Blood Supply to the Central Nervous System

Question 1

What percentage of cardiac output goes to the brain?

Answer 1

10-20%

Question 2

What percentage of liver glucose does the brain use?

Answer 2

66%

Question 3

State the 2 main sources of blood supply to the brain?

Answer 3

Vertebral arteries (posteriorly) 
Internal carotid arteries (anteriorly)

Question 4

State the major artery that the vertebral arteries branch off and describe the path of the vertebral arteries to the brain.

Answer 4

Subclavian artery

VA’s pass through the transverse foramina of the cervical vertebrae + through the foramen magnum into the brain

Question 5

Describe the circle of Willis (posterior to anterior)

Answer 5

2 vertebral arteries form Basilar artery (just infront of pons)
Basilar splits to produce 2 posterior cerebral arteries
Each has a branch (posterior communicating artery) to the middle cerebral artery
Branching off the MCA are the anterior cerebral arteries (which are joined by the anterior communicating artery)

Question 6

State the names of the venous sinuses that are at the top and bottom of the falx cerebri.

Answer 6

Superior sagittal sinus

Inferior sagittal sinus

Question 7

What is the name given to the place where all the sinuses meet?

Answer 7

Confluence of sinuses

Question 8

What connects the inferior sagittal sinus to the confluence of sinuses?

Answer 8

Straight sinus

Question 9

What vessel does the inferior sagittal sinus join with to form the straight sinus?

Answer 9

Great cerebral vein

Question 10

Which sinus ascends to join the confluence of sinuses?

Answer 10

Occipital sinus

Question 11

Which 2 sinuses run along the temporal bone?

Answer 11

Superior petrosal sinus

Inferior petrosal sinus

Question 12

Which main sinus drains into the internal jugular vein through the jugular foramen?

Answer 12

Sigmoid sinus

Question 13

Which sinus connects the confluence of sinuses to the sigmoid and superior petrosal sinuses?

Answer 13

Transverse sinus

Question 14

Which sinus runs along the sphenoid and parietal bones?

Answer 14

Sphenoparietal sinus

Question 15

Which sinuses run on either side of the pituitary stalk?

Answer 15

Anterior + posterior intercavernous sinuses

Question 16

Which extension of dura mater separates the cerebellum from the inferior portion of the occipital lobe?

Answer 16

Tentorium cerebelli

Question 17

Define Stroke.

Answer 17

A rapidly developing focal disturbance of brain function of presumed vascular origin that lasts > 24 hours

Question 18

Define Transient Ischaemic Attack (TIA).

Answer 18

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

Question 19

What percentage of strokes are caused by infarction and what percentage are caused by haemorrhage?

Answer 19

85% infarction

15% haemorrhage

Question 20

State 2 causes of occlusions.

Answer 20

Thrombus (formation of a blood clot)

Embolus (plugging of a small vessel by material carried from a larger vessel)

Question 21

Describe the perfusion fields of the brain.

Answer 21

ACA: medial part of both hemispheres
MCA: extends laterally, emerges through the lateral fissure between the frontal and temporal lobes – supplies the front 2/3 of the lateral part of the hemisphere
PCA: occipital lobe + inferior part of temporal lobe

Question 22

Describe the features of a disturbance in the anterior cerebral artery.

Answer 22

Paralysis of contralateral leg > arm, face
Disturbance of intellect, executive function + judgement
Loss of appropriate social behaviour

Question 23

Describe the features of a disturbance in the middle cerebral artery.

Answer 23

"CLASSIC STROKE"
Contralateral hemiplegia: arm > leg  
Contralateral hemisensory deficits  
Hemianopia 
Aphasia- left-sided lesion as language centres are more on the left than the right

Question 24

Describe the features of a disturbance in the posterior cerebral artery.

Answer 24

Visual deficits:
Homonymous hemianopia (loss of visual field on same side of both eyes)
Agnosia (unable to recognise what you are seeing)

Question 25

Which parts of the brain are involved in speech and understanding language?

Answer 25

Broca’s area: speech

Wernicke’s area: understanding language

Question 26

What are lacunar infarcts?

Answer 26

Small cavities that appear in the brain due to small vessel occlusion
Clinical deficit is dependent on location of the small vessel occlusion
Associated with Hypertension

Question 27

State the 4 types of haemorrhagic stroke and their likely causes.

Answer 27

Extradural: rapid onset, caused by trauma
Subdural: slow onset, caused by trauma
Subarachnoid: ruptured aneurysms
Intracerebral: spontaneous hypertensive rupture of small vessels

Question 28

What is the difference between the dura in the vertebral column compared to the brain?

Answer 28

Dura in the vertebral column has 1 layer

Dura in the skull has 2 layers

Question 29

What are the 2 layers of dura in the skull called?

Answer 29

Periosteal and Meningeal

Question 30

What is the name given to the fold of dura that extends between the medial surfaces of the two hemispheres?

Answer 30

Falx Cerebri

Question 31

Why are extradural haemorrhages more rapid onset than subdural haemorrhages?

Answer 31

They are caused by rupture of a meningeal ARTERY (blood strips dura away from skull, increasing pressure) whereas subdural haemorrhages are caused by rupture of veins in the skull

Question 32

Define infarction

Answer 32

Degenerative changes which occur in tissue following occlusion of an artery

Question 33

Define cerebral ischaemia

Answer 33

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

Question 34

List 5 main risk factors for stroke

Answer 34

Age 
Hypertension 
Cardiac disease
Smoking
Diabetes mellitus