Week 9 - Circulation - finished

Question 1

How long does it take for neuro SSx to appear after ischemia in the brain?

Answer 1

seconds

Question 2

What does the blood deliver to the brain?

Answer 2

O2 and glucose

Question 3

Can the brain use anything but glucose for energy?

Answer 3

No

Question 4

What does the blood remove from the brain?

Answer 4

It removes lactic acid and CO2, which can become neurotoxic if they build up

Question 5

Information about the regulation of blood and O2 content of blood to the brain:

Answer 5

The CNS self regulates the delivery and distribution of blood by sensing the momentary pressure changes in its main arteries of supply, the internal carotids. It controls the arterial oxygen tension by monitoring respiratory gas levels in the internal carotid artery and in the cerebrospinal fluid (CSF) near the medulla oblongata. The control systems used by the brain are exquisitely sensitive and sophisticated, but they can be rendered useless when a distributing artery spontaneously ruptures or is slammed shut by an embolus.

Question 6

Stroke is the number what cause of death in the western world?

Answer 6

3rd

Question 7

What % of body mass does the brain account for?

Answer 7

2%

Question 8

How much of our CO does the brain receive?

Answer 8

15%

Question 9

What % of total O2 consumption does the brain account for?

Answer 9

20%

Question 10

What are the 2 types of stroke?

Answer 10

Haemorrhagic and occlusive

Question 11

What are the major arteries that supply the brain? How do these arteries supply the whole brain?

Answer 11

Anterior Cerebral Artery
Posterior Cerebral Artery
Middle Cerebral Artery

These 3 arteries anastomose to protect and supply the superficial aspect of each hemisphere. From there superficial arteries, smaller penetrating arteries arise to supply deeper structures. For the most part, these deeper areas are the end zones and receive no collateral supply.

Question 12

What are the major inputs to the circle of Willis?

Answer 12

The internal carotid arteries and the vertebral arteries

Question 13

Is the circle of Willis always anatomically the same in every person?

Answer 13

No, it is one of the most anaotmically variable places in the body.

Question 14

Where do the vertebral arteries fuse and what do they fuse into

Answer 14

They fuse at the pontomedullary junction and fuse into the basilar artery.

Question 15

Is it the anterior or the middle cerebral artery that is the direct continuation of the internal carotid arteries?

Answer 15

The middle. The anterior cerebral artery is the branch off the internal carotid artery.

Question 16

Why is the middle cerebral artery the most likely place for a stroke/an embolism to go?

Answer 16

Because it is the direct continuation of the internal carotid, so the embolism will most likely just flow directly along the artery, rather than possibly going through the branch for the anterior cerebral artery.

Question 17

What are the SSX of middle cerebral artery infarction? (heaps so just name a few and understand the part fo the brain the MCA supplies and what the affects may be)

Answer 17

Contralateral weakness and sensory loss

Mostly affecting face and arms due to somatotropic organisation of pre and post central gyri

Distal limbs affected more so than proximal as the trunk and proximal limbs appear to have some level of bilateral cortical coding (PMA and SMA)

Forehead, pharynx and jaw also have bilateral representation

+ve babinski

Often period of hypotonia which progresses to spasticity with hyperreflexia

Proprioceptive and discrimination are often lost giving rise to ataxia

Pain and temp sensation are often altered but are rarely lost

Vision is often impaired due to damage to the optic radiations:
- parietal: inferior quadrantanopsia
- temporal: superior quadrantanopsia
(divisions of the MCA in the visual area, only one quarter of the visual field will be lost)

Depending of the hemisphere affected there may also be disturbances of language or spatial perception

Dominant hemisphere: difficulties with language may present as a Broca’s, Werknicke’s or global aphasia (cannot produce or interpret speech)

Parietal damage may cause motor apraxias (loss of motor pattern of something that they have done a lot of times e.g. doing up a button)

Non-dominant: Hemiinattention

Neurologial deficit may be more specific if one of the end zone has been affected.

Question 18

SSX of anterior cerebral artery infarction:

Answer 18

Motor and sensory phenomena but tend to be the contralateral leg, most profoundly the distal limb

Maybe urinary incontinence (due to motor cortex destruction or destruction of the area which codes specifically for the inhibition of bladder emptying

Maybe speech distrurbances

Sympathetic motor apraxia may arise from the damage to the corpus callosum which connects the cortex to the contralateral motor cortex.

