blood supply to CNS

Question 1

what are the 2 main sources of blood to brain?

Answer 1

• internal carotid arteries
• vertebral arteries
• 2 sets come together at base of brain to form Circle of Willis

Question 2

what comes from circle of Willis?

Answer 2

• 3 main pairs of cerebral arteries

- these supply anterior, middle, posterior cerebrum

Question 3

where does the common carotid artery bifurcate and into what?

Answer 3

• goes up the neck, bifurcates at level of laryngeal prominende
• splits into:
  1. internal carotid artery (has no branches outside cranial cavity)
  2. external carotid artery (branches lots outside cranial cavity –> supplies structures of face)

Question 4

what is the vertebral artery?

Answer 4

• branch from each subclavian

- passes up through transverse foramens of cervical vertebrae to go to base of skull

Question 5

what are the 2 main feeds to circle of Willis?

Answer 5

• internal carotid arteries (ant): pass through base of skull, arrive towards front of brain
• 2 vertebral arteries (post): come together to form basilar artery

Question 6

describe the venous drainage of brain

Answer 6

• venous blood drains from cerebral veins
• venous blood then circulates in venous sinuses
• cerebral veins drains most of venous blood into superior saggital sinus
• venous blood then circulates to back of head
• moves laterally though lateral sinus + sigmoid sinus
• becomes continuous with internal jugular vein

Question 7

define stroke

Answer 7

cerebrovascular accident
rapdily developing focal disturbance of brain function of presumed vascular origin
lasts for more than 24 hours

Question 8

what 2 things can stroke be due to?

Answer 8

• 85% = infarction

- 15% = haemorrhage

Question 9

what is a TIA?

Answer 9

rapidly developing focal disturbance of brain function or presumed vascular origin that resolves completely within 24 hours

Question 10

what is infarction?

Answer 10

degenerative changes which occur in tissue following occlusion of an artery

Question 11

define cerebral ischaemia

Answer 11

lack of sufficient blood supply to nervous tissue

results in permanent damage if blood flow is not restored quickly

Question 12

what does it look like if there is interruption of flow to the anterior cerebral artery

Answer 12

• paralysis of contralateral leg more then arm and face
• frontal lobe function is affected
• disturbance of intellect, executive function and judgment

Question 13

what does it look like if there is interruption of flow to the middle cerebral artery

Answer 13

• classic stroke
• contralateral hemiplegia in arm more than leg
• contralateral hemisensory deficits
• blindness over half field of vision
• aphasia (impairment of language)

Question 14

what does it look like if there is interruption of flow to the posterior cerebral artery

Answer 14

• visual deficits

- receptive aphasia (can’t understand speech)

Question 15

what are lacunar infarcts?

Answer 15

• lacune = small cavity
• appear in deep structures of brain due to small vessel occlusion
• associated w/ hypertension

Question 16

what 4 things can a haemorrhagic stroke be?

Answer 16

• extradural: trauma, immediate effects, inc. IOP
• subdural: trauma, lower pressure so delayed effects
• subarachnoid: ruptured aneurysm of basal vessels
• intracerebral (spontaneous hypertension)