  • If LP will be delayed (CT needed, patient unstable): give antibiotics FIRST, then CT, then LP
  • Blood cultures should be drawn before antibiotics when possible (do not delay abx for cultures)

Lumbar Puncture

  • CT BEFORE LP only if:
    • Immunocompromised, history of CNS disease
    • New-onset seizures
    • Papilledema
    • Focal neurologic deficits
    • Altered level of consciousness (GCS <10-12)
  • CSF findings:
Parameter Bacterial Viral TB/Fungal
Opening pressure Elevated (>20 cm H2O) Normal/mild ↑ Elevated
WBC 1000-5000+ (PMN predominant) 10-500 (lymphocytes) 50-500 (lymphocytes)
Glucose <40 mg/dL (or CSF:serum <0.4) Normal Low
Protein Elevated (>250 mg/dL) Mild elevation Elevated
Gram stain Positive in 60-90% Negative Negative (AFB rarely +)

Labs

  • Blood cultures (before antibiotics if possible)
  • CBC, BMP, lactate, coagulation studies
  • Procalcitonin (may help distinguish bacterial from viral; level >0.5 ng/mL supports bacterial)
  • CSF studies: cell count with differential, protein, glucose, Gram stain, culture
  • Consider: CSF lactate, HSV PCR, cryptococcal antigen, meningitis/encephalitis PCR panel

Management

Empiric Antibiotics (Give IMMEDIATELY if Suspected)

  • Adults <50 years:
    • Ceftriaxone 2g IV q12h + vancomycin 15-20 mg/kg IV q8-12h
  • Adults >50 years, immunocompromised, or alcoholics:
    • Ceftriaxone 2g IV q12h + vancomycin 15-20 mg/kg IV q8-12h + ampicillin 2g IV q4h (Listeria coverage)
  • Neonates:
    • Ampicillin + gentamicin (or ampicillin + cefotaxime)
  • Post-neurosurgical/VP shunt:
    • Vancomycin + cefepime (or meropenem)

Dexamethasone

  • Dexamethasone 0.15 mg/kg IV q6h x 4 days
  • Give with or just before FIRST dose of antibiotics[3]
  • Greatest benefit in pneumococcal meningitis (reduced mortality and hearing loss)
  • If given >1 hour after antibiotics, benefit is reduced — do not withhold antibiotics for dexamethasone

Viral Meningitis

  • Supportive care (analgesia, antiemetics, IV fluids)
  • If HSV encephalitis suspected: acyclovir 10 mg/kg IV q8h (do NOT wait for confirmation)

Meningococcal Prophylaxis

  • Close contacts of confirmed N. meningitidis require prophylaxis:
    • Rifampin 600 mg PO q12h x 2 days OR
    • Ciprofloxacin 500 mg PO x 1 dose (preferred for adults) OR
    • Ceftriaxone 250 mg IM x 1 dose (preferred for pregnant women)
  • Notify public health

Disposition

  • Admit all patients with suspected bacterial meningitis to ICU or monitored bed
  • Viral meningitis: may discharge if well-appearing, tolerating PO, reliable follow-up
  • Repeat LP not routinely needed if clinically improving

See Also

References

  1. ↑ van de Beek D, et al. Community-acquired bacterial meningitis. Nat Rev Dis Primers. 2016;2:16074. PMID 27808261
  2. ↑ van de Beek D, et al. Clinical features and prognostic factors in adults with bacterial meningitis. N Engl J Med. 2004;351(18):1849-1859. PMID 15509818
  3. ↑ de Gans J, van de Beek D. Dexamethasone in adults with bacterial meningitis. N Engl J Med. 2002;347(20):1549-1556. PMID 12432041
  • Tunkel AR, et al. Practice guidelines for the management of bacterial meningitis. Clin Infect Dis. 2004;39(9):1267-1284. PMID 15494903
  • Brouwer MC, et al. Epidemiology, diagnosis, and antimicrobial treatment of acute bacterial meningitis. Clin Microbiol Rev. 2010;23(3):467-492. PMID 20610819
  • McGill F, et al. Acute bacterial meningitis in adults. Lancet. 2016;388(10063):3036-3047. PMID 27265346
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