CNS Infection Flashcards
What are the cardinal features of meningism?
- headache
- neck stiffness
- photophobia
What is meningococcaemia?
presence of neisseria meningitidis in the blood
What is meningitis?
Inflammation of the meninges (arachnoid and pia mater)
What are the most common bacterial causes of meningitis in neonates (<1 month)?
- Beta-haemolytic streptococci
- Gram negative bacilli (e.g. E. coli, proteus)
- Listeria (less common)
What are the most common bacterial causes of meningitis in children <5yrs
- Neisseria meningitidis
- Streptococcus pneumoniae
- Haemophilus influenzae
What are the most common bacterial causes of meningitis in 5-60 year-olds?
- Neisseria meningitidis
- Streptococcus pneumoniae
What are the most common bacterial causes of meningitis in elderly (>60yrs)?
- Streptococcus pneumoniae
- Gram negative bacilli
- Listeria (less common)
What is a common bacterial cause of meningitis in immunocompromised, diabetic or pregnant people?
Listeria
What are the most common viral causes of meningitis?
Enteroviruses (e.g. coxackie)
HSV-1
VZV
Mumps
What are the 4 possible origins of infection in meningitis?
1) direct inoculation through skull trauma
2) direct spread from adjacent structures (sinuses, middle ear)
3) haematological (bacteraemia)
4) malignant (e.g. septic emboli from infective endocarditis vegetation)
Describe the two special tests during examination that indicate meningism
Kernig’s sign:
- pain in neck when extending the knee with hip flexed
Brudzinski’s sign:
- involuntary flexion of knees/hips on flexion of neck
Describe the classical clinical features of bacterial meningitis
- acute, severe, generalised headache
- fever
- neck stiffness
- altered mental state (e.g. drowziness, irritability)
- vomiting
- photophobia
In what scenario do you find a non-blanching petechial rash?
Meningococcal meningitis (late sign)
What are the most common clinical features of viral meningitis?
- acute headache
- irritability
- meningism
- with/without fever
At what level do you carry out a lumbar puncture?
Between L3-L4 spinous processes
When is LP contra-indicated and why?
Raised ICP
Risk of uncal herniation
What are the 2 most important investigations to carry out early in suspected meningitis?
1) Lumbar puncture
2) Blood cultures
Describe the expected LP results in bacterial meningitis, including:
- appearance
- cells count and type
- protein
- glucose
- turbid
- very high cell count, mainly polymorphonuclear neutrophils
- v high protein
- v low glucose
Describe the expected LP results in viral meningitis, including:
- appearance
- cells count and type
- protein
- glucose
- clear
- increased cell count (not as high as bacterial), mainly monocytes
- normal or slightly raised protein
- normal or slightly decreased glucose
Describe the expected LP results in encephalitis, including:
- appearance
- cells count and type
- protein
- glucose
- clear
- slightly increased cell count (not as high as bacterial/viral meningitis), mainly monocytes
- normal or slightly raised protein
- normal glucose
Apart from biochemical analysis of CSF, what other tests should be done with CSF?
Gram stain and culture
PCR
A patient has bacterial meningitis. CSF culture shows gram negative diplococci - what is the most likely diagnosis?
N. meningitidis
A patient has bacterial meningitis. CSF culture shows gram positive diplococci - what is the most likely causative organism?
S. pneumoniae
A patient has bacterial meningitis. CSF culture shows chains of gram positive cocci - what is the most likely causative organism?
Beta-haemolytic strep
