Imaging approach to neuroinfections Flashcards

1
Q

What are several outbreaks found in this century?

A

Encephalitis

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2
Q

What is Encephalitis?

A

Infection or inflammation of the brain parenchyma

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3
Q

What is endemic in some countries?

A

Tuberculosis

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4
Q

What is an infection where children are born with no brain parenchyma?

A

Zika virus

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5
Q

What is an example of a zika virus?

A

Ebola

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6
Q

Where is there a common cause of neurological morbidity?

A

Endemic areas

e.g. South East Asia

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7
Q

Where is it common for focal epilepsy to occur?

A

South East Asia

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8
Q

What is an example of focal epilepsy?

A
  1. Tuberculosis

2. Cysticercosis

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9
Q

What is an example of urbanisation and encroachment on natural environment, ease of world travel and climate change?

A

Mosquito-borne diseases

  • Malaria
  • Dengue
  • Viral encephalitides
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10
Q

What is an example of immunosuppressed and immunodeficient states?

A
  1. Post-transplant
  2. Chemotherapy
  3. Disease modifying therapy
  4. Recreational drug use HIV
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11
Q

What does BBB keep?

A

Brain and spinal cord safe from other pathogens

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12
Q

What brings down all of the immune system?

A

HIV

vulnerable to pathogens

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13
Q

What can be treated with immunotherapy?

A

Multiple Sclerosis

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14
Q

What are huge problems?

A

Immunotherapy and immunodeficient states

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15
Q

What is a prion?

A

Transmissible virus and protein particles

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16
Q

What is an example of disease transmission that prions can cause?

A

CJD

Affects elderly - Rapid deterioration and death

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17
Q

What used to be called mad cow disease?

A

CJD

No treatment

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18
Q

What are barriers to infection?

A
  1. Mechanical and physiological barriers
  2. Between parenchyma and the skin
  3. physical barriers
  4. Dura mater
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19
Q

What are several layers that give rise to protection from the scalp?

A
  1. Skin
  2. Tissues
  3. Bone
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20
Q

What is more important than the skull?

A

Dura mater

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21
Q

What sits across the brain surface?

A

Arachnoid

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22
Q

What is found within the nervous tissue?

A

Astrocytes

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23
Q

What are brain and spinal cord called?

A

Sancturary

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24
Q

What is found in the heart?

A

Bugs

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25
Q

What can happen around the sinuses? Give examples.

A
  1. Infections
    - Mastoid area
    - nasal sinus
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26
Q

What is absent in CSF?

A

Soluble anticryptocococcal factors

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27
Q

What protects against the host inflammatory response?

A

Polysaccharide capsule

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28
Q

What destroys BBB?

A

Bacterial lipopolysaccharides

They have invasiveness into the CNS

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29
Q

What is an example of a bacterium that has different mechanisms?

A

Listeria

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30
Q

What has a protective coating?

A

Fungus

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31
Q

What is vasculitis and infarcts?

A

Brain damage from bacterial toxins and immune responses

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32
Q

What are antigens?

A
  1. Bacteria

2. Viruses

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33
Q

When is there a response?

A

When the body recognises the foreign antigens

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34
Q

What are examples of manifestations that goes from outside to inside?

A
  1. Meningeal
  2. Calvarial
  3. Ventricular
  4. Parenchyma’s
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35
Q

What are examples of meningeal CNS infections?

A
  1. Leptomeningeal
  2. Pachymeningeal
  3. Arachnoiditis
  4. Effusions
  5. Empyema
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36
Q

What is example of calvarial CNS infections?

A

Osteomyelitis

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37
Q

What are examples of ventricular CNS infections?

A
  1. Choroid plexitis
  2. Hydrocephalus
  3. Pneumocephalus
  4. Ventriculitis
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38
Q

What is it called when the ventricles are blocked?

A

Hydrocephalus

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39
Q

What are extra-axial complications?

A
  1. Meningeal
  2. Calvarial
  3. Ventricular
    Found on the surface of the brain
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40
Q

What are found inside the brain parenchyma?

A

Parenchymal lesions

These are intra-axial lesions/manifestations

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41
Q

When is it called encephalitis?

A

When it involves the grey matter

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42
Q

When is it called a myelitis?

A

When it involves the spinal cord

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43
Q

When is it called an abscess?

A

If it forms a puss shaped cavity

44
Q

When is it called a cyst?

A

If it it a free fluid

45
Q

What is Granuloma?

A

A reaction of the bugs antigen and the body’s response

46
Q

What is a scar of the brain formed by?

A

Glial tissues e.g. neurons and astrocytes

47
Q

What are astrocytes?

A

Supporting cells

48
Q

What is the process of scar tissue in the brain called?

A

Gliosis caused by astrocytes

49
Q

What is the role of Imaging?

A
  1. Location and extent of the involvement e.g. load of disease process
  2. Type of infection
  3. Detection of complications
  4. Guidance to biopsy and therapy
50
Q

What is it very rare for a virus to cause?

A

Abscess

51
Q

Where are Abscesses very common in?

A
  1. Bacterium infections

e. g. funguses and bacteria

52
Q

What are the CNS infections approach?

A
  1. Supporting clinical features, background information and laboratory findings
  2. Pathogens vary
  3. Imaging of neuraxis to include spinal cord and caudal equina
  4. Choice of tools and tricks
53
Q

When is CD4 count essential?

A

when dealing with HIV patients

CD4 counts go down and viral load goes up

54
Q

How do pathogens vary?

A
Based on locations of infection within CNS
Geographic exposures
Vaccination status
Age
Surgical intervention
Immune suppression
55
Q

What are examples of extent of involvement?

