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brain and behaviour > basic imaging of the cns > Flashcards

basic imaging of the cns Flashcards

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1
Q

what are some of the landmarks which help us identify which part of the brain you’re looking at?

A

lateral fissure, central sulcus, tentorium cerebelli

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2
Q

what are supratentorial structures?

A

structures above the tentorium

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3
Q

what are infratentorial structures? name some

A

below the tentorium. E.g. cerebellum, brainstem, pons and medulla

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4
Q

what does the frontal lobe contain?

A 
motor cortex (post-central gyrus)
pre-frontal cortex
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5
Q

what does the motor cortex control?

A

direct control of voluntary muscles via the brainstem and cord

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6
Q

what do neurons of the motor cortex give off?

A

o Neurons give off myelinated axons which condense and become closely packed together to form corticospinal tracts. Run through white matter tracts (internal capsule) through midbrain + decussates at cranio-cervical junction

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7
Q

what do strokes affecting the medial aspect of the motor cortex affect?

A

the lower limb

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8
Q

what do strokes affecting the lateral aspect of the motor cortex affect?

A

the face/upper limb is more affected

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9
Q

what does the parietal lobe do?

A

integration of sensory information

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10
Q

what does the parietal lobe do?

A
  • Primary somatosensory cortex (Post Central Gyrus)
  • Visuospatial Processing
  • Complex Sensory Processing
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11
Q

what is the most common view used in CT scans?

A

axial

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12
Q

what effect do lesions to the frontal lobe have?

A

motor effects

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13
Q

what effect do lesions to the parietal lobe have?

A

sensory effects

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14
Q

what are the functions of the temporal lobe?

A

Auditory perception, language, speech, memory, emotional response

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15
Q

what does the occipital lobe contain?

A

primary visual cortex

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16
Q

how do the lens of the eye look in an MRI and why?

A

very dark

doesnt contain a lot of free water

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17
Q

what are the ventricles?

A

communicating cavities in the brain filled with CSF. 2 lateral ventricles, one third ventricle and one fourth ventricle.

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18
Q

what is another name for the interventricular foramen?

A

foramina of monro

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19
Q

what does the interventricular foramen connect?

A

connect 3rd ventricle to lateral ventricles

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20
Q

what happens when the interventricular foramen is blocked?

A

lateral ventricles to blow up –> hydrocephaly

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21
Q

what lesion commonly leads to the interventricular foramen becoming blocked?

A

colloid cyst

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22
Q

what is the foramen of magendie?

A

foramen which drains CSF from 4th ventricle into the cisterna magna

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23
Q

what are the foramina of luschka?

A

two foramina that link the 4th ventricle to the cerebellopontine cistern.

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24
Q

what does the cerebral aqueduct connect?

A

connects third and fourth ventricles

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25
Q

what does the 4th ventricle look like on an MRI?

A

horseshoe

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26
Q

what are the basal ganglia and where are they found?

A

Deep grey matter structures. Situated at the base of the forebrain –> group of subcortical nuclei

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27
Q

what commonly causes haemorrhages of the basal ganglia?

A

hypertension

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28
Q

where are the thalami?

A

Large gray matter structure in the caudal part of the forebrain

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29
Q

what do the thalami do?

A

Relays sensory and motor signals to the cerebral cortex and is involved in regulating consciousness.

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30
Q

what is the internal capsule and where is it found?

A

white matter tract. Inferomedial part of each hemisphere. Fibres to and from C. cortex.

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31
Q

what does the corticospinal tract do?

A

carries motor information from primary motor cortex to lower motor neurons.

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32
Q

what is the function of the cerebellum?

A

Motor control, coordination, posture/balance, equilibrium

33
Q

where is the cerebellum?

A

beneath the tentorium

34
Q

what blood vessel supplies the cerebellum?

A

basilar artery

35
Q

how does the basilar artery present on an MRI?

A

black hole

36
Q

what makes up the brainstem?

A

midbrain, pons and medulla

cranial nerve nuclei 3-12 and the white matter tracts

37
Q

how often are x-rays used for the skull? in what situations are they used?

A

rarely

Depressed skull # or penetrating injury only

38
Q

what type of imaging is used in acute situations?

A

CT

39
Q

explain how a CT is carried out?

A

Person placed in machine that consists of a rotating X-ray source: travels in a helical motion to image a full body to the array of detectors that lie underneath

40
Q

how is attentuation measured in a CT?

A

Houndsfield Units

41
Q

how do different mediums appear on a CT and what are their houndsfield units?

A 
o	Air – very black (-1000)
o	Fat – black (-100)
o	Water – dark grey (0)
o	Brain – grey (+40) 
o	Blood – white (+90)
o	I Contrast – white (+100)
o	Bone – very white (+1000)
42
Q

why are CTs used in acute trauma?

