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BB2 > Blood Supply to the Brain > Flashcards

Blood Supply to the Brain Flashcards

1
Q

How much of the cardiac output does the brain receive (%)?

A

15%

Average brain blood flow = 46mL/100 grams of brain per minute

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2
Q

How much of the total body oxygen and body glucose does the brain use (%)?

A

20% and 25% respectively

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3
Q

How long of anoxia until a person is unconscious? How long for permanent unconsciousness?

A

20 seconds

More than 5 minutes

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4
Q

What is special about the arteries in/around the brain?

A

They have very thin walls compared to arteries in other areas of the body, so they are easily blocked/distorted/ruptured.

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5
Q

What is special about the veins in/around the brain?

A

They have no valves, and also no muscles or elasticity to help venous return (they rely on gravity).

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6
Q

How much of the total cerebral blood flow is from the internal carotid arteries?
Where is the rest from?

A

80%

Vertebral arteries

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7
Q

Can the anterior and posterior communicating arteries normally be seen on an angiogram?

A

No, because under normal situations they are closed. They only open if the pressure in one of the hemisphere drops (i.e. when the pressure is no longer equal on both sides).

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8
Q

How many % of the population have the classic Circle of Willis?

A

34.5%

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9
Q

Name two common variations of the Circle of Willis.

A

Having a large anterior communicating artery

Having one large posterior communicating artery and one small one

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10
Q

What artery supplies the caudate (ACA, MCA or PCA)?

A

ACA (deep branches)

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11
Q

What artery supplies the putamen and globus pallidus (ACA, MCA or PCA)?

A

MCA

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12
Q

What artery supplies the thalamus (ACA, MCA or PCA)?

A

PCA (deep branches)

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13
Q

What do the vertebral arteries supply? (2)

A

Spinal cord

Dorsal medulla of brainstem (PICA)

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14
Q

What does the basilar artery supply? (2)

A

Pons

Cerebellum

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15
Q

What does the posterior cerebral artery supply? (5)

A 
Inferior and medial temporal cortex
Inferior and medial occipital cortex
Thalamus
Posterior internal capsule
Midbrain
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16
Q

Describe the venous drainage of the brain, and how CSF flows back into venous blood.

A

Superficial cerebral veins cross the subarachnoid space and pierce the dura as they enter intracranial (dural) venous sinuses.
Arachnoid granulations allow CSF to flow into venous blood of sinuses but prevent backflow of blood into sub-arachnoid space.

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17
Q

What are the major causes of stroke? (7)

A 
Hypertension (36%)
Head injury (trauma)
Atherosclerosis
Aneurysm (36%)
Alcoholics
Arteriovenous malformation (11%)
Elderly
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18
Q

What are the two types of stroke?

A 
Ischaemic stroke (71%)
Cerebral/intracerebral haemorrhage (26%)
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19
Q

What are two causes for ischaemic stroke?

A

Atherosclerosis

Embolism

20
Q

What are two causes for hemorrhagic stroke?

A

Trauma

Spontaneous

21
Q

What can be seen in patients with a MCA stroke of the dominant hemisphere? (2)
Which arteries are often involved?

A

Global aphasia and sensorimotor loss on contralateral face, upper limb and trunk
Striate arteries

22
Q

What can be seen in patients with a MCA stroke of the non-dominant hemisphere?

A

Neglect syndrome

23
Q

What can be seen in patients with an ACA stroke? (4)

A

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

24
Q

What can be seen in a patients with a PCA stroke? (3)

A

Contralateral homonymous hemianopsia
Reading and writing deficits
Impaired memory

25
Q

What is a TIA?

A

A transient ischaemic attack, causing a temporary loss of brain function for less than 30 minutes. It comes on suddenly but resolves within 24 hrs.

26
Q

Do all those who suffer TIAs have strokes?

A

No, but it is a warning sign of heart attack or stroke.

6% of patients who have TIAs have a heart attack/stroke in the first month, 12% in the first year and 27% in five years.

27
Q

What are the symptoms of a TIA of the anterior circulation? (4)

A

Motor weakness
Hemi-sensory loss
Dysarthria
Transient monocular blindness

28
Q

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

A

Vertigo
Diplopia
Ataxia
Amnesia

29
Q

What is extradural/epidural haematoma characterised by in terms of clinical presentation?

A

May present with lucid period immediately after trauma, followed by unconsciousness (“talk and die” syndrome).
This is a rapid bleed, as it is arterial (or large venous sinus). As blood collects between the dura mater and the skull, it compresses intracranial structures and cranial nerve III.

30
Q

What are the symptoms of an extradural haematoma? (2)

A

Weakness of extremities on contralateral side

Loss of visual field on contralateral side (due to compression of PCA)

31
Q

How is an extradural haematoma diagnosed?

A

CT or MRI - a convex lense can be seen. The expansion stops at the sutures because the dura is tightly attached here.

32
Q

What arteries are commonly implicated in extradural haematomas? (2)

A

Middle meningeal artery (temperoparital area, pterion)

Anterior ethmoidal artery (frontal)

33
Q

What can cause a subdural haematoma? (2)

Where does the blood collect?

A

Trauma (acute or subacute) - high speed acceleration and deceleration
Ageing (chronic)

Between dura mater and arachnoid mater (subdural space)

34
Q

What are the symptoms of a subdural haematoma? (5)

A 
Irritability
Seizures
Headache
Numbness
Disorientation
35
Q

How is a subdural haematoma diagnosed on CT? How are they differentiated from extradural haematomas?

A

A crescent shape with concave surface can be seen. They can also have a convex appearance so can look like extradural, BUT they can cross the suture lines (unlike extradural).

36
Q

What vessels are implicated in subdural haematoma?

What does this mean in terms of the speed of the bleed?

A 
Bridging veins
Slower onset (venous bleed)
37
Q

Where does the bleed occur in subarachnoid haematoma?
What causes this? (2)
Is it a venous or an arterial bleed?

A

Between arachnoid and pia mater (in the subarachnoid space)
Ruptured aneurysm or a head injury
Arterial

38
Q

What are the symptoms of a subarachnoid haematoma? (4)

A

Severe headache
Vomiting
Confusion
Lowered level of consciousness

39
Q

How is a subarachnoid haematoma diagnosed on CT?

A

White signal diffuse over sulci on both sides

40
Q

How else might a subarachnoid haematoma be diagnosed?

A

Lumbar puncture - evidence of blood or bilirubin

41
Q

What are the three types of cerebral aneurysms?

A

Saccular
Fusiform
Berry

42
Q

Are men or women at higher risk of cerebral

aneurysms?

A

Women (3:2)

43
Q

How many people develop a brain aneurysm?

A

1 in 15

44
Q

Where are four likely places that aneurysms develop?

A

Between the ACA and the anterior communicating artery (40%)
Where the MCA branches (34%)
Where the ICA and posterior communicating artery connect (20%)
Where the basilar splits into the PCA (4%)

45
Q

What artery is occluded in lateral medullary syndrome (Wallenberg syndrome)?

A

PICA

46
Q

What are the symptoms of Wallenberg syndrome? (8)

A 
Vertigo
Nystagmus
Nausea and vomiting
Dysarthia
Dysphonia
Loss of pain and temp in body (contralateral)
Loss of pain and temp in face (ipsilateral)
Loss of gag reflex
47
Q

What syndrome is associated with Wallenberg syndrome? On which side?

A

Horner syndrome (ipsilateral)

BB2 (32 decks)

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