Anatomy of blood flow in the CNS and consequences of disruption

Question 1

What proportion of body weight does the brain make up?

Answer 1

2%

Question 2

What proportion of cardiac output does the brain use?

Answer 2

10-20%

Question 3

What proportion of body oxygen consumption is the brain responsible for?

Answer 3

20%

Question 4

What proportion of liver glucose does the brain use?

Answer 4

66%

Question 5

What are the sources of blood supply to the brain?

Answer 5

Internal carotid arteries

Vertebral arteries

Circle of Willis

Cerebral arteries

Question 6

Label the following diagram:

Answer 6

Question 7

What is the advantage of the anterior and posterior communicating arteries in the circle of Willis?

Answer 7

Compensatory blood flow from contralateral internal carotid artery if one is occluded, e.g. in stroke.

Question 8

Describe venous drainage of the brain.

Answer 8

Cerebral veins within brain.

No veins in cranial cavity.

Venous sinuses- folds of dura mater, drain towards confluence in sinuses (back of head), down into the neck towards the internal jugular vein.

Question 9

Which artery of the circle of Willis is unpaired?

Answer 9

Anterior communicating artery

Question 10

What is a stroke?

Answer 10

Cerebrovascular accident (CVA).

Rapidly developing focal disturbance of brain function of presumed vascular origin and of >24 hours duration.

Infarction (85%) or haemorrhage (15%).

Question 11

What is a transient ischaemic attack (TIA)?

Answer 11

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

Question 12

What is infarction?

Answer 12

Degenerative changes which occur in tissue following occlusion of an artery.

Question 13

What is cerebral ischaemia?

Answer 13

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

Question 14

What is thrombosis?

Answer 14

Formation of a blood clot (thrombus).

Question 15

What is embolism?

Answer 15

Plugging of a small vessel by material carried from larger vessel, e.g. thrombi from the heart or atherosclerotic debris from the internal carotid.

Question 16

What are the causes of occlusions?

Answer 16

Thrombosis

Embolism

Question 17

What are the main risk factors for stroke?

Answer 17

Age

Hypertension

Cardiac disease

Smoking

Diabetes mellitus

Question 18

Discuss the epidemiology of stroke.

Answer 18

3rd most common cause of death in UK.

100,000 deaths in UK per annum.

50% of survivors are permanently disabled.

70% show an obvious neurological deficit.

Question 19

Label the following diagram of perfusion areas of the brain:

Answer 19

Question 20

Label the following diagram of perfusion areas of the brain:

Answer 20

Question 21

What symptoms may result from a stroke affecting the anterior cerebral artery?

Answer 21

Paralysis of contralateral leg > arm, face

Disturbance of intellect, executive function and judgment (abulia)

Loss of appropriate social behaviour

Question 22

What symptoms may result from a stroke affecting the middle cerebral artery?

Answer 22

‘Classic stroke’

Contralateral hemiplegia: arm > leg

Contralateral hemisensory deficits

Hemianopia

Aphasia (L sided lesion)

Question 23

What symptoms may result from a stroke affecting the posterior cerebral artery?

Answer 23

Visual deficits:

• homonymous hemianopia
• visual agnosia

Question 24

What is a lacunar infarct?

Answer 24

Lacune is a small cavity.

Appear in deep structures as a result of small vessel occlusion.

Deficit is dependent on anatomical location.

Hypertension is a risk factor.

Caused by occlusion or haemorrhage.

Question 25

What are the different types of haemorrhagic stroke?

Answer 25

Extradural- trauma, immediate effects. Subdural- trauma, delayed effects. Subarachnoid- ruptured aneurysms. Intracerebral- spontaneous hypertensive.