Meningitis Flashcards
Define meningitis.
Life-threatening inflammation of the meninges caused by various bacteria/viruses
What are the risk factors for meningitis?
- <5 or >65years
- Crowding
- Exposure to pathogens
- Non-immunised infants - Haemophilus influenzae type b, pneumococcal, or meningococcal meningitis
- Immunodeficiency
- Asplenia/hyposplenic state e.g. SCD
- Cranial anatomical defects/VP shunts
- Cochlear implants
- Contiguous infection - inusitis, pneumonia, mastoiditis, and otitis media.
What pathogens is each of these associated with?
Neonates
- Group B streptococcus – GBS is found in the vaginal canal. When giving birth, especially in long vaginal delivery you are likely to pass it on. Usually it is tested for and prophylactic antibiotics give.
- E coli –
- Listeria monocytogenes – less likely
Children and teenagers
- Neisseria meningitidis
- Haemophilus influenzae (vaccination at about 3 months old)
Adults and elderly
- Streptococcus pneumoniae
- Listeria monocytogenes
What bacteria most commonly cause meningitis?
- Neisseria meningitidis (meningococcal meningitis)
- Streptococcus pneumoniae (pneumococcal meningitis)
- Haemophilus influenzae type b (Hib meningitis)
Others: Listeria, GBS, E coli
Which viruses can commonly cause meningitis?
- Enteroviruses are most common cause
- Measles
- West Nile virus
- Herpes viruses (HSV2)
- Varicella zoster
- Mumps
What are the most common causes of aseptic meningitis?
80-90% are viral
- Enteroviruses - e.g. Coxsackie group B or Echoviruses
- Herpes simplex (1&2)
What are the rash presentations in N. meningitidis?
Non-blanching rash (80%) - usually confirms that the cause is Neisseria meningitidis
Maculopapular (13%)
No rash (7%)
*% relate to presentation in children.
What are the early features of meningitis?
- Headache
- Fever
- Leg pains
- Cold hands and feet
- Abnormal skin colour
What are the later features of meningitis?
- Meningism ***
- Low GCS, coma
- Seizures (~20%) +/- focal CNS signs (~20%) ± opisthotonus
- Petehial rash (non-blanching, 1 or 2 spots or none)
- Shock: prolonged capillary refill time, DIC, reduced BP
What investigations would you do for meningitis?
- LP - CSF cell count and differential, protein, glucose, MC&S, antigen detection
- Blood culture (x2)
- Blood/CSF PCR - good if antibiotics already given
- MRI>CT head scan - MRI better for CNS infections; brain infarction, cerebral oedema, and hydrocephalus are common findings especially in pneumococcal meningitis.
- Throat swab - one for bacteria and another for viruses
Other:
- CRP, FBC, coagulation screen
- VBG - lactate >4mmol/L indicates shock
- U&Es - may show acidosis
- Other investigations, LFT, glucose. CXR. Consider HIV, TB tests.
What is the opening pressure in bacterial meningitis? How much CSF is needed?
_>_20cmCSF or higher
At least 15ml needed for investigation
When should you delay LP in meningitis?
Shock
Sepsis or rapidly progressing rash
Severe respiratory or cardiac compromise
Confirmed/known bleeding or high risk of bleeding
Raised intracranial pressure, indicated by:
- Focal neurological signs
- Papilloedema
- Continuous or uncontrolled seizures
- Glasgow Coma Scale score ≤12.
NB: still give antibiotics
What are the differences between CSF is bacterial, viral and TB/fungal infection?
Normally CSF is CLEAR, low WCC, normal proteins, glucose, negative gram stain
Bacteria CSF is RURBID, high WCC (neutrophils AKA polymorphs), high protein (because neutrophils enter first which count as proteins), low glucose, positive gram stain
Viral CSF is CLEAR/cloudy, high WCC (lymphocytes), high protein (not as high), glucose normal (viruses don’t consume glucose), no gram stain
TB/fungi – CLEAR/cloudy, high WCC (lymphocytes), high protein, slightly low glucose (because some used for respiration).
What is Kernig’s sign?
Kernig’s sign: with the patient supine and the thigh flexed to a 90° right angle, attempts to straighten or extend the leg are met with resistance.
Positive in meningitis
What is Brudzinski’s sign?
Brudzinski’s signs: flexion of the neck causes involuntary flexion of the knees and hips, or passive flexion of the leg on one side causes contralateral flexion of the opposite leg.
Positive in meningitis