Cerebral vasculature

Question 1

What percentage of cardiac output does the brain take up?

Answer 1

10-20%

Question 2

What percentage of liver glucose does the brain take up?

Answer 2

66%

Question 3

What are the key arteries supplying the brain?

Answer 3

• common carotid artery (runs up side of neck and divides into external and internal carotid)
• internal carotid artery (goes up into cranial cavity)
• vertebral artery (goes up posteriorly through transverse foramen of cervical vertebrae, so protected by bone)

Question 4

Where do the vertebral arteries pass through on their way to the cranial cavity?

Answer 4

foramen magnum

Question 5

What arteries fuse to form the basilar artery (sitting on base of pons)?

Answer 5

vertebral arteries

Question 6

What does the basilar artery divide into?

Answer 6

posterior cerebral arteries

Question 7

What is the advantage of the circle of Willis arrangement?

Answer 7

if there is a blockage, there is theoretically a chance of compensatory flow from the other side

N.B. posterior communicating arteries v. thin, so weak compensation between anterior and posterior circulation

Question 8

What is the passage of venous blood drainage from the cranial cavity?

Answer 8

cerebral veins–> then via the venous sinuses in the dura mater:
superior sagittal sinus–> venous blood drains down to back of head to occipital sinus–> then transversely then down through sigmoid sinus–> into internal jugular vein

Question 9

What vein drains from the brain to the straight sinus to the confluence of sinuses?

Answer 9

Great cerebral vein of Galen

Question 10

What are the 3 layers of the meninges?

Answer 10

• dura mater
• arachnoid mater (above subarachnoid space)
• pia mater

Question 11

What are the 4 types of intracranial haemorrhage?

Answer 11

1. Extradural
2. Subdural
3. Subarachnoid
4. Intracerebral

Question 12

What is an extradural haemorrhage?

Answer 12

• occurs in trauma–> fracture of pterion–> rupture of artery supplying dura–> pressure buildup+ dura stripped from skull
• ACUTE onset
• SURGICAL EMERGENCY

Question 13

What is a subdural haemorrhage?

Answer 13

(there is a small space between dura and arachnoid where blood can accumulate)

• trauma
• DELAYED clinical effects
• venous bleed
• lower pressure

Question 14

What is a subarachnoid haemorrhage?

Answer 14

• usually at base of brain at circle of Willis
• weakness in blood vessel walls: aneurysms…often no symptoms until rupture
• generally congenital
• in hypertensive patients–> may burst and produce bleed in subarachnoid space

Question 15

What is an intracerebral haemorrhage?

Answer 15

• spontaneous in chronic hypertensive patients

- inside brain!

Question 16

What is a stroke?

Answer 16

• cerebrovascular accident (CVA)
• “rapidly developing focal disturbance of brain function of presumed vascular origin and of >24hrs duration”
• thrombo-embolic (85%) blockage
• haemorrhage (15%) esp. subarachnoid haemorrhage

Question 17

What is a transient ischaemic attack (TIA)?

Answer 17

• rapidly developing focal disturbance of brain function of presumed vascular origin that RESOLVES completely within 24hrs
• could be a minute or seconds
• lost coordination briefly
• warning for subsequent stroke

Question 18

What is an infarction?

Answer 18

degenerative changes which occur in tissue following occlusion of an artery–> dead tissue (cellular response to lack of perfusion)

Question 19

What is cerebral ischaemia?

Answer 19

lack of sufficient blood supply to nervous tissue resulting in permanent damage if blood flow is not restored quickly
(not anoxia, bc lack of EVERYTHING, not just oxygen)

Question 20

What is a thrombus?

Answer 20

formation of a blood clot/thrombus

form of embolism

Question 21

What is an embolism?

Answer 21

plugging of a small vessel by material carried from larger vessel e.g. thrombi from the heart or atherosclerotic (fatty deposits) debris moving up to brain, blocking vessels
N.B. air and fat can also cause emboli

Question 22

What are the risk factors for stroke?

Answer 22

• age
• hypertension
• cardiac disease
• smoking
• diabetes mellitus

Question 23

What are the 3 main cerebral arteries and their perfusion fields?

Answer 23

• anterior cerebral artery: supplies midline structures all the way until parietal-occipital fissure
• middle cerebral artery: supplies most of lateral surface of brain and subcortical deep structures
• posterior cerebral artery: supplies occipital lobe and inferior part of temporal lobe

Question 24

What symptoms are associated with anterior cerebral artery damage?

Answer 24

• paralysis of contralateral structures (leg more than arm and face)
• disturbance of intellect, personality change, executive function and judgement
• loss of appropriate social behaviour

Question 25

What symptoms are associated with middle cerebral artery damage?

Answer 25

- "classic stroke" - contralateral hemiplegia/paralysis: arm more than leg (or complete, as deep structures also supplied) - contralateral hemisensory deficits - hemianopia (loss of one half of vision field) - aphasia (lack of normal speech)

Question 26

What symptoms are associated with posterior cerebral artery damage?

Answer 26

visual deficits - homonymous hemianopia - visual agnosia e.g. prosopagnosia (can't recognise faces you've known for a long time)