CNS infections and meningitis

Question 1

1. What are the routes of entry into the CNS?

Answer 1

Haematogenous (MOST COMMON)
Direct implantation
Local extension
PNS into CNS

Question 2

3. What is aseptic meningitis?

Answer 2

Meningitis that is caused by viruses and is not purulent

Question 3

4. What can neurological damage be caused by in meningitis?

Answer 3

Direct bacterial toxicity
Indirect inflammatory response, cytokine release and oedema
Shock, seizures and cerebral hypoperfusion

Question 4

5. What are the three types of meningitis?

Answer 4

Acute (hours to days)
Chronic (days to weeks)
Aseptic (caused by viruses so there is no pus)

Question 5

6. Name three organisms that cause acute meningitis.

Answer 5

Neisseria meningitidis
Streptococcus pneumoniae
Haemophilus influenzae

Question 6

7. How many serotypes of N. meningitidis are there?

Answer 6

3 – A, B and C

NOTE: the meningitis vaccine is for meningitis C (although there is one available for meningitis B)

Question 7

8. List some other, rarer bacterial causes of acute meningitis.

Answer 7

Listeria monocytogenes
Group B Streptococcus
Escherichia coli

Question 8

10. How long does N. meningitidis take to cause infection?

Answer 8

< 10 days

Question 9

11. What are the four processes that occur in septicaemia?

Answer 9

Capillary leak – albumin and other plasma proteins lead to hypovolaemia
Coagulopathy – leads to bleeding and thrombosis, endothelial injury results in platelet release reactions, the protein C pathway and plasma anticoagulants are affected
Metabolic derangement – particularly acidosis
Myocardial failure – and multi-organ failure

Question 10

13. List some complications of TB meningitis.

Answer 10

Tuberculous granulomas
Tuberculous abscesses
Cerebritis

Question 11

14. What is a typical MRI feature of TB meningitis?

Answer 11

Leptomeningeal enhancement

Question 12

16. What are the most common causative organisms in aseptic meningitis?

Answer 12

Coxsackie group B viruses

Echoviruses

Question 13

17. Which age group is susceptible to aseptic meningitis?

Answer 13

< 1 year

NOTE: normally self-resolving after 1-2 weeks

Question 14

18. How is encephalitis transmitted?

Answer 14

Haematogenous (either person-to-person or through vectors such as mosquitoes)

Question 15

19. List some viruses that cause encephalitis.

Answer 15

Mumps
Measles
Enteroviruses
Herpes viruses

Question 16

20. What is becoming a leading cause of encephalitis worldwide?

Answer 16

West Nile virus

Question 17

21. Which bacterium is associated with causing encephalitis?

Answer 17

Listeria monocytogenes

Question 18

22. Name two types of amoeba that cause encephalitis.

Answer 18

Naegleria fowleri

Acanthamoeba species and Balamuthia mandrillaris

Question 19

23. What is toxoplasmosis and how is it spread?

Answer 19

Obligate intracellular parasite

Spread via oral, transplacental or organ transplant route

Question 20

25. List some organisms that can cause brain abscesses.

Answer 20

Staphylococci
Streptococci
Gram-negative organisms (mainly in neonates)
TB 
Actinomyces and Nocardia species

Question 21

26. Name a common spinal infection and how does it spread?

Answer 21

Pyogenic vertebral osteomyelitis

direct spinal trauma

Question 22

28. What are some long-term consequences of pyogenic vertebral osteomyelitis?

Answer 22

Permanent neurologic defects
Significant spinal deformity
Death

Question 23

29. List some risk factors for pyogenic vertebral osteomyelitis.

Answer 23

Age 
IVDU 
Long-term systemic steroids 
Diabetes mellitus 
Organ transplantation 
Cancer 
Malnutrition

Question 24

31. List some other useful tests for suspected meningitis.

Answer 24

Blood culture 
Throat swab
Blood PCR 
Sputum culture 
Urine culture

Question 25

32. What studies can be done with CSF?

Answer 25

``` Colour/clarity Cell counts Chemistry (protein and glucose) Stains (Gram, auramine, India Ink etc.) Cultures PCR ```

Question 26

33. Describe the typical CSF analysis results of: a. Bacterial meningitis b. Aseptic meningitis c. Tuberculous meningitis

Answer 26

``` a. Bacterial meningitis Turbid High polymorphs High protein Low glucose b. Aseptic meningitis Clear High lymphocytes High protein Normal glucose c. Tuberculous meningitis Clear High lymphocytes High protein Low glucose ```

Question 27

34. Describe the Gram-stain and microscopic appearance of: a. S. pneumoniae b. N. meningitidis c. L. monocytogenes d. TB e. Cryptococcus

Answer 27

a. S. pneumoniae Gram-positive alpha-haemolytic diplococci b. N. meningitidis Gram-negative non-haemolytic diplococci c. L. monocytogenes Gram-positive rods d. TB Stains positively with Ziehl-Neelsen (red and blue) e. Cryptococcus Stains positively with India ink (appears like an orbit – yeast in the middle with a capsule around the outside)

Question 28

35. What is another key clinical feature of Cryptococcal meningitis?

Answer 28

High opening pressure

Question 29

37. What is the generic therapy used in meningitis?

Answer 29

Ceftriaxone 2 g IV BD If > 50 years or immunocompromised = amoxicillin 2 g IV 4 hourly NOTE: this is because ceftriaxone does NOT cover Listeria

Question 30

38. What is the generic therapy used in meningo-encephalitis?

Answer 30

Aciclovir 10 mg/kg IV TDS Ceftriaxone 2 g IV BD If > 50 years or immunocompromised = amoxicillin 2 g IV 4 hourly

Question 31

39. Name the specific therapy for meningitis caused by: a. S. pneumoniae b. N. meningitidis c. H. influenzae d. Group B Streptococcus e. Listeria f. Gram-negative bacilli g. Pseudomonas

Answer 31

``` a. S. pneumoniae Pen G 18-24 mu/day b. N. meningitidis Ceftriaxone 4 g/day c. H. influenzae Cefotaxime 12 g/day d. Group B Streptococcus Pen G 18-24 mu/day e. Listeria Ampicillin 12 g/day f. Gram-negative bacilli Cefotaxime 12 g/day g. Pseudomonas Meropenem 6 g/day ```