Meningitis

Question 1

Definition of Meningitis:

Answer 1

• Inflammation of the meninges

Question 2

Meningitis: Causative organisms

Answer 2

• Viral (most common)
  
  • Echo
  • Polio
  • Herpes
  • Mumps (rare due to MMR)
• Bacteria (most dangerous)
  
  • Neisseria meningitidis
  • Strep pneumoniae
  • Haemophilus influenzae (rare if immunised)
    
    • Neonates
      
      • Group B haemolytic strep
      • E. coli
      • Listeria monocytogenes

Question 3

Pathophysiology of meningitis

Answer 3

• Damage caused by exaggerated inflammatory response rather than the organism itself
  
  • Cerebral oedema
  • ↑ intracranial pressure
  • ↓ cerebral perfusion
    
    • Cerebral cortical infarction
    • Hydrocephalus (fibrin deposits block resorption of CSF by the arachnoid villi)

Question 4

Clinical features of meningitis:

• Septic
• Non-specific
• Meningeal

Answer 4

• Septic signs (commonly present before meningeal signs)
  
  • Fever / Hypothermia (ominous)
  • Tachycardia
  • Tachypnoea
  • Cold extremities (prolonged capillary refill)
  • Hypotension
  • Colour change
• Non-specific signs (infants and young children)
  
  • Fever
  • Poor feeding
  • Vomiting
  • Irritability
  • Lethargy
  • Headache
  • Drowsiness
  • Seizures
  • Reduced consciousness
  • Bulging fontanelle (late sign)
• Classic meningeal signs (comparatively late, less likely in younger children)
  
  • Photophobia
  • Nuchal rigidity (Other causes: tonsillitis, subarachnoid bleed)
  • Kernig’s sign (Resistance to extending the knee when hip flexed)
  • Brudzinski’s sign (Hips flex on bending head forward)
  • Opisthotonus (arched back)
  • Purpuric rash (meningococcal disease)

Question 5

Investigations for meningitis

Answer 5

• Lumbar puncture
  
  • Microbiology
    
    • Gram stain/culture/virology/antibiotic sensitivity
  • Haematology
    
    • Cell count and differential (↑ polymorphs, bacterial)
  • Chemistry
    
    • Glucose (↓ bacterial)
    • Protein (↑)
    • Lactate (↑, more sensitive than glucose)
• If lumbar puncture contraindicated/partially treated meningitis:
  
  • Rapid antigen test (blood/urine)
  • PCR
  • Blood culture
  • Throat swab
• Bloods
  
  • CRP (↑ viral, ↑↑↑ bacterial)
  • Blood glucose (vs. CSF)

Question 6

Management of meningitis

Answer 6

*Any suspicion of meningococcal disease (febrile, purpuric rash), give IM benzyl-penicillin before hospital admission*

• Supportive therapy - ABC
  
  • Secure airway
  • High-flow oxygen
  • Fluid resuscitation (saline, colloids)
  • +/- inotropes (dobutamine)
• Empirical treatment
  
  • Ceftriaxone if >3months
  • Cefotaxime/gentamicin + amoxicillin/ampicillin if <3 months
    
    • If penicillin/cephalosporin-allergic - Chloramphenicol
  • Plus Dexamethasone if >1 month (↓ risk of deafness)
• If pre-coning signs (↑ ICP) - Mannitol
• Prophylaxis
  
  • Rifampicin or Ciprofloxacin
• Prevention
  
  • Childhood immunisation programme
    
    • Meningitis C
    • Haemophilus influenza type b (Hib)
    • Pneumococcal