Meningitis

Original article by Tom Leach | Last updated on 27/5/2014
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Definitions

  • Meningitis – although this technically only means inflammation of the meninges, it is usually taken to mean infection.
  • Meningitis is far more common in infants and children than in adults.
 

Causes

There are a wide range of causes of meningism; typically: viral, bacterial and endogenous (e.g. malignancy, autoimmune disease, subarachnoid haemorrhage). Prions and protozoa can also cause the disease.
  • Viral disease is the most common form, and is typically self limiting
  • Bacterial disease is more rare, and incidence has declined with vaccination, but the disease can be much more severe.
 

Clinical features

There are some features that all varieties have in common, and some only found with varying causes:
  • Headache
  • Irritability
  • Stiff neck – not always present in infants
  • Photophobia
  • HR - tachycardia
  • Kernig’s Sign – flex the hip, with the knee flexed. Now extend the knee. Positive test if there is spasm of the hamstrings.
  • Brudzinski’s sign – passively flex the neck. Positive test if there is flexion of the hip and/or knee.
  • Fever – (infective causes only)
  • Altered level of consciousness
  • Poor feeding / vomiting
  • SEIZURES – generally infective causes only
  • Focal neurological signs are rare
  • Signs of shock – particularly in bacterial disease
  • Cold extremities – a general sign of severe illness in a child
  • Vague symptoms – commonly the symptoms may not be as clear as those listed above. Any unwell child with lethargy, malaise, vomiting, poor feeding, irritability
  • Late signs
    • Bulging fontanelle
    • Neck stiffness
    • Opisthotonos – arched back
    • Rash – generally only seen with bacterial causes. The rash is typically petechial/purpuric, and NON-BLANCHING! Suggests septicaemia (not a sign of meningitis on its own)
    • Fall in BP
  • Purpura in a febrile child is meningitis until proven otherwise!
 

Malignant Causes

 

Viral Meningitis

Much less severe than bacterial, and usually self limiting.
  • 2/3 of cases of meningitis are viral
 

Causes

  • Echovirus
  • Mumpsrare in the UK due to MMR
  • Herpes group: EBVHerpes simplex, Varicella zoster (chicken pox), HSV type 2 – Mollaret’s Meningitis
  • Influenza
 

Treatment

Symptomatic. Ibuprofen and calpol may be given to reduce fever.
 

Bacterial Meningitis

  • 80% of cases are in the under 16’s
  • 5-10% mortality
  • 10% of surviving patients will have long term neurological impairment
 
Bacterial meningitis often presents when a known infection is already present, and is particularly common with septicaemia.  However, it can present with no apparent known infection. It has reduced in incidence.
  • Mortality is double if the presentation is with symptoms of septicaemia, rather than symptoms solely of meningitis.
 

Prevention

Meningococcal Vaccine – this is a vaccine that prevents against meningitis caused by the A,C X, Y & Z variaints of the Nisseria Meningitidis bacterium. There is no protection against the B strain of this bacterium. It has greatly reduced the incidence of bacterial meningitis, but the B strain of NM, and other bacterial causes are still present.
 

Causes

These vary with age:
Neonate – 3 months:
  • E. Coli and other coliforms
  • Group B Strep
  • Listeria Monocytogenes

3 months – 6 years

  • Nisseria Meningitidis aka meninigococcus
  • Streptococcus Pneumoniae
  • Haemaphilus Influenzae

6 Years+

  • Nisseria Meningitidis
  • Streptococcus Pneumoniae
 
...and also with location. Most common infectious agents by location:

Western Europe:

  • Streptococcus Pneumoniae
  • Nisseria Meningitidis

USA

  • Haemaphilus Influenzae

India

  • Haemophilus Influenza B
  • Streptococcus Pneumoniae
 
Listeria is more common in immunocompromised patients and those over 50
 
Meningococcus – is particularly severe, and has a worse prognosis than other types of meningitis. It can kill a previous well child within hours. However, it also has the lowest risk of long-term complications in patients who fully recover.
  • Also this is the variety of infection that is particularly associated with the non-blanching purpuric rash.
Meningococcal disease may not:
  • Cause fever
  • Raise WCC. WCC may infact be low!
  • Look for cold peripheries – peripheral shutdown of circulation.
 
Haemophilus – the use of the HiB vaccine has greatly reduced the number of infections. It used to be the second most UK cause, and most common US cause of meningitis, but is now rare.
 
Pneumococcus – used to be rare, but with the massive reduction in HIB and MenC cases, this is now relatively common. Associated with high mortality (10%) and morbidity (30% have long term consequences), however, there is now a conjugate pneumococcal vaccine given to all children, that should reduce rates of infection in the future.
 
Tuberculosisvery rare in the UK!
  • 2-3 week insidious onset
  • Meningism may/may not be present
  • History of TB contact (usually within the family)
  • Most will have:
    • Positive Mantoux
    • Abnormal CXR
  • Acid-fast bacilli may be present in early morning urine and the CSF
  • Cultures can be very slow – so treatment should be started when there is clinical suspicion.
    • High mortality and morbidity in those where treatment is not started until there are focal signs
    • 4 anti-TB drugs for 2 months, with reduced dosing over the following 10 months.
    • Dexamethosone should be given in the first month to reduce the risk of complications.
 
