Arterial supply to the brain

Question 1

Which arteries make up the anterior and posterior circulation of the brain?

Answer 1

Anterior: ICA (off aortic arch)

Posterior: vertebral arteries (branches of subclavian a), ascends through transverse foramina of C1-C6 (not C7)

Question 2

What are the main branches of the ICA (anterior circulation)?

Answer 2

• Opthalmic a (1st branch off ICA)
• Anterior cerebral a
• Middle cerebral a (largest artery supplying largest territory)
• (Anterior choroidal a)

Question 3

What is the name of the artery that connects the 2 anterior cerebral arteries on either side?

Answer 3

Anterior communicating artery; site of anastamosis between L + R anterior cerebral a’s

Question 4

Which structures do the anterior cerebral arteries supply?

Answer 4

• Course towards midline and arch over corpus callosum
• Along medial aspect of hemispheres
• Supply medial apsect of hemispheres

Question 5

Which structures do the middle cerebral arteries supply?

Answer 5

• Lateral surface of cerebral hemispheres
• Incl deeper structures, cortex, deep white matter (via deep branches)
• Courses laterally

Question 6

What are the main divisions of the middle cerebral artery that supply the lateral surfaces of hemispheres?

Answer 6

• MCA superior division
• MCA inferior division

Divisions of the middle cerebral artery system

Question 7

Via what branches does the middle cerebral artery supply deeper structures of the brain?

What deeper structures does this artery supply?

Answer 7

Lenticulostriate arteries; small branches of MCA​​

Supplies;

Internal capsule; pathway connecting cortex to rest of CNS

Basal ganglia

Question 8

Relate the arterial supply of the brain and homunculus to the presentations of strokes occluding different arteries

Answer 8

Homunculus:

• Lower limbs represented MEDIALLY
• Upper limbs/face represented LATERALLY

Thus;

Stroke due to anterior cerebral a occlusion = lower limb paralysis (ACA supplies medial aspects of hemispheres)

Stroke due to middle cerebral a occlusion = face/upper limb paralyssis (MCA supplies lateral aspects of hemispheres)

Question 9

Which artery connects the anterior and posterior circulations of the brain?

Answer 9

Posterior communicating artery

Question 10

Name the 2 main branches of the vertebral arteries

Answer 10

• Anterior spinal; supplies anterior 2/3 of spinal cord
• Posterior inferior cerebellar a; supplies posterior inferior aspect of cerebellum, medulla

Question 11

Which midline artery is formed by joining of the 2 vertebral arteries?

Answer 11

Basilar artery

Question 12

Name the main branches of the basilar artery and the structures they supply

Answer 12

• Pontine arteries; pons, including descending corticospinal fibres (occlusion can cause locked-in syndrome; loss of motor pathways descending down to brainstem + cord)
• Anterior inferior cerebellar a; cerebellum, pons
• Superior cerebellar a; cerebellum, midbrain
• Posterior cerebral a; courses posteriorly; supplies occipital lobe + inferior temporal lobe

Question 13

What structure do cerebellar arteries supply en passent?

Answer 13

Brainstem;

Midbrain- superior cerebellar a

Pons- anterior inferior cerebellar a

Medulla- posterior inferior cerebellar a

Question 14

Which structures does the posterior cerebral artery supply?

Answer 14

• Posterior cerebrum
• Occipital lobe; visual system
• Inferior temporal lobe
• Thalamus (via thalamoperforator + thalamogeniculate branches)
• Midbrain en passent

Postero-inferior aspect of cerebrum

Question 15

Via which branches does the posterior cerebral artery supply the thalamus?

Answer 15

Thalamoperforator + thalamogeniculate branches

Question 16

Apart from the postero-inferior cerebrum and thalamus, what other structure does the posterior cerebral artery supply?

Answer 16

Midbrain (brainstem) en passent

Thus, posterior circulation infarcts can affect the brainstem

Question 17

What would be the result of occlusion of the pontine arteries (branches of basilar a)?

Answer 17

• Pontine a’s: supply pons, travel along anterior aspect of pons
• Supply motor pathways down to spinal cord
• LOCKED IN SYNDROME; destroyed descending motor pathways to brainstem + cord

Question 18

Why can occlusion of the posterior cerebral artery affect the somatosensory system?

Answer 18

As the thalamoperforator and thalamogeniculate branches of the posterior cerebral artery can be affected, which supply the thalamus

Question 19

Draw an overview of the blood supply to the brain

Answer 19

Question 20

Which artery is most commonly affected by stroke?

Answer 20

Middle cerebral artery