Lecture 7- Cerebral blood supply to the brain

Question 1

summary of posterior circulation

Answer 1

• Vertebral artery join together to form basilar artery
  
  • Branches of VA
    
    • Posterior inferior cerebellar arteries (PICA)
    • Anterior spinal artery
      
      • Branches come off each VA to converge and form the ASA (runs down surface of the spinal cord)
    • Anterior inferior cerebellar arteria (AICA)
• Basilar artery- one of the few midline arteries in the body (use as main landmark)
  
  • Branches of BA
    
    • Many small branches going into the pons- Pontine arteries (supplying corticospinal fibres running down through the pons)
    • Superior cerebellar artery
    • 2 posterior cerebral arteries

Question 2

summary of anterior circulation

Answer 2

• Internal carotids ascend up carotid canal and become the middle cerebral arteries
  
  • Other branches of internal carotids
    
    • Anterior cerebral arteries
      
      • Anterior communicating arteries connect both ACAs
    • Posterior communicating arteries (connect anterior and posterior circulation)

Question 3

physiological relevance of circular arrangement

Answer 3

Blockage at one point can be compensated for by blood flowing in retrograde manner to bypass blockage

Question 6

the middle cerebral artery arises as a continuation of the

Answer 6

internal carotids

Question 7

course of the MCA

Answer 7

• Run laterally and go over the insular cortex and emerges through sylvian (lateral fissure) fissure onto the surface of the cerebral hemisphere
  
  • Branches of the MCA= the lenticular striate arteries

Branches of the MCA emerge superiorly and inferiorly from the sylvian fissure

Question 8

which parts of the brain does middle cerebral artery supply

Answer 8

Supplies very large area of the brain

• Branches of the MCA emerge superiorly and inferiorly from the sylvian fissure (look at third photo) supplying the lateral aspect of the cerebral hemisphere supplying some
  
  • Frontal
  • Parietal
  • Temporal lobes
• Also supplies some deeper structures

Question 9

If MCA occluded e.g. stroke

Answer 9

• Primary motor cortex could be affected
• Lenticular striate arteries some of the most common arteries to be blocked
• Fibres in optic radiation can be affected

Question 10

The lenticulostriate (lateral striate) arteries

• Most commonly occluded arteries in stroke
  
  • Can lead to lacunar stroke/infarct (very diverse clinical effects)
• Numerous very small branches
• Lenticulostriate arteries branch of the MCA as it runs laterally and into the lentiform nucleus and into the internal capsule and sometimes into the thalamus

Question 11

lacunar stroke

Answer 11

shows tiny holes (lacunar) caused by blockage of lenticulostriate arteries- tiny stroke

• Can be found in the:
  
  • Basal ganglia
  • Internal capsule
  • Near the thalamus

Question 12

lacunar stroke in the basal ganglia

Answer 12

parkinsonian disorder

Question 13

lacunar in the internal capsule

Answer 13

• If lacunar occurs here- pure motor stroke since internal capsule mostly contains cortical spinal projections

Question 14

lacunar stroke in the thalamus

Answer 14

pure sensory stroke (sensory relay station)

Question 15

course of the ACA

Answer 15

• Arises as one of the branches of the internal carotid (as well as MCA)
  
  • Grey matter distribution: ACA loops back all over the superior surface of the corpus callosum and sends multiple branches to the medial aspect of the cerebral hemisphere (mostly frontal and parietal lobes)
  • White matter distribution: as the ACA loops around the CC it will send lots of branches into the white matter of the CC

Question 16

which parts of the brain does the ACA suppluy

Answer 16

• Doesn’t actually supply many anterior structures
• Supplies structures near to the midline

Question 17

If ACA occluded e.g. stroke

Answer 17

• Will mostly affect lower half of body- due to medial distribution (think homunculus)
• Could also cause damage to CC- causing disconnection between the 2 hemispheres

Question 18

Subfalcine herniation

Answer 18

Most common form of intracranial herniation and occurs when calcarine sulcus is pushed under the falx cerebri compressing the ACA leading to stroke syndrome

Question 19

course of the PCA and which areas of the brain it supplies

Answer 19

Posterior cerebral arteries

• Arises as a bifurcation from the basilar artery
• Loop around midbrain and run along the inferior surface of the posterior hemisphere
  
  • Cortical distribution: supplying the occipital lobe and the inferior aspect of the temporal lobe
  • Subcortical (inner structures) distribution: branches of the PCA supply the midbrain and perforating branches up to the thalamus

Question 20

If PCA occluded e.g. stroke

Answer 20

• Visual disturbances (O)
• Auditory processing problems (T)
• Memory problems (T)

Question 21

The vertebra-basilar system

Answer 21

Main distribution network for the posterior circulation of the brain- i.e. the cerebellum and brainstem

Question 22

blood supply to the midbrain, pons and cerebellum

Answer 22

• Left vertebral artery forms basilary artery (running over surface of the pons)
• Basilar artery bifurcates into the Posterior Cerebral Artery and just proximally the superior cerebellar artery –> both supplying the midbrain as they reach their ultimate targets
  
  • Pontine branches on the basilar artery supply the pons
  • Important to ensure the cortical spinal tract is perfused
    
    • If occluded and not perfused- locked in syndrome (can only move eyes)
      
      • Cortical spinal tract death –> no movement
      • Midbrain still supplied so can move eyes
• Anterior inferior cerebellar arteries supply the inferior surface if the cerebellum. Pons also receives branches from the AICA
• Posterior inferior cerebellar artery (PICA) supplies the posterior inferior surface of the cerebellum. Medulla oblongata also receives branches from the PICA
  
  • If blockage distal- cerebellar stroke
  • If blockage proximal – brainstem stroke
• Anterior medulla is supplies by branches coming off the vertebral arteries itself

Question 23

locked in syndrome

Answer 23

if cortical spinal tracts not suppplied by the pontine branches on the basilar artery

• Cortical spinal tract death –>no movement
• Midbrain still supplied so can move eyes

Question 24

Arterial supply to the cord

• *

Answer 24

• Major vessels
  
  • Anterior spinal artery (runs in the anterior sulcus of spinal cord)
    
    • Arises as the confluence of 2 branches of VA
    • Supplies anterior 2/3 of spinal cord
  • Paired posterior spinal artery (dorsal aspects)
    
    • Supplies posterior1/3 of spinal cord

Question 25

what supplies the anterior and posterior spinal artery

Answer 25

• segmental a. coming off the aorta
• Another important artery to think about: Adamkiewicz arteries major tributary to the lower part of the spinal cord
  
  • Particularly vulnerable in AA aneurysm repairs –> spinal cord syndromes

Question 26

Different tracts fall under

Answer 26

diff territories of spinal arteries

Question 27

Anterior spinal artery supplies the

Answer 27

anterior 2/3 of the spinal cord

• Including
  
  • Grey matter of ventral horn
  • Corticospinal tract
  • Spinothalamic tract

Question 28

• Posterior spinal arteries supply the
  *

Answer 28

posterior 1/3 of the spinal cord

• Including
  
  • Most of dorsal horn
  • Dorsal column

Question 29

Can we predict clinical effect of blockage of PSA or ASA?

Answer 29

yes

Question 30

ASA blockage​

Answer 30

• Midline vessel
  
  • Bilateral effect
  • Loss of spinothalamic tract modality below level of blockage
  • Upper motor neurone signs below level of blockage de to interruption of CST

Question 31

PSA blockage (less common)