Blood supply to the CNS

Question 1

What are the demands of the brain?

Answer 1

• 2% body weight
• 10-20% CO
• 20% of O2 consumption
• 66% of liver glucose

-> the brain is very vulnerable if the blood supply is impaired

Question 2

What are the 2 sources of blood supply to the brain?

Answer 2

• vertebral arteries
• internal carotid arteries

-> form the circle of Willis and the cerebral arteries

Question 3

Venous drainage of the brain

Answer 3

• cerebral veins
• venous sinuses
• dura mater
• internal jugular vein

Question 4

Stroke

Answer 4

Cerebrovascular accident (CVA)
=> rapidly developing focal disturbance of brain function of presumed vascular origin and of >24 hours duration

85% due to infarction, 15% due to haemorrhage

Question 5

TIA

Answer 5

= transient ischaemic attack

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

Question 6

“Infarction”

Answer 6

Degenerative changes which occur in tissue following occlusion of an artery

Question 7

Cerebral Ischaemia

Answer 7

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

• hypoxia/anoxia

Question 8

Causes of occlusions

Answer 8

Thrombosis
- formation of a blood clot (thrombus)

Embolism
- plugging of small vessel by material carried from larger vessel e.g. thrombi from the heart or atherosclerotic debris from the internal carotid

Question 9

Epidemiology of Stroke

Answer 9

• 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 10

What are the main risk factors for stroke?

Answer 10

• Age
• Hypertension
• Cardiac disease
• Smoking
• Diabetes mellitus

Question 11

Stroke affecting the anterior cerebral artery

Answer 11

• Paralysis of contralateral leg > arm, face
• Disturbance of intellect, executive function and judgement (abulia)
• Loss of appropriate social behaviour

Question 12

What does the anterior cerebral artery (ACA) supply?

Answer 12

midline portions of the frontal lobes and superior medial parietal lobes

Question 13

Stroke affecting the middle cerebral artery

Answer 13

• “Classic stroke”
• Contralateral hemiplegia: arm > leg
• Contralateral hemisensory deficits
• Hemianopia
• Aphasia (L sided lesion)

Question 14

What does the middle cerebral artery supply?

Answer 14

A portion of the frontal lobe and the lateral surface of the temporal and parietal lobes, including the primary motor and sensory areas of the face, throat, hand and arm, and in the dominant hemisphere, the areas for speech

Question 15

Stroke affecting the posterior cerebral artery

Answer 15

Visual deficits

- homonymous hemianopia
- visual agnosia

Question 16

Lacunar infarcts

Answer 16

• Lacune is a small cavity
• Appear in deep structures as a result of small vessel occlusion
• Deficit is dependent on anatomical location
• Hypertension

Question 17

haemorrhage stroke

Answer 17

• Extradural - trauma, immediate effects
• Subdural - trauma, delayed effects
• Subarachnoid - ruptured aneurysms
• Intracerebral – spontaneous hyper-tensive

Question 18

What does the posterior cerebral artery (PCA) supply?

Answer 18

occipital lobe