Blood Supply of Telencephalon and Diencephalon Flashcards
How many anterior and posterior communicating arteries are there? Where does posterior come off?
One anterior and two posterior communicating arteries.
Posterior: most rostral branchecs of basilar artery
What forms the Circle of Willis?
- Anterior communicating artery
- Posterior communicating arteries
- Proximal parts of anterior, middle, and posterior cerebral arteries
Why is there normally little exchange of blood between the right and the left sides of the brain?
The cerebral arterial circle equalizes blood flow
What branches primarily supply the diencephalon, basal ganglia, and internal capsule?
Central branches of Circle of Willis
Where does the anterior cerebral artery arise and where does it run?
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
Where does the anterior cerebral artery end? Where do its branches extend?
Just rostral to the parietoccipital sulcus
Branches extend onto the lateral convexity of the cerebral cortex
What does occlusion of the anterior cerebral artery cause?
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
What is the origin of the middle cerebral artery considered to be?
The continuation of the internal carotid artery
What is the course of the middle cerebral artery? What are its two branches?
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
What critical gyri does the middle cerebral artery NOT supply?
Superior frontal gyrus - supplied by anterior cerebral artery
Inferior temporal gyrus - supplied by posterior cerebral artery
What artery supplies the superior parietal lobules?
Anterior cerebral artery
What are the possible symptoms of MCA branch occlusion (highly variable)? Think of vision
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
What can cause global aphasia?
If both anterior and posterior branches of MCA are occluded
What can cause left hemineglect + left visual field and somatosensory deficits?
Occlusion of right MCA in region of inferior parietal lobule
What is the most diagnostic feature of MCA occlusion?
Gaze preference towards side of lesion, due to destruction of frontal eye field on that side.
What forms the posterior cerebral artery?
Bifurcation of the basilar artery
What is the course of the posterior cerebral artery?
Courses laterally over cerebral peduncles, then on medial + inferior surfaces of temporal and occipital lobes
What happens when the PCA is occluded always?
Contralateral homonymous hemianopsia
What happens if PCA occlusion extends to splenium of corpus callosum?
Alexia without agraphia -> cannot read (no vision) but is able to write, as Wernicke’s + Broca’s are intact
What can happen in large PCA infarcts?
Involvement of thalamus + internal capsule, leading to aphasia (if left dominant hemisphere) + affects from internal capsule lead to hemiparesis + hemisensory loss
What is the etiology of macular sparing?
This area of area 17 is saved in PCA infarct since it is supplied by both MCA and PCA.
What are the three important arteries of the central arteries?
- Medial striate artery (recurrent artery of Heubner)
- Medial lenticulostriate arteries (MLSA)
- Lateral lenticulostriate arteries (LLSA)
Where does the medial striate artery arise? What does it supply?
Anterior cerebral artery (largest branch)
Supplies the head of the caudate + putamen + anterior limb of internal capsule
Where do the medial lenticulostriate arteries arise? What do they supply?
Arise from proximal middle cerebral artery
Supply globus pallidus and medial putamen (lenticular formation)
Where do the lateral lenticulostriate arteries arise?
Arise from distal middle cerebral artery
Where do the anterior choroidal arteries arise and what do they supply?
Arise from internal carotid, and supply the choroid plexus, hippochampus, basal ganglia, and posterior limb of internal capsule + LGN thalamus
What does occlusion of anterior choroidal artery cause?
Contralateral homonymous hemianopsia (due to LGN lesion)
What do the posterior choroidal arteries arise from and what do they supply?
Arise from posterior cerebral arteries, supply dorsal midbrain (tectum / colliculi) + diencephalon and choroid plexus of 3rd and lateral ventricles
