Meningitis

Inflammation of the meninges and subarachnoid space, that can be divided into:

Meningitis in the immunocompromised can present with non-specific features and with more exotic causative organisms.

Epidemiology and Risk Factors

General risk factors:

  • Immunosuppression
  • Extremes of age
  • Cochlear implants
  • Trauma
    • CSF leak
    • Base of skull fracture

For meningococcal meningitis:

  • Unvaccinated

For pneumococcal meningitis:

  • Splenectomy
  • Unvaccinated

Pathophysiology

Series of processes:

  • Infection
    Predominantly via droplet or saliva. Common routes include:
    • Nasopharyngeal colonisation
    • Middle ear
    • Sinusitis
    • Dental
  • Cytokine production
  • Meningitis
  • Hydrocephalus
    • ↑ ICP
    • ↓ CPP
  • Vasculitis
  • Thrombosis

Aetiology

Community acquired:

  • Bacterial:
    • S. pneumoniae
    • N. meningitidis
      • Peak incidence in first year of life
        Following loss of maternal antibody, and prior to development of antibody to community exposures.
      • Rare in the immunocompetent adult
        ↑ Risk in high-density living, e.g. dormitories.
      • Characteristic:
        • Myalgias and arthralgias
        • Purpuric or petechial rash
          May progress to purpura fulminans.
      • Exquisitely antibiotic sensitive
      • Complicated by:
        • Adrenal insufficiency secondary to acute adrenal haemorrhage Waterhouse-Friedrichsen syndrome.
        • Pericarditis
    • H. influenzae
      Most common cause prior to vaccination.
    • L. monocytogenes
      Rare, and generally confined to the lightly immunocompromised:
      • Elderly
      • Splenectomy
      • Alcohol dependency
      • Diabetes
      • Malignancy
  • Viral:
    • Enteroviruses
      • Coxsackie
    • Herpes simplex
    • Mumps
    • Echoviruses
    • Toscana virus

Purpura fulminans is covered in detail at Purpura Fulminans.

Nosocomial:

Nosocomial meningitis is rare.

  • Staphylococcus spp.
    Particularly with intracranial devices, or following neurosurgery.
  • E. coli
  • Pseudomonas spp.
  • Klebsiella spp.
  • Acinetobacter spp

Immunocompromised:

  • Cryptococcus neoformans
    • Chronic meningitis
    • India ink stain and antigen testing on CSF
    • ↑↑ Opening pressures
  • Tuberculosis meningitis
    • Normal glucose
    • PMN predominance
  • Toxoplasmosis

Neonatal:

  • Group B Streptococci
    S. agalactiae.
  • E. Coli
  • L. monocytogenes
  • H. Influenzae
    Prior to vaccination.

Assessment

Clinical features typically rapidly evolve over hours, and relate to:

Viral meningitis presents with similar symptoms to bacterial meningitis, but is generally less severe.

  • Meningeal inflammation
    • Fever
    • Headache
    • Neck stiffness
    • Photophobia
  • Encephalopathy
    • Altered level of consciousness
    • Irritability
    • Seizures
      Paediatric.
  • Causative organism
    • Meningococcal disease
      • Rash
        Haemorrhagic, petechial, purpuric.
      • Digital gangrene
      • Skin necrosis
      • Signs of coagulopathy
Meningococcal Rash

Subtle Meningococcal Rash

In the immunocompromised:

  • Low-grade fever
  • Behavioural changes

Kernig’s sign is neither sensitive or specific of meningeal irritation.

Diagnostic Approach and DDx

Investigations

Bedside:

Laboratory:

Details of CSF findings in meningitis are covered under Cerebrospinal Fluid Analysis.

