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Differentiating Causes of Dizziness: Assessment of Vestibular Function

Author Julia Casazza covers Differentiating Causes of Dizziness: Assessment of Vestibular Function on BackTable ENT

Julia Casazza • Mar 27, 2024 • 31 hits

The vertigo and vomiting associated with labyrinthitis can mimic that of more serious conditions – including stroke. Fortunately, a battery of physical exams and quantitative tests exist to help clarify the nature of a given vestibular injury. New York City-based otologist and neurotologist Dr. Sujana Chandrashekar recently sat down with BackTable to describe how she evaluates suspected vestibular injury.

This article features excerpts from the BackTable ENT Podcast. We’ve provided the highlight reel in this article, but you can listen to the full podcast below.

The BackTable ENT Brief

• When evaluating a patient with dizziness, imbalance, or vertigo, the first step is to identify whether the pathology in question affects the peripheral or central vestibular system. Central vestibular lesions are caused by stroke or other brain injury and thus require urgent management.

• Frenzel glasses – illuminated glasses with 20D lenses – can be used to uncover suppressed nystagmus.

• Videonystagmography (VNG) and posturography provide quantitative insight into vestibular function.

• A positive Romberg test indicates damage to the dorsal columns of the spinal cord or the vestibular system of the inner ear. The Fukuda Stepping test enables clinicians to identify the laterality of a vestibular lesion.

Differentiating Causes of Dizziness: Assessment of Vestibular Function

Table of Contents

(1) Central vs. Peripheral Vestibular Disease in the Dizzy Patient

(2) Testing the Vestibular Ocular System

(3) Assessing Balance & Coordination in the Dizzy Patient

Central vs. Peripheral Vestibular Disease in the Dizzy Patient

Initial evaluation of the dizzy patient focuses on differentiating peripheral vestibular lesions (e.g. labyrinthitis) from central vestibular lesions (e.g. stroke). Start by looking for spontaneous nystagmus. If the patient does not have spontaneous nystagmus, Frenzel glasses can remove visual fixation to uncover suppressed nystagmus. A patient with a peripheral vestibular lesion will have horizontal rotary nystagmus, where the initial movement is fast and correction is slower. Patients with central vestibular lesions have pure horizontal, vertical, or torsional nystagmus with pupils that move at a constant speed.

Labyrinthitis is a peripheral vestibular lesion. In some cases, inflammation causes sensorineural hearing loss. If testing supports diagnosis of labyrinthitis, patients should undergo hearing testing. Audiograms are preferred, but Weber and Rinne tests will suffice for a severely symptomatic patient.

[Dr. Sujana Chandrashekar]
You can do a nice 512 Hertz tuning fork test. Just do a Weber and a Rinne. Just make sure that there's some hearing in that ear. Then you want to, as best as possible, do some vestibular testing that you can do, that doesn't require really any machines. I must tell your listeners, the best article on this is written by JA Goebel, and it's, the ten-minute exam of the dizzy patient. It is excellent. He just breaks down really complicated vestibulo-ocular, vestibulo-spinal, central-peripheral vestibular disorders into, what are you looking for and what bucket can you put the patient in? Because you want to say, is this a central bucket or a peripheral bucket?

In this case, in an acute vestibulopathy situation, you're really looking at peripheral being vestibular or ear as opposed to oculomotor or something else. What you want to do is once you've examined the patient, and you happen to have what I think was bullous myringitis, which is very common after a URI, very common with the blebs, very common with a little bit of mixed, a little sensorineural component, like everything you're telling me sounds like that.

Often with serous labyrinthitis or viral labyrinthitis or viral neuronitis or vestibular neuritis, which are all the same thing, you actually don't see much of anything. Maybe they tell you they had a cold a couple of days ago. Maybe they didn't. You want to see if there's an acute otitis media. You want to see if there's something to give you a clue. Then you want to start looking at the eyes in particular.

If you're ready, we can dive into the thing that makes everybody really nervous. I remember when I was a resident, my chair, the late Dr. Noel Cohen, asked us to write an essay on nystagmus and like what it meant and how you look and this and that. I wrote and I wrote and I wrote because I am nothing if not a nerd and able to put lots of words on paper. He just returned that paper to me. He was left-handed with left-handed handwriting on top in red. It said, where'd you come up with this idea?

