4.2 Blood supply to the brain

Question 1

what are the 2 main sources of arterial blood supply to the brain?

Answer 1

o The anterior circulation is fed by the internal carotid arteries
o The posterior circulation is fed by the vertebral arteries

Question 2

what is the blood supply to the majority of the cerebral hemispheres?

Answer 2

internal carotid arteries

Question 3

what aspects of the brain are supplied by the vertebral arteries?

Answer 3

brainstem, cerebellum, some of the temporal lobe and the occipital lobe

Question 4

where is the middle cerebral artery?

Answer 4

direct continuation of the internal carotid artery

Middle cerebral arteries run laterally from the internal carotid after it passes through the carotid canal

Question 5

what are the branches of the middle cerebral arteries?

Answer 5

cortical branches = MCA superior division and MCA inferior division
deep branches = lenticulostriate arteries

Question 6

what is the function of the cortical branches of the MCA?

Answer 6

Cortical branches emerge from the lateral fissure (Sylvian fissure) to supply the lateral
aspect of the cerebral hemisphere (cortex and underlying white matter), including lateral parts of the frontal and parietal lobes as well as the superior temporal lobe

Question 7

what is the function of the lenticulostriate arteries?

Answer 7

supply deep grey matter structures:
lentiform nucleus
caudate
internal capsule

Question 8

what are lacunes?

Answer 8

little holes in the brain that occur due to blockage of the tiny lacunar arteries of the MCA

Question 9

what is the clinical outcome of a lacunar stroke?

Answer 9

Clinical outcome depend on location of the lacune. Blockage in internal capsule is likely to create a pure motor stroke. Thalamus is a pure sensory stroke. Basal ganglia is parkinsonian like features. Lacunar strokes very diverse.

Question 10

describe the structure of the anterior cerebral artery?

Answer 10

a branch of the internal carotid artery that run anteriorly and superiorly
anastomose together in the midline via the anterior communicating artery
vessels loop over the corpus callosum and send branches to the adjacent cortex

Question 11

what does the anterior cerebral artery supply?

Answer 11

medial structures of the cerebral hemispheres:
corpus callosum
medial parietal and frontal lobes
anterior most aspect of the frontal lobe

Question 12

why can a sub falcine herniation lead to a secondary stroke?

Answer 12

a sub falcine herniation occurs when there is mass effect causing medial direction of the ipsilateral cingulate gyrus beneath the free edge of the falx cerebri due to raised intracranial pressure. This can compress the anterior cerebral artery causing an anterior storke

Question 13

what is the basilar artery?

Answer 13

Midline vessel formed from the confluence of the vertebral arteries

Question 14

what is the posterior communicating arteries?

Answer 14

2 paired arteries in the brain that occur during the terminal bifurication of the basilar artery.
connects the anterior circulation to the posterior circulation to form the circle of willis

Question 15

what does the basilar artery supply?

Answer 15

Supplies occipital lobe, inferior temporal lobe and
thalamus (via thalamoperforator and thalamogeniculate branches)
Also supplies midbrain en passant

Question 16

what is the blood supply to the midbrain?

Answer 16

superior cerebellar

posterior cerebral artery

Question 17

what is the blood supply to the pons?

Answer 17

the pontine arteries

Question 18

describe the blood supply to the cerebellum

Answer 18

Superior cerebellar artery supplies the superior aspect of the
cerebellum and midbrain en passant
Anterior inferior cerebellar artery the supplies the antero-
inferior aspect of the cerebellum and lateral pons en passant
Posterior inferior cerebellar arteries supply the inferior aspect of the cerebellum and also the lateral aspect of the medulla

Question 19

before converging to form the basilar artery the vertebrae arteries give 2 important branches. what are they?

Answer 19

Anterior spinal arteries converge in the midline to supply the anterior
2/3 of the spinal cord
Posterior inferior cerebellar arteries supply the postero-inferior aspect of the cerebellum en passant

Question 20

describe the blood supply to the spinal cord

Answer 20

The anterior and 2 posterior spinal arteries are fed with blood throughout most of the length of the cord by segmental vessels coming off of the aorta. At the top of the cord, the anterior spinal artery arises from the confluence of two branches of the vertebral arteries.

Question 21

what parts of the spinal cord is supplied by the posterior spinal arteries?

Answer 21

dorsal 1/3 of the spinal cord
dorsal column pathway
some or most of the dorsal horns

Question 22

what parts of the spinal cord is supplied by the anterior spinal artery?

Answer 22

anterior 2/3rds of the spinal cord

• all of the ventral horns and some of the dorsal horns sometimes
• spinothalamic tracts
• lateral cortical tracts

Question 23

what would be the clinical manifestation of a blockage of the anterior spinal artery?

Answer 23

bilateral loss of spinothalamus tract modalities below the level of the blockage and upper motor neurone signs below the level of the blockage due to interruption of the corticospinal tract.

Question 24

what would be the clinical manifestations of a blockage of the posterior spinal artery?

Answer 24

If blocked we can get bilateral but more often than not we get unilateral affects as the posterior spinal arteries are not midline and are instead paired. Would get ipsolateral loss of dorsal column modalities below the level of the lesion.