Blood Supply of Telencephalon and Diencephalon

Question 1

How many anterior and posterior communicating arteries are there? Where does posterior come off?

Answer 1

One anterior and two posterior communicating arteries.

Posterior: most rostral branchecs of basilar artery

Question 2

What forms the Circle of Willis?

Answer 2

1. Anterior communicating artery
2. Posterior communicating arteries
3. Proximal parts of anterior, middle, and posterior cerebral arteries

Question 3

Why is there normally little exchange of blood between the right and the left sides of the brain?

Answer 3

The cerebral arterial circle equalizes blood flow

Question 4

What branches primarily supply the diencephalon, basal ganglia, and internal capsule?

Answer 4

Central branches of Circle of Willis

Question 5

Where does the anterior cerebral artery arise and where does it run?

Answer 5

Arises from internal carotid as the anterior communicating artery, in a loop passes dorsal to optic nerve, moving medially until it communicates with opposite side of anterior communicating artery.

Runs in longitudinal fissure, in medial surface of hemisphere and posteriorly on superior surface of corpus callosum + other medial gyri

Question 6

Where does the anterior cerebral artery end? Where do its branches extend?

Answer 6

Just rostral to the parietoccipital sulcus

Branches extend onto the lateral convexity of the cerebral cortex

Question 7

What does occlusion of the anterior cerebral artery cause?

Answer 7

Loss of blood supply to paracentral lobule: contralateral motor and sensory loss of the lower limb.

Also, reappearance of contralateral grasp reflex from frontal lobe lesion

Question 8

What is the origin of the middle cerebral artery considered to be?

Answer 8

The continuation of the internal carotid artery

Question 9

What is the course of the middle cerebral artery? What are its two branches?

Answer 9

Enters the lateral fissure, between temporal lobe and insula

Superior branch: Supplies the lateral convexity of the superior hemisphere

Inferior branch: Courses downward from lateral fissure, supplies temporal lobe

Question 10

What critical gyri does the middle cerebral artery NOT supply?

Answer 10

Superior frontal gyrus - supplied by anterior cerebral artery

Inferior temporal gyrus - supplied by posterior cerebral artery

Question 11

What artery supplies the superior parietal lobules?

Answer 11

Anterior cerebral artery

Question 12

What are the possible symptoms of MCA branch occlusion (highly variable)? Think of vision

Answer 12

Contralateral spastic paralysis - sparing lower limb
Contralateral sensory loss - sparing lower limb
Broca’s and Wernicke’s aphasia
Optic radiations ischemia could lead to one-sided visual deficit

Question 13

What can cause global aphasia?

Answer 13

If both anterior and posterior branches of MCA are occluded

Question 14

What can cause left hemineglect + left visual field and somatosensory deficits?

Answer 14

Occlusion of right MCA in region of inferior parietal lobule

Question 15

What is the most diagnostic feature of MCA occlusion?

Answer 15

Gaze preference towards side of lesion, due to destruction of frontal eye field on that side.

Question 16

What forms the posterior cerebral artery?

Answer 16

Bifurcation of the basilar artery

Question 17

What is the course of the posterior cerebral artery?

Answer 17

Courses laterally over cerebral peduncles, then on medial + inferior surfaces of temporal and occipital lobes

Question 18

What happens when the PCA is occluded always?

Answer 18

Contralateral homonymous hemianopsia

Question 19

What happens if PCA occlusion extends to splenium of corpus callosum?

Answer 19

Alexia without agraphia -> cannot read (no vision) but is able to write, as Wernicke’s + Broca’s are intact

Question 20

What can happen in large PCA infarcts?

Answer 20

Involvement of thalamus + internal capsule, leading to aphasia (if left dominant hemisphere) + affects from internal capsule lead to hemiparesis + hemisensory loss

Question 21

What is the etiology of macular sparing?

Answer 21

This area of area 17 is saved in PCA infarct since it is supplied by both MCA and PCA.

Question 22

What are the three important arteries of the central arteries?

Answer 22

1. Medial striate artery (recurrent artery of Heubner)
2. Medial lenticulostriate arteries (MLSA)
3. Lateral lenticulostriate arteries (LLSA)

Question 23

Where does the medial striate artery arise? What does it supply?

Answer 23

Anterior cerebral artery (largest branch)

Supplies the head of the caudate + putamen + anterior limb of internal capsule

Question 24

Where do the medial lenticulostriate arteries arise? What do they supply?

Answer 24

Arise from proximal middle cerebral artery

Supply globus pallidus and medial putamen (lenticular formation)

Question 25

Where do the lateral lenticulostriate arteries arise?

Answer 25

Arise from distal middle cerebral artery

Question 26

Where do the anterior choroidal arteries arise and what do they supply?

Answer 26

Arise from internal carotid, and supply the choroid plexus, hippochampus, basal ganglia, and posterior limb of internal capsule + LGN thalamus

Question 27

What does occlusion of anterior choroidal artery cause?

Answer 27

Contralateral homonymous hemianopsia (due to LGN lesion)

Question 28

What do the posterior choroidal arteries arise from and what do they supply?

Answer 28

Arise from posterior cerebral arteries, supply dorsal midbrain (tectum / colliculi) + diencephalon and choroid plexus of 3rd and lateral ventricles