I don't know. I don't know. I guess I thought it made sense when I wrote it down. I think we have a tendency to make things seem more complicated than they are. It's beautiful to understand the complexity of the central and peripheral vestibular system. For the patient in front of you and for your own sanity, if you want to talk about not burning out, simple things that allow you to truly break it into buckets of central versus peripheral are very helpful.

You're going to first start by looking for a spontaneous nystagmus. You're just going to have the patient sitting in front of you. You're going to have them with their best corrected vision. If they wear glasses or contacts, they should be wearing them. Just look for, at rest, do they have nystagmus at zero degree with their glasses or their natural vision? Then you can put Frenzel glasses on them and see if you remove visual fixation. The Frenzel glasses, if nobody knows, are sort of like Coke bottle bottom glasses. They really just remove the visual fixation so that your eyes can't compensate for whatever baseline nystagmus is going on

You just say, is it present or is it absent? Normal people don't walk around with nystagmus. Then you're going to say, well, is it a jerk nystagmus or is it a pendular nystagmus? Is there a fast and slow phase or are both phases very similar to each other, which would be pendular nystagmus? Then you're going to say, is it directional? Is it a vertical nystagmus? Is it a horizontal nystagmus? Is it direction changing or direction fixed? If you have them look to the right, does it stay beating in the same direction or does it change directions when you have them look over to the left?

Is there an effect of fixation? If you put the Frenzel lenses on, does it change? Then is there an effect of eccentric gaze? If you have them look up and out or down and out, does something happen to the nystagmus? This is sort of, it sounds complicated, but if you make it almost a recipe for how to check, you can actually figure it out. What happens, either they have no nystagmus or, which is normal, or in peripheral pathologies, the nystagmus is an acute peripheral pathology, like labyrinthitis, spontaneous, it's direction fixed, meaning that it doesn't change direction when you look right or left. It's usually horizontal or rotary. It's usually a jerk nystagmus with the fast phase being away from the site of lesion.

If you think about it, it's jerking away and then slowly compensating back to the site of lesion. It's usually enhanced with gaze in the direction of the fast phase or when you remove visual fixation with a Frenzel lens, right? I'm going to say that again, just because this is the part where everybody gets crazy. Again, for peripheral, acute peripheral lesions, you're going to look for spontaneous, direction fixed, horizontal rotary nystagmus. It's going to be a jerk type of nystagmus with the fast phase away from the site of lesion, and it's going to be enhanced with gaze in the direction away from the site of lesion. In the fast phase, or if you put Frenzel lenses on.

Listen to the Full Podcast

Labyrinthitis Unpacked: Clinical Perspectives & Management with Dr. Sujana Chandrasekhar on the BackTable ENT Podcast)
Ep 154 Labyrinthitis Unpacked: Clinical Perspectives & Management with Dr. Sujana Chandrasekhar
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Testing the Vestibular Ocular System

Function of the vestibular ocular system can be assessed using ocular alignment tests, dynamic visual acuity tests, and with videonystagmography (VNG). Ocular alignment tests require the examiner to cover one eye and look for skew in the other. Ocular misalignment suggests an otolith issue. During dynamic visual acuity testing, the examiner rotates the patient’s head at a 2 Hz frequency and asks the patient to read off lines from a Snellen chart. A patient with no vestibular pathology will lose two lines, one with a unilateral peripheral lesion will lose 2-3, and one with bilateral peripheral lesions will lose at least 3. If more quantitative testing of the vestibular ocular reflex is desired, VNG should be performed.

[Dr. Sujana Chandreshekar]
You can look for the alternate cover tests of ocular alignment. You have the patient just looking at you and you cover one eye, you cover the other eye and you look for skew. If it's an otolith lesion, so it's a vertical ocular misalignment. The vestibular tone is wrong.

If it's a peripheral lesion, you'll see a transient skew deviation with the lower eye on the side of the lesion. Acutely, that may be absent. You may not see that in the acute phase. With central lesions, this is usually associated with head tilt and an ocular counter-roll. You'll see the patient sort of compensating for it. You want to look for gaze-evoked nystagmus. We just talked about nystagmus at rest, right? Spontaneous nystagmus. We do take our finger and put it in front of people's eyes, right? What you don't want to do is stress the system.

