30 - CNS Infections Flashcards
Types of CNS infections
Meningitis (most important) Encephalitis (second-most important) Myelitis (spinal cord) Neuritis (nerves) Brain abscesses Subdural empyema Epidural abscess
Proportion of meningitis cases in less-developed countries
~96%
Case fatality of meningitis in less-developed countries
~50%
Age group in which meningitis is most common
Under one eyar
Age group in which meningitis case fatality ratio is highest
Over 65 years old
Aseptic meningitis
Inflammation of the meninges not caused by bacteria (mostly viral).
Can be non-infectious: malignancy, drugs (NSAIDs), inflammatory conditions.
Main viral causes of meningitis
Enteroviruses (coxsackie, echo)
Herpes viruses are less common (HSV, CMV, VZV, HHV6, EBV)
Are bacteria or viruses more likely to cause meningitis?
Viruses
Treatment of viral meningitis
Self-limiting, no long-term consequences. Wait for it to subside.
Dangerous meningitises
Those caused by bacteria.
Three most common bacterial causes of meningitis
H influenzae, N meningitidis, S pneumoniae (all capsulated, can evade immune system)
N meningitidis morphology
G- diplococcus
Most common N meningitidis causing meningitis in the world
Type A.
Most common N meningitidis causing meningitis in developed countries
B and C
Bacteria causing meningitis encountered by neonates (meningitis in first 3 months of life)
E coli
Group B streptococcus
Listeria monocytogenes
Broad stages of bacterial invasion of meninges and resulting meningitis
1 - 10
- Colonisation of nasopharngeal mucosa
- Invasion of bloodstream
- Survival and multiplication
4 Crossing of BBB - Invasion of meninges
- Increased permeability of BBB
7/8. Pleocytosis and increased ICP - Release of proinflammatory compounds
- Neuronal injury