Cerebral Vasculature

Question 1

How much Cardiac Output does the brain use?

Answer 1

10-20%

Question 2

How much O2 does the brain consume?

Answer 2

20%

Question 3

How much liver glucose does the brain use?

Answer 3

66%

Question 4

Why is the brain vulnerable when blood supply is impaired?

Answer 4

Due to it’s high metabolic demands

Question 5

Which arteries supply the brain?

Answer 5

• Internal carotid (entry through the carotid canal)

- vertebral artery (foramen magnum)

Question 6

Arteries in the brain?

Answer 6

The Circle of Willis
(2 x vertebral > basilar artery > posterior cerebral > posterior communicating > middle cerebral (internal carotid) > anterior cerebral > anterior communicating)

Question 7

Where does atherosclerotic build-up occur most often in the cerebral arteries/circle of willis?

Answer 7

Where it divides.

Question 8

What happens if there is an effective blockage of the cerebral arteries in the Circle of Willis?

Answer 8

Theoretical chance of compensatory flow from the other side.
Realistically compensation between the posterior and anterior cerebral arteries is weak as P communicating are very thin.

Question 9

Venous drainage of the brain?

Answer 9

Drains mainly through venous sinuses in the dura mater (through the cerebral veins) > internal jugular vein

Question 10

Order of venous drainage through the sinuses?

Answer 10

superior (+inferior) sagittal sinus + straight sinus> confluence of sinuses > sigmoid sinus (lateral/transverse drainage)

Question 11

What are the different types of intracranial haemorrhage

Answer 11

• extradural
• subdural
• subarachnoid
• intracerebral

Question 12

Where do sinuses form?

Answer 12

In between the meningeal (inner) and periosteal (outer) layers of the dura mater

Question 13

What causes a extradural cranial haemorrhage?

Answer 13

• trauma

- high pressure arterial bleed

Question 14

What causes a subdural cranial haemorrhage?

Answer 14

• trauma

- low pressure, venous bleed

Question 15

What causes a subarachnoid cranial haemorrhage?

Answer 15

Ruptured aneurysms
(normally congenital)
- blood vessel weakness
- may burst in hypertensive patients

Question 16

What causes a intracerebral cranial haemorrhage?

Answer 16

• spontaneous hypertensive

normal in chronic hypertensives

Question 17

Where is a fragile point in the head?

Answer 17

Pterion

Question 18

Why is the Pterion so vulnerable?

Answer 18

Protects the artery supplying the dura (if ruptured causes an extradural bleed)

Question 19

Where do Extradural bleeds occur?

Answer 19

Between the dura and the skull, builds up pressure (arterial)

Question 20

How do extradural bleeds present?

Answer 20

• Acute onset
• surgical emergency
• high intracranial pressure

Question 21

Where do subdural bleeds occur?

Answer 21

Between the dura and the arachnoid.

small amount of space

Question 22

How do subdural bleeds present?

Answer 22

• Delayed onset of symptoms

- venous, lower pressure bleed

Question 23

Where do subarachnoid haemorrhages most commonly occur?

Answer 23

• Base of the brain, near the circle of willis

Question 24

Stroke Definition

Answer 24

(CVA)
cerebrovascular accident
rapidly developing disturbance of brain function of a presumed vascular origin for >24 hours

Question 25

What does a rapid onset stroke indicate?

Answer 25

Likely vascular origin | exclusion of differentials must occur

Question 26

What is a thrombo-embolic stroke and how common is it?

Answer 26

Stroke due to blockages | 85% of strokes

Question 27

What is a haemorrhage stroke and how common is it?

Answer 27

Stroke due to brain bleed | 15% of strokes

Question 28

Transient Ischaemic Attack (TIA)

Answer 28

same as stroke but resolved in 24 hours (no residual deficits) rapidly developing focal disturbance of brain function of a presumed vascular origin that completely resolves in 24 hours

Question 29

TIA time span?

Answer 29

normally can be from 30 seconds - 1 minute

Question 30

What does a TIA indicate?

Answer 30

Subsequent stroke further down the line | cause of TIA may worsen

Question 31

Infarction

Answer 31

Degenerative tissues that occur in the tissue due to occlusion of an artery (tissue death)

Question 32

Cerebral Ischaemia

Answer 32

Lack of sufficient blood supply to nervous tissue which leads to permanent damage if blood supply is not restored quickly.

Question 33

How is Ischaemia different from hypoxia?

Answer 33

Ischaemia is a lack of everything, not just O2

Question 34

Thrombosis definition

Answer 34

Formation of a blood clot (thrombus) | can be a form of embolism

Question 35

Embolism definition

Answer 35

Plugging of a small vessel by material carried from a larger vessel

Question 36

Examples of embolism

Answer 36

- thrombi from the heart - atherosclerotic debris from the internal carotid - fat - air (IV injections)

Question 37

Strokes and Public Health

Answer 37

- 3rd most common cause of death (100,000 deaths/year) - 50% of survivors are permanently disabled - 70% show an obvious neurological deficit

Question 38

Risk Factors of Stroke

Answer 38

- Age - Hypertension - Cardiac Disease - Smoking - Diabetes Mellitus (effects on vasculature)

Question 39

Where does the Anterior Cerebral artery perfuse?

Answer 39

- midline structures (about 1cm strip) | - all the way back to the parietal-occipital fissure

Question 40

Where does the Middle Cerebral artery perfuse?

Answer 40

- most of lateral surface of the brain | - most of the subcortical (deep) structures in the brain

Question 41

Where does the Posterior Cerebral artery perfuse?

Answer 41

- mostly the occipital lobe | - inferior part of the temporal lobe

Question 42

Symptoms of stroke of the Anterior Cerebral Artery

Answer 42

- paralysis of contralateral structures (opposite to the perfusion of brain) (most likely the leg) - front lobe damage, disturbance of intellect, executive function and judgement (abulia - decreased frontal function) also, possible loss of appropriate social behaviour.

Question 43

Symptoms of a Middle Cerebral Artery stroke?

Answer 43

'Classic Stroke' - (deep motor structures): contralateral hemiplegia (arm>leg) - (sensory cortex): contralateral hemisensory deficits. - (runs from eye to occipital) Hemianopia (loss of half the visual field) - Aphasia, lack of normal speech (Left-sided lesion)

Question 44

Symptoms of a Posterior Cerebral Artery stroke

Answer 44

``` - The occipital region of the brain Visual Deficits: - Homonymous hemianopia - Visual Agnosia - Prosop Agnosia (unable to recognise faces) ```

Question 45

Indication of Infarction

Answer 45

Loss of clear differentiation between white and grey matter.