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
• 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%
• 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

• Subarachnoid hemorrhage
• Encephalitis
• Brain abscess
• Subdural hemorrhage / epidural abscess
• Stroke
• Viral meningitis
• Carcinomatous meningitis
• Drug-induced meningitis (NSAIDs, IVIG, TMP-SMX)

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
• 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

• Encephalitis
• Subarachnoid hemorrhage
• Lumbar puncture
• Meningitis (peds)
• Brain abscess
• Sepsis

References

• 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