CNS Infections Flashcards
What are the routes of entry for CNS infections?
- Haematonogenous spread (most common)
- direct implantation - trauma/ surgery
- local extension (e.g. cripiform plate)
- PNS to CNS (especially viruses)
How can you clinicaly differentiate between meningitis and encephalitis?
Meningitis classical triad of headaches, photophobia + meningism
Encephalitis can have addititnal symptoms: Disturbance of brain functions
What is the prognosis of an menigits?
10% mortality
5% morbidity
What are the main different classifications of meningitis?
- Acute (bacterial)
- Chronic (TB, other bacterial )
- aseptic (can be acute or chronic)
What are the main causative organisms of meningitis?
How can you differentiate between them?
- Neisseriga meningitidis (gram -ve)
- Strep. pneumoniae (gram +ve)
Other than Neisseria Meningitidis + Strep pneumonia, what other causative orgnaisms would you suspect in an elderly +immunosuppressed) patient in Meningitis?
- Haemophilus influenzae (just elderly)
Others (mainly for specific)
- Listeria monocytogenes (immunosuppressed)
What are the causative organisms of acute meningitis in the neonate?
- Group B Strep
- Listeria monocytogenes
- E. coli
Why is importnat to differentiate between isolated meningitis and septicaemia and meningitis?
Generally with septicaemaia
LP often contraindicated
What is the main causative organism of chronic meningitis?
TB
What are the main causitive orgnaisms of aseptic mentingiits?
Viral
Viral meningitis = Most common infection of the CNS (more common than bacterial meningitis)
Enteroviruses cause 80-90 of aseptic meningitis if organism can be identified ( coxackie A&B, echoviruses)
What are the main causative organisms to cause encephalitis?
Viral
Most common: HSV1
Worldwide: more tropical viruses (Flaviviridae, e.g. west nile virus)
What are some bacterial causes of encephatlitis?
Generally relatively rare compared to viral
- Listeria monocytogenes (worse prognosis than meningitis)
Amoebia (usually deadly)
- Naegleria fowleri (Bath of Baths - warm water9
- Toxoplasmosis - immunocompromised (cats)
What is the main aetiology of brain abscesses?
Generally via direct extension
(otitis media, mastoiditis, paranasal sinuses, etc)
What are the main pathogens causing brain abscesses?
Usually from site of origin (e.g. Streptococci (both aerobic and anaerobic)
Staphylococci etc.
What are the main aetioloies of spinal infections?
Via spread of vertebral infection
Direct spinal trauma
What is the main way of investigating CNS infecttions?
- MRI: Way better for parenchyma in infections
- LP (might make CT necessary)
Other than Brain imaging + LP, what other investigations should be done in inviestigation of meningitis?
- Blood culutre
- Blood pCr if available (currently not)
- Throat swap: haemophilis and meninggococcus9
What are normal white cells counts in CSF?
under 5
>5: abnormal
If neutrophils: bacterial
if lymphocytes: viral
What is the appearance of CSF/ CSF analysis in
* bacterial infection
* viral infection
* tuberculosis infection
What is the stain used in identifying cryptococcus meningitis?
Indian ink stains negative
What is the first-line management of Meningitis?
Ceftriaxone 2g IV BD
If immunocompromised or >50
Amoxicillin (additional)
What is the first line treatment for meningo - encephalitis?
Meningitis (Cetriaxone 2g IV BD + Amox if indicated)
+ Aciclovir IV 10mg/kg iv tds
