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Brain and Behaviour Year 2 > Blood Supply to the Brain > Flashcards

Blood Supply to the Brain Flashcards

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1
Q

How much of body weight does the Brain take up in percentage

A
  • 2% of body weight
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2
Q 
what amount of 
- cardiac output 
- total body oxygen 
- totally body glucose 
does the brain receive
A
  • Receives 15% if cardiac output
  • uses 20% of total body oxygen
  • 25% of total body glucose
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3
Q

What is the average brain blood flow

A

46ml/100g of brain per minute

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4
Q

How much time of anoxia leads to unconsciousness and then permanent unconsciousness

A
  • 20 seconds of anoxia lead to unconsciousness – means that short term storage of glucose and oxygen means that there is 20 seconds of anoxia before unconsciousness
  • Greater than 5 minutes of anoxia leads to permanent unconsciousness (coma which can potentially be reversible, but longer than 5 minutes can cause death)
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5
Q

how is blood flow in the brain regulated

A
  • Flow is regulated by autoregulation so you maintain 46ml/per 100g of brain - Normotensive cerebral blood flow = ~50mL per 100g of brain tissue per min if cerebral perfusion pressure between 60-160mmHg on systolic can have serious low blood pressure and the brain will still be perfused
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6
Q

What are the arteries like in the brain

A
  • Arteries are thin walled, easily blocked, distorted or ruptured so you can get aneurysms or dissections of various arteries going to the brain
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7
Q

describe the venous drainage of the brain

A
  • Veins, no valves, thin walled, no muscles or elasticity to help return
  • the brain has dural venous sinuses that drain the venous drainage of the brain and eventually enter the internal jugular vein
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8
Q

What has a big effect on increasing blood flow to the brain

A

hypercapnia

- if oxygen decreases this can also increase blood flow to the brain but not as much

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9
Q

what does venous return of the brain rely on

A
  • Venous return relies on gravity as the blood drains downwards, the venous sinuses don’t expand very much, space to collect the blood and rely on gravity for the flow of blood
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10
Q

What is the arterial supply to the brain

A
  • Carotids = 80% of the total cerebral blood flow

- Vertebral arteries = 20% of the total cerebral blood flow

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11
Q

describe the carotid (anterior) supply to the brain

A

Internal carotid arteries go in through the carotid canal through into the cavernous sinus and then come out and into the internal part of the skull this gives us the anterior blood supply to the brain

Once the internal carotid artery goes through the cavernous artery it continues as the middle cerebral artery but it also sends of branches that become the anterior cerebral artery, ophthalmic branch

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12
Q

What artery supplies the face and the dura

A
  • The external carotid artery supplies the face, sends of a branch that goes into the skull and supplies the dura – this is the middle meningeal artery which goes into the skull via foramen spinosum which supplies the dura and the meningeal
  • Middle meningeal is found at the pterion
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13
Q

what is the middle mengineal artery a branch of

A

external carotid artery

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14
Q

which foramen does the middle meningeal artery go through

A

foramen spinous

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15
Q

describe the posterior circulation (vertebral) arteries

A
  • Of the subclavian artery is the vertebral artery which travels up through the transverse foramen of the cervical vertebrae, this goes into the skull via foramen magnum and supplies the posterior supply of the brain, this also supplies the brainstem
  • The vertebral arteries become the basilar which divides into inferior cerebral
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16
Q

How many people have the circle of Willis

A

34.5%

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17
Q

Why do we not usually use the circle of willis

A
  • This is because in normal situations don’t use the circle of Willis, this is because under normal situations the anterior and posterior communicating arteries are closed, this is because the pressure in the right and left ICA are the same, only when there is a pressure change on one side is when you are able to open the communicating arteries
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18
Q

What are common variations of the circle of Willis

A
  • One posterior communicating small one large

- Anterior communicating large

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19
Q

what does the middle cerebral artery go through to reach the outside of the brain

A
  • Goes between the temporal and parietal lobe to reach the outside
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20
Q

what does the middle cerebral artery supply

A
  • Sends of branches into the temporal and parietal lobe to supply the basal ganglia, internal capsule and deep structures these are the lateral striate arteries and medial striate arteries that branch of the middle cerebral arteries
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21
Q

what does the anterior cerebral artery supply

A
  • Goes forwards between the hemispheres and supplies the medial surface of the brain and the corpus callosum
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22
Q

what does the posterior cerebral artery supply

A

o Inferior and medial aspects of temporal and occipital cortex
o Thalamus and posterior internal capsule
o Midbrain