The anterior cerebral is more commonly associated with bilateral infarcts than the other cerebral arteries due to the common congenital malformation of both arteries arising from a single trunk

Bilateral infarct often gives rise to severe behavioural disturbances and personality changes which may even include muteness

Question 19

SSX of the posterior cerebral artery

Answer 19

Unilateral destruction of the calcarine cortex, in some cases which may even be bilateral if occluded at the point of bifurcation.

Macular vision will typically be spared due to the common supply by the MCA. The peripheral vision will be gone, by the central vision will be in tact.

The thalamus may be affected giving hemisensory loss and spontaneous pain.

Subthalamic nucleusmay be affected giving contralateral hemiballismus

Midbrain may be affected giving ipsilateral oculomotor palsy and contralateral hemiparesis or ataxia.

Question 20

Spinal cord circulation, what is it supplied by.

Answer 20

2 posterior spinal arteries and one anterior spinal artery.

Question 21

What is the anterior spinal artery a branch of?

Answer 21

A branch of the vertebral arteries

Question 22

What does the anterior and posterior spinal artery supply?

Answer 22

Anterior spinal arteries:
Supplies the ant. 2/3 of the cord
Including the ant. and lat. horns
Supplies anterior inferior part of the medulla including the pyramids, medial lemniscus and some of the CN XII fibres

Posterior spinal arteries:
In combination supply the posterior 1/3 of the cord
This includes the dorsal horns and columns
At the level of the medulla supply the dorsal column nuclei also

Question 23

Do the anterior and posterior spinal arteries adequately supply the whole spinal cord?

Answer 23

No, only the Cx segments. After that radicular arteries compensate.

Question 24

What do the radicular arteries supply? Where do they arise from? How do they enter the vertebral canal?

Answer 24

Supply each level via the anterior and posterior spinal a.’s

They also supply the vertebrae and meninges

Arise from spinal branches of the vertebral, deep Cx, ascending Cx, posterior intercostal, Lx & lateral sacral a.’s

Follow the spinal nerves and divide into dorsal and ventral along the line of the spinal n. roots, hence they enter the vertebral canal via the IVF

Question 25

What does the greater radicular artery supply?

Answer 25

Makes a great contribution to the anterior spinal a. and provides most of the blood supply to the inferior 2/3 of the spinal cord

Much larger than the other radicular vessels

Question 26

What are the main arteries that supply the brainstem?

Answer 26

Dorsolateral Medulla: PICA 
Anterior Medulla: anterior spinal and vertebral arteries 
Pons: basilar branches 
Midbrain: 
- Basilar artery
- Superior Cerebellar artery
- PCA

Question 27

What are the posterior vertebral arteries a branch of?

Answer 27

The posterior inferior cerebellar artery

Question 28

Where does the PICA arise from?

Answer 28

Typically arise from the vertebral a.’s but may come from the basilar

Question 29

What does the PICA give rise to?

Answer 29

Typically give rise to the posterior spinal a.’s

Question 30

What does the PICA supply?

Answer 30

Supplies the dorsolateral zone of the medulla, the inferior portion of the cerebellum and the choroid plexus of the 4th ventricle, stroke gives rise to Wallenberg’s syndrome

This includes:
Medial and inferior vestibular nuclei
Inferior cerebellar peduncle
Nucleus ambiguus & intra-axial fibres of CN IX & X
ALS
Spinal trigeminal nucleus & tract
Hypothalamospinal tract to give Horner’s syndrome

Question 31

What is the basilar artery formed by and where does this happen?

Answer 31

Is formed by the vertebral a.’s at the pontomedullary junction

Question 32

What does the basilar artery give rise to?

Answer 32

Gives rise to the pontine a.’s, AICA + the labyrinthine a. and the superior cerebellar a.’s

Question 33

What do the pontine arteries supply?

Answer 33

Supply the cortiospinal tracts at the pontine level and the fibres of CN VI

Question 34

What does the AICA give rise to?

Answer 34

Typically gives rise to the labyrinthine a. for the supply of the cochlea and vestibular apparatus

Question 35

What does the AICA supply?

Answer 35

Supplies the inferior surface of the cerebellum, the nucleus and intra-axial fibres of CN VII, spinal trigeminal nucleus and tract, vestibluar nuclei, cochlear nuclei, intra-axial fibres of CN VIII, ALS and the inferior & middle cerebellar peduncles

Also contributes to the supply of the hypothalamospinal tract

Question 36

Where does the superior cerebellar artery arise from?

Answer 36

The Basilar artery

Question 37

What does the superior cerebellar artery supply?

Answer 37

Supplies the superior surface of the cerebellum and the superior cerebellar peduncle

Also sends penetrating branches in to supply the deep cerebellar nuclei

Supplies the superior and lateral pons including the ALS