30 - CNS Infections

Question 1

Types of CNS infections

Answer 1

Meningitis (most important) 
Encephalitis (second-most important)
Myelitis (spinal cord)
Neuritis (nerves)
Brain abscesses
Subdural empyema
Epidural abscess

Question 2

Proportion of meningitis cases in less-developed countries

Answer 2

~96%

Question 3

Case fatality of meningitis in less-developed countries

Answer 3

~50%

Question 4

Age group in which meningitis is most common

Answer 4

Under one eyar

Question 5

Age group in which meningitis case fatality ratio is highest

Answer 5

Over 65 years old

Question 6

Aseptic meningitis

Answer 6

Inflammation of the meninges not caused by bacteria (mostly viral).
Can be non-infectious: malignancy, drugs (NSAIDs), inflammatory conditions.

Question 7

Main viral causes of meningitis

Answer 7

Enteroviruses (coxsackie, echo)

Herpes viruses are less common (HSV, CMV, VZV, HHV6, EBV)

Question 8

Are bacteria or viruses more likely to cause meningitis?

Answer 8

Viruses

Question 9

Treatment of viral meningitis

Answer 9

Self-limiting, no long-term consequences. Wait for it to subside.

Question 10

Dangerous meningitises

Answer 10

Those caused by bacteria.

Question 11

Three most common bacterial causes of meningitis

Answer 11

H influenzae, N meningitidis, S pneumoniae (all capsulated, can evade immune system)

Question 12

N meningitidis morphology

Answer 12

G- diplococcus

Question 13

Most common N meningitidis causing meningitis in the world

Answer 13

Type A.

Question 14

Most common N meningitidis causing meningitis in developed countries

Answer 14

B and C

Question 15

Bacteria causing meningitis encountered by neonates (meningitis in first 3 months of life)

Answer 15

E coli
Group B streptococcus
Listeria monocytogenes

Question 16

Broad stages of bacterial invasion of meninges and resulting meningitis
1 - 10

Answer 16

1. Colonisation of nasopharngeal mucosa
2. Invasion of bloodstream
3. Survival and multiplication
   4 Crossing of BBB
4. Invasion of meninges
5. Increased permeability of BBB
   7/8. Pleocytosis and increased ICP
6. Release of proinflammatory compounds
7. Neuronal injury

Question 17

Pleocytosis

Answer 17

Abnormal numbers of lymphocytes in CSF

Question 18

Symptoms of meningitis in children
1
2
3
4
5
6
7

Answer 18

Headache
Nausea
Stiff neck
Photophobia 
Fever
Seizures
Altered mental state

Question 19

Meningitis that can also present with rash

Answer 19

Meningococcaemia.

Gives a purpuric (non-blanching) rash

Question 20

Diagnosis of bacterial meningitis

Answer 20

Look for bacteria in CSF

Question 21

Normal CSF pressure

Answer 21

Under 150mm H2O

Question 22

White cell count of normal CF

Answer 22

5x10^6/L

Question 23

Protein in normal CSF

Answer 23

Under 0.4g/L

Question 24

Glucose in normal CSF

Answer 24

Over 60% of that in blood

Question 25

Good animal model for meningitis

Answer 25

Ferrets

Question 26

Appearance of CSF in viral meningitis

Answer 26

``` Normal pressure and appearance. Increased white cel count Negative Gram stain Slightly increased protein Normal glucose ```

Question 27

Appearance of CSF in bacterial meningitis

Answer 27

``` Raised ICP Cloudy appearance Very elevated white cell count Positive Gram stain Raised protein Decreased glucose ```

Question 28

Appearance of CSF in TB meningitis

Answer 28

``` Raised ICP Cloudy CSF Elevated white cell count ZN positive stain Very increased protein Very decreased glucose ```

Question 29

White cell count at which CSF becomes cloudy

Answer 29

Extremely elevated

Question 30

Why can't CSF samples be delayed?

Answer 30

Neutrophils and other white cells die off | Glucose decreases significantly with time

Question 31

Gram stain in those with bacterial meningitis

Answer 31

Normal 40% of the time (bacteria just aren't detected)

Question 32

Can CSF values alone be used to diagnose bacterial meningitis?

Answer 32

No

Question 33

Effect of antibiotic treatment on CSF

Answer 33

Normalise values except for white cell count, which remains elevated

Question 34

Four things to consider when treating meningitis patients (in order of when to perform)

Answer 34

Resuscitation / Life support Fluids (SIADH->moderate restriction) Antibiotics Steroids

Question 35

Most common deficit on surviving bacterial meningitis

Answer 35

Hearing loss

Question 36

What is not affected in meningitis?

Answer 36

Brain is not inflamed

Question 37

Symptom of encephalitis that is almost always present

Answer 37

Altered mental state

Question 38

Most common, and important cause, of encephalitis

Answer 38

HSV

Question 39

How is HSV encephalitis treated?

Answer 39

Acyclovir

Question 40

Meningoccus that is vaccinated against

Answer 40

Group C. | New vaccine for B (not given routinely in Australia)