CNS infections - cellular pathogens

Question 1

In which age group do CNS infections most commonly occur?

Answer 1

0-4 years

Paediatric disease

Question 2

In which age group do CNS infection have the highest mortality rate?

Answer 2

>65 years

Question 3

What are the major categories of causes of meningitis?

Answer 3

Viral

Bacterial

Other (eg. TB)

Non infectious

Question 4

What is the most common casue of meningitis?

Answer 4

Viral

Usually enterovirus

Question 5

Even though viral meningitis is more common than bacterial meningitis, why is bacterial meningitis more worrying?

Answer 5

Viral meningitis does not cause sequelae, whereas bacterial meningitis does

Bacterial meningitis is more harmful, viral is self-limiting

Question 6

What is aspetic meningitis?

Answer 6

Any form of meningitis that is not caused by bacteria

Question 7

Which three bacteria are the commonest causes of meningitis?

Answer 7

H.influenza

N.meningitidis

S.pneumoniae

Question 8

Which of the bacterial causes of meningitis is the biggest killer?

Answer 8

In Africa, H.influenza A

Question 9

Why are H.influenza, N. meningitidis and S.pneumoniae the commonest causes of bacterial meningitis?

Answer 9

These bacteria are best at evading the immune system

Encapsulated with polysaccharide capsule > evade phagocytosis and complement activation

Question 10

At less than three months of age, which additional causes of meningitis are infants susceptible to?

Answer 10

Those acquired in the birth canal

Group B strep, Listeria and E.coli

Question 11

Describe the host and bug factors that determine the likelihoods of infection?

Answer 11

Question 12

Describe how pathogens are able to penetrate defences and cause CNS infection?

Answer 12

Question 13

What are the major clinical features of meningitis?

Answer 13

Non-specific: fever, vomiting/nausea, headache, irritable and stop feeding (children)

More specific: stiff neck, altered mental state, bulging fontanelle, photophobia, seizures

Question 14

What are the major signs and symptoms of bacterial meningitis?

Answer 14

Fever

Vomiting

Stiff neck

Photophobia

Difficult to wake

Confused

Non-blanching rash

Seizures

Question 15

What are the signs and symptoms of meningococcal septicaemia?

Answer 15

Non-blanching rash plus:

Fever

Vomiting

Lethargy

Muscle ache/joint apin

Cold extremities

Leg pain

Pale/mottled skin

Breathlessness

Confusion

Difficult to wake

Question 16

Which investigations are usually carried out to diagnose meningitis?

Answer 16

CSF

Skin scraping

?Blood

?Neuroimaging

Question 17

Why don’t blood samples provide a definitive diagnosis for meningitis?

Answer 17

May be changes in blood present that are not specific to meningitis

Question 18

What are the normal values for CSF?

Answer 18

Question 19

Why can CSF values be unreliable whej diagnosing menigitis?

Answer 19

CSF values differ with age, and meningitis is predominately a paediatric disease

Question 20

Describe the CSF values for viral, bacterial and tuberculous meningitis?

Answer 20

Question 21

Describe viral, bacterial and tuberculous meningitis in terms of protein and white cell count in the CSF?

Answer 21

Viral: normal-high protein, normal-high white cells

Bacterial: high protein, very high white cells

Tuberculous: very high protein, high white cells

Question 22

What are the major contraindications for a lumbar puncture?

Answer 22

Raised ICP

Shock

Extensive purpura

Unstable convulsions

Coagulation abnormalities

Loacl superficial infection

Respiratory insufficiency

Question 23

Is CSF that is normal in appearrance necessarily normal?

Answer 23

No

Need large cell change to change appearance of CSF

Question 24

Why is delay in CSF analysis a problem?

Answer 24

CSF cell count rapidly declines due to cell lysis

Unreliable if not measured immediately

Question 25

What is the problem in using CSF values to diagnose meningitis?

Answer 25

Some bacterial patients will present like viral patients, and vice versa

Question 26

What is the treatment for meningitis?

Answer 26

Resuscitation/life support Fluids Antibiotics Steroids

Question 27

Which antibiotics are used to treat meningitis?

Answer 27

Intravenous 3rd generation cephalosporin For paediatrics, add those that target the ones from the birth canal

Question 28

What is the most common complication of bacterial meningitis?

Answer 28

Hearing loss

Question 29

How is encephalitis treated?

Answer 29

Acyclovir

Question 30

What is encephalitis?

Answer 30

Inflammation of the brain

Question 31

What is the most common cause of encephalitis?

Answer 31

Almost always viral: HSV

Question 32

Describe the conscious state in meningitis vs encephalitis?

Answer 32

Meningitis: normal consciousness Encephalitis: altered conscious state

Question 33

Describe how meningitis can be prevented?

Answer 33

Conjugate vaccines