W10 - CNS infections + meningitis

Question 1

What are the 4 routes of entry for pathogens to CNS?

Answer 1

1. Haematogenous spread (most common)
2. Direct implantation - i.e. trauma, surgery
3. Local extension - 2ndary to established infections i.e. externa otitis spread to mastoid and then CNS
4. PNS into CNS - viruses, i.e. rabies

Question 2

What CNS region is inflamed in meningitis?

Answer 2

Inflammatory process of meninges + CSF

Question 3

What CNS region is inflamed in meningoencephalitis?

Answer 3

Inflammation of meninges + brain parenchyma

Question 4

What is the mortality rate of meningitis? What is the main neurological sequelae in meningitis survivors?

Answer 4

10% mortality
5% of survivors develop sensorineural deafness

Question 5

What are the symptoms (9) of meningitis?

Answer 5

1. Fever
2. Headache
3. Neck stiffness
4. Photophobia
5. Drowsiness
6. Vomiting
7. Joint pain
8. Fits
9. Rash (non-blanching, due to meningococcal meningitis)

Question 6

6 causative agents of acute meningitis

Answer 6

Neisseria meningitidis
Streptococcus pneumoniae
Haemophilus influenzae
Listeria monocytogenes
Group B Streptococcus
Escherichia coli

Question 7

With N. meningitides, what % of infected individuals have meningitis only, septicaemia only, and meningitis + septicaemia

Why is this important?

Answer 7

50% meningitis
10% septicaemia
40% septicaemia AND meningitis

have to see if patient has signs of septicaemia => if YES, DO NOT PROCEED TO DO LUMBAR PUNCTURE B/C THEY MIGHT HAVE ABNORMAL CLOTTING.

Question 8

If untreated, how does septicaemia proceed?

Answer 8

Capillary leak => hypovolaemia
Deranged coagulopathy => bleeding + thrombosis
Metabolic derangement => usually acidosis
finally, myocardial failure => MOF

Question 9

What is the main cause of chronic meningitis? What is seen on scans?

Answer 9

Tuberculous chronic meningitis
=> tuberculous granumolas, tuberculous abscesses

Question 11

Aseptic meningitis:

A) How do patients present?

B) What is the most likely cause?

C) What is the clinical course usually?

Answer 11

A) headache, neck stiffness, photophobia, sometimes a non-specific rash

B) Most commonly due to Enteroviruses Coxsackievirus group B or Echoviruses

• 2nd most common cause herpes simplex virus 1 or 2

C) self-limited and resolves in 1-2 weeks

Question 12

How does N meningitiidis spread?

Answer 12

From person-to-person, from asymptomatic carriers (through nasopharyngeal mucosa in susceptible individual)

Question 13

How does encephalitis usually spread?

Answer 13

caused by virus and transmission is commonly either person-to-person, or through vectors: monsquitoes, lice, or ticks

Question 14

What are the common viruses that cause encephalitis?

Answer 14

1) HSV 1 & 2
2) Measles, mumps
3) Varicella zoster
4) EBV/CMV
5) Enteroviruses (Coxsackie A & B; Echovirus; polio)
6) Rabies
- Now on a rise: West Nile River (WNR) virus

Question 15

What do you consider in a person who appears to have encephalitis but is enterovirus (-) and herpes (-)?

Answer 15

Consider WNV as a cause!

Question 16

Name bacterial (1), amoebic (2), and protozoic (1) causes of encephalitis

Answer 16

Bacteria:

1. Listeria monocytogenes (usually in immunocompromised)

Amoeba:

1. Naegleria fowleri (habitat warm water)
2. Acanthamoeba species => also causes brain abscess, aseptic or chronic meningitis

Protozoa:

1. Toxoplasma gondii (which causes toxoplasmosis)

Question 17

How does toxoplasmosis spread?

Answer 17

1. Ingestion (raw meat; undercooked meat; oocytes from contact with cat litter/soil)
2. Transplacental (mom to fetus)
3. Organ transplantation

Question 18

What are the aetiology (5) of brain abscesses?

Answer 18

1. Otitis media
2. Mastoiditis
3. Paranasal sinuses
4. Endocarditis
5. Haematogenously

Question 19

What are the common infectious agents (6) present in brain abscesses?

