Blood supply to the CNS

Question 1

The sources of blood to the brain

Answer 1

• internal carotid arteries (front)
• vertebral arteries (back)

-These sources give rise to the Circle of Willis

Question 2

Venous drainage of the brain

Answer 2

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

Question 3

Stroke

Answer 3

Cerebrovascular accident
-rapidly developing focal disturbance of brain function of presumed vascular origin and of >24 hours duration

Causes:

• infarction (85%)
• haemorrhage (15%)

Question 4

Transient Ischaemic Attack

Answer 4

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

Question 5

Infarction

Answer 5

Degenerative changes which occur in tissue following occlusion of an artery

Question 6

Cerebral ischaemia

Answer 6

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

Causes:

• hypoxia
• anoxia

Question 7

Causes of occlusions

Answer 7

Thrombosis
-blood clot formation (thrombus)

Embolism
-plugging of small vessel by material carried from larger vessel (eg: thrombi from the heart or atherosclerotic debris from the internal carotid)

Question 8

Main risk factors for stroke

Answer 8

• age
• hypertension
• cardiac disease
• smoking
• diabetes mellitus

Question 9

Disturbance of the anterior cerebral artery

Answer 9

• disturbance of contralateral leg > arm, face
• disturbance of intellect, executive function and judgement (abulia->absence of willpower)
• loss of appropriate social behaviour

Question 10

Disturbance of the middle cerebral artery

Answer 10

CLASSIC STROKE

• contralateral hemiplegia=arm>leg
• contralateral hemisensory deficits
• hemianopia (vision loss over half of the vision field)
• aphasia->language impairment (left sided lesion)

Question 11

Disturbance of the posterior cerebral artery

Answer 11

-visual defects (homonymous hemianopia, visual agnosia)

Question 12

Haemorrhagic stroke (extradural) causes

Answer 12

• trauma

- immediate effects

Question 13

Haemorrhagic stroke (subdural) causes

Answer 13

• trauma

- delayed effects

Question 14

Haemorrhagic stroke (subarachnoid) causes

Answer 14

-ruptured aneurysms

Question 15

Haemorrhagic stroke (intracerebral) causes

Answer 15

-spontaneous hypertensive

Question 16

Demands of the brain

Answer 16

2% body weight but uses:
-10-20% cardiac output
-20% body oxygen consumption
66% liver glucose

Hence, brain is vulnerable if blood supply is impaired

Question 17

Lacunar infarcts

Answer 17

-Type of ischaemic stroke

Question 18

Perfusion field of the anterior cerebral artery

Answer 18

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Question 19

Perfusion field of the middle cerebral artery

Answer 19

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Question 20

Perfusion field of the posterior cerebral artery

Answer 20

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