Blood Supply

Question 1

What is an aneurysm?

Answer 1

dilation of vessel of wall

• common at branch points (ex: ACA, Acomm, Basilar)
• lead to subarachnoid hemorrhage
• mass effects on other things

Question 2

What is a vascular territory?

Answer 2

region of tissue supplied by an artery

Question 3

What are the 2 major arteries that supply brain? where?

Answer 3

Internal carotids As: antero-superior cerebrum, ant. diencephalon
Vertebral As: posteroinferior, brainstem, cerebellum, post. diencephalon

Question 4

Where does the ICAs enter brain? What are its branches?

Answer 4

through carotid canals - over foramen lacerum

• SIPHON @ cavernous sinus
• PComms, ACAs, anterior choroidal As, MCAs

Question 5

Where does the vertebral Arteries enter the brain? What are its branches

Answer 5

-from Subclavin As in transverse foramena > foramen magnum > merge => Basilar A on ventral pons

> PICA
Basilar : AICA, PCA, Superior Cerebellar As
Anterior spinal artery

Question 6

Name the vessels involved in Circle of Willis

Answer 6

2 Posterior Cerebral As
2 Posterior Communicating As
2 Anterior Cerebral As
1 Anterior Communicating A
2 Internal Carotid As

Question 7

What are 2 common variations in Circle of Willis

Answer 7

1 large Acomm > most ACA comes from 1 ICA

or large Pcomm and small PCA > ICA supplies PCA territory instead of VAs

Question 8

Terriotory of ACAs

Answer 8

medial surface, frontal pole

Question 9

Territory of PCAs

Answer 9

inferior surface, occipital pole

Question 10

Territory of MCAs

Answer 10

superior-lateral surface, temporal pole

Question 11

What is a watershed area? What is the relevance?

Answer 11

-border zone of tissue receiving blood from 2 major vessels
-but at the end so loss of blood > perfusion deficit
-these areas are first to suffer
(30% perfussion loss > electrical activity fails
10% loss > neurons die)

Question 12

What is the blood supply for spinal cord?

What are segmental medullary arteries?

Answer 12

-vessels connecting radicular As around cord to the ASAs and 2PSAs on cord

Aorta > intercostal A > Spinal Branches > Radicular As > ASAs and PSAs < Vertebral arteries

Question 13

What are dura sinuses?

Answer 13

folds of dura - contain CSF and blood

Question 14

Distinguish 3 types of Intracranial bleeds

-where? give ex.

Answer 14

1. extradural: aka epidural > lens shape lesion
   ex: tearing meningeal A
2. subdural:
   ex: tearing cerebral vein as it cross bt subarachnoid space to venous sinus > opens the space bt arachnoid and dura matters
3. subarachnoid
   ex: cerebral A
   - fast onset, immediate headache because of ICP

Question 15

What are arteriovenous malformations?

Answer 15

direct a-v connections with no cap beds

• mass effects
• rupture > hemmorhage

Question 16

What is embolism?

Answer 16

-occlusion of vessel from anything blocking blood flow
> infarction, ischemia
Thrombus = embolism from a clot

Question 17

What is CSF? fnc?

Answer 17

• buoyancy - prevent compression, protect brain from impact, equalize pressure
• turned over 3x/day
• remove metabolites
• clear, colourless, low in protein, cells, IgG
• continuous with interstitial fluid
• ventricles lined with ependymal cells (have NO tight junctions)
• total volume = 140ml, most in subarachnoid space

Question 18

How is the blood-brain barrier maintained?

Answer 18

2: blood-ISF barrier and blood-CSF barrier
- continuous capillaries with tight jncs bt endothelial cells: prevent leaking
- water, gases, lipid-soluble can diffuse through
- transporters required for others

Question 19

What is hydrocephalus?

Answer 19

-increase CSF, enlarged ventricles, increase pressure
-due to
1. Noncommunicating (Obstruction) > enlarged lateral/3rd ventricles
ex: narrowing of aqueduct
2. Communicating (impaired absorption) > all ventricle enlarged
-caused by agenesis of arachnoid granulations, blockage
(usually cause 2)

Question 20

What happens with blood-brain barrier breaks down?

What are possible causes?

Answer 20

-leaky > vasogenic edema - increase ICP
-mass effect > midline shift
-on MRI, see gadolinium outside of blood vessel
ex cause: tumour, inflammation

Question 21

Describe CSF production.

Answer 21

Choroid plexus in lateral, 3rd, 4th ventricles

• invagination of vessels through ependymal cells into ventricles > villi
• have FENESTRATED capillaries
• tight junctions bt ependymal cells

Question 22

How is CSF reabsorbed?

Answer 22

1. via arachnoid granulations in dura sinuses > venous space

2. into lymphatics

Question 23

What is monro-kellie doctrine?

Answer 23

1. skull is closed compartment: brain, blood, CSF
2. intracranial space is fixed
3. changes to contents > change intracranial pressure nd redistribute contents

Question 24

What is the ICP?

Answer 24

intracranil pressure = 5-7mmhg/9-12 mmhg

• formed by CSF movement from ventricle to subrachnoid space
• INCREASE > dysfnc > organ failure (sleepiness, confusion, LOC, coma, death)

Question 25

How much blood goes to the brain?

Answer 25

15% of CO
if blood flow decrease> ischemia > neuronal cell death
Normal cerebral blood flow = 50-55ml.min.100g brain
Cell death @ 8-10ml/min/100g

Question 26

What are causes of intracranial htn?

Answer 26

• CSF obstruction (hydrocephalus): aqueduct stenosis; subarachnoid hemorrhage
• increase content: tumour, hemorrhage
• brain edema: trauma, encephalopathy
• small changes autoregulated (vi moving CSF from intracranial space)

Question 27

How can we lower ICP?

Answer 27

1. decrease CSF
2. decrease CBV: normalize pCO2 and PO2, maximize venous flow
3. relieve mass effect

Question 28

Where are cerebral veins located? What do they cross to empty to dura sinus?

Answer 28

Subarachnoid space. Cross subdural space to go to sinus (invagination of dura)

Question 29

Why is the confluence of sinus not a true confluence?

Where does straight and superior sinus empty?

Answer 29

It doesn’t all meet at confluence.
Straight > left transverse
Superior sagital> rt transverse

Question 30

Where do all sinuses drain to?

Answer 30

Internal Jugular veins