Meningitis

Meningitis is inflammation of the meninges. The meninges are the lining of the brain and spinal cord. This inflammation is usually due to a bacterial or a viral infection.

Neisseria meningitidis is a gram negative diploccous bacteria. They are circular bacteria (“-cocci”) that occur in pairs (“diplo-”). It is commonly known as meningococcus.

Meningococcal septicaemia is when the meningococcus bacterial infection is in the bloodstream. Meningococcal refers to the bacteria and septicaemia refers to infection in the blood stream. Meningococcal septicaemia is the cause of the classic “non-blanching rash” that everybody worries about as it indicates the infection has caused disseminated intravascular coagulopathy (DIC) and subcutaneous haemorrhages.

Meningococcal meningitis is when the bacteria is infecting the meninges and the cerebrospinal fluid around the brain and spinal cord.

 

Bacterial Meningitis

Bacterial meningitis is inflammation of the meninges caused by a bacterial infection. The most common causes of bacterial meningitis in children and adults is Neisseria meningitidis (meningococcus) and Streptococcus pneumoniae (pneumococcus).

In neonates the most common cause is Group B Streptococcus (GBS). GBS is usually contracted during birth from the GBS bacteria that can often live harmlessly in the mothers vagina.

 

Presentation

Typical symptoms of meningitis are fever, neck stiffness, vomiting, headache, photophobia, altered consciousness and seizures. Where there is meningococcal septicaemia children can present with a non-blanching rash. Other causes of bacterial meningitis do not usually cause the non-blanching rash.

Neonates and babies can present with very non-specific signs and symptoms such as hypotonia, poor feeding, lethargy, hypothermia and a bulging fontanelle. For this reason NICE recommend lumbar puncture as part of the investigations for all children:

  • Under 1 months presenting with fever
  • 1 – 3 months with fever and are unwell
  • Under 1 years with unexplained fever and other features of serious illness

There are two special tests you can perform to look for meningeal irritation:

  • Kernigs Test
  • Brudzinski’s Test

Kernig’s test involves lying the patient on their back, flexing one hip and knee to 90 degrees and then slowly straightening the knee whilst keeping the hip flexed at 90 degrees. This creates a slight stretch in the meninges and where there is meningitis will produce spinal pain or resistance to this movement.

Brudzinski’s test involves lying the patient flat on their back and gently using your hands to lift their head and neck off the bed and flex their chin to their chest. A positive test is when this causes the patient to involuntarily flex their hips and knees.

 

Management of Bacteria Meningitis

Meningococcal septicaemia and bacterial meningitis are medical emergencies and should be treated immediately.

Community

Children seen in the primary care setting with suspected meningitis AND a non blanching rash should receive an urgent stat injection (IM or IV) of benzylpenicillin prior to transfer to hospital as time is so important:

  • < 1 year – 300mg
  • 1-9 years – 600mg
  • > 10 years and adults – 1200mg

This shouldn’t delay transfer. Where there is a true penicillin allergy transfer should be the priority rather than other antibiotics.

Hospital

Ideally a blood culture and a lumbar puncture for cerebrospinal fluid (CSF) should be performed prior to starting antibiotics however if the patient is acutely unwell antibiotics should not be delayed.

Send blood tests for meningococcal PCR if meningococcal disease is suspected. This tests directly for the meningococcal DNA. It can give a result quicker than blood culture depending on local services and will still be positive after the bacteria has been treated with antibiotics.

There should be a low threshold for treating suspected bacterial meningitis, particularly in babies and younger children. Always follow the local guidelines however typical antibiotics are:

  • < 3 months cefotaxime plus amoxicillin (the amoxicillin is to cover listeria contracted during pregnancy from the mother)
  • > 3 monthsceftriaxone

Vancomycin should be added to these if there is a risk of penicillin resistant pneumococcal infection such as from recent foreign travel or prolonged antibiotic exposure.

Steroids are also used in bacterial meningitis to reduce the frequency and severity of hearing loss and neurological damage. Dexamethasone is given 4 times daily for 4 days to children over 3 months if the lumbar puncture is suggestive of bacterial meningitis.

Bacteria meningitis and meningococcal infection are notifiable diseases so public health need to be informed of all cases.

 

Post Exposure Prophylaxis

Exposure to a patient with meningococcal infections such as meningitis or septicaemia are at risk of contracting this illness. This risk of highest for people that have had close prolonged contact within the 7 days prior to the onset of the illness. The risk of developing this disease decreases 7 days after the exposure so if no symptoms have developed at this point they are unlikely to develop the illness.

Post exposure prophylaxis is guided by public health. The usual antibiotic choice for this is a single dose of ciprofloxacin. It should be given as soon as possible and ideally within 24 hours of the initial diagnosis.

 

Viral Meningitis

The most common causes of viral meningitis are herpes simplex virus (HSV), enterovirus and varicella zoster virus (VZV). A sample of the CSF from the lumbar puncture should be sent for viral PCR testing.

Viral meningitis tends to be milder than bacterial and often only requires supportive treatment. Aciclovir can be used to treat suspected or confirmed HSV meningitis

 

Lumbar Puncture

A lumbar puncture involves inserting a needle into the lower back to collect a sample of cerebrospinal fluid (CSF). The spinal cord ends at the L1-L2 vertebral level so the needle is usually inserted into the L3-L4 intervertebral space. Samples are sent for bacterial culture, viral PCR, cell count, protein and glucose. A blood glucose sample should be sent at the same time so that it can be compared to the CSF sample. The samples need to be sent immediately.

Cerebrospinal Fluid

Normal

Bacterial

Viral

Appearance

Clear

Cloudy

Clear

Protein

0.2 – 0.4 g/L

> 1.5 g/L

Mildly raised or normal

Glucose

0.6 – 0.8

< 0.5

0.6 – 0.8

White Cell Count

< 5

> 1000 and neutrophils

> 1000 and lymphocytes

Culture

Negative

Bacteria

Negative

TOM TIP: Interpreting lumbar puncture results is a common exam question. It is easier to think about what will happen to the CSF with bacteria or viruses living in it rather than trying to rote learn the results. It makes sense that bacteria swimming in the CSF will release proteins and use up the glucose. Viruses don’t use glucose but may release a small amount of protein. The immune system releases neutrophils in response to bacteria and lymphocytes in response to viruses.

 

Complications

  • Hearing loss is a key complication
  • Seizures and epilepsy
  • Cognitive impairment and learning disability
  • Memory loss
  • Focal neurological deficits such as limb weakness or spasticity

 

Last updated March 2019
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