A

v sensitive to trauma and blood

43
Q

how does an actute haemorrhage look on a CT?

A

white

44
Q

how does an acute extradural hematoma look on a CT?

A

lens shaped

45
Q

what happens in an acute extradural haematoma?

A

Build- up of blood occurs between the dura mater and skull. As the haematoma expands, it peels the dura away off the bone and presses in on the brain

46
Q

what is coning?

A

when blood presses down from the hematoma through the foramen magnum and down the brainstem

47
Q

what happens in a left sided subdural hematoma?

A

collection of blood below the inner layer of the dura but external to the brain and arachnoid membrane. Falx cerebri is shifted to the side from the midline.

48
Q

what is a hypertensive bleed?

A

weakening of vessels due to high blood pressure: causes them to leak.

49
Q

what is a subarachnoid haemorrhage?

A

bleeding into the subarachnoid space normally due to a rupture of an aneurysm.

50
Q

why does a subarachnoid haemorrhage lead to hydrocephalus?

A

o Blood in the subarachnoid space stops the resorption of CSF

51
Q

what is an amyloid angiopathy and where is it found?

A

superficial, found in the cortex/grey matter

52
Q

what people get amyloid angiopathies?

A

elderly patients get it

53
Q

how can aneurysms be detected?

A

CT scans

54
Q

how can CT scans be used to find aneurysms?

A

• Blood vessels filled with contrast medium so it shows up on a CT (contains iodine bc its absorbed by x-rays). 100ml of contrast injected into a vein with a pump and wait for it to go up to the brain. As soon as it enters the brain, a CT is taken (so only arteries show up, not veins)

55
Q

if there are many aneurysms, how do you know which one bled?

A

the largest one bled

56
Q

what are the advantages of CT scans?

A 
Excellent Bone Detail 
Good for blood and calcium observation
Limited soft tissue detail 
Vascular/perfusion in 3D 
CT guided biopsy
57
Q

what are the disadvantages of a CT scan?

A

X-Ray dose (can be dangerous)

Limited soft tissue resolution (can also be bad).

58
Q

what magnetic field do mris use?

A

constant 1.5 Tesla static magnetic field

59
Q

how is the radiofrequency field pulse applied in mris?

A

via a coil

60
Q

how is an image created in MRIs?

A

o Every water proton acts as a bar magnet.
o H+ line up with the magnetic field (which runs along the main Z axis of the body). H+ ions spin.
o When the RF is turned off, H+ stop spinning and emit an RF back to the coil and an image is created.

61
Q

what magnetic items are not allowed in the room during an mri?

A

pacemakers, metal hip replacements, shrapnels from warzones, cochlear implants, aneurysm clips (the ones in the last 10 years are safe to put in)

62
Q

what pulse sequences are used in MRIs?

A

T1 and T2

63
Q

how does CSF look in a T1 weighted MRI?

A

black

64
Q

how does CSF look in a T2 weighted MRI?

A

white

65
Q

what is an advantage of T1W?

A

allows for better anatomy

66
Q

what is a disadvantage of T1W?

A

less sensitive to pathology than T2W

67
Q

what substance can T1W identify?

A

fat

68
Q

what contrast agent is useful in T1 weighted?

A

gadolinium

69
Q

what pathologies is T2 weighted sensitive to?

A

can see the demyelination of axons occurring in MS; tumours, inflammation, infection, ischaemia, scarring

70
Q

what are characteristics of T2W?

A

High sensitivity, low specificity.

71
Q

how does bacterial meningitis look on imaging?

A

not normally seen on imaging

72
Q

how does TB meningitis look on imaging?

A

severe inflammation / thickening of meninges around the basal cisterns

73
Q

what does diffusion weighted imaging look at?

A

looks at water diffusion

74
Q

why is diffusion weighted imaging used in acute stroke treatment?

A

as soon as an area of brain loses its brain perfusion, the cells become hypoxic and water is trapped inside them

75
Q

where are white matter tracts found?

A
  • Connecting the two hemispheres
  • Connecting the brain to the spine
  • Connecting adjacent parts of the brain
76
Q

what are advantages of MRI?

A

Excellent characterization of lesions
Imaging in any place (axial, coronal, sagittal)
No radiation

77
Q

what are disadvantages of MRI?

A

Prolonged scanning time

Strong magnetic field

78
Q

give reasons for CT being better than MRI?

A 
Quick 
Easily available 
1st line 
Acute trauma, stroke and blood
Perfusion 
Radiation
79
Q

give reasons for MRI being better than CT?

A 
Time consuming 
Multiplanar 
Strong magnetic field.
No radiation 
Functional 
Spectroscopic

brain and behaviour (24 decks)

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