Cerebral Vasculature Flashcards

1
Q

How much Cardiac Output does the brain use?

A

10-20%

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2
Q

How much O2 does the brain consume?

A

20%

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3
Q

How much liver glucose does the brain use?

A

66%

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4
Q

Why is the brain vulnerable when blood supply is impaired?

A

Due to it’s high metabolic demands

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5
Q

Which arteries supply the brain?

A
  • Internal carotid (entry through the carotid canal)

- vertebral artery (foramen magnum)

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6
Q

Arteries in the brain?

A

The Circle of Willis
(2 x vertebral > basilar artery > posterior cerebral > posterior communicating > middle cerebral (internal carotid) > anterior cerebral > anterior communicating)

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7
Q

Where does atherosclerotic build-up occur most often in the cerebral arteries/circle of willis?

A

Where it divides.

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8
Q

What happens if there is an effective blockage of the cerebral arteries in the Circle of Willis?

A

Theoretical chance of compensatory flow from the other side.
Realistically compensation between the posterior and anterior cerebral arteries is weak as P communicating are very thin.

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9
Q

Venous drainage of the brain?

A

Drains mainly through venous sinuses in the dura mater (through the cerebral veins) > internal jugular vein

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10
Q

Order of venous drainage through the sinuses?

A

superior (+inferior) sagittal sinus + straight sinus> confluence of sinuses > sigmoid sinus (lateral/transverse drainage)

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11
Q

What are the different types of intracranial haemorrhage

A
  • extradural
  • subdural
  • subarachnoid
  • intracerebral
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12
Q

Where do sinuses form?

A

In between the meningeal (inner) and periosteal (outer) layers of the dura mater

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13
Q

What causes a extradural cranial haemorrhage?

A
  • trauma

- high pressure arterial bleed

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14
Q

What causes a subdural cranial haemorrhage?

A
  • trauma

- low pressure, venous bleed

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15
Q

What causes a subarachnoid cranial haemorrhage?

A

Ruptured aneurysms
(normally congenital)
- blood vessel weakness
- may burst in hypertensive patients

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16
Q

What causes a intracerebral cranial haemorrhage?

A
  • spontaneous hypertensive

normal in chronic hypertensives

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17
Q

Where is a fragile point in the head?

A

Pterion

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18
Q

Why is the Pterion so vulnerable?

A

Protects the artery supplying the dura (if ruptured causes an extradural bleed)

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19
Q

Where do Extradural bleeds occur?

A

Between the dura and the skull, builds up pressure (arterial)

20
Q

How do extradural bleeds present?

A
  • Acute onset
  • surgical emergency
  • high intracranial pressure
21
Q

Where do subdural bleeds occur?

A

Between the dura and the arachnoid.

small amount of space

22
Q

How do subdural bleeds present?

A
  • Delayed onset of symptoms

- venous, lower pressure bleed

23
Q

Where do subarachnoid haemorrhages most commonly occur?

A
  • Base of the brain, near the circle of willis
24
Q

Stroke Definition

A

(CVA)
cerebrovascular accident
rapidly developing disturbance of brain function of a presumed vascular origin for >24 hours

25
Q

What does a rapid onset stroke indicate?

A

Likely vascular origin

exclusion of differentials must occur

26
Q

What is a thrombo-embolic stroke and how common is it?

A

Stroke due to blockages

85% of strokes

27
Q

What is a haemorrhage stroke and how common is it?

A

Stroke due to brain bleed

15% of strokes

28
Q

Transient Ischaemic Attack (TIA)

A

same as stroke but resolved in 24 hours
(no residual deficits)
rapidly developing focal disturbance of brain function of a presumed vascular origin that completely resolves in 24 hours

29
Q

TIA time span?

A

normally can be from 30 seconds - 1 minute

30
Q

What does a TIA indicate?

A

Subsequent stroke further down the line

cause of TIA may worsen

31
Q

Infarction

A

Degenerative tissues that occur in the tissue due to occlusion of an artery (tissue death)

32
Q

Cerebral Ischaemia

A

Lack of sufficient blood supply to nervous tissue which leads to permanent damage if blood supply is not restored quickly.

33
Q

How is Ischaemia different from hypoxia?

A

Ischaemia is a lack of everything, not just O2

34
Q

Thrombosis definition

A

Formation of a blood clot (thrombus)

can be a form of embolism

35
Q

Embolism definition

A

Plugging of a small vessel by material carried from a larger vessel

36
Q

Examples of embolism

A
  • thrombi from the heart
  • atherosclerotic debris from the internal carotid
  • fat
  • air (IV injections)
37
Q

Strokes and Public Health

A
  • 3rd most common cause of death (100,000 deaths/year)
  • 50% of survivors are permanently disabled
  • 70% show an obvious neurological deficit
38
Q

Risk Factors of Stroke

A
  • Age
  • Hypertension
  • Cardiac Disease
  • Smoking
  • Diabetes Mellitus (effects on vasculature)
39
Q

Where does the Anterior Cerebral artery perfuse?

A
  • midline structures (about 1cm strip)

- all the way back to the parietal-occipital fissure

40
Q

Where does the Middle Cerebral artery perfuse?

A
  • most of lateral surface of the brain

- most of the subcortical (deep) structures in the brain

41
Q

Where does the Posterior Cerebral artery perfuse?

A
  • mostly the occipital lobe

- inferior part of the temporal lobe

42
Q

Symptoms of stroke of the Anterior Cerebral Artery

A
  • paralysis of contralateral structures (opposite to the perfusion of brain)
    (most likely the leg)
  • front lobe damage, disturbance of intellect, executive function and judgement (abulia - decreased frontal function)
    also, possible loss of appropriate social behaviour.
43
Q

Symptoms of a Middle Cerebral Artery stroke?

A

‘Classic Stroke’

  • (deep motor structures): contralateral hemiplegia (arm>leg)
  • (sensory cortex): contralateral hemisensory deficits.
  • (runs from eye to occipital) Hemianopia (loss of half the visual field)
  • Aphasia, lack of normal speech (Left-sided lesion)
44
Q

Symptoms of a Posterior Cerebral Artery stroke

A
- The occipital region of the brain 
Visual Deficits: 
- Homonymous hemianopia 
- Visual Agnosia
- Prosop Agnosia (unable to recognise faces)
45
Q

Indication of Infarction

A

Loss of clear differentiation between white and grey matter.