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Sc 25 David's weakness > Blood supply to the Brain > Flashcards

Blood supply to the Brain Flashcards

1
Q

Brain

  • Has immense metabolic needs
A

Brain:

  • 2% of body weight
  • receives 17% of cardiac output
  • uses 20% of oxygen consumed by whole body

RAPID LOSS OF CONSCIOUSNESS IF BLOOD SUPPLY INTERRUPTED

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2
Q

What are the 2 arterial routes to the brain?

A
  • Internal carotids
  • Vertebral Arteries
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3
Q

Internal Carotid Artery

Forms the Anterior circulation

Course: Very sinuous course lateral to body of sphenoid bone emerging adjacent to optic chiasm.

A
  • Enters the Cranium via the Carotid Canal into the Middle Cranial Fossa
  • Opthalmic Artery
    • ​pre-terminal branch; passes into orbit via the optic foramen
    • major blood supply to the eye
    • Central artery of the retina
      • ​end-artery; occulsion leads to blindness as it’s the only supply to there
  • Hypophyseal arteries - arise from intra-cavernous section of ICA to supply the neurohypophysis
  • 2 terminal branches (ICA terminates lateral to the Optic Chiasm and gives rise to):-
    • Anterior cerebral - the two are linked by the anterior communicating artery
    • Middle Cerebral
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4
Q

Vertebral arteries

Ascend through the upper six cervical vertebrae to enter the cranium via the FORAMEN MAGNUM

Course: Run along the lateral surface of the medulla before fusing together on the ventral surface of the Pons to form the Basilar artery.

A

Main branches:

  • Posterior cerebral artery-
    • principal terminal branch of the basilar, supplies the occipital lobe of the cerebral hemisphere
    • posterior communicating arteries pass between here and the internal carotid artery on each side
  • Basilar artery
    • fusion of left and right vertebral artery
  • Left & right verterbral arteries individually

Branches of the subclavian arteries in the root of neck

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5
Q

Circle of Willis:

A
  • Connects the anterior and posterior circulations
  • Surrounds the optic chiasm and pituitary on base of brain and lies under the Internal Capsule
  • Arterial supplies from the Internal Carotid and the Vertebral Arteries anastomose together here
  • Anastomoses provide an alternative route for arterial supply if normal route is occluded
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6
Q

Blood supply to the Cerebellum and the Peduncles

A
  • Superior cerebellar artery,
  • anterior cerebellar artyery
  • inferior cerebellar artery
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7
Q

Why is the Basilar artery important to the PONS?

A
  • It has lots of pontine branches that come off it (the Basilar) that supply the PONS
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8
Q

What is the blood supply to the inner ear?

A

Labryinthine Artery, which is a branch of the Anterior Inferior Cerebellar Artery

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9
Q

What from the Circle of Willis supplies the hypothalamic area, the basal ganglia and the internal capsule?

A

Small perforating arteries that arises from the Circle of Willis supply these areas

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10
Q

Middle Cerebral Artery

A
  • Largest of the three cerebral arteries
  • Passes into the lateral fissure and supplies the lateral aspect of the cerebral hemisphere
  • Commonly affected in stroke
  • Supplies the lateral cortical areas including; primary motor and sensory areas, receptive speech area, auditory area and Broca’s expressive speech area.
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11
Q

Occlusion of the MCA leads to:

A
  • Contralateral paralysis & sensory and motor deficits of lower face area
  • Aphasia (if dominant hemisphere, usually the left)
  • Hemianopia (loss of part of visual field, not being able to see either the R or L from the centre of your field of vision) of contralateral visual fields (thalamo-visual cortex tract)
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12
Q

Anterior Cerebral Artery

A
  • Courses medially above the optic nerve and passes into the great longitudinal fissure, between the frontal lobes of the cerebral hemispheres.
  • Supplies:
    • motor and sensory cortices for the lower limb
    • narrow lateral band of frontal and parietal cortices
    • medial surfaces of the frontal and parietal lobes
    • corpus callosum
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13
Q

Occlusion of the ACA leads to:

A
  • Paralysis and sensory deficits to CONTRALATERAL leg and perineum
  • Mental confusion and dysphasia
  • *Sometimes contralateral face, tongue and upper limb due to internal capsule
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14
Q

Posterior Cerebral Artery

A
  • Principal terminal branch of the basilar artery
  • Supplies
    • occipital and temporal lobes of the cerebral hemisphere
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15
Q

Occlusion of the PCA leads to:

A
  • Blindness in contralateral visual field
  • Hippocampal memory problems, but usually only short term
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16
Q

What supplies the Medial rim of lateral surface of the Cerebral Hemispheres?

A

Anterior and posterior cerebral arteries

  • rim is susceptible to watershed infarcts as it is supplied by the most distal branches that come off the cerebral arteries.

Watershed infarcts - around the rim; common in large heart attacks with large drop in B.P

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17
Q

What kind of shape is the Carotid canal?

