CNS Infection: Meningitis Flashcards
Epidemiology
Immunocompromised =
- Extremes of age (children and elderly)
- Infection (HIV)
- Medication (chemotherapy)
Non-immunised = H.influenza , pneumococcal and meningococcal meningitis
Crowded environment = student living in halls of residence are a commonly affected demographic
Risk factors
Winter
Organ dysfunction
- Absent or non-functioning spleen
Smoking
Most common bacterial causes of meningitis
Neisseria meningitis (meningococcus) = capsular group B accounts for majority of cases
Streptococcus pneumoniae (pneumococcus) = most common cause of bacterial meningitis in adults
Most common viral causes of meningitis
Enteroviruses
e.g. coxsackievirus
Causes of meningitis in neonates (0-3 months)
Group B Alpha haemolytic strep (s.agalactiae) = COLONISES MATERNAL VAG
Listeria monocytogenes
E.coli
S.pneumoniae
Causes of meningitis in infants (3m-6y)
S. pneumo
N. meningitidis
H. influenzae (less common due to vaccination)
Causes of meningitis in adults (6-60 years)
S. pneumo
N. meningitidis
Causes of meningitis in elderly (60 + years)
S. pneumo
N. meningitidis
Listeria monocytogenes
Which bacteria is most likely to affect pregnant women
Listeria Monocytogenes
N. meningitidis
Gram negative diplococcus
Vaccines available - men B + C, men ACWY
10% mortality
NON-BLANCHING PURPURIC RASH (meningococcal septicaemia -> DIC -> v.easy bleeds)
S. pneumoniae
gram positive streptococci
PCV vaccine
25% mortality
Group B strep
Gram positive streptococci
MC of neonatal meningitis as COLONISES MATERNAL VAGINA
Listeria monocytogenes
Gram positive bacillus
Affects extremes of age and maternal pregnant women (found in cheese)
Pathophysiology
Meningitis describes inflammation of the leptomeninges (the arachnoid and pia mater) and usually occurs due to a bacterial, viral, or fungal infection. It can also be caused by trauma, cancer, or drugs.
Meningococcal septicaemia = when the meningococcal bacterial infection is in the bloodstream = cause of the classic ‘non-blanching rash’ = sign of DIC + Subcutaneous haemorrhages
Signs
Kernig’s sign: Severe stiffness of the hamstrings causes an inability to straighten the leg when the hip is flexed to 90 degrees
Brudzinski sign: severe neck stiffness causes the hip and knees to flex when the neck is flexed
Petechial or purpuric non-blanching rash: associated with meningococcal disease (N. meningitidis)
Pyrexia
Reduced GCS
Symptoms
Meningism
- headache
- photophobia
- neck stiffness
Fever
Nausea and Vomiting
Seizures
Altered consciousness
Lethargy
Neonates presentation (HHELP)
Hypotonia
Hypothermia
bulging fontanElle
Lethargy
Poor feeding
Papilloedema
1) venous enlargement
2) optic disc blurring
3) haemorrhages near optic disc
4) loss of venous pulsation
- Bilateral if there is increased intracranial pressure
Diagnosis
Lumbar puncture + CSF analysis
- sample taken from L3/4 and analysed
Bloods
- FBC = leucocytosis
- CRP
- blood glucose = required in all patients and for comparison with CSF glucose
Bacterial CSF analysis
Opening pressure = high
Appearance = cloudy yellow
WCC = increased neutrophilia
Protein = High >1g/L
Glucose (vs serum level) = Low < 50% serum level
Viral CSF analysis
Opening pressure = normal
Appearance = clear, normal
WCC = increased lyphocytes
Protein = <1g/L
Glucose (vs serum level) = normal < 60% serum level
Fungal CSF analysis
Opening pressure = high
Appearance = cloudy + fibrinous
WCC = increased lymphocytosis
Protein = High >1g/L
Glucose (vs serum level) = Low < 50% serum level
Management
Dexamethasone: ideally should be administered before or with the first dose of antibiotics once in hospital
Ceftriaxone/ Cefotaxime (3rd gen cephalosporins)
- amoxicillin - covers listeria
Bacteria specific treatment
Empirical antibiotics: aged < 3 months = IV cefotaxime and amoxicillin
Empirical antibiotics: aged 3 months - 50 years = IV cefotaxime
Empirical antibiotics: aged > 50 years = IV cefotaxime and amoxicillin
Meningococcal meningitis = IV benzylpenicillin (or cefotaxime)
Pneumococcal meningitis = IV cefotaxime
Haemophilus influenzae meningitis = IV cefotaxime
Listeria monocytogenes meningitis = IV amoxicillin and gentamicin
