Acute bacterial meningitis

Pathogenesis

Causes (vary with demographic):

  • Bacterial
    • Pneumonia
    • Neisseria Meningitidis
    • Listeria monocytogenes: elderly, immunosuppressed
    • Haemophilus influenza: children
    • Gram negatives: elderly, immunosuppressed
    • TB: immunosuppressed
    • Staphylococci: neurosurgery patients
  • Fungal
    • Cryptococcus neoformans
  • Viral
    • HSV2
    • Enterovirus

Pathophysiology

Presentation

Symptoms evolve over days:

  • Fever
  • Headache
  • Meningism: photophobia, neck stiffness
  • Confusion/decreased GCS
  • Sepsis

Signs on exam:

  • General appearance:
    • Septic
    • Rash
  • Mental status
    • Decreased GCS
  • Cranial nerve function
    • Cranial neuropathies
    • Papilloedema
  • Meningism
    • Photophobia
    • Neck stiffness: passive & active
    • Brudzinski: neck flexion >> hip flexion
    • Kernig’s: hip flexion prevents knee extension

Early complications:

  • Cranial neuropathies
  • Communicating hydrocephalus
  • Seizures
  • Cerebral venous sinus thrombosis
  • Focal neurological deficits

Investigation

  • Blood tests: cultures, FBC, U&E, coagulation, VBG
    • ↑WCC: neutrophilia
    • ↑CRP
  • Lumbar puncture
    • Findings
      • ↑WCC: neutrophilia
      • ↑Protein
      • ↓Glucose
      • Organisms
    • Contra-indications
      • Sepsis
      • Haemodynamic instability
      • Coagulopathy
      • Seizures
  • CT head: indicated prior to LP in the following settings
    • Decreased GCS
    • Raised ICP
    • Focal neurological deficit
    • Seizures

Management

  • IV antibiotics: initially empiric, then narrow the spectrum once organisms identified on blood culture / CSF gram stain / culture
    • Ceftriaxone 2g BD
    • + Ampicillin 2g QDS for elderly/immunosuppressed
    • Pen-allergic: chloramphenicol + vancomycin
  • Dexamethasone
    • Effective in pneumococcal meningitis only
  • IV fluids
  • Treat close contacts/high-risk contacts with oral ciprofloxacin for meningococcal disease
  • Notify Public Health England