CNS Infections Flashcards
What is CNS infection?
Infection of the meninges (coverings of brain and spinal cords)
Pathogenesis of CNS infections?
- Microorganisms reach the meninges either by direct extension from the ears, nasopharynx, cranial injury, congenital meningeal defect or by blood stream spread
- Strep pneumonia and Neisseria are by far the most common cause of meningitis
What is neisseria meningitidis?
Gram negative cocci in pairs
Where does Neisseria meningitidis gain access to meninges?
Through blood stream
What is streptococcus pneumoniae?
Alpha haemolytic gram positive cocci in chains
Most common type of meningitis
What is listeria monocytogenes?
Gram +ve bacilli
Only really causes illness is neonates, elderly and immunosuppressed
What causes chronic meningitis?
Tuberculosis meningitis
-Presents generally as non-specific ill-health
Treatment of tuberculosis Meningitis?
Treated similarly to pulmonary TB with:
- Rifampicin
- Isoniazid
- Ethambutol
- Pyrazinamide
Presentation of bacterial meningitis?
- Headache
- Neck stiffness
- Fever
- Photophobia
- Vomiting
- Intense malaise
- Petechial rash in meningococcal infection
Viral meningitis?
Almost always benign self-limiting condition lasting 4-10 days
-Headache for some months
Investigations for suspected meningitis?
CRP & WBC
PCR tests from blood samples
Throat swab for culture
CSF sample from lumbar puncture can be done unless contraindicated
Typical CSF findings for viral meningitis?
Cells: 10^1-10^3 lymphocytes
Gram stain: -ve
Protein: Normal or slightly high
Glucose: Usually normal
Typical CSF findings for bacterial meningitis?
Cells: 10^1- 10^4 neutrophils
Gram stain: Positive
Protein: High
Glucose: Less than 70% of blood glucose (because bacteria using glucose up)
Typical CSF findings in tuberculosis?
Cells: 10^1-10^3
Gram stain: +ve or _ve
Protein: High or v high
Glucose: Less than 60% of blood glucose
Treatment of bacterial meningitis?
Ceftriaxone IV 2g bd + dexamethasone just before or started with ABs
