Blood supply to the CNS

Question 1

What proportion of the CO, oxygen consumption, and liver glucose does the Brain demand

Answer 1

10-20% CO
20% O2 consumption
66% liver glucose

Question 2

What are the two sources of blood supply to the brain

Answer 2

Interbal carotid arteries
Vertebral arteries
(Circle of Willis -> Cerebral arteries)

Question 3

What is the venous drainage system for the brain

Answer 3

Cerebral veins drain into Venous sinuses from Dura mater at the back of the head
Drainage into the Internal jugular vein

Question 4

Define stroke

Answer 4

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

Question 5

What are the causes of stroke

Answer 5

Infarction (85%)

Haemorrhage (15%)

Question 6

Define Transient Ischaemic attack (TIA)

Answer 6

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

Question 7

Define infarction

Answer 7

Degenerative changes which occur in tissue following occlusion of an artery

Question 8

Define cerebral ischaemia

Answer 8

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

Question 9

What are the causes of occlusions

Answer 9

Thrombosis (formation of a blood clot)

Embolism (plugging of small vessel by material carried from larger vessel)

Question 10

What are the risk factors for stroke

Answer 10

Age
Hypertension
Cardiac disease
Smoking
Diabetes mellitus

Question 11

What occurs if stroke occurs due to 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 occurs if stroke occurs due to the middle cerebral artery

Answer 12

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

Question 13

What occurs if stroke occurs due to the posterior cerebral artery

Answer 13

Visual deficits
homonymous hemianopia
visual agnosia

Question 14

What is a lacune

Answer 14

Small cavity

Question 15

What is a lacunar infarct

Answer 15

Appear in deep structures as a result of small vessel occlusion
Deficit is dependent on anatomical location
generally associated with hypertension

Question 16

What are the three layers of the meninges from the outermost layer and describe them

Answer 16

Dura mater - tough and protective, adherent to bone, space between forms sinuses
Arachnoid mater - thin membrane attached to the dura
Pia mater - delicate membrane closely adherent to the brain and spinal cord

Question 17

Which layer of the meninges contains CSF

Answer 17

Subarachnoid space between arachnoid mater and Pia mater contains the CSF

Question 18

Describe epidural haemorrhage

Answer 18

arterial bleeding
headache, drowsiness, vomiting, seizure
promptly after injury
between dura mater and skull

Question 19

Describe subdural haemorrhage

Answer 19

between Pia mater and dura mater
venous bleeding
headache, drowsiness, vomiting, seizure
symptoms delayed by days or weeks

Question 20

Describe extradural haemorrhage

Answer 20

Trauma, immediate effects

Question 21

What are subarachnoid haemorrhages often due

Answer 21

Often due to ruptured aneurysms (Berry aneurysms)

Question 22

Describe intracerebral haemorrhage

Answer 22

spontaneous hyper-tensive

Question 23

Describe the circle of willis

Answer 23

Basilar artery sits in front of the pons
Basilar splits to give the two posterior cerebral artery
Middle cerebral artery is the largest form the internal carotid -> anterior cerebral artery
Small anterior communicating artery between two anterior cerebral artery

Compensatory flow means that it can supply blood even when a carotid artery is blocked

Question 24

Which parts of the brain do the cerebral arteries supply

Answer 24

Anterior cerebral artery perfuses frontal lobe and strip across top
Middle cerebral artery supplies lateral part of brain
Posterior cerebral artery supplies occipital lobe and inferior part of the temporal lobe