Answer 19

1. Streptococci (both aerobic and anaerobic)
2. Staphylococci,
3. Gram-negative organisms. (particularly in neonates)
4. Mycobacterium tuberculosis
5. fungi
6. parasites

NOTE how 1 & 2 are the common causes of infective endocarditis as well

Question 20

Name 1 common form of vertebral infections

Answer 20

Pyogenic vertebral osteomyelitis

Question 21

Name 3 ways in which infection can spread to vertebrae to cause spinal infections

Answer 21

1. Direct open spinal trauma
2. from infections in adjacent structures
3. Haematogenous spread

Question 22

What are 7 risk factors for developing spinal infections?

Answer 22

1. advanced age
2. IVDU
3. long-term systemic steroids
4. diabetes mellitus
5. Organ transplantation
6. Malnutrition
7. Cancer

Question 23

______ is superior to ______ in detecting parenchymal abnormalities such as abscesses and infarctions.

Answer 23

MRI is superior to CT

Question 24

In CSF studies; what is neutrophils and what is lymphocytes associated with?

Answer 24

Neutrophils = bacterial meningitis

Lymphocytes = viral meningitis

Question 25

Describe the following for bacterial meningitis:

colour

cells/L

G stain

protein (g/l)

glucose (mmol/l)

Answer 25

colour = turbid, purulent

cells/L = 100-2000 polymorphs

G stain = + results

protein (g/l) = 0.5-3.0 g/L

glucose (mmol/l) = 0.2-2 mmol/L

Question 26

Describe the following for aseptic meningitis: colour cells/L G stain protein (g/l) glucose (mmol/l) Name 4 causes

Answer 26

colour = clear or slightly turbid cells/L = 15-500 lymphocytes G stain = NEGATIVE results protein (g/l) = 0.5-1.0 g/L glucose (mmol/l) = Normal (2.2-3.3) causes: viral meningiits, partially antibiotic treated bacterial meningitis, encephalitis, brain abscess

Question 27

Describe the following for TB meningitis: colour cells/L G stain protein (g/l) glucose (mmol/l)

Answer 27

colour = clear or slightly turbid cells/L = 30-500 lymphocytes or some polymorphs G stain = NEGATIVE results, SCANTY ACID FAST BACILLI protein (g/l) = 1.0-6.0 g/L glucose (mmol/l) = 0.2-2 mmol/L causes: TB meningitis, brain abscess, cryptococcal meningitis

Question 28

A 20 year old woman presents with headache and neck stiffness. What do you see? What is the causative pathogen?

Answer 28

Gram + diplococci streptococcus pneumoniae

Question 29

A 18 year old man present with headache and neck stiffness. What do you see? What is the causative pathogen?

Answer 29

Gram negative cocci Neisseria meningitidis

Question 30

A 65 year old presents with headache and neck stiffness. What do you see? What is the causative pathogen?

Answer 30

Gram positive rod Listeria monocytogenes

Question 31

A 45 year old presents with headache and neck stiffness. What stain is this? What is the causative pathogen?

Answer 31

Ziehl-Neelson stain mycobacterium tuberculosis

Question 32

A 35 year old presents with headache and neck stiffness. What stain is this? What is the causative pathogen?

Answer 32

India ink stain encapsulated yeast = cryptococcus neoformans

Question 33

Describe a normal CSF study in terms of: colour cells/L G stain protein (g/l) glucose (mmol/l)

Answer 33

colour = clear cells/L = 0-5 leukocytes G stain = NEGATIVE protein (g/l) = 0.15-0.4 g/L glucose (mmol/l) = 60% blood glucose level, usually 2.2-3.3 mmol/L

Question 39

Highly suspected meningitis, awaiting culture results. Which abx do you treat with?

Answer 39

Ceftriaxone 2g IV BD if \>50years or immunocompromised add: _Amoxicillin_ 2g IV 4hourly

Question 40

Suspected meningo-encephalitis, awaiting culture results. What treatment do you give?

Answer 40

Aciclovir 10 mg/kg IV TDS Ceftriaxone 2g IV BD If \>50years or immunocompromised, add: _Amoxicillin_ 2g IV 4 hourly