CNS infection

Encephalitis?

• Meningitis – Inflammation of meninges
• Encephalopathy
  • Change in behaviour, altered consciousness or extreme drowsiness
• Encephalitis
  • Suspected if infective cause of above
  • More commonly have convulsions (often focal) and focal neurological deficits
  • Usually HSV OR enterovirus, influenza, herpesviruses and Mycoplasma pneumoniae
• Meningoencephalopathy
  • Mixture of above

Aetiology – Bacterial meningitis

• <2-3 months
  • Group B streptococci
  • E. coli
  • Listeria
• Older children
  • Neisseria meningitidis
  • S. pneumoniae
  • Staphylococcus aureus
  • Hib (rare now)
  • Mycobacterium tuberculosis (prolonged time in countries with high prevalence)

Aetiology – Bacterial meningitis

• Meningococcus
  • Serogroup C has reduced since conjugate vaccine
  • Serogroup B (91% now)
  • Serogroup C (2-3%)
• Pneumococcus
  • Rate of 7 valent pneumococcal vaccine serotypes (14, 6B, 18C, 19F, 4, 23F and 9V) has reduced dramatically
    • Been replaced by 19A and 16F to some degree

Aetiology – Viral meningitis

• Enteroviruses (85-95%)
  • Coxsackie
  • Echovirus
• Herpesviruses (meningoencephalitis)
  • HSV 1 and 2
  • HHV-6,7,8
  • VZV
  • CMV
  • EBV

Aetiology – Fungal meningitis

• Cryptococcus neoformans is most common
  • Almost exclusively in immunocompromised

Clinical presentation

• Up to 58% of children with meningitis have received antibiotics prior to presentation to ED
  • May alter presentation
  • Always consider in any sick infant or child
• Enteroviral tend to present in summer/autumn with non-specific constitutional symptoms, diarrhoea, cough, myalgia but IMPOSSIBLE TO DIFFERENTIATE BACTERIAL vs. VIRAL on clinical grounds alone

Clinical presentation

• Resistance to being picked up or distress on walking may be the only clue to meningeal irritation in young children
• Kernig’s sign
  • Inability to extend leg when hip flexed
• Brudzinski’s sign
  • Flexion of head causes reflex flexion of legs
• Nuchal rigidity
• All have low positive and negative predictive value

Investigations

• LP (unless contraindicated) – see following slides
  • Remember, CT does not rule out raised ICP, herniation can occur with a normal CT and a true cause and effect relationship between LP and coning has not been clearly established
• LP Results
  • Microscopy and gram-stain
    • Organisms seen in 60-80% of bacterial meningitis cases (provided no Ab’s prior)

Investigations

• LP Results
  • Cell count
    • Biochemistry and WCC remains the same after antibiotic therapy but culture may be precluded
    • Sterilisation of CSF occurs 2 hours after Ceftriaxone for N. meningitidis and 4 hours for S,  pneumoniae
    • Seizures do not cause raised cell count in absence of meningitis
    • In early meningitis, cell count may be normal
    • Enteroviral meningitis typically has predominant neutrophilia up to 24 hours
  • PCR
    • Sensitivity and specificity is very high for N. meningitidis, HSV and enterovirus
  • Latex agglutination
    • Helpful only for Hib

CSF findings

Lumbar puncture contraindications

• Treat immediately and delay LP for 1-2 days +- CT if:
  • Coma
  • Signs of raised ICP
  • Shock
  • Respiratory compromise
  • Focal neurological signs or seizures
  • Recent seizure (within 30 min or not regained full consciousness afterwards)
  • Coagulopathy/thrombocytopaenia
  • Local infection
  • Febrile child with purpura (suspected meningococcal)

Investigations

• BC, throat swab, skin swab may yield causative organism
• BSL at same time as CSF glucose
• Chem20
  • Hyponatraemia occurs in 1/3 of children
• FBC and CRP – Mainly for response to therapy
• CT or MRI
  • Warranted if focal neurology/seizures, encephalopathy and may show HSV encephalitis (temporal lobe involvement common)
• EEG
  • Warranted if focal seizures or encephalopathy

Management of suspected bacterial meningitis

• <2mo (RCH guidelines)
  • Cefotaxime 50mg/kg q6h + BenPen 60mg/kg IV (q12h if wk 1; q6-8h if wk 2-4; q4h if >4wks)
  • No steroids
  • Cefotaxime can be changed to daily ceftriaxone if >1mo
• Age >3 months
  • Ceftriaxone 50mg/kg q12h + Dexamethasone 0,15mg/kg q6h for 4 days

Management of suspected bacterial meningitis

• Vancomycin unnecessary unless high levels of resistance known in geographic area/previous hospitalisation
  • Rates of pneumococcal vancomycin resistance have dropped significantly since pneumococcal vaccination
• Steroids
  • Protect complications (particularly audiological) in Hib if used before first dose of antibiotics (Ceftriaxone) and particularly in Hib meningitis
  • Reduced morbidity and mortality in pneumococcal meningitis in adults
  • Beneficial as per Cochrane review of paediatric and adult cases
  • Recommended for children >4 weeks up to 1 hour after first dose of antibiotic 0.15mg/kg dexamethasone IV (max 10mg) q6h for 4 days
  • Recommended to be given 15-30 minutes prior to first dose (but do not delay antibiotics for >30 minutes)

Fluid management

• Careful management is key as SIADH is prominent
• Monitor weight, urine output, serum sodium, hydration status and neurological state
• Normal maintenance is recommended now
  • Vs. ½ or 2/3 maintenance as in the past
  • Fluid restrict only if sodium <130 or signs of fluid overload
  • Fluid restriction has been associated with worse neurological outcomes

Management of viral meningitis

• Viral meningitis
  • Supportive care
  • Most cases self-limiting
  • Consider acyclovir if suspicion of encephalitis or HSV
• Encephalitis
  • Acyclovir

Prevention

• Chemoprophylaxis
  • Index case if only treated with penicillin (does not eradicate carriage)
  • Intimate, household, day-care contacts exposed to index case within 10 days of onset
  • Mouth-to-mouth or direct contact with airway secretions (i.e. intubation)
  • Ab: Rifampicin BD for 2 days/ceftriaxone IM stat or ciprofloxacin 500mg PO stat
• Droplet precautions until 24 hours of therapy
• Vaccination
  • Meningococcus:
    • MenC given at 12mo
    • MenB available via prescription
    • MenACWY vaccine available if travelling overseas
  • Pneumococcus: 7 valent conjugate since 2005 (21 valent less immunogenic)
  • Hib

Complications

• Bacterial meningitis
  • 4.5% mortality rate
  • 10-20% of survivors suffer intellectual, cognitive or auditory impairment
• Viral meningitis
  • Usually self-limiting without complication
• Viral encephalitis
  • HSV encephalitis has 80% mortality without treatment and 50% of survivors have neurological sequelae

Brain abscess

• Fever, headache and focal neurological deficit
• Dx by CT or MRI
• Causes
  • Oral viridans streptococci
  • Anerobes
  • Gram-negatives
  • S. aureus
• Empiric treatment
  • Flucloxacillin + Cefotaxime + Metronidazole

Last Updated on October 28, 2020 by Andrew Crofton