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23
Q

what does the basilar artery supply

A

o Pons

o cerebellum

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24
Q

What do the vertebral arteries supply

A

o Spinal cord – posterior and anterior spinal arteries
o Dorsal medulla of brainstem – PICA supplies this, this comes of the verebtral arteries before they fuse and form the basilar (supplies the cerebellum and the medulla)

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25
Q

where do superficial cereal veins usually cross

A
  • Superficial cerebral veins cross the subarachnoid space – don’t usually exit the skull, drain into the Dural sinuses
  • These pierce dura (bridging veins) as they enter intracranial (Dural) venous sinuses
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26
Q

what do arachnoid granulation allow

A
  • Arachnoid granulations allow the CSF to flow into venous blood of sinuses but prevent backflow of blood into the subarachnoid space
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27
Q

What are the two layers of the dura mater

A
  • periosteal(attached to the inner part of the skull)

- meningeal layer (folds on to the brain and goes down into the brain folds)

28
Q

describe the drainage through the dural sinuses

A
  • superior and inferior sagittal sinuses drain into the confluence of the sinuses which is the back of the skull and is the collection point for the superior sagittal and straight sinus which drains from the inferior sagittal sinus
  • From the confluence it drains into the internal jugular
29
Q

what drains the inferior sagittal sinus

A

straight sinus

30
Q

What is the largest dural sinus

A
  • superior sagittal sinus, this is also the sinus that drains the most
31
Q

name the percentages of dominance of venous drainage

A

• Often venous drainage has left or right dominance
– 8-27% equally dominant
– 36-15% left dominant transverse sinus
– 54-58% right dominant transverse sinus

32
Q

what does venous drainage dominance match

A
  • it matches the internal jugular vein
33
Q

What are the major causes of stroke

A
  • Atherosclerosis
  • Hypertension
  • Aneurysm
  • Elderly – as we age our brain shrinks and gets smaller, bridging veins shrink and get torn, dura is attached to the inside of the skull, bridging veins are now having to go over a longer distance are going to get stretched and tear
  • Head injury
  • Alcoholics- brain shrinks in long term alcoholics
  • Arteriovenous malformation
34
Q

what is an ischemic stroke

A

blocked an artery, usually block one artery and this is a specific area of the brain that is damaged

35
Q

What percentage of strokes are ischaemic

A

80%

36
Q

name the types of ischaemic stroke

A
  • Atherosclerosis (thrombotic)

* Embolism

37
Q

what percentage of strokes are cerebral haemorrhages

A

20%

38
Q

what are cerebral haemorrhages caused by

A
  • Trauma

* Spontaneous (hemorrhagic stroke)

39
Q

what can happen when MCA stroke occurs

A

– Dominant hemisphere(depends which hemisphere, tend to be the left hemisphere)
• Global aphasia (don’t understand and cant generate speech), can also have expressive and receptive aphasia if brocas or wernickes area is developed, – left hemisphere damage
• Sensorimotor loss on contralateral face, upper limb and trunk (for either left or right hemisphere)

– If it’s the Non-dominant hemisphere that is damaged
• Neglect syndrome

40
Q

What arteries are usually affected in MCA stroke

A

– Striate arteries often involved- often take a sharp right turn of the middle cerebral artery into the deeper structures of the brain

41
Q

What is neglect syndrome

A

• Neglect syndrome – more specific for right hemisphere damaged and right parietal lobe – this is where you ignore what is in the left side of the visual field or the left side of the body

42
Q

what happens in the anterior cerebral artery stroke

A

– Contralateral sensorimotor loss below waist – effects the medial wall, therefore effects below the waist
– Urinary incontinence
– Personality defects – if in the frontal lobe
– Split-brain syndrome

43
Q

What are the effects of the posterior cerebral artery stroke

A

– Contralateral homonymous hemianopsia
– Reading and writing deficits
– Impaired memory (memory is in the temporal lobe which is largely supplied by PCA)

44
Q

what is the definition of a transient ischemic attacks

A

A transient episode of neurologic dysfunction caused by focal brain, spinal cord, or retina ischemia, without acute infarction

45
Q

How is a diagnosis of a TIA made

A

made on symptoms alone

46
Q

how likely are you to have a stroke or a heart attack after a TIA

A

5% in 1st 48 hours
10% within 90 days
30-40% in 3-5 years

47
Q

What are the symptoms of TIA in

  • anterior circulation
  • posterior circulation
A

– Anterior circulation
• Motor weakness
• Hemi-sensory loss
• Dysarthria - difficult or unclear articulation of speech
• Transient monocular blindness – if ophthalmic artery

