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Flashcards in Tutorial 1: Brain imaging Deck (29):
1

What colour is bone on MRI?

Black

2

What is 'windowing'?

A bit like adjusting the focus so either the bone is in focus or the soft tissue is in focus.

3

What are the CT signs of stroke?

Haemorrhagic stroke
- new blood (high attenuation - bright), old blood - less bright
- Mass effect - e.g. squashing of the sulci, smaller ventricles, asymmetry

Ischaemic stroke
- Thrombus in vessel - hyperdense (i.e. high attenuation)

4

What are the symptoms of a cerebellar stroke?

Dysdidokinesis
Ataxia
Nystagmus
Intention tremor
Staccato speech
Hypotonia

Also inattention/neglect of one side

5

What are the features of a SAH on CT.

Darker foramen magnum (should be bright - CSF). S

6

What are the main differences between CT and MRI techniques of brain imaging?

- CT provides detailed evaluation of cortical bone
- CT allows accurate detection of calcification and metal foreign bodies
- CT can be performed at no risk to the patient with implantable medical devices, such as cardiac pacemakers, ferromagnetic vascular clips, and nerve stimulators
- CT is much faster than MRI, making it the study of choice in cases of trauma and other acute neurological emergencies
- CT can be obtained at considerably less cost than MRI, and is sufficient to exclude many neurological disorders

- MRI does not use ionizing radiation, and is thus preferred over CT in children and patients requiring multiple imaging examinations
- MRI has a much greater range of available soft tissue contrast, depicts anatomy in greater detail, and is more sensitive and specific for abnormalities within the brain itself
- MRI scanning can be performed in any imaging plane without having to physically move the patient
- MRI contrast agents have a considerably smaller risk of causing potentially lethal allergic reaction
- MRI allows the evaluation of structures that may be obscured by artifacts from bone in CT images

7

When is CT commonly used in neuroimaging?

In stroke to exclude haemmorhage. Preferably within 1 hour or 24 hours.

8

What are the CT signs of a stroke?

Haemorrhagic stroke
- Blood – hyperdense (bright)
- Mass effect

Ischaemic stroke
- Thrombus in vessel – hyperdense
- Loss of grey/white
- Oedema – hypodense (dark)
- Mass effect

9

What appears hyperdense on CT?

- New blood
- Bone

10

What appears hyperdense/hypodense on T1 and T2 weighted MRI scans.

T1 - white matter is white, grey matter is grey, fat is bright (also protein, melanin, contrast)

T2 - white matter is grey, grey matter is white, CSF is bright

11

What does TACI stand for? What are the clinical features?

Total Anterior Circulation Infarct.

Higher dysfunction
- Dysphasia
- Visuospatial disturbances
- Decreased level of consciousness
Homonymous hemianopia
Motor and Sensory Defects (≥2/3 of face, arm, leg)

12

What does PACI stand for? What are the clinical features?

Partial Anterior Circulation Infarct

2 out of 3 features of
- Higher dysfunction
- Dysphasia
- Visuospatial disturbances
- Homonymous hemianopia
- Motor and Sensory Defects (>2/3 of face, arm, leg)
Higher dysfunction alone
Partial Motor or Sensory Defect

13

What does POCI stand for? What are the clinical features?

Posterior Circulation Infarct

Cranial nerve palsy AND contralateral motor/sensory defect
Bilateral motor or sensory defect
Eye movement problems (e.g.nystagmus)
Cerebellar dysfunction
Isolated homonymous hemianopia

14

What is a lacunar stroke?

a type of stroke that results from occlusion of one of the penetrating arteries that provides blood to the brain's deep structures.

15

When is MRI most useful?

For soft tissue imaging - detecting early stroke/acute brain injury.

16

What regions of the brain are supplied by the anterior cerebral artery.

Medial frontal lobe
Anterior frontal lobe
Superior frontal lobe
Lateral parietal lobe
Superior parietal lobe

17

What regions of the brain are supplied by the middle cerebral artery?

Lateral frontal lobe
Lateral parietal lobe
Superolateral temporal lobe
Anterior tip of temporal lobe

18

What regions of the brain are supplied by the posterior cerebral artery?

All of the occipital lobe
Most of medial temporal lobe
Inferior temporal lobe

19

What is the commonest cause of a SAH?

Tear of the middle meningeal artery.

20

What is the clinical presentation of a SAH?

Thunderclap occipital headache (classic)
Menigism
Vomiting
Confusion
Coma

21

What does new blood look like on CT?

Bright white

22

What does bone look like on CT?

Bright white

23

What does CSF look like on CT?

Hypodense (black)

24

What does fat look like on CT?

Hypodense

25

What does calcified tissue look like on CT?

Hyperdense

26

What does oedema look like on CT?

Hypodense

27

What does infarcted tissue look like?

Hypodense

28

What does old blood look like?

Hypodense

29

How does one differentiate between subarachnoid, extradural and subdural haemmorhage on CT?

Extra-dural - hyperdense lentiform shape, mass effect, doesn't cross sulci

Subdural - Thin wedge of hyperdense blood that doesn't leak into the sulci

Sub-arachnoid - Hyperdense blood surrounding the brain and penetrating the sulci