CNS Infections

Question 1

What are the routes of entry for CNS infections?

Answer 1

1. Haematonogenous spread (most common)
2. direct implantation - trauma/ surgery
3. local extension (e.g. cripiform plate)
4. PNS to CNS (especially viruses)

Question 2

How can you clinicaly differentiate between meningitis and encephalitis?

Answer 2

Meningitis classical triad of headaches, photophobia + meningism

Encephalitis can have addititnal symptoms: Disturbance of brain functions

Question 3

What is the prognosis of an menigits?

Answer 3

10% mortality
5% morbidity

Question 4

What are the main different classifications of meningitis?

Answer 4

1. Acute (bacterial)
2. Chronic (TB, other bacterial )
3. aseptic (can be acute or chronic)

Question 5

What are the main causative organisms of meningitis?

How can you differentiate between them?

Answer 5

• Neisseriga meningitidis (gram -ve)
• Strep. pneumoniae (gram +ve)

Question 6

Other than Neisseria Meningitidis + Strep pneumonia, what other causative orgnaisms would you suspect in an elderly +immunosuppressed) patient in Meningitis?

Answer 6

3. Haemophilus influenzae (just elderly)

Others (mainly for specific)

• Listeria monocytogenes (immunosuppressed)

Question 7

What are the causative organisms of acute meningitis in the neonate?

Answer 7

• Group B Strep
• Listeria monocytogenes
• E. coli

Question 8

Why is importnat to differentiate between isolated meningitis and septicaemia and meningitis?

Answer 8

Generally with septicaemaia
LP often contraindicated

Question 9

What is the main causative organism of chronic meningitis?

Answer 9

TB

Question 10

What are the main causitive orgnaisms of aseptic mentingiits?

Answer 10

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)

Question 11

What are the main causative organisms to cause encephalitis?

Answer 11

Viral
Most common: HSV1

Worldwide: more tropical viruses (Flaviviridae, e.g. west nile virus)

Question 12

What are some bacterial causes of encephatlitis?

Answer 12

Generally relatively rare compared to viral

1. Listeria monocytogenes (worse prognosis than meningitis)

Amoebia (usually deadly)

• Naegleria fowleri (Bath of Baths - warm water9
• Toxoplasmosis - immunocompromised (cats)

Question 13

What is the main aetiology of brain abscesses?

Answer 13

Generally via direct extension
(otitis media, mastoiditis, paranasal sinuses, etc)

Question 14

What are the main pathogens causing brain abscesses?

Answer 14

Usually from site of origin (e.g. Streptococci (both aerobic and anaerobic)
Staphylococci etc.

Question 15

What are the main aetioloies of spinal infections?

Answer 15

Via spread of vertebral infection

Direct spinal trauma

Question 16

What is the main way of investigating CNS infecttions?

Answer 16

1. MRI: Way better for parenchyma in infections
2. LP (might make CT necessary)

Question 17

Other than Brain imaging + LP, what other investigations should be done in inviestigation of meningitis?

Answer 17

1. Blood culutre
2. Blood pCr if available (currently not)
3. Throat swap: haemophilis and meninggococcus9

Question 18

What are normal white cells counts in CSF?

Answer 18

under 5
>5: abnormal

If neutrophils: bacterial
if lymphocytes: viral

Question 19

What is the appearance of CSF/ CSF analysis in
* bacterial infection
* viral infection
* tuberculosis infection

Answer 19

Question 20

What is the stain used in identifying cryptococcus meningitis?

Answer 20

Indian ink stains negative

Question 21

What is the first-line management of Meningitis?

Answer 21

Ceftriaxone 2g IV BD

If immunocompromised or >50
Amoxicillin (additional)

Question 22

What is the first line treatment for meningo - encephalitis?

Answer 22

Meningitis (Cetriaxone 2g IV BD + Amox if indicated)

+ Aciclovir IV 10mg/kg iv tds