Vertebral arteries- collateral flow Flashcards
Vertebral basilar system provides how much cerebral blood flow?
20-30%
In the case of Vertebral occlusion near its origin flow is shunted to where? (2)
thyrocervical and costocervical trunks
What occurs in a vertebral artery occlusion?
- flow is shunted to the thyrocervical and costocervical trunks
- Compensatory enlargement of the opposite Vertebral artery occurs
Where do the vertebral arteries arise?
Subclavian arteries
how do the vertebral arteries course?
- where on cervical spine?
- cephalad within the vertebral foramen on the transverse processes of the cervical spine C6-C2
How do the vertebral arteries enter the skull?
Through the foramen megnum
How to the vertebral arteries run intracranially?
anterior to the brain stem to form the Basilar A.
What is a normal variant of the vertebral arteries?
- what % of patients?
left vertebral artery may arise directly from the aortic arch- seen in 6% of patients
The basilar artery connects to the circle of willis via?
PCAA
Symptoms and signs of posterior circulation ischemia-vertobrobasilar territory
Dizziness / vertigo
Drop attacks/loss of consciousness
Difficulty ambulating/loss of balance
Ataxia(loss of full control of body movements)
Inability to maintain erect posture/muscular coordination
Upper extremity hypotonia/bilateral parasthesia
Blindness/blurred vision/diplopia/hemianopia/bilateral visual defects
Nystagmus(rapid involuntary movements of the eye)
Poorly reactive pupils
Difficulty focusing and reading
Memory loss
Somnolence(sleepiness or drowsiness)
Normal blood flow pattern- vertebrals?
- resistance
- simular to
- velocity range
- low-resistant
- simular to ICA
- velocity range from 20-60cm/s
What is images more frquently the right or left vertebral artery?
Right vertebral is imaged 80% of time
Left vertebral is imaged 60% of time
What part of the vertebral arteries is least likely to be diseased?
Mid portion is seen with least difficulty-least likely level diseased
What vertebral artery is larger? (LT OR RT)
Left
What % of vertebral arteries are hypoplastic?
7-10%
what should the vertebral flow direction be?
Antegrade (towards head)
Spectral tracing must be displayed in correct directional orientation to rule out?
suspected Subclavian Steal Syndrome=SSS
Vertebral flow-normal?
- flow pattern?
- windows?
- velocities?
- Normal flow pattern: Low resistant
- Window not always present
- Velocities 40-60 cm/s
Vertebral arteries taking on a high resistant flow pattern and no diastolic component implies?
- Distal VA stenosis or occlusion
- Hypoplastic VA
S/S: dizziness and unsteady walking
Collateral pathway if there is a LT SCA origin occlusion or high grade stenosis?
Flow is reversed in the ipsilateral vertebral artery
Subclavian steal syndrome
SSS is and results from?
- A short low resistant path (along the subclavian artery) becomes a high resistant path (due to narrowing)
- hemodynamically significant stenosis or occlusion in proximal subclavian arteries can result in the vertebral acting as a collateral pathway
SSS blood flows?
- Blood flows around the narrowing via the arteries that supply the brain (left and right vertebral artery, left and right internal carotid artery)
- The blood flow from the brain to the upper limb in SSS is considered to be stolen as it is blood flow the brain must do without
Compensatory flow may be seen in the vertebral artery in the presence of?
ipsilateral carotid occlusive disease
Increased peak velocities in the vertebrals show their ability to?
maintain flow via circle of Willis to cerebrum
High-grade stenosis in SCA-SSS?
- side
- PSV
- Signal
- artifact
- BP
- distal flow
- reversed flow
- More common on the left side
- High PSV >500cm/s
- Loss of normal triphasic signal
- Color aliasing
- Decreased ipsilateral Brachial Artery systolic BP- 40mmhg difference between arms
- Damped flow distally (monophasic)
- Reversed flow ipsilateral VA
When the VA has not completely reversed, exercising the arm will do what?
completely reverse the signal below the baseline
