Meningitis

• Meningitis is caused by inflammation of the meninges- the outer membranes that cover the brain and spinal cord.
• Viral meningitis is more common than bacterial meningitis, but all cases should be treated as bacterial until proven otherwise, as bacterial meningitis has a high mortality
• Meningitis can be caused by bacteria, viruses, fungi, or be non-infective (secondary to some cancers including leukaemia and lymphoma, autoimmune diseases or drugs).
• Young age is the most significant risk factor. Other risk factors include winter season, asplenia, immunocompromise, organ dysfunction, smoking and overcrowding
• Bacterial meningitis:

  • Most common in infants, with a second incidence peak in teenagers and young adults
  • Transmitted via droplet spread and usually requires frequent or prolonged close contact
• Most common bacterial organisms in neonates:

  • Most common = Streptococcus agalactiae (group B strep)
  • Escherichia coli
  • Streptococcus pneumoniae
  • Listeria monocytogenes
• Most common bacterial organisms in babies over 3 months, children and adults:

  • Neisseria meningitidis (in 11-17 year olds)
  • Streptococcus pneumoniae (most common in all other ages)
  • Haemophilus influenzae type b
• Meningococcal disease:

  • Bacterial meningitis causes by Neisseria meningitides
  • Meningococcal sepsis (causes classical rash)
  • Or a combination of both
• Pneumococcal disease refers to disease caused by invasive Streptococcus pneumoniae:

  • Pneumonia
  • Meningitis
  • Sepsis
• Vaccines are available for meningococcal subgroups A, B, C, W and Y, Hib and 13 serotypes of pneumococcus
• Aseptic meningitis:

  • CSF has white blood cells on microscopy but the gram stain is negative and no bacteria are cultures on standard media
  • Viral meningitis - accounts for over half of all cases
  • Fungal meningitis
  • Atypical bacterial meningitis - TB, syphilis and Lyme disease
• Most common viral meningitis pathogens:

  • Enteroviruses - echovirus and coxsackievirus
  • Others - mumps, HSV, herpes zoster, HIV, measles and influenza
• Classically described as the triad of fever, neck stiffness and altered mental state; in reality, this picture is only seen in 44% of adults with bacterial meningitis and is even less specific in children.
• Early symptoms and signs:

  • often vague and non-specific
  • Fever, headache, nausea/vomiting, lethargy
• Later, more specific signs:

  • Neck stiffness or back rigidity
  • Kernig's sign
  • Brudzinski's sign
  • Non blanching rash (meningococcal disease)- petechiae or purpura
  • Photophobia
  • leg pain
  • Mottled skin
  • Altered mental state
  • Prolonged CRT
  • Shock
  • Neurological symptoms - seizures, paresis
• Kernig's sign = pain and resistance on passive knee extension with hips fully flexed
• Brudzinski's sign = knees and hips flex on bending the head forward
• Bedside investigations:

  • Vital signs - signs of sepsis
  • Blood sugar - always required if an altered mental state is present
• Lab investigations:

  • U&Es
  • CRP
  • FBC
  • Clotting studies - especially if petechial rash or sepsis
  • Blood cultures
  • Blood gases
  • Meningococcal PCR
• CT head is sometimes performed if there are focal neurological deficits

  Cannot exclude raised intracranial pressure
• Cerebrospinal fluid (CSF) culture is the gold standard investigation for diagnosing bacterial meningitis, and 90% of acute bacterial meningitis cases have CSF WBC >100 cells/ microlitre
• If possible, lumbar puncture should be performed within the hour before antibiotic treatment is commenced. If performing an LP will delay antibiotic treatment longer than this hour, antibiotics should be given and the LP performed later.
• LP contraindications:

  • Raised ICP
  • Shock
  • Extensive spreading purpura
  • Convulsions (until stabilised)
  • Coagulation abnormalities
• CSF is analysed for cell count (to count and identify the WBCs), gram stain (to identify bacteria), glucose, protein, lactate and culture. Other tests include bacterial and viral PCRs.
• It is important to take a blood glucose level alongside (ideally just before) the LP so the ‘paired’ CSF and blood samples can be analysed
• Management:

  1. Supportive treatments- fluids, nutritional support, analgesia, antipyretics, antiemetics
  2. Treatment of the causative organism
  3. Treatment of any complications - metabolic disturbances, raised ICP and seizures
• Meningitis is a notifiable disease and therefore needs to be reported to Public Health England
• • Initially, all cases of suspected meningitis should be treated as bacterial until proven otherwise
  • Further management will then be guided by the LP findings
• Bacterial meningitis in primary care:

  • Urgent transfer to hospital
  • If there is suspected meningococcal sepsis then IM or IV benzylpenicillin can be given
• Bacterial meningitis initial empirical therapy:

  • Children >3 months and adults - IV ceftriaxone
  • Children <3 months - IV cefotaxime + amoxicillin/ampicillin (covers for listeria)
• IV dexamethasone is indicated in certain situations (i.e. children >3 months with bacteria on gram stain, frankly purulent CSF or CSF WBC >1000 cells/ microlitre)
• For confirmed meningococcal disease, prophylactic antibiotics should be given to close contacts within 24 hours (usually ciprofloxacin or rifampicin) 
• Viral meningitis treatment:

  • No specific treatment, supportive management only
  • If there are concerns about encephalitis, IV aciclovir is used (the treatment for herpes simplex encephalitis)
• Pneumococcal meningitis is associated with a poorer outcome than meningitis caused by Neisseria meningitidis or Haemophilus influenzae type b (Hib)
• Acute complications of meningitis:

  • Sepsis
  • Septic shock
  • Disseminated intravascular coagulation
  • Cerebral oedema
  • Coma
  • Raised ICP
  • Subdural effusions
  • SIADH
  • Peripheral gangrene
  • Death
• 30–50% of survivors of acute bacterial meningitis experience permanent neurological sequelae
• Common long term bacterial meningitis complications:

  • Hearing loss
  • Seizures
  • Motor deficit
  • Cognitive impairment
  • Hydrocephalus
  • Visual disturbance
• CSF appearance:

  • Normal = clear/colourless
  • Bacterial meningitis = cloudy/turbid
  • Viral meningitis = usually clear
• CSF WBCs:

  • Normal = 0-5 (primarily lymphocytes)
  • Bacterial meningitis = >100 (Primarily leukocytes/neutrophils)
  • Viral meningitis = >100 (primarily lymphocytes)
• CSF protein:

  • Normal = 0.15-0.45 g/L
  • Bacterial meningitis = >0.5 g/L
  • Viral meningitis = >0.5 g/L