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BB2 > Blood Supply to the Brain > Flashcards

Blood Supply to the Brain Flashcards

1
Q

What proportion of body weight does the brain make up?

A

2%

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2
Q

How much cardiac output does the brain receive?

A

15%

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3
Q

How much total body oxygen does the brain use?

A

20%

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4
Q

How much total body glucose does the brain use?

A

25%

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5
Q

What is the average brain blood flow?

A

46mL/100g of brain per minute

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6
Q

What causes unconsciousness?

A

20 seconds of anoxia

> 5 minutes = permanent unconsciousness

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7
Q

By is blood flow regulated?

A

Auto-regulation

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8
Q

What is the normal rate of cerebral blood flow?

A

Normotensive cerebral blood flow = 50mL per 100g of brain tissue per minute when cerebral perfusion pressure is between 60-160mmHg

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9
Q

What increases cerebral blood flow?

A

Low oxygen

High cCO2

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10
Q

What are cerebral arteries like?

A

Thin walled, easily blocked/distorted/ruptured

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11
Q

What are cerebral veins like?

A

No valves, thin walled, no muscles or elasticity to help return

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12
Q

What is the main arterial supply to the brain?

A

Internal carotid - 80%

Vertebral arteries - 20%

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13
Q

What does a normal angiogram show?

A

Anterior communicating and posterior communicating are closed

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14
Q

What are some common variations of the circle of willis seen on an angiogram?

A
  • one posterior communicating small and one large

- anterior communicating is large

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15
Q

What are the main posterior circulation branches?

A
  • vertebral arteries
  • basilar artery
  • posterior cerebral artery
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16
Q

What do the vertebral arteries supply?

A
  • spinal cord -> posterior and anterior spinal arteries

- dorsal medulla of brainstem -> PICA

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17
Q

What does the basilar artery supply?

A

Pons and cerebellum

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18
Q

What does the posterior cerebral artery supply?

A
  • inferior and medial aspects of temporal and occipital cortex
  • thalamus and posterior internal capsule
  • midbrain
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19
Q

What is the superficial venous drainage?

A
  • superficial cerebral veins cross subarachnoid space -> pierce dura via bridging veins to enter intracranial dural venous sinuses -> joins with CSF coming from arachnoid granulations in sinuses
20
Q

What is the role of arachnoid granulation?

A

Allow CSF flow into venous blood of sinuses and prevent backflow into sub-arachnoid space

21
Q

What are the major causes of stroke?

A 
Atherosclerosis
Hypertension
Aneurysm
Elderly
Head injury - trauma
Alcoholics
Arteriovenous malformation
22
Q

What causes an ischemic stroke?

A

Atherosclerosis or embolism

23
Q

What causes a cerebral haemorrhage?

A

Trauma

Spontaneous haemorrhage stroke

24
Q

What can a MCA stroke affect?

A
  • dominant hemisphere
  • striate arteries
  • non-dominant hemisphere
25
Q

What are the effects of an MCA stroke?

A

Dominant hemisphere -> global aphasia, sensorimotor loss of contralateral face, upper limb and trunk
Non dominant hemisphere -> neglect syndrome

26
Q

What are the effects of an ACA stroke?

A

Contralateral sensorimotor loss below waist
Urinary continence
Personality defects
Split-brain syndrome

27
Q

What are the effects of a PCA stroke?

A
  • contralateral homonymous hemianopia
  • reading and writing deficits
  • impaired memory
28
Q

What is a TIA?

A

Temporary loss of brain function
less than 30 mins
sudden onset but 24 hour resolves
warning sign of heart attack or stroke

29
Q

What are symptoms of a TIA affecting the anterior circulation?

A
  • motor weakness
  • hemi-sensory loss
  • dysarthria
  • transient monocular blindness
30
Q

What are the symptoms of a TIA affecting the posterior circulation?

A
  • vertigo
  • diplopia
  • ataxia
  • amnesia
31
Q

What is a extra-axial bleed?

A

Outside of the brain tissue

32
Q

Where can extra-axial bleeds occur?

A

Epidural hematoma
Subdural hematoma
Subarachnoid hematoma

33
Q

What are the features of an epidural hematoma?

A

Traumatic
Blood between dura mater and skull
Rapid arterial bleeding or large venous sinuses

34
Q

What are the features of a subdural hematoma?

A

Traumatic/ageing
blood between dura mater and arachnoid mater
rupture to bridging veins

35
Q

What are the features of a subarachnoid hematoma?

A 
Spontaneous
between arachnoid and pia mater
ruptured aneurysm or head injury
arterial
most frequent traumatic brain lesion
36
Q

How does a epidural hematoma present?

A

With lucid period immediately after trauma followed by unconsciousness

37
Q

Which vessels are affected in an epidural hematoma?

A

Middle meningeal artery (pterion)

Anterior ethmoidal artery (frontal)

38
Q

What is the mechanism of an epidural hematoma?

A
  • blood compresses intracranial structures -> CN III
  • weakness of extremities on opposite side of lesion
  • loss of visual field opposite to lesion
39
Q

How do you diagnose an epidural hematoma?

A

CT or MRI
Convex lens
Do not cross suture lines

40
Q

What are the types of subdural hematoma?

A

Acute - after high speed acceleration/deceleration
Subacute - cerebral contusions
Chronic - slower onset as venous bleed

41
Q

What are the symptoms of subdural hematoma?

A

Irritability, seizures, headache, numbness, disorientation

42
Q

How do you diagnose a subdural hematoma?

A

CT - crescent shaped with concave surface

can look epidural but cross suture lines

43
Q

What are the symptoms of a subarachnoid hematoma?

A

Severe headache (thunderclap)
vomiting
confusion
lowered level of consciousness

44
Q

How do you diagnose a subarachnoid hematoma?

A
  • CT white diffuse over sulci on both sides
  • lumbar puncture blood evidence
  • bilirubin
45
Q

What are the 3 types of cerebral aneurysm?

A
  • saccular
  • fusiform
  • berry
46
Q

Why are aneurysms dangerous?

A

May rupture

BB2 (31 decks)

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