Ocular VEMP - Patient Preparation for Assessment

This video demonstrates the preparation and electrode placement for clinicians to perform an ocular VEMP.

Transcript

Darren Whelan: Hi, I'm Darren, and this is my colleague Leigh, and today I'm going to play the role of the clinician and Leigh is going to play the role of the patient in this demonstration of an ocular VEMP.

Now Leigh doesn't have any previous balance issues and neither is he reporting any symptoms today, we've conducted an audiogram, so he's hearing is satisfactory in both sides.

And we've also done a middle ear assessment using Wideband Tympanometry.

So now we're going to get his skin prepared ready for the ocular VEMP.

Now in the literature, there are two montages that are referred to, some may be more familiar with the traditional montage where we place the electrodes, both electrodes, underneath each eye.

Today, we're going to use the what's called the alternative montage.

So we're going to place the electrodes under each eye.

But we're also going to place an electrode just on the bridge of the nose.

This is also seen on the chin in some montage descriptions, so let's get the skin prepared, so we'll take some electrode gel.

We don't need a great deal here just to prepare the skin, so we'll take a little pea size amount, and then start preparing the skin.

So we're going to rub in the areas where we're going to place our electrode montage, so one up at the top here where we're going to place the ground, bridge of the nose and then underneath each eye.

So now sometimes we can get the patient to look up to do this, we can also just pull the skin to create a little tighter area.

And now we're ready to put our electrodes into position, so we're using surface electrodes we place our ground in position, just squeezing around the outside, so we don't remove any of the conductive gel.

For this one on the bridge of the nose, again, trying to keep this nice and central, we use this for the reference for both the right and the left sides.

Now because we can't see the inferior oblique muscle, we look at the central part of the eye.

And the montage suggests that we just place sweeping out to the side.

So place that in position this is delicate skin under the eye, so we do have to be careful as we place them and being mindful of eyelashes as well.

Patient is looking up to help us, you can place and just gently press.

Next, we'll take the electrode we are placing on the bridge of the nose, again, keeping that tidy.

Now the trick with this is that we know where the ocular VEMP is a crossed response.

So we're placing the right electrode actually underneath the left eye, tidy that, and that leaves us with the left electrode to place it around and underneath the right eye.

We’ll check our impedances, and those are nicely balanced at around four kiloohms.