Generally, the bacteria involved in meningitis are common causes of upper respiratory tract infections. They can also e contracted through close contact, and thus outbreaks of meningitis can often occur , particularly in cramped living conditions, and in hot, dry climates.
 

Pathophysiology

  • Usually after or concurrent with septicaemia
  • Most of the damage comes from host response, and not infective organism
  • Activated leukocytes release inflammatory mediators, which result in cerebral oedema. This causes increased ICP and decreases blood flow to the brain.
 

Investigations

Lumbar punctureCSF analysis is diagnostic in most cases. However! – if antibiotics have been given before lumbar puncture takes places, they can give false negative readings – so be wary of giving the all clear. Rapid antigen scan and PCR can aid diagnosis in these situations. The CSF picture will be that of high white cell count, but negative culture in these cases of partially treated meningitis. Ensure patient is stable and you have excluded raised ICP before lumbar puncture! Contraindications for lumbar puncture include:
  • Focal neurological signs
  • Cardiorespiratory distress
  • Signs of RICP – e.g. coma, high BP, low HR, papilloedema, bulging fontanelle.
  • Coagulopathy
  • Thrombocytopaenia
  • Local infection at site of LP
  • Don’t delay starting antibiotics to wait for lumbar puncture!
 

CSF Test Results

Disease
Cell types
White cells
Appearance
Glucose
Protein
Gram
Normal
Lymphocytes
0.4
Colourless
>60% of blood glucose
<0.45 g/dl
-ve
Viral
Lymphocytes
10 – 2000
Colourless
Normal
Normal / ↓
-ve
Bacterial
Polymorphs
1000 – 5000
Turbid
Low*
Normal / ↑
+ ve
Polymorphs / lymphocytes mixed
50 – 5000
Colourless / turbid / viscous
Low*
-ve
Fungal
Lymphocytes
50 – 500
Colourless
Low
+/-
Malignant
Lymphocytes
0 – 100
Colourless
Low
Normal / ↑
-ve
*It is not that the bacteria are using up the glucose, it is that the infection alters glucose metabolism in the CSF – BUT – its handy to remember it as if: The bacteria eat up the glucose, but the viruses don’t!
 

Other Investigations

  • FBC – for WCC / trombocytopaenia
  • Blood glucose / blood gas – checking for acidosis
  • CRP (↑)
  • Blood culture
  • Throat swab culture
  • Rapid antigen test – can use blood, CSF or urine
  • Urine dipstick
  • If TB Suspected:
    • X-ray
    • Mantoux
    • Early morning urine
    • Gastric washings
  • MRI / CT may be performed in rare circumstances.
 

Management

If there is any suspicion of bacterial meningitis, then DO NOT DELAY TREATMENT FOR FURTHUR ASSESMENT! – initiate the treatment immediately! If you have an especially low index of suspicion in a child with non-specific symtoms you may consider re-assessment in 4-6 hours.
Presentation in the community - Initiate antibiotic treatment as soon as meningococcal infection is suspected (within 30 minutes of arrival!).
  • A Third generation cephalosporin (e.g. Cefotaxime, cephalexin) is a good broad spectrum choice (given IV – usually given in hospital), and Benzylpenicillin may be considered as an alternative give IM!
  • Resistance is increasing, but still rare in the UK. If you are worried, whilst waiting for cultures, you could add rifampicin or vancomycin.
  • Most third generation cephalosporins have to be given IV.
  • Listeria infections are best treated with a combination of ceftriaxone and ampicillin).

At hospital

  • An MDT approach, with intensive care bed strategy should be used.
  • Treat shock (if present). Use IV fluids – isotonic crystalloid or colloid. Up to 60ml/Kg can be given, in the form of 3 boluses of 20ml/Kg.
  • Frozen plasma / platelet infusions
  • Consider adding dexamethasone – this steroid is typically added to the treatment regimen in those older than neonatal age. This reduces the risk of long-term complications- particularly deafness.
  • Consider ventilation
  • Continue antibiotics
  • Patients are often most sick 8-12 hours after treatment – due to release of bacterial toxins when the bacteria are killed by the antibiotics.
 

Complications

Cerebral
  • Hearing lossthe result of inflammatory damage to the cochlear hair cells. All children should have an audiological assessment after meningitis infection. Hearing deficiencies can be treated with a cochlear implant or hearing aid. The earlier the implant can be placed, the greater the chance of success – as the cochlear can calcify if no treatment is given, and then treatment is ineffective.
  • Vasculitis – can cause cranial nerve lesions
  • Cerebral Infarct – can cause focal seizures, and may cause long-term epilepsy
  • Subdural effusion – associated with particular infective agents (haemaphilus influenzae, pneumococcus strains). Diagnosis is confirmed by CT. Most cases resolve spontaneously.
  • Hydrocephalus – can occur if there is reduced reabsoprtion of CSF. The patient may require a ventricular shunt.
  • Cerebral abscess – child may have signs of a space occupying lesion. Diagnosis confirmed by CT, and drainage will be required.
 

Prophylaxis

  • Rifampicin is given to all household contacts of a patient with meningococcal meningitis, and to those with a young child with haemophilus influenzae infection.
  • If the patient has Meningitis C, then the Men C vaccine should be given to all household contacts