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So the final thing for the neck ultrasound in terms of vessels is going to be

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vertebral waveforms. So we do this as part of every carotid ultrasound workup.

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This is what a normal vertebral artery waveform looks like.

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It has integrated low resistance flow, and it again reflects that continuous

0:17

perfusion of the posterior circulation instead of the anterior, which is what

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you're seeing with the ICA. One of the things that we are looking for with

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vertebral artery flow is we are looking to evaluate for a process called subclavian

0:29

steal. And so that's when you have a stenosis that involves the proximal portion of

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the subclavian artery. You can actually, because of that stenosis, see reversal of

0:39

flow in the vertebral artery, where it essentially steals flow from that posterior

0:44

circulation to perfuse down the arm.

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And so this is not just like a one size fits all process.

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This is where you have progression as that subclavian stenosis worsens.

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And so you can see that this article from 2000 described these waveforms

1:01

where you can get progression of reversal over time.

1:04

So you can see as this looks a little bit different, it almost has a bunny ear

1:08

appearance to it in the waveform in early systole.

1:12

We have a little bit of a dip here. This is the earliest form of progression

1:16

towards steal. As you go further down, you can see a bigger dip.

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You see we're not getting to the baseline and it's a type II at that point.

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We progress then to hitting the baseline in systole.

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You can see the progressive reversal here.

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And then as we get to type IV, you can actually see a pretty steep deflection below

1:34

the baseline. Now, this is not an abnormal waveform if you're looking at something

1:38

that's like a high resistance waveform, but this is a low resistance, always

1:42

forward flow circulation and should not look like this.

1:45

And so eventually once you get there, you progress to complete steal where you have

1:49

essentially persistent retrograde vertebral flow where the entire waveform just

1:53

flips over. And so in this process, the vertebral artery is basically going to

1:57

become a collateral to supply the arm.