CNS Infections Flashcards

1
Q

In what ways can the CNS become infected?

A

Direct invasion by neurotropic micro-organisms

Iatrogenic

Latent viral infection

Toxin mediated disease

Immune mediated disease

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2
Q

What does neurotropic mean?

A

Micro-organism has a tendency to attack the CNS

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3
Q

Give an example of a CNS infection caused by direct invasion by neurotropic micro-organisms?

A

Encephalitis
Meningitis
Meningoencephalitis

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4
Q

Give some examples of iatrogenic causes of CNS infection?

A

Neurosurgery

Shunts: to drain excess fluid on the brain in hydrocephalus

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5
Q

Give an example of a latent viral infection that causes CNS infection?

A

Shingles: Herpes Zoster

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6
Q

Give some examples of toxin mediated CNS infections?

What does ‘toxin mediated’ mean?

A

Botulism

Tetanus

The pathogen releases a toxin that causes the damage to the body

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7
Q

Give an example of some immune mediated diseases that are linked with CNS infections?

A

Guillain Barre
Post-infection inflammation

ADEM + AHLE
(diseases to do with demyelination)

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8
Q

What is Guillain Barre syndrome briefly?

A

When the body’s immune system attacks the peripheral nervous system

It occurs shortly after an infection, this triggers the immune system to go into overdrive

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9
Q

What is meningitis?

A

Inflammation of the meninges

Often caused by infection, but not always

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10
Q

What are the clinical features of meningitis?

A

Fever

Severe headache

Meningismus:

  • photophobia
  • neck stiffness

Altered mental state, not always

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11
Q

What is meningismus?

A

Symptoms that meningitis causes:

  • photophobia
  • neck stiffness
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12
Q

Only meningitis causes meningismus.

True or false?

A

False!

Can be caused by encephalitis and para-meningeal infections too

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13
Q

What is a para-meningeal infection?

A

Just another type of infection, such as tonsillitis

They can cause meningismus

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14
Q

What can cause meningitis?

A

Infection:

  • bacteria
  • virus
  • fungal
  • tuberculous

Non-infectious:

  • tumours + cysts
  • drugs
  • autoimmune: SLE
  • post-neurosurgery
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15
Q

When you see a patient with meningitis-like symptoms what should you do?

A

Always err on the side of caution and check for bacterial meningitis

It is very severe and if missed can be fatal

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16
Q

Which are common bacteria that cause meningitis in adults and children?

A

Neisseria meningitidis

Strep. pneumoniae

Listeria monocytogenes

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17
Q

Which are common bacteria that cause meningitis in neonates?

A

E. coli

Group B strep

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18
Q

Which pathogen is screened for in pregnant women? Why?

A

Group B streptococci

It can be picked up by neonates in the birth canal and can cause meningitis

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19
Q

Which viruses cause meningitis?

A

Mumps

Enteroviruses (like polio)

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20
Q

Investigations of meningitis?

A

Lumbar puncture promptly!

Analyse:

  • cell count
  • protein level
  • glucose level

Blood cultures

CT: check for raised inter-cranial pressure

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21
Q

What is meningococcal septicaemia?

A

Septicaemia: infection in the bloodstream

Caused by a meningococcal pathogen

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22
Q

What’s the difference between meningococcal septicaemia and meningitis?

A

Meningitis is just inflammation of the meninges

Meningococcal septicaemia occurs as a result of meningitis and is infection of the bloodstream

23
Q

Clinical features of meningococcal septicaemia?

A

Purpural, non-blanching rash

24
Q

If you see a Purpural rash that doesn’t blanch, what have they likely got?

A

Meningococcal septicaemia

25
Q

What is chronic meningitis and what causes it?

A

When symptoms last over weeks

  • Mycobacterium tuberculosis
  • Syphilis
  • Lyme disease
  • Fungal
  • Parasitic
  • Non-infectious, drugs
26
Q

Why should you check inter-cranial pressure using a CT scan before you do a lumbar puncture?

