Collateral Circulation

Question 1

____% of cardiac output supply the brain

Answer 1

15%

Question 2

___% CCA blood goes to the ICA

Answer 2

80%

Question 3

*The most common collateral pathway involves (1)

Answer 3

The circle of Willis

Question 4

*What is the second most important route of collateral flow?

Answer 4

Peri-orbital circulation

Question 5

Peri-orbital branches of the ICA (3)

Can communicate with (2)

Answer 5

Peri-orbital branches:

• Frontal A
• Supraorbital A
• Nasal artery A

Communicate with:

• Superficial temporal A
• Facial A

Question 6

The intracranial-extracranial anastomoses occur between (2)

Answer 6

Orbital branch of superficial temporal (ECA branch)
+
Opthalmic A (ICA branch)

Question 7

Only ____% of patients have complete Circle of Willis

Answer 7

50%

Question 8

What are the 3 major collateral routes

Answer 8

Circle of Willis
Posterior cerebral circulation
ECA branches

Question 9

Some patients don’t reveal any symptoms of cerebrovascular disease even with total occlusion of both ICAs

Answer 9

True -

Question 10

How do collaterals develop?

Answer 10

Because of a change in pressure gradient between the vessels caused by a stenosis

Question 11

Cellular death can occur in _____ mins

Answer 11

3-8 mins

Question 12

In hemodynamics, what is the most limiting?

Answer 12

Width - poiseuille’s law

Question 13

Will blood take a long wide path or a short narrow path?

Answer 13

Long & wide

Question 14

Adequate arterial perfusion relies on (3)

Answer 14

Blood pressure
Cardiac output
Blood volume

Question 15

The vertebral-basilir system provides how much cerebral blood flow

Answer 15

20-30%

Question 16

Normal Vertebral A flow:

velocity & waveform

Answer 16

Low resistant, monophonic, large EDV

20-60 cm/s

Question 17

What is the least likely level for VA to be diseased?

Answer 17

Mid portion

Question 18

What side VA is more commonly larger?

Answer 18

Left more common than right

Question 19

Vertebral flow:
Abnormal traits &
What can this imply (2)

Answer 19

High resistant flow with no diastolic waveform

Implies: distal VA stenosis/occlusion, hypoplastic VA

Question 20

S/S VA disease (2)

Answer 20

Dizziness & unsteady walking

Question 21

What side is SSS most commonly seen?

Answer 21

Left side

Question 22

what arteries can SSS involve? (3)

Answer 22

RT subclavian A
LT subclavian A
INN A

Question 23

What will you see with SSS? (Describe SCA, Brachial A, VA)

Answer 23

-SCA
high PSV >500 cm/s
Short low-resistant path becomes high resistant due to narrowing
Loss of tri-phasic signal
Aliasing
Damped flow distally (monophonic)

• Decreased ipsilateral (same side) brachial artery systolic BP - (20-40 mmHg pressure difference between arms)
• Reversed flow ipsilateral VA to supply the arm