–	Posterior circulation
•	Vertigo
•	Diplopia
•	Ataxia
•	amnesia
48
Q

name the three types of extral axial bleeding

A
  • epidural (extradural) haematoma
  • subdural haematoma
  • subarachnoid hematoma
49
Q

describe the characteristic of an epidural (extradural) haematoma

A

– Traumatic
– Blood between dura mater and the skull
– Bleeding rapid (arterial*)
– 2.7-4% of Traumatic brain injury
– Mortality 10% if they are caught early – person seems fine and the next minute they have collapsed

50
Q

what can cause a epidural (extradural) haematoma

A

– most common artery that is affected is the middle meningeal artery as it is the pterion a thin part of the skull and as it is an artery is bleeds rapidly, another type is if the head injury is over a Dural sinus then they will bleed out so you can get a venous one

51
Q

describe the characteristics of a subdural haematoma

A

– Traumatic / Ageing(Chronic)
– Blood between dura mater and arachnoid mater – pushing onto the brain surface
– Rupture to bridging veins – therefore they tend to be venous drainage that has been affected
– These spread more
– Acute 12-29% of severe TBI
– Mortality 40-60%

52
Q

describe the characteristics of a subarachnoid haematoma

A 
–	Spontaneous
–	Between arachnoid and pia 
–	Ruptured aneurysm or head injury
–	1-7% of strokes
–	Arterial
–	Most frequent traumatic brain lesion
53
Q

what arteries can cause an extradural haematoma

A

– Middle meningeal A. (temperoparital area, pterion)
– Ant. Ethmoidal A. (frontal)
– These arteries peal of the periosteal dura, the dura is more firmly attached at the suture lines so these areas of blood don’t pass the suture lines, therefore as the blood collects they compress intracranial structures

54
Q

What are the symptoms of extradural (epidural) haematoma

A

– As blood collects it compresses intracranial structures
– Compress cranial nerve III
– Weakness of extremities on opposite side of lesion (crossed pyramid pathways)
– Loss of visual field opposite to lesion (compress of PCA)

55
Q

how do you diagnose a extradural(epidural) haematoma

A

– CT or MRI
– Convex lens (biconvex, hyperdensity)
– Expansion stops at the sutures because dura is more tightly attached here - then presses inwards

56
Q

What is the treatment of an extradural(epidural) haematoma

A
  • Remove the blood clot and remove the compression of the brain
57
Q

describe the types of subdural haematoma

A

• Acute, subacute or chronic
– Acute after high speed acceleration and deceleration – brain moves and if it moves forwards and then backwards as it accelerates and decelerates this shears the bridging veins
– Associated with cerebral contusions
– Slower onset as venous bleed

58
Q

what are the symptoms of a subdural haematoma

A 
–	Irritability
–	Seizures
–	Headache
–	Numbness
–	Disorientation
59
Q

How do you diagnose a subdural haematoma

A

– CT scan - Crescent shaped, concave hyperdensity
– They cross the suture lines
– The blood accumulates and is able to cross the suture lines

60
Q

What is the treatment of a subdural haematoma

A
  • get rid of the blood clot
61
Q

What are the symptoms of a subarachnoid haematoma

A

• Symptoms
- Severe headache (thunderclap) due to compression of the brainstem and confusion and fluctuations of consciousness
–
– Vomiting
– Confusion
– Lowered / fluctuating levels of consciousness

62
Q

What is the diagnosis of a subarachnoid haematoma

A

– CT - White signal diffuse over sulci on both sides
– Lumbar puncture - Evidence of blood in 3% of people with normal CT
– Also bilirubin

63
Q

what are the three types of a cerebral aneurysm

A

– Saccular
– Fusiform
– Berry

64
Q

describe the characteristics of a cerebral aneurysm

A

• 1:15 people develop a brain aneurysm
• Women at higher risk 3:2
• Danger comes if it ruptures
– Subarachnoid haemorrhage

65
Q

What is the treatment of a cerebral aneurysm

A
  • Coil embolism – heat it burn it and close it off
66
Q

What is a cerebral arteriovenous malformation and how do you treat them

A
  • Problem at capillary bed between arteries and veins
  • Can grow and be quite large
  • Treatment is gamma knife to close them off and try to get rid of them

Brain and Behaviour Year 2 (36 decks)

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