Cervical VEMP - Patient Preparation for Assessment

This video demonstrates the preparation and electrode placement for clinicans to perform a cervical VEMP. You can read the full transcript below.

Preparatory tests

Amanda Goodhew: My name is Amanda and I'm here with Leigh today who is going to be playing the role of my patient.

And we're going to be looking at how to do a cervical VEMP, also known as a cVEMP.

The first thing before we run the VEMP test is to do a few preparatory tests, which we've already done.

So we've done video otoscopy, and we've got nice clear ears, which is fantastic.

We've done a pure tone audiogram, and we've also run a wideband tympanogram.

And both ears were normal on the wideband tympanogram, and the results of the right ear are shown on the screen behind me at the moment.

Type of stimulation

So we can use the results of our tymps to guide us in terms of what type of stimulation to use for VEMP testing.

We can use air conduction via insert earphones, or supra-aural headphones, or we can also use bone conduction.

And because we've got normal tymp results today, I'm going to use air conduction.

But if I did have something abnormal on the tymp like a flat tymp, then I might be inclined to use the bone conduction because that will help us to overcome that middle ear dysfunction and deliver an appropriately loud amount of stimulation.

Today we'll use insert earphones.

Description of electrode montage

So the first thing that we need to do before we can start the actual VEMP test is to get the patient ready.

So we need to place some electrodes onto Leigh's forehead, one on the soft portion here just above the clavicular joint.

And then we're going to pop two electrodes, one on each sternocleidomastoid muscle.

So this is the large muscle that runs the length of the neck here.

And the cVEMP response is recorded from this muscle.

So if we stimulate the right ear, we record from the right muscle.

If we stimulate the left ear, we record from the left SCM muscle.

What we need to do is place the electrode in the upper third portion of that muscle.

And it's really important that we get this symmetrical on both sides.

So we don't want one electrode that's higher than the other, we want to make sure that we place them in the same place on both sides so that we get as symmetrical a recording as possible.

Skin preparation

So the first thing we need to do is use some gauze, or some cotton wool and some electrode gel just to clean the skin, so that we get that really good contact between the electrodes and the skin, in order that we can get really low impedances for our test.

So that's the first thing that we'll do now.

So I've got a little bit of gauze which has some electrode gel on it, and we're just going to use this to start cleaning the skin.

So we'll do the high forehead first, which is where we're going to place the ground electrode.

And you don't need to scrub too hard.

We're just trying to clear off any excess sort of oils, moisturizer, dead skin cells, makeup in certain cases.

And I tend to then just turn the gauze over and wipe off any excess electrode gel as well, so we've got a dry surface to deal with.

Now the next one I'm going to do is the clavicular joint.

So this is where we're going to be placing the vertex electrode.

This is the preferred montage.

However, if you have any difficulty accessing this portion, you can put the vertex on the low forehead for cVEMP testing.

But ideally, we do want to get that position there in between those two bony portions.

So I'm just going to scrub here.

Again, you don't want to be too rough, it is a sensitive area.

But we want those good contacts with our electrodes.

Lovely stuff, just dry that off. Lovely.

So now we need to do the two SCM muscles.

So I'm just going to get Leigh to demonstrate how we can actually identify the SCM muscle.

So if you could turn your head to the left, we can see that is the muscle there.

And in Leigh's case, we've actually got quite an easily identifiable SCM muscle, however, you could also get him to tilt his chin down to the shoulder a bit more, that can make it pop a little bit extra.

The other thing you can do is get him to press against your hand and sort of lean his head forward.

And there you get a really, really strong contraction of the muscle.

So in some cases, people who've got larger necks, this is really useful because it can help you to really identify that muscle there.

So we're going to be going, as I say, for about the top third.

So think I'll be placing my electrode around here.

So now I can see that, I know where to place my electrode gel and then place my electrode and then we'll also make sure that we do exactly the same location on the other side to be a symmetrical as possible.

Lovely.

And if I could get you to turn towards me this time, that's fabulous.

Again, we can see a nice contraction there.

And if you lean against, we get that extra little bit of pop, should you need it.

You don't always need to get them to do that, but that's also a technique that we can use during the testing to ensure that we've got an appropriate amount of muscle contraction for the actual recording.

We'll go into that a little bit later.

Super, just dry that off. Fabulous.

Electrode montage

So let's get the electrodes on.

These are my preferred electrodes, they are really, really sticky, so they stay down.

But they're also particularly nice for VEMP because they wrap around that SCM muscle quite well.

So we'll get the first one, the ground, on the high forehead; you just want to press on the white region around the outside.

The conductive gel sits in the middle of the electrode, we don't want to press too much on that because it might disperse.

But if we don't have great impedances, that is something we can do that can sometimes improve those impedances - just get that gel moving a little bit more.

This one we can put on the clavicular joint.

So I am just going to place it pointing upwards so that I've got access to that tab to place the electrode cable onto.

Again, you don't want to press too hard.

Pressing on that is not a pleasant experience for the patient.

So we just want to gently tap it and make sure that it's on in situ.

If you press too hard, it can be a bit unpleasant.

Again, if I could get you to turn your head to the left, and we can see that SCM muscle.

I can see a nice sort of slightly pink shade to the skin there where I did the electrode gel scrubbing.

With these electrodes, you can either go sideways on like that, which will wrap around the muscle, or you can go upright like that, it doesn't make a huge amount of difference.

I prefer to go sideways on just because I feel like it curves around the muscle, and then I've got all sides of the muscle covered.

But there's nothing wrong with doing it upright either.

So we'll just place that on there.

Thank you very much.

And if I could get you to turn back to look at me, if you just, yeah, straight on, then I can judge how to get it symmetrical.

Again, I can see that slightly pink shaded area of the skin where we did the electrode gel.

So if you now turn a little bit further, I can just make sure I get that in the right spot.

That's lovely.

So that's looking really symmetrical, which is fantastic.

If you just look straight back at me again.

Yeah, they look pretty even.

I'm happy with those.

Connecting the electrode cables

So the next thing is to connect up the electrode cables, if I could loop this over your head so that you're nice and comfortable.

Thank you.

And I'm just going to clip this onto here.

So our high forehead for VEMP is the ground.

So that is the black cable plugged into the ground port there.

And then the white is into the vertex which is going on the clavicular joint down here.

And then as I said for cVEMP testing, it's right ear - right SCM muscle.

So we put the red one on the right side, and the blue, left one on the left side.

Fantastic.

Impedance check

And we can check our impedances by pressing the imp button.

And I can see those are all below, below one and a half, all pretty even there.

So between one and one and a half.

So those are really good, really low impedances.

As always, it's important that our impedances are balanced.

That's the kind of key issue there.

So those were all very similar across which I'm really happy with.

So now we have got our preparation done.

All we need to do is pop the insert earphones in and start running the test.