Blood Supply to the Brain

Question 1

What proportion of body weight does the brain make up?

Answer 1

2%

Question 2

How much cardiac output does the brain receive?

Answer 2

15%

Question 3

How much total body oxygen does the brain use?

Answer 3

20%

Question 4

How much total body glucose does the brain use?

Answer 4

25%

Question 5

What is the average brain blood flow?

Answer 5

46mL/100g of brain per minute

Question 6

What causes unconsciousness?

Answer 6

20 seconds of anoxia

> 5 minutes = permanent unconsciousness

Question 7

By is blood flow regulated?

Answer 7

Auto-regulation

Question 8

What is the normal rate of cerebral blood flow?

Answer 8

Normotensive cerebral blood flow = 50mL per 100g of brain tissue per minute when cerebral perfusion pressure is between 60-160mmHg

Question 9

What increases cerebral blood flow?

Answer 9

Low oxygen

High cCO2

Question 10

What are cerebral arteries like?

Answer 10

Thin walled, easily blocked/distorted/ruptured

Question 11

What are cerebral veins like?

Answer 11

No valves, thin walled, no muscles or elasticity to help return

Question 12

What is the main arterial supply to the brain?

Answer 12

Internal carotid - 80%

Vertebral arteries - 20%

Question 13

What does a normal angiogram show?

Answer 13

Anterior communicating and posterior communicating are closed

Question 14

What are some common variations of the circle of willis seen on an angiogram?

Answer 14

• one posterior communicating small and one large

- anterior communicating is large

Question 15

What are the main posterior circulation branches?

Answer 15

• vertebral arteries
• basilar artery
• posterior cerebral artery

Question 16

What do the vertebral arteries supply?

Answer 16

• spinal cord -> posterior and anterior spinal arteries

- dorsal medulla of brainstem -> PICA

Question 17

What does the basilar artery supply?

Answer 17

Pons and cerebellum

Question 18

What does the posterior cerebral artery supply?

Answer 18

• inferior and medial aspects of temporal and occipital cortex
• thalamus and posterior internal capsule
• midbrain

Question 19

What is the superficial venous drainage?

Answer 19

• superficial cerebral veins cross subarachnoid space -> pierce dura via bridging veins to enter intracranial dural venous sinuses -> joins with CSF coming from arachnoid granulations in sinuses

Question 20

What is the role of arachnoid granulation?

Answer 20

Allow CSF flow into venous blood of sinuses and prevent backflow into sub-arachnoid space

Question 21

What are the major causes of stroke?

Answer 21

Atherosclerosis
Hypertension
Aneurysm
Elderly
Head injury - trauma
Alcoholics
Arteriovenous malformation

Question 22

What causes an ischemic stroke?

Answer 22

Atherosclerosis or embolism

Question 23

What causes a cerebral haemorrhage?

Answer 23

Trauma

Spontaneous haemorrhage stroke

Question 24

What can a MCA stroke affect?

Answer 24

• dominant hemisphere
• striate arteries
• non-dominant hemisphere

Question 25

What are the effects of an MCA stroke?

Answer 25

Dominant hemisphere -> global aphasia, sensorimotor loss of contralateral face, upper limb and trunk Non dominant hemisphere -> neglect syndrome

Question 26

What are the effects of an ACA stroke?

Answer 26

Contralateral sensorimotor loss below waist Urinary continence Personality defects Split-brain syndrome

Question 27

What are the effects of a PCA stroke?

Answer 27

- contralateral homonymous hemianopia - reading and writing deficits - impaired memory

Question 28

What is a TIA?

Answer 28

Temporary loss of brain function less than 30 mins sudden onset but 24 hour resolves warning sign of heart attack or stroke

Question 29

What are symptoms of a TIA affecting the anterior circulation?

Answer 29

- motor weakness - hemi-sensory loss - dysarthria - transient monocular blindness

Question 30

What are the symptoms of a TIA affecting the posterior circulation?

Answer 30

- vertigo - diplopia - ataxia - amnesia

Question 31

What is a extra-axial bleed?

Answer 31

Outside of the brain tissue

Question 32

Where can extra-axial bleeds occur?

Answer 32

Epidural hematoma Subdural hematoma Subarachnoid hematoma

Question 33

What are the features of an epidural hematoma?

Answer 33

Traumatic Blood between dura mater and skull Rapid arterial bleeding or large venous sinuses

Question 34

What are the features of a subdural hematoma?

Answer 34

Traumatic/ageing blood between dura mater and arachnoid mater rupture to bridging veins

Question 35

What are the features of a subarachnoid hematoma?

Answer 35

``` Spontaneous between arachnoid and pia mater ruptured aneurysm or head injury arterial most frequent traumatic brain lesion ```

Question 36

How does a epidural hematoma present?

Answer 36

With lucid period immediately after trauma followed by unconsciousness

Question 37

Which vessels are affected in an epidural hematoma?

Answer 37

Middle meningeal artery (pterion) | Anterior ethmoidal artery (frontal)

Question 38

What is the mechanism of an epidural hematoma?

Answer 38

- blood compresses intracranial structures -> CN III - weakness of extremities on opposite side of lesion - loss of visual field opposite to lesion

Question 39

How do you diagnose an epidural hematoma?

Answer 39

CT or MRI Convex lens Do not cross suture lines

Question 40

What are the types of subdural hematoma?

Answer 40

Acute - after high speed acceleration/deceleration Subacute - cerebral contusions Chronic - slower onset as venous bleed

Question 41

What are the symptoms of subdural hematoma?

Answer 41

Irritability, seizures, headache, numbness, disorientation

Question 42

How do you diagnose a subdural hematoma?

Answer 42

CT - crescent shaped with concave surface | can look epidural but cross suture lines

Question 43

What are the symptoms of a subarachnoid hematoma?

Answer 43

Severe headache (thunderclap) vomiting confusion lowered level of consciousness

Question 44

How do you diagnose a subarachnoid hematoma?

Answer 44

- CT white diffuse over sulci on both sides - lumbar puncture blood evidence - bilirubin

Question 45

What are the 3 types of cerebral aneurysm?

Answer 45

- saccular - fusiform - berry

Question 46

Why are aneurysms dangerous?

Answer 46

May rupture