MI: CNS Infections and Meningitis Pt.1

Question 1

What are the routes of entry into the CNS?

Answer 1

• Haematogenous
• Direct implantation
• Local extension
• PNS into CNS (rabies)

Question 2

What is the most common route of entry for pathogens?

Answer 2

Haematogenous

Question 3

What is aseptic meningitis?

Answer 3

Meningitis that is caused by viruses and is not purulent

Question 4

What are the causes of neurological damage in meningitis

Answer 4

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

Question 5

What are the three types of meningitis?

Answer 5

• Acute (hours to days) - bacterial
• Chronic (days to weeks) - TB and weird
• Aseptic (caused by viruses so there is no pus)

Question 6

Name three organisms that cause acute meningitis.

Answer 6

• Neisseria meningitidis
• Streptococcus pneumoniae
• Haemophilus influenzae

Question 7

How many serotypes of N. meningitidis are there?

Answer 7

N. meningitidis can be classified into 12 serogroups based on its capsular polysaccharide; serogroups A, B, C, W, X, and Y are the primary causes of meningococcal disease worldwide

Question 8

List some other, rarer bacterial causes of acute meningitis.

Answer 8

• Listeria monocytogenes
• Group B Streptococcus
• Escherichia coli

Question 9

How does N. meningitidis enter the body?

Answer 9

Through the nasopharyngeal mucosa in susceptible individuals

NOTE: only 1% of carriers of N. meningitidis have pathogenic strains

Question 10

How long does N. meningitidis take to cause infection?

Answer 10

< 10 days

Question 11

What are the four processess that occur in septicaemia?

Answer 11

• 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

This is why you dont do lumbar pucture - they’ll bleed out

Question 12

Outline the presentation of TB meningitis.

Answer 12

• Similar presentation to bacterial meningitis but much longer to present (weeks instead of days)
• More likely to involve brain and cause neurological changes
• Tends to occur in immunocompromised patients
• No rash

Question 13

List some complications of TB meningitis.

Answer 13

• Tuberculous granulomas
• Tuberculous abscesses
• Cerebritis

Question 14

What is a typical MRI feature of TB meningitis?

Answer 14

Leptomeningeal enhancement
(arachnoid and pia mater appear brighter)

Question 15

What is the most common infections of the CNS?

Answer 15

Aseptic meningitis (aseptic = negative CSF bacterial cultures)

Question 16

What are the most common causative organisms in aseptic meningitis?

Answer 16

Enteroviruses:

• Coxsackie group B viruses
• Echoviruses

Question 17

Which age group is susceptible to aseptic meningitis?

Answer 17

< 1 year

NOTE: normally self-resolving after 1-2 weeks

Question 18

List some viruses that cause encephalitis.

Answer 18

• Herpes virus 1 (MOST COMMON)
• Mumps
• Measles
• Enteroviruses

Question 19

What is becoming a leading cause of encephalitis worldwide?

Answer 19

West Nile virus

NOTE: this is transmitted by mosquitoes and birds

Question 20

How is West nile in the UK

Answer 20

Infects birds
Birds migrate
Affects southern europe
people go on holiday