  • Blood
    • FBE
    • Blood cultures
    • UEC
    • BSL
  • Urine
    • Pneumococcal urinary antigen
      Significantly ↓ sensitivity for meningitis compared with pneumonia, but cheap and non-invasive.
  • LP
    • Required to completely confirm diagnosis
    • However, contraindications are common:
      • Coagulopathy
      • ↑ ICP, or significant clinical concern of such
    • Empirical antibiotics should be commenced if there is delay performing LP
    • Urgent Gram stain and culture
    • Specific antigen investigations:
      • Viral PCR
        • Herpes simplex PCR
      • Mycobacterium TB PCR
      • Mycobacterial stain and cultures
      • India Ink stain and Cryptococcal antigen
      • Pneumococcal urinary antigen
        95% sensitive if used on CSF.

Imaging:

Indications for CT prior to LP:

  • ↑ BP with ↓ HR
  • Focal neurology
  • ↓ Conscious state
  • New seizures
  • Predisposition to infection
  • History of CVA or space-occupying lesions
  • Papilloedema
  • CT
    ↑ ICP or space-occupying lesion.

Other:

Management

Resuscitation:

Specific therapy:

Duration of antimicrobial therapy depends on the organism:

  • N. meningitidis: 5 days
  • S. pneumoniae: 10-14 days
  • L. monocytogenes: 21 days
  • Pharmacological
    • Antimicrobial therapy
      • Empiric therapy
        • Foundation:
          • Ceftriaxone 2g IV Q12H
            Or cefotaxime 2g IV Q6H.
          • Dexamethasone 10mg IV Q6H
            • Give with or before first dose of antibiotics
            • Continue up to 4 days in S. pneumoniae, and H. Influenze in children.
          • Acyclovir 10mg/kg IV
            Indicated for viral meningitis caused by VZV or HSV.
        • If immunocompromised:
          i.e. Age >60, diabetes, alcohol misuse, malignancy, immunosuppressants:
          • Add ampicillin 2g Q4H
            Amoxycillin can be used as an alternative.
        • If Gram positive cocci on Gram stain:
          For concern of resistant S. pneumoniae; can be de-escalated once the penicillin MIC is known.
          • Add vancomycin
          • Consider replacing ceftriaxone with cefepime or meropenem
      • Cryptococcal meningitis
        • Initial therapy:
          • Amphotericin B
          • 5-fluorocytosine
        • Fluconazole
    • Anticonvulsants
      • Benzodiazepines for seizure control
  • Procedural
  • Physical

Dexamethasone is associated with:

  • ↓ Mortality in S. pneumoniae
  • ↓ Deafness in adults and in children with H. Influenzae
  • ↓ Neurological sequelae

Management of seizures is covered under Seizures.

Supportive care:

Disposition:

  • ICU admission in:
    • Rapidly evolving rash
    • GCS ⩽12
    • Organ support
    • Seizures

Preventative:

  • Prophylaxis is recommended for close contacts
    Ciprofloxacin 500mg.
  • Meningococcal vaccination
  • Public health notification

Marginal and Ineffective Therapies

  • Intrathecal antibiotics
    Not recommended.
  • Prophylactic anticonvulsants

Anaesthetic Considerations

Complications

  • Death
  • D
    • Hydrocephalus
    • Cerebral infarction
    • Seizure
      25% of cases.
  • H
    • DIC
      Meningococcal meningitis.

Prognosis

Bacterial meningitis:

  • Usually fatal without treatment
  • Mortality ~20%
    ↑ In patients with:
    • Seizures
    • Delays to treatment
    • Extremes of age
    • Pneumococcal meningitis

Viral meningitis:

  • Usually lasts 7-10 days

Poor prognostic features:

  • Cranial nerve palsies
  • ↓ GCS
  • ↑ ESR
  • ↑ CSF protein
  • ↓ CSF leucocytes

Key Studies

References

  1. Bersten, A. D., & Handy, J. M. (2018). Oh’s Intensive Care Manual. Elsevier Gezondheidszorg.
  2. Starr M, Rajapaksa S. Meningococcal sepsis. Australian Journal for General Practitioners. 2010 May;39(5):276–8.