Meningitis

Meningitis is inflammation of the leptomeninges and underlying CSF.  Causes can be infective (bacterial/viral/fungal) or non-infective (cancer syndromes, autoimmune disorders and drug-induced)

Background

  • Whilst viral meningitis is more common (around 2/3 cases), bacterial meningitis (particularly caused by Neisseria meningitidis- otherwise known as meningococcal meningitis) is far more severe and can be life threatening.  As such, a patient with meningism should be presumed to have meningococcal disease until proven otherwise.
  • Incidence of bacterial meningitis is around 2500/year in UK; possibly double that for viral
  • Mortality from bacterial meningitis ranges from 10-30% (viral meningitis is significantly lower).  If patients present with decreased consciousness and/or neurological deficits, the mortality/morbidity rate is nearer 90%.

Cause

Viral

  • Enteroviruses (e.g. coxsackievirus) are by far most common in both adults and children
  • In anyone who has not received MMR, these viruses should be considered, especially if there have been symptoms of mumps, measles or rubella.
  • Herpes simplex is probably next most common (type 2 > type 1), followed by Varicella Zoster, and rarely other viruses e.g. EBV, Parvovirus etc
  • In patients who have recently been travelling, consider West Nile Virus or Tick-borne viruses

Bacterial

  • In neonates
    • Group B Strep, Listeria and E coli are the most common organisms
  • In infants and young children
    • Neisseria meningitidis (meningococcal); Strep pneumoniae and H Influenzae in patients who haven’t been immunised
  • Adults/older children
    • Streptococcus pneumoniae is most common (>50%); followed by Group B Strep and Neisseria meningitidis (~15% each); occasionally H influenzae or Listeria; rarely TB or syphillis (in immunocompromised host)
  • In older/immunocompromised patients
    • Streptococcus pneumoniae, Listeria monocytogenes, TB, Gram-negative organisms.
  • Hospital acquired meningitis can often be resistant and aggressive
    • Kliebsiella, E coli, Pseudomonas, S aureus

Risk Factors

  • NB Rarely will there be predisposing factors listed below.  Occasionally there will be a preceding illness caused by the pathogenic organism e.g. throat/nose/sinus/ear infection.
  • Head operations/open injury and/or spinal procedures (particularly S aureus and pseudomonas)
  • Immunocompromised patients (e.g. hypogammaglobulinaemia, hyposplenism, chronic steroid use, alcoholism/drug abuse, defective complement system (C4))
  • Diabetes
  • Pregnancy
  • Chronic renal or liver failure

Presentation

  • Viral and bacterial meningitis present with
    • Acute onset fever
    • Headache
    • Photophobia
    • Neck stiffness
    • Nausea/vomiting
    • Irritability
    • Change in conscious level/ confusion
  • The main differences between viral and bacterial causes:
    • Viral disease tends to develop slowly (over days) and may present initially with prodromal symptoms e.g. lethargy/malaise, low-grade fever, myalgia, that can resolve prior to meningeal symptoms (usually by about 36-48 hours)
    • Bacterial disease can deteriorate rapidly (within hours) and usually presents with a more severe fever (>39).  Bacterial (particularly meningococcal) disease can also present with a non-blanching, purpuric or petechial rash
  • Seizures can also be a feature, particularly in children, and can be mistaken for febrile seizures.  Focal neurological signs are less common.
  • In severe, fulminant disease, patients may present in septic shock/cardiorespiratory arrest
  • In neonates, a bulging fontanelle is a late sign.

Investigations

NICE recommend

  • FBC (raised WCC); CRP (raised) and coagulation screen (particularly in rash to investigate platelet count)
  • Blood culture
  • Whole-blood PCR for N meningitidis (if positive, treat as confirmed meningococcal meningitis)
  • Lumbar puncture (unless contraindicated)
    • Contraindications include: signs/evidence of raised intracranial pressure (e.g. reduced or fluctuating level of consciousness, relative bradycardia and hypertension, focal neurological signs, abnormal posture or posturing, unequal, dilated or poorly responsive pupils, papilloedema, abnormal 'doll's eye' movements, pressure headache, vomitting; signs on scans); shock; extensive spreading rash; coagulation abnormalities; respiratory failure
    • Send for culture/sensitivity, WCC (>5 cells/μl; >20 in neonates), RBC, protein and glucose
      • NB DO NOT WITHHOLD ANTIBIOTIC TREATMENT FOR LUMBAR PUNCTURE

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  • Lumbar puncture should only be repeated in neonates who deteriorate/have persistent/re-emergent fever and/or new clinical findings.  Do not perform repeat LP in those receiving Abx tx who are recovering.

Empirical and definitive Treatment

  • In the pre-hospital setting, if bacterial meningitis is suspected, administer IM/IV injection of benzylpenicillin (1.2g adults; 600mg children <10; 300mg children <1)

NB If a patient presents with signs of shock, treat as ABCDE.

  • For children under 3 months
    • IV Cefotaxime and amoxicillin (based on weight) for at least 14 days
      • (chloramphenical if penicillin allergic)
      • Alter once confirmed pathogen-
        • group B strep or gram-negative bacilli- cefotaxime for 14 days or 21 days, respectively
        • L monocytogenes- amoxicillin/ampicillin for 21 days
        • Meningococcal- ceftriaxone for 7 days
  • For older children
    • IV Ceftriaxone for at least 10 days
      • meningococcal – 7 days
      • pneumococcal – 14 days
      • H influenzae – 10 days
    • + IV Dexamethasone with or just before the first dose
  • For adults
    • 2g IV Ceftriaxone bd + 0/15mg/kg IV Dexamethasone with the first dose for at least 10 days
      • Add amoxicillin (2mg IV qds) if >55 years old
  • If there is any suspicion of a viral encephalitis (NB NOT MENINGITIS), IV Aciclovir should be used.  VIRAL MENINGITIS will usually resolve spontaneously, but will often receive treatment for bacterial disease given the significant risks.
  • NB Bacterial meningitis is notifiable, and contact tracing is required
    • Prophylaxis with ciprofloxacin and vaccination booster is recommended for close contacts (prolonged or transient) (not for staff colleagues, school pupils, friends etc

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