4 - Anatomy of Bloodflow in the CNS and Consequences of Disruption

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 two main sources of blood supply to the brain?

Answer 3

Vertebral arteries (posteriorly)
Internal carotid arteries (anteriorly)

Question 4

Generally, what do the external and internal carotids supply?

Answer 4

external carotid - supplies the face

internal - Ames its way up tot the skull and supplies the cerebral hemispheres

Question 5

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

Answer 5

Subclavian artery
The vertebral arteries pass through the transverse foramina of the cervical vertebrae and through the foramen magnum into the brain

Question 6

Draw the circle of Willis.

Answer 6

DO NOT FORGET the superior cerebellar artery and the anterior inferior cerebellar arteries

(cerebral arteries are the main feed arteries to the brain)

Question 7

What are the 2 arteries that enter at the the brain posteriorly?

Answer 7

vertebral arteries

from the foramen magnum

Question 8

What artery is formed from the joining o the 2 vertebral arteries?
What does this artery then go to form when it bifurcates?

Answer 8

basilar artery

bifurcates to form the posterior cerebral artery

Question 9

Give the order of venous drainage of blood in the brain?

Answer 9

cerebral veins
venous sinuses
dura mater
internal jugular veins

Question 10

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

Answer 10

Superior sagittal sinus

Inferior sagittal sinus

Question 11

Which sinus runs along the top between 2 folds of dura?

Answer 11

superior sagittal sinus

Question 12

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

Answer 12

Confluence of sinuses

Question 13

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

Answer 13

Straight sinus

Question 14

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

Answer 14

Great cerebral vein

Question 15

Which sinus ascends to join the confluence of sinuses?

Answer 15

Occipital sinus

Question 16

Which two sinuses run along the temporal bone?

Superior petrosal sinus

Answer 16

Inferior petrosal sinus

Question 17

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

Answer 17

Sigmoid sinus

Question 18

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

Answer 18

Transverse sinus

Question 19

Which sinus runs along the sphenoid and parietal bones?

Answer 19

Sphenoparietal sinus

Question 20

Which sinuses run on either side of the pituitary stalk?

Answer 20

Anterior and posterior intercavernous sinuses

Question 21

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

Answer 21

Tentorium cerebelli

Question 22

Define Stroke.

Answer 22

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

Question 23

Define Transient Ischaemic Attack (TIA).

Answer 23

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

Question 24

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

Answer 24

85% infarction

15% haemorrhage

Question 25

State two causes of occlusions.

Answer 25

Thrombus | Embolus

Question 26

Describe the perfusion fields of the brain.

Answer 26

The anterior cerebral artery supplies the medial part of both hemispheres The middle cerebral artery extends laterally and emerges through the lateral fissure between the frontal and temporal lobes – it supplies the front 2/3 of the lateral part of the hemisphere The posterior cerebral artery supplies the medial and lateral parts of the posterior part of the hemisphere

Question 27

Describe the location of the leg in the motor and sensory homunculus compared to the arm.

Answer 27

Leg is more MEDIAL

Question 28

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

Answer 28

Contralateral hemiplegia in the LEG more than the arm Disturbance of intellect and executive function Loss of appropriate social behaviour

Question 29

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

Answer 29

This is a CLASSIC STROKE Contralateral hemiplegia in the ARM more than the leg Contralateral hemisensory deficits Hemianopia Aphasia (can’t speak) – left-sided lesion of the middle cerebral artery will result in aphasia because the language centres are more on the left side than the right

Question 30

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

Answer 30

The posterior cerebral artery supplies the occipital lobe, which is where the primary visual cortex is located This causes visual defects such as homonymous hemianopia and visual agnosia (unable to recognise what you are seeing)

Question 31

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

Answer 31

Broca’s area – speech | Wernicke’s area – understanding language

Question 32

What are lacunar infarcts?

Answer 32

``` Small spaces (lacunae) that appear in the brain due to small vessel occlusion The clinical deficit is dependent on the location of the small vessel occlusion Hypertension can cause lacunar infarcts ```

Question 33

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

Answer 33

Extradural – rapid onset – caused by trauma Subdural – slow onset – caused by trauma Subarachnoid – usually caused by ruptures aneurysms Intracerebral – usually due to spontaneous hypertensive rupture of small vessels

Question 34

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

Answer 34

The dura in the vertebral column has ONE layer whereas the dura in the skull has TWO layers

Question 35

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

Answer 35

Periosteal and Meningeal

Question 36

What are the arachnoid granulations?

Answer 36

projections of the arachnoid membrane into the dural sinuses that allow CSF entrance from the subarachnoid space into the venous system

Question 37

What are emissary veins? | Why are they important?

Answer 37

veins that connect the extracranial venous system with the intracranial venous sinuses They connect the veins outside the cranium to the venous sinuses inside the cranium. i.e. they pass through the top of the skull they are important because they are another route of infection. infection of the scalp can spread through these veins and cause meningitis

Question 38

Does subdural and extradural space exist?

Answer 38

extradural space does not exist subdural scape does exist CSF is in subarachnoid space

Question 39

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

Answer 39

Falx Cerebri

Question 40

Why are extradural haemorrhages more rapid onset than subdural haemorrhages?

Answer 40

Extradural haemorrhages are caused by rupture of a meningeal ARTERY (high pressure) whereas subdural haemorrhages are caused by rupture of veins in the skull