A

S shaped

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18
Q

What supplies the Internal Capsule and parts of the Basal Ganglia?

A
  • Supplied by relatively small “central” or “perforating” arteries that branch from the Circle of Willis, largely supplied by the anterior and middle cerebral arteries.
  • Occlusion or rupture of these arteries can cause:
    • contralateral motor and sensory deficits
19
Q

What supplies the Ventral Midbrain

A
  • Posterior Central or
  • perforating arteries (supply the inner tissues of the brain)
20
Q

What are the Internal Capsule and Basal Ganglia supplied by?

A

Perforating Arteries

  • Recurrent Artery of Heubner
    • ​comes off the Ant. Cerebral Artery
    • @ lvl of Optic Chiasm usually
  • Lenticulostriate arteries
    • ​arise @ commencement of the MCA
21
Q

What makes up the Brainstem?

A
  • Medulla
  • Pons
  • Cerebellum
22
Q

What supplies the Pons and Cerebellum?

A

Basilar Artery

23
Q

What supplies the Medulla?

A

Vertebral Artery

24
Q

Occlusion of the Vertebral and Basilar arteries lead to?

A
  • Instantly fatal due to coma (reticular formation) and loss of respiratory control
  • Cerebellar defects
  • Cranial nerve defects
  • Deafness if labyrinthine artery affected
  • Infarction of ventral pons, leads to loss of all voluntary movements except eyes, the senses are spared - LOCKED IN SYNDROME
25
Q

Which artery supplies which bit of the brain?

ACA

MCA

PCA

A
26
Q

Anastamoses

Good?

A

provide an alternative route for arterial supply if normal route occluded

27
Q

When are anastamoses bad?

A

Aneurysms

Berry aneurysm:

  • sub-arachnoid haemorrhage can occur if this bursts
  • v high mortalitly and morbidity
  • can occur anywhere around C of Willis
  • it is a swelling of the blood vessel

coiling of the berry aneursym can clot off the aneurysm - surgical procedure

28
Q

Hemiparesis

A

Weakness of the entire Left OR Right side of the body

29
Q

Hemiplegia

A

most severe form of hemiparesis

complete paralysis of half of the body

30
Q

Where do intracranial veins drain into?

A

Dural venous sinuses

e.g. Superior Sagittal venous sinus

31
Q

Venous Drainage of the brain

A
  • Deep and superficial veins of the brain drain into the dural venous sinuses then into internal jugular via the jugular foramen in posterior cranial fossa

Venous sinuses are enclosed by dural folds and lined by endothelium

32
Q

How does the sigmoid sinus exit the skull?

A

via the Jugular foramen into the “superior jugular bulb” (inital dilated bit of) the Internal Jugular Vein

33
Q

Middle Meningeal Artery

A
  • branch of the maxillary artery
  • enters the intracranial region via foramen spinosum
  • supplies bones of the vault
34
Q

What can usually happen to the Pterion and what are its consequences?

A

Usally fractured since it is weak

can lead to MMA damage and bleeding

causing an EXTRA-DURAL HAEMORRHAGE

35
Q

What is the blood supply to the spinal cord?

comes from high up and has to travel all the way down the spinal cord

A

2 different sources:

  • Spinal arteries
    • posterior
    • anterior
  • Radicular arteries

This dual system makes stroke of the spinal cord v rare

36
Q

Spinal Arteries

where do they come from?

A

Posterior spinal arteries:

  • from the Vertebrals or Posterior Inferior Cerebellar

Anterior Spinal arteries:

  • from the Vertebrals
37
Q

Radicular arteries

where do they come from and what do they enter through?

A
  • From segmental arteries;
    • which branch from the aorta in thoracic and lumbar regions
  • Enter via the Interverbral Formaina
  • Come in with the nerve roots
  • become more prominent the further away you go from the brain
    *
38
Q

Venous drainage of Spinal cord

A
  • Posterior spinal vein
  • Anterior spinal vein
  • posteriolateral spinal vein
  • radicular veins

All drain into the INTERNAL VERTEBRAL VENOUS PLEXUS

39
Q

What are the 2 types of stroke?

A

Haemorrhagic:

  • bleeding

Ischaemic:

  • Lack of blood
  • Occluded artery
40
Q

Extradural haemorrhage

A
  • between skull and dura,
  • e.g. from meningeal arteries may be higher pressure, more prolonged, push onto brain
41
Q

Subdural haemorrhage

A
  • between dura and arachnoid,
  • e.g. from superior cerebral vein, low pressure, slow accumulation, clots in subdural space and pushes on brain

COMMON IN THE ELDERLY

42
Q

Sub-arachnoid haemorrhage

A
  • between arachnoid and pia,
  • e.g. from ruptured aneurysms in Circle of Willis, sudden, very painful, one cause of a “stroke”, bleeds into sub-arachnoid space
43
Q

Intracerebral haemorrhage

A
  • within brain tissue itself
  • another cause of stroke
  • usually occurs when on blood thinners etc

Sc 25 David's weakness (8 decks)

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