Cerebral Vasculature

Question 1

Why does the brain have a large vascular supply?

Answer 1

Makes up 2 % of body weight but uses:

• 10-20% of cardiac output
• 20% of body O2 consumption
• 66% of liver glucose

Therefor brain is very vulnerable if blood is impaired

Question 2

How does blood get to the brain?

Answer 2

Common carotid artery comes off brachiocephalic artery and runs up side of neck. At the laryngeal prominence it divides into external and internal carotid. Internal carotid passes up through carotid canal into cranial cavity

Vertebral artery (first branch of subclavian) passes through transverse foramen into foramen magnum and into the cranial cavity 8

Question 3

What arteries make up the brain?

Answer 3

Circle of willis

Main arteries are internal carotid artery and two vertebral arteries

Question 4

Hw does the blood exit the brain?

Answer 4

Through venous drainage:

Dural sinuses drain blood form the cranial cavity. Made of 2 layers (periosteal and meningeal layers of dura mater) which separate to form venous sinuses.

These cerebral veins drain into the venous sinuses in the dura mater (which emerged into the confluence of sinuses) and then into the internal jugular vein

Question 5

Is there any epidural space in the brain?

Answer 5

No. No space between the skull and the dura

Question 6

What are the 4 types of intracranial hemorrhage and what are their causes?

Answer 6

Extradural: trauma, immediate clinical effects (arterial bleed causing high pressure between dura and skull). Happens between skull and periosteal layer of dura

Subdural: trauma, can be delayed clinical effects (venous, lower pressure). Happens in subdural space

Subarachnoid: ruptured aneurysms. Happens near circle of willis where blood circulates in subarachnoid space

Intracerebral: spontaneous hypertensive. Involves bleed in the brain material itself

Question 7

What is a stroke?

Answer 7

AKA. Cerebrovascular accident (CVA)

Definition: “rapidly developing focal disturbance of brain function of presumed vascular origin and of >24 hours duration

Question 8

What are the 2 kinds of stokes?

Answer 8

Thrombo-embolic (85%) or haemorrhage (15%)

Question 9

What is a transient ischaemic attack (TIA)?

Answer 9

rapidly developing focal disturbance of brain function of presumed vascular origin that resolves completely within 24 hours

Question 10

What is an infarction?

Answer 10

Degenerative changes which occur in tissue following blockage of an artery

Question 11

What is cerebral ischaemia?

Answer 11

Lack of sufficient blood supply to nervous tissue resulting in permanent damage if blood flow is not restored quickly

Question 12

What is a thrombosis?

Answer 12

Formation of a blood clot (thrombus)

Question 13

What is an embolism?

Answer 13

Plugging of small vessel by material carried from larger vessel e.g. thrombi from the heart or atherosclerotic debris from the internal carotid (fat and air can cause this)

Question 14

What is a thromboembolic stroke?

Answer 14

A stroke with both a thrombosis and embolism

Question 15

How many people does stroke affect?

Answer 15

3rd commonest cause of death
100,000 deaths in UK per annum
50% of survivors are permanently disabled
70% show an obvious neurological deficit

Question 16

What are risk factors of stroke?

Answer 16

Age
Hypertension
Cardiac disease
Smoking
Diabetes mellitus

Question 17

What are cerebral artery perfusion fields?

Answer 17

Middle cerebral artery- supplies much of the lateral side and subcortical brain

Anterior cerebral artery- perfuses back to parietal occipital fissure and a midstrip of the brain

Posterior cerebral artery- occipital and inferior temporal lobe

Question 18

What are symptoms due to damage to anterior cerebral artery?

Answer 18

Paralysis of contralateral structures (leg > arm, face)

Disturbance of intellect, executive function and judgement (abulia)

Loss of appropriate social behaviour

Question 19

What are symptoms due to damage to middle cerebral artery?

Answer 19

“Classic stroke”

Contralateral hemiplegia (paralysis of half of body): arm > leg

Contralateral hemisensory deficits

Hemianopia

Aphasia (L sided lesion)- lack of normal speech

Question 20

What are symptoms due to damage to the posterior cerebral artery?

Answer 20

Visual deficits:

• homonymous hemianopia
• visual agnosia (unable to recognise things you see)

Question 21

What is atherosclerosis and what can it cause?

Answer 21

Hardened deposits of fat which can break away into arteries and cause stroke

Question 22

What major public health campaign makes people aware of strokes?

Answer 22

Face
Arms
Speech
Time