Neuro7 - Arterial Supply to the Brain

Question 1

Function of the circle of Willis

5 arteries making up the circle of Willis

Answer 1

Function - collateral circulation to the brain
- narrowing redirects blood flow, preserving perfusion
- however, the circle is highly variable between people so this may not always work perfectly

1.) Anterior Cerebral Artery - left and right
- anastamoses of the L/R internal carotid artery

2.) Anterior Communicating Artery
- anastomoses of the L/R anterior cerebral artery

3.) Internal Carotid Artery - left and right
- the MCA is not considered part of the circle

4.) Posterior Communicating Artery - left and right
- anastamoses of the anterior and posterior circulation
- connects ICA/MCA to the posterior cerebral artery

5.) Posterior Cerebral Artery - left and right
- forms the base of the circle of willis

Question 2

3 main arteries of the anterior circulation

Internal Carotid (4 branches)
Anterior Cerebral (ACA)
Middle Cerebral (MCA)

Answer 2

1.) Internal Carotid Artery - makes up anterior circulation
- enters the brain via the carotid canal
- branches: ophthalmic, anterior cerebral, posterior communicating, anterior choroidal
- continues into brain as the middle cerebral artery

2.) Anterior Cerebral Artery - supplies the medial aspect of the cerebral hemisphere (frontal and parietal lobes)
- vessels loop over the corpus callosum (supplying it) and sends branches to the medial cortex

3.) Middle Cerebral Artery - supplies the lateral aspect of the cerebral hemisphere (frontal, parietal and superior temporal lobe)
- emerges through the lateral/sylvian fissure
- contains largest territory so most involved in strokes
- also supplies the deep white matter and structures
- distally splits into superior and inferior divisions

Question 3

8 main arteries of the posterior circulation

Vertebral and Anterior Spinal
Basilar and Pontine
Posterior Cerebral
Cerebellar x3

Answer 3

1.) Vertebral Arteries - makes up posterior circulation
- right and left anastomose to form the basilar artery

2.) Anterior Spinal Artery - comes off L/R vertebral arteries and anastomoses, travelling downwards
- supplies anterior 2/3 of the spinal cord
- occlusion/damage –> spinal cord stroke

3.) Basilar Artery - midline artery
- bifurcates distally to form the left and right PCA

4.) Pontine Arteries - multiple branches off basilar
- supplies the pons (motor pathways to the spinal cord)
- occlusion –> ‘locked in syndrome’, where all you can move is your eyes

5.) Posterior Cerebral Artery - supplies the posterior aspect of the cerebral hemisphere (occipital and inferior temporal lobe)
- formed by the bifurcation of the basilar artery
- loops around the midbrain to reflect it’s shape
- deep branches also supplies the midbrain

6.) Cerebellar Arteries - supplies cerebellum/brainstem
- superior cerebellar: branch off basilar near PCA and also supply the midbrain
- anterior inferior cerebellar: branch off basilar under pontine arteries also supplying the pons
- posterior inferior cerebellar: branch off vertebral arteries also supplying the medulla

Question 4

Deep branches of the MCA and PCA

Distal Divisions of the MCA
Deep Branches of the MCA
Deep Branches of PCA x2

Answer 4

1.) Distal Divisions of the MCA
- superior: lateral frontal lobe (inc PMC and Broca’s area)
- inferior: lateral parietal lobe and superior temporal
lobe (sensory cortex, Wernicke’s, optic radiations)

2.) Deep Branches of the MCA - lenticulostriate arteries
- lentiform nucleus, internal capsule, and basal ganglia
- multiple branches off the proximal MCA

3.) Deep Branches of PCA - supplies thalamus (midbrain)
- thalamogeniculate and thalamoperforator arteries
- supplies the LGN and medial wall of lateral ventricle
- occlusion affects the somatosensory system