1B cerebral vasculature

Question 1

How much cardiac output, O2 and glucose consumption does the brain use and what does this mean?

Answer 1

• Only makes up 2% of body weight but uses:
  
  • 10-20% cardiac output
  • 20% body O2 consumption
  • 66% of liver glucose
• Brain is therefore very vulnerable if blood supply is impaired

Question 2

What is the blood supply to the brain from the heart?

Answer 2

• Common carotid form brachiopulmonary artery splits into external and internal carotid arteries at level of laryngeal prominence
  
  • Internal carotid artery goes through carotid canal into cranial cavity
• First branch of subclavian artery from brachiopulmonary artery is vertebral artery which goes through transverse foramen of cervical vertebrae and goes through foramen magnum into cranium

Question 3

What is the advantage of the arrangement of arteries in the brain?

Answer 3

If you have blockage in one of the internal carotid arteries for example, there’s a chance of compensatory flow from other side

Question 4

What is the venous drainage of the brain?

Answer 4

• Cerebral veins in brain drain into venous sinuses in dura mater which drains into the internal jugular vein
• Superior sagittal sinus → occipital confluence of sinuses → drains transversally through sigmoid sinus into IJV back to heart

Question 5

Describe venous drainage to brain in depth

Answer 5

• Blood goes from superior sagittal sinus to confluence
• Also from inferior sagittal sinus (along bottom of falx cerebri) to confluence
• Also from great cerebral vein down straight sinus to confluence
• Also through transverse into sigmoid sinus and goes through jugular foramen and becomes IJV

Question 6

What are the four types of intercranial haemorrhage?

Answer 6

• Extradural (red)
• Subdural (blue)
• Subarachnoid (purple)
• Intracerebral (yellow)

Question 7

What happens in extradural haemorrhage?

Answer 7

• Trauma, immediate clinical effects
• Arterial, high pressure

Question 8

What happens in subdural haemorrhage?

Answer 8

• Trauma, can be delayed clinical effects
• venous, lower pressure

Question 9

What happens in subarachnoid haemorrhage?

Answer 9

• Ruptured aneurysms- generally congenital
• Usually happens near circle of Willis and can burst due to hypertension
• Called the ‘thunderclap headahce’

Question 10

What happens in intracerebral haemorrhage?

Answer 10

Spontaneous hypertensive

Question 11

Identify this haemorrhage

Answer 11

Subdural

Dura has been reflected and blood clot is underneath the dura

Blood has spread through space over whole hemisphere

Question 12

Identify this haemorrhage

Answer 12

Intracerebral

Due to rupture in vessel of hypertensive patient

Question 13

Identify this haemorrhage

Answer 13

Extradural

Blood clot is outside the dura

Question 14

Identify this haemorrhage

Answer 14

Subarachnoid

Often called berry aneurysm- congenital

Question 15

What is a stroke aka cerebrovascular attack (CVA)?

Answer 15

A rapidly developing focal disturbance of brain function of presumed vascular origin and of >24 hours duration

Question 16

What two reasons are strokes caused by?

Answer 16

• 85% are thrombo-embolic (blockages in vessels)
• 15% are haemorrhagic

Question 17

What is a transient ischaemic attack (TIA)?

Answer 17

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

Question 18

What is an infarction?

Answer 18

Degenerative changes which occur in tissue when it loses its blood supply after occlusion of an artery

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
• Ischaemia is a lack of everything in blood, not just oxygen

Question 20

What is a thrombosis?

Answer 20

Formation of a blood clot (thrombus)

Question 21

What is an embolism?

Answer 21

• Plugging of small vessel by material carried from larger vessel e.g. thrombi from the heart or atherosclerotic debris from the internal carotid
• Fat and air (from syringe) could cause an embolism

Question 22

What are the risk factors for stroke?

Answer 22

• Age
• Hypertension
• Diabetes mellitus
• Smoking
• Cardiac disease

Question 23

What happens if anterior cerebral artery has a problem?

Answer 23

• Paralysis of contralateral structures (leg more than arm or face)- due to primary motor cortex damage
• Disturbance of intellect, executive function and judgement (breakdown of frontal lobe function is called abulia)- due to frontal lobe damage
• Loss of appropriate social behaviour- due to frontal lobe damage

Question 24

What happens if middle cerebral artery has a problem?

Answer 24

• ‘classic stroke’
• Contralateral hemiplegia (paralysis) → arm more than leg- due to motor cortex damage
• Contralateral hemisensory deficits- due to somatosensory cortex damage
• Hemianopia- loss of one half of visual field- due to occipital lobe damage
• Aphasia (Left sided lesion)- loss of speech- due to Broca’s/Wernicke’s area damage

Question 25

What happens if posterior cerebral artery has a problem?

Answer 25

Problems are due to occipital lobe damage

• visual deficits
• Homonymous hemianopia- not being able to see
• Visual agnosia- not able to interpret what we see

Question 26

What is the major risk factor for stroke in this image?

Answer 26

Yellow discolouration in walls of vessels is a build up of atheroma (fatty deposits) that cause atherosclerosis (hardening of arteries)

These deposits can break away and go into smaller vessels and block them to cause stroke

Question 27

What cerebral artery has been occluded here?

Answer 27

There is evidence of infarction in the perfusion field of the right middle cerebral artery- can see the dead tissue