CNS Infections

Question 1

What does pyogenic meningitis mean?

Answer 1

Thick layer of suppurative exudate covers the leptomeninges over the surface of the brain and there are neutrophils in the subarachnoid space

Question 2

Name four common pathogens that cause meningitis

Answer 2

Strep pneumonia/pneumococcal
Neisseria Meningitis
Haemophilus influenza
Listeria monocytogenes

Question 3

Describe strep pneumonia

Answer 3

Gram positive coccus found in the nasopharynx
Often in neonates, elderly, patients with cribiform plate fractures or diabetes/alcoholics
May be linked to cochlear implants

Question 4

Describe Neisseria Meningitis

Answer 4

Gram negative diplococcus found in the throat
Gains access to meninges through the blood stream
Often in young people particularly crowded areas leading to outbreaks
Endotoxin produces symptoms

Question 5

What does haemophilus influenza require to grow?

Answer 5

Blood factors

Question 6

Why is h.influenza meningitis rare?

Answer 6

Vaccination

Question 7

Describe listeria monocytogenes

Answer 7

Gram positive bacilli, bacteraemia illness most commin in immunocompromised, diabetics, alcoholics or elderly patients

Question 8

How does bacterial meningitis present?

Answer 8

Fever, stiff neck, headache, vomiting, photophobia, rash, confusion, lethergy

Question 9

State three ways of which bacteria can spread to the meninges

Answer 9

Nasopharyngeal colonisation
Direct extension of bacteria (sinusitis, brain abscess)
From remote foci of infection (endocarditis, pneumonia)

Question 10

What is the treatment for bacterial meningitis?

Answer 10

Ceftriaxone
Dexamethasone
Amoxicillin if >60 or immunocompromised

Question 11

If a patient has been to a penicillin resistant country in last 6 months what is given instead of amoxicillin?

Answer 11

Vancomycin

Question 12

If a patient is penicillin allergic what can be used?

Answer 12

Chloramphenicol

Question 13

State the complications of bacterial meningitis

Answer 13

Purulence - clusters at base of the brain, convexities of sulci and exudate around nerves
Invasion - pia mater prevents abscess formation
Cerebral oedema
Ventriculitis/hydrocephalus

Question 14

What is aseptic meningitis?

Answer 14

Meningitis not caused by bacteria - can be infectious or non-infectious

Question 15

In aseptic meningitis what are the features of CSF

Answer 15

Low WBC
Minimal protein
Normal glucose

Question 16

Describe viral meningitis

Answer 16

Common in late summer/autumn often due to enteroviruses. Associated with travel and can be diagnosed by stool sample , throat swab or CSF PCR

Question 17

How is viral meningitis treated?

Answer 17

Supportive and self limiting

Question 18

Define encephalitis

Answer 18

Infection of the brain parenchyma often due to a virus

Question 19

How does encephalitis present?

Answer 19

Insidious onset, stupor, coma, seizures, paralysis, confusion, psychosis, behavioural/mental changes

Question 20

How is encephalitis investigated?

Answer 20

Lumbar puncture
EEG
MRI
Ask specific questions to identify virus

Question 21

What will an MRI of encephalitis look like?

Answer 21

Pus and oedema in gyrus and sulci

Question 22

What treatment is given initially in encephalitis?

Answer 22

Aciclovir

Question 23

When must a lumbar puncture not be performed?

Answer 23

If there is a possibility of increased ICP

Question 24

Describe the CSF findings in viral meningitis

Answer 24

10^1 - 10^3 lymphocytes
Gram stain will be negative
No antigen
Normal protein and glucose

Question 25

Describe CSF findings in bacterial meningitis

Answer 25

10^1 - 10^4 polymorphs 
Gram stain will be positive 
Antigen test will be positive 
High protein 
Low glucose, <70% blood glucose

Question 26

What are warning signs in a patient with suspected meningitis?

Answer 26

Low/fluctuating GCS
Focal neurology 
Seizure 
Shock 
Bradycardia/hypertension 
Papilloedema