A

Lumbar puncture is contraindicated if they have raised inter-cranial pressure

Doing a lumbar puncture will lower pressure in spinal cord, and since brain is at higher pressure than it wants to be it could herniate downwards: coning

27
Q

Management of meningitis?

A

Start antibiotics immediately in all cases of suspected bacterial meningitis

You can always stop them if tests prove otherwise later

Supportive, ITU care

28
Q

What drugs do you use to treat meningitis?

A

Cefotaxime
Amoxicillin

Dexamethasone, a steroid if suspected pneumococcal meningitis

29
Q

How do you select antibiotics to use to treat meningitis?

A

Ones that are appropriate for the pathogen

Ones that can cross blood-brain barrier

Ones that are safe at high doses

30
Q

When are steroids indicated in meningitis treatment?

A

If suspected pneumococcal meningitis

31
Q

When analysing the CSF, what would you suspect the pathogen was if protein was raised?

A

Bacteria

Or TB

32
Q

When analysing the CSF, what would you suspect the pathogen was if there were an excess of polymorphs?

A

Bacterial

33
Q

What is encephalitis?

A

Inflammation of actual brain parenchyma

Often caused by infection

34
Q

What causes encephalitis?

A

Viral infection most often
Immunosupression: AIDS
IV drug use

Auto-immune
Liver failure

35
Q

Which viruses often cause encephalitis?

A

Herpes simplex
Other herpes
Enteroviruses, like mumps

36
Q

Clinical features of encephalitis?

A
Fever
Headache
Decreased consciousness
Confusion
Coma
Seizures
Focal weakness
Meningismus
37
Q

Investigation of encephalitis?

A

CT and MRI show oedema often in the temporal lobes

CSF fluid analysis shows a moderate increase of WBCs

Blood:
Viral serology could indicate cause

38
Q

Management of encephalitis?

A

Anti-virals

Supportive care

39
Q

What is a cerebral abscess?

A

An abscess (an accumulation of pus) in the brain

40
Q

Can you get abscesses in the spinal column?

A

Yes

In the epidural or subdural space, though they are rare

41
Q

What causes cerebral abscesses?

A

Local spread from a local infection, i.e. ear or sinus

Haematological spread

42
Q

What pathogens often cause cerebral abscesses?

A

Staph. aureus
Strep. pyogenes

Gram -ves
Anaerobes
Parasites, fungal etc.

43
Q

Clinical features of cerebral abscess?

A

Fever
Headache
Seizures

Focal neurological signs: like a stroke, signs depend on where the abscess is in the brain

44
Q

Investigation of cerebral abscess?

A

CT scan

NOT lumbar puncture, due to risk of coning

45
Q

What is ‘coning’ of the brain?

A

Herniation of the cerebellum down through the foramen magnum

Causes compression of the brainstem, causing death/damage

46
Q

Management of cerebral abscess?

A

Anti-microbials

Drainage/aspiration (rarely)

47
Q

What is shingles?

A

A painful acute inflammation of the nerve ganglia

Caused by a virus that lies dormant for years and gets reactivated

48
Q

What virus causes shingles?

A

Herpes Zoster

49
Q

How does herpes zoster cause shingles?

A

After an infection, often in childhood (chickenpox) the virus lies dormant in the dorsal root ganglia

It gets reactivated for unknown reasons, and causes shingles

50
Q

Clinical features of shingles?

A

Dermatomal distribution:

Pain and tingling precede a rash
Chicken-pox like rash
Very painful

This develops on the dermatome of the nerve that the virus is affecting

Often affects lower thorax

Or ophthalmic division of trigeminal nerve, affecting face

51
Q

What is the shingles rash like?

A

Papules and vesicles

Weeping

52
Q

Management of shingles?

A

Anti-virals

53
Q

What is a complication that occurs from shingles?

A

Post-herpetic neuralgia

Pain that persists after shingles
Very disabling

54
Q

How can you prevent shingles?

A

Vaccination of all adults over age 60