Lecture 7- Cerebral blood supply to the brain Flashcards Preview

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Flashcards in Lecture 7- Cerebral blood supply to the brain Deck (31)
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1
Q

summary of posterior circulation

A
  • 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
2
Q

summary of anterior circulation

A
  • 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)
3
Q

physiological relevance of circular arrangement

A

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

4
Q
A
5
Q
A
6
Q

the middle cerebral artery arises as a continuation of the

A

internal carotids

7
Q

course of the MCA

A
  • 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

8
Q

which parts of the brain does middle cerebral artery supply

A

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
9
Q

If MCA occluded e.g. stroke

A
  • 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
10
Q

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
A
11
Q

lacunar stroke

A

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

  • Can be found in the:
    • Basal ganglia
    • Internal capsule
    • Near the thalamus
12
Q

lacunar stroke in the basal ganglia

A

parkinsonian disorder

13
Q

lacunar in the internal capsule

A
  • If lacunar occurs here- pure motor stroke since internal capsule mostly contains cortical spinal projections
14
Q

lacunar stroke in the thalamus

A

pure sensory stroke (sensory relay station)

15
Q

course of the ACA

A
  • 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
16
Q

which parts of the brain does the ACA suppluy

A
  • Doesn’t actually supply many anterior structures
  • Supplies structures near to the midline
17
Q

If ACA occluded e.g. stroke

A
  • 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
18
Q

Subfalcine herniation

A

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

19
Q

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

A

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
20
Q

If PCA occluded e.g. stroke

A
  • Visual disturbances (O)
  • Auditory processing problems (T)
  • Memory problems (T)
21
Q

The vertebra-basilar system

A

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

22
Q

blood supply to the midbrain, pons and cerebellum

A
  • 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
23
Q

locked in syndrome

A

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
24
Q

Arterial supply to the cord

  • *
A
  • 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
25
Q

what supplies the anterior and posterior spinal artery

A
  • 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
26
Q

Different tracts fall under

A

diff territories of spinal arteries

27
Q

Anterior spinal artery supplies the

A

anterior 2/3 of the spinal cord

  • Including
    • Grey matter of ventral horn
    • Corticospinal tract
    • Spinothalamic tract
28
Q
  • Posterior spinal arteries supply the
    *
A

posterior 1/3 of the spinal cord

  • Including
    • Most of dorsal horn
    • Dorsal column
29
Q

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

A

yes

30
Q

ASA blockage

A
  • 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
31
Q

PSA blockage (less common)

A