A
  1. Multi-focal
  2. Diffuse
  3. Atypical clinical or CSF findings
56
Q

What are the imaging modalities for CNS infections: Approach?

A
  1. CT
  2. FLAIR
  3. T2
  4. DWI
  5. Gd-T1w
  6. Othera
57
Q

CT

A

Readily availible

It has a limited role

58
Q

FLAIR

A

Neuroparenchymal features

Meningeal processes

59
Q

T2

A

Extra-axial collections

cyst, abscess, granuloma

60
Q

DWI

A
Cerebritis
Abscess
Empyema
Ventriculitis
Ischaemic complications 
Cryptococcomas vs pseudocysts
61
Q

Gd-T1w

A

BBB breach

62
Q

Others

A

MR spectroscopy, perfusion, MRA, vessel wall imaging, PET

63
Q

When is surgical intervention required?

A

If the puss is on the surface of the brain (parenchyma) or inside the brain (abscess)

64
Q

What is puss?

A
  1. Dead tissue

2. Thick molecule and is shown clearly on DWI image => Restricted diffusion

65
Q

How is Gadolinium shown?

A

Enhancement
Tells you that BBB is breached
Doesn’t tell you which infection it is

66
Q

What does MR spectroscopy give?

A

Different chemical signatures

An abscess has different chemicals and metabolites

67
Q

What is everything that is hyperintense (white) due to?

A
  1. Calcium
  2. Haemorrhage
    (acute haemorrhage/haemotoma)
68
Q

When can infarction and haemorrhage only happen?

A

Coming from a systemic cell (endocarditis)

69
Q

When does an infarct occur?

A

When the bug blocks the middle cerebral artery

70
Q

What is anything that appears white on FLAIR image?

A

Abnormal

71
Q

What is involved in herpes encephalitis?

A

Limbic system

Results in ganglion cells

72
Q

What is FLAIR used to look for?

A
  1. Parenchymal regions
  2. Meningeal regions
  3. Extra-axial features
73
Q

How is acute infarct on DWI observed?

A

If the lesion was in the territory of middle cerebral artery

74
Q

What is restricted diffusion?

A
  1. Bright on DWI

2. Dark on ADC map

75
Q

What are the few pathologies that restricted diffusion have?

A
  1. Acute ischaemia
  2. Pure content - puss material
  3. Lesions that have big molecules/marcomolecules
76
Q

What shows restricted diffusion?

A

Anything that is vicious

77
Q

What does antibiotic kill?

A

Bacteria

Dilutes the puss

78
Q

What doesnt show free fluid motion?

A

Vascular degeneration

79
Q

What does SWI show?

A

Disorders that are associated with intracranial calcification or iron deposition

  • Vasculitis
  • Deep vein thrombosis
  • Septicaemia
80
Q

What is abnormal on SWI?

A

Anything which is black or dark grey

81
Q

What is a classic example of malaria?

A

Deep vein thrombosis

82
Q

What can clog the liver veins?

A

Malaria

83
Q

What is very typical of bacterial infection?

A

Leptomeningeal

84
Q

What are all the features of Inflammation?

A
  1. Swelling
  2. Oedema
  3. Enhancement
  4. Permeability
  5. Gliosis
85
Q

Why does hydrocephalus obstruct the ventricles?

A

Bunch of cysts

86
Q

What are the 3 common metabolites found in the brain?

A
  1. NAA
  2. Choline
  3. Creatine
87
Q

What is Febrile Meningeal Syndrome?

A

Commonest infection observed in children

88
Q

What are the symptoms of Febrile meningeal syndrome?

A
  1. Acute confusion
  2. Fever
  3. Rash
89
Q

Febrile Meningeal Syndrome

A

85% of acute bacterial meningitis: Pneumococcus or Streptococcus

Lumbar puncture and urgent consecutive initiation of antibiotic therapy without prior imaging

90
Q

Imaging in Mengitis

A
  1. If the infection is severe
  2. In case of immunosuppresison
  3. H/O head trauma or neuro-surgery
  4. Unfavourable course under antibiotic therapy
  5. Bacteria other than pneuomoccocus or meningococcus
  6. To detect osseous/ dural breach in relapsing meningitis
91
Q

What can mimic any for of infection?

A

Tuberculosis

92
Q

What is subdural empyema?

A

Abscess collection on the surface of the brain

93
Q

What are examples of Intra-axial lesions?

A
  1. Focal mass lesions
  2. Diffuse lesions
  3. Multifocal lesions
94
Q

What is examples of Focal mass lesions?

A
  1. Cerebritis
  2. Abscess
  3. Granuloma
  4. Cyst
95
Q

What is example of Diffuse lesions?

A
  1. Leukoencephalopathy

2. Encephalitis

96
Q

What is examples of Multifocal lesions?

A
  1. Encephalitis

2. Myelitis

97
Q

What is Cerebritis?

A

Localised inflammation of the brain

98
Q

What is Encephalitis?

A

More diffused inflammation of the brain

99
Q

How can cerebritis be identified on imaging?

A

Hypointense and restriction

100
Q

What is a lesion that is bright on T2 and restricted on diffusion?

A

Abscess

101
Q

What is a lesion that is bright on T2 but does not restrict on diffusion?

A

Cyst

102
Q

What is Nocardiosis?

A

Renal transplant patients (70%)

Post-operative infections

103
Q

What has peculiar affinity for CNS?

A

Listeria

104
Q

What affects the medial temporal lobes?

A

Herpes encephalitis

105
Q

What does each bacterium cause?

A

Metabolism

106
Q

What are Bacteria with specific affinity for CNS?

A
  1. Bacilli
  2. Gram-postive bacteria
  3. Spirochetes
  4. Mycobacteria
107
Q

What does pyogenic mean?

A

It causes pus formation