4b.) Arterial Supply to the Brain

Question 1

State the two main arterial sources for the brain and describe which regions of brain each supplies

Answer 1

• Anterior circulation
  
  • from internal carotid arteries
  • supplies most of cerebral hemispheres
• Posterior circulation
  
  • from vertebral arteries
  • supplies the brainstem, cerebellum, some of temporal lobe and the occiptial lobe

Question 2

Which part of brain does anterior ciruclation supply?

Answer 2

Most of cerebral hemispheres

Question 3

Which parts of brain does posterior circulation supply?

Answer 3

• Brainstem
• Cerebellum
• Occipital lobe
• Some of temporal lobe

Question 4

Label this diagram of the arterial supply to the brain

Answer 4

*** MUST KNOW THIS

Question 5

What is the circle of Willis?

Which arteries does it include?

Answer 5

Circulatory anastomoes that supplies blood to brain and surrounding structures, includes:

• Anterior communicating artery
• Anterior cerebral arteries
• Internal carotid arteries
• Posterior communicating arteries
• Parts of posterior cerebral arteries

Question 6

Discuss which areas of brain the middle cerebral artery supplies

Answer 6

• Cortical branches
  
  • Emerge from lateral fissure to supply lateral aspect of cerebral hemisphere (cortex and the underlying white matter)
  • Parts of the cerebral hemisphere it supplies includes lateral parts of frontal and parietal lobes and the superior temoral lobe
• Deep branches (lenticulostriate arteries):
  
  • Supply deep grey matter structures including lentiform nucleus, caudate nucleus and the internal capsule

Question 7

Which cerebral artery is a direct continuation of the ICA?

Answer 7

Middle cerebral artery (it is the largest of the cerebral arteries)

Question 8

Discuss the path of the anterior cerebral artery

Answer 8

• Branch of internal carotid
• Left and right anterior cerebral arteries anastomose in midline via anterior communicating artery
• Vessels loop over corpus callosum and send branches to the adjacent cortex

Question 9

Discuss which areas of the brain the anterior cerebral arteries supply

Answer 9

*Remember, it loops over corpus callosum and sends branches to adjacent cortex

• Cortical branches supply:
  
  • Medial aspect of frontal lobe
  • Medial aspect of parietal lobe
• Also branches to corpus callosum

*NOTE: in image, A= anterior cerebral arteries, M=middle cerebral arteries, P=posterior cerebral arteries

Question 10

What is the basilar artery and where is it found?

Answer 10

Midline vessel formed by confluence/anastomoses of the vertebral arteries

Question 11

State the branches of the basilar artery

Answer 11

• Anterior inferior cerebellar artery
• Pontine arteries
• Superior cerebellar artery
• Posterior cerebral artery (terminal bifurcation of the basilar artery)

Question 12

The posterior cerebral arteries are the terminal bifurcation of the basilar artery; describe which areas of the brain the posterior cerebral arteries supply

Answer 12

• Occipital lobe
• Inferior temporal lobe
• Thalamus (via thalamoperforator and thalamogeniculate branches)
• Midbrain en passant

*Then remember posterior communicating arteries branch from these to connect with anterior circulation

Question 13

Posterior cerebral arteries supply the thalamus via what two branches?

Answer 13

• Thalamoperforator
• Thalamogeniculate

Question 14

What are the lenticulostriate arteries?

Answer 14

Deep branches of the middle cerebral artery that supply deep grey matter structures including the lentiform nucleus, caudate nucleus and internal capsule

Question 15

Describe the arterial supply to the cerebellum (include which arteries supply what region of cerebellum and which artery they have branched from)

Answer 15

• Superior cerebellum= superior cerebellar artery (branch of basilar artery)
• Anterior inferior cerebellum= anterior inferior cerebellar artery (branch of basilar artery)
• Posterior inferior cerebellum= posterior inferior cerebellar artery (branch of vertebral artery)

*NOTE: since these branches pass over brainstem as basilar artery is ventral to brainstem the branches also supply the brainstem as they pas over it (more detail on another flashcard)

Question 16

Describe the arterial supply to the brain (include which arteries supply with region and where these arteries branch from)

Answer 16

• Midbrain:
  
  • superior cerebellar artery (branch of basilar artery)
  • branches from posterior cerebral artery
• Pons:
  
  • pontine arteries (branches of basilar artery)
  • anterior inferior cerebellar artery supplies lateral pons (branch of basilar artery)
• Medulla:
  
  • posterior inferior cerebellar artery (branch of vertebral artery)

*REMEMBER: if it runs over it, it will generaly supply it

Question 17

Pontine arteries supply the pons (alongside the anterior inferior cerebellar artery); what fibres do the pontine arteries also supply?

Answer 17

Descending corticospinal fibres

Question 18

Describe the blood supply to the anterior 2/3 of the spinal cord

Answer 18

Anterior spinal arteries converge in midline to supply the anterior 2/3 of spinal cord

Question 19

Describe how someone can get locked in syndrome

Answer 19

• Pontine arteries supply motor pathways to spinal cord
• If blocked, then lose blood supply to motor pathways in spinal cord- leading to locked in syndrome
• =condition in which a patient is aware but cannot move or communicate verbally due to complete paralysis of nearly all voluntary muscles in the body except for vertical eye movements and blinking

Question 20

What structures are in centre of the circle of Willis?

Answer 20

• Pituitary
• Optic chiasm

Question 21

If you have an occlusion in the circle of Willis blood will be able to find another way around and prevent ischaemia; true or false

Answer 21

FALE/not always true

Circle of Willis is highly variable so this may be the case in some individuals and not in others

Question 21

What does the opthalmic artery supply?

Answer 21

Structures of the orbit

Question 22

What is Wallenberg syndrome?

Which artery is occluded in this syndrome?

Answer 22

Wallenberg syndrome is a rare condition in which an infarction, or stroke, occurs in the lateral medulla hence the posterior inferior cerebellar artery must be occluded

Question 23

Where is the basillar artery?

Answer 23

Anterior/ventral to brainstem. So all its branches go posteriorly

Question 24

Which artery would have to be occluded for you to get stroke of the spinal cord?

Answer 24

Anterior spinal artery (can occur after aortic aneuryseum)

Question 25

What deficits would you experience if you occluded the posterior cerebral arteries?

Answer 25

Posterior cerebral arteries supplies occpital lobe, inferior temporal lobe and thalamus hence can get deficits relating to any of these.

If lack of blood supply to thalamus will get somatosensory problems because remember for both DMCL and spinothalamic tracts the second order neurones syanapse with third order neurones in thalamus

Question 26

If a patient presents with the following where would you hypothesise the stroke to be and why:

• Paralysis of lower limb
• Paralysis of face and upper limb

Answer 26

• Paralysis of lower limb: anterior cerebral artery because this supplies medial aspect of frontal and aprietal lobes- lower limb is medial aspect of homunculus
• Paralysis of upper limb: middle cerebral artery because this supplies the lateral aspect of frontal and parietal lobes aswell as superior temporal lobe- upper limb and face is lateral aspect of homunculus

Question 27

Which artery is most commonly involved in stroke?

Answer 27

Middle cerebral artery

Question 28

Where is the internal capsule?

Answer 28