When you're doing gaze-evoked nystagmus, you want to go 20 or 30 degrees horizontal and 10 or 20 degrees vertical. You don't want to go all the way to the end of the visual field because actually we have physiologic nystagmus at the end of our visual field. You're looking for gaze-evoked nystagmus, you're going to see direction fixed, which is more obvious in the direction of the fast phase, which we said was away from the site of lesion.

In central nystagmus, you're going to see that that gaze-evoked nystagmus is direction-changing. You could have rebound nystagmus. It's a little funny looking. Nystagmus that doesn't seem to point to either one side or the other, you really do have to think about central phenomenon there. On VNGs, when you guys order them or read them, you'll see all this saccades and smooth pursuit testing. For VNG, they do it with lights on a light bar in the office. You can again do it with your finger or you can have some dots on the wall.

Really, if these are abnormal, if they can't do smooth pursuit properly or have really jumpy saccade testing, like going from one dot to another dot to another dot, those are really central findings. If there are saccadic intrusions, they are sometimes reported with paraneoplastic syndrome, but often with anxiety. People who are just like weaked out by the test.

You can check for dynamic visual acuity. You have the patient hold a Snellen eye chart and you see where they can read the chart comfortably. Then you rotate their head at about two hertz constantly like this, while they continue to read the eye chart. Normal people lose less than two lines of visual acuity on the eye chart. With a unilateral vestibular lesion, they lose two or maybe three lines. With bilateral, they lose more than three lines. Then it's quite variable with central.

Assessing Balance & Coordination in the Dizzy Patient

Testing balance and coordination can help clinicians correctly identify a neurologic lesion. During the Romberg test, the patient stands with his feet close together, hugs himself, and then closes his eyes. Normal balance relies on functioning of the visual system, the dorsal columns of the spinal cord, and the peripheral vestibular system. At least two of these components must be intact to elicit a “negative Romberg.” If the patient falls over after closing his eyes, this is considered a positive test, which indicates damage to the dorsal columns or the peripheral vestibular system. During the Fukuda stepping test, the patient extends his arms and marches for 50 steps with his eyes closed; rotation greater than thirty degrees constitutes a positive result. The affected side is the one that the patient rotates towards.

Fine finger movement, posturography, and gait testing measure coordination. To assess fine finger movement, ask the patient to take his thumb and touch each finger on the same hand. Slowed coordination or difficulty completing the task suggest central cerebellar dysfunction. Posturography quantifies abnormalities in patient posture. Gait testing (e.g. the timed “get up and go” test that requires a patient to rise from his chair, walk ten meters, turn around, and return to the chair) assesses ambulation.

[Dr. Sujana Chandrashekar]
It's dysdiadochokinesis. It's like the coolest word ever. It has a Y, it has a CH, it has a K. It's awesome. I remember learning it from a neurology professor on a rotation up at the Harlem Hospital. I'm like, that is, patty cake is basically the test of dysdiadochokinesis. I love that. That's where you have the patient sort of essentially play patty cake with themselves and make sure that they can do palm down, palm up in an alternating fashion. If they can't do that, that's a significant peripheral sign.

Then you're going to look also for fine finger movement. You're going to basically have them take their thumb and touch their fingers in alternating, just have them do this, where they're just basically finger to four, three, two, one, one, two, three, four. That should be able to be done without difficulty.

If you have a dizzy patient without a really significant unilateral ear pathology, and all of these findings look abnormal, you're really looking at a central dysfunction, an acute central dysfunction. I think that's a really important bucket. You really want to very much know. Then you want to look for Romberg testing. This is later on, right? This was you maybe two weeks later. Okay. Can you do a sharpened Romberg?

What's a sharpened Romberg? Put your feet as together as possible, cross your arms so that you're essentially hugging yourself and just stand straight. Then you as the examiner should stand on either side of the person with your hands out, not touching them, but ready to catch them should they start tipping over. Then you say, okay, now close your eyes. You will find that as a young person like you, Ashley, compensated, you would find that you swayed more maybe week one and a lot less week two. By week three, you really didn't sway at all. Sometimes people do fall over because they're so bad. You really, unless you like picking people up off the floor, you should probably catch them.

There are in fact, posturography is a great way to identify people who may have a physiologic sway. Because we know how much is physiologic sway. If there's a secondary gain or there's some other reason, you will find that it's a very, if you test enough people in your office, or in the clinic, you will find that you can recognize physiologic versus aphysiologic very readily.

You can find that with the Romberg. You can find that with a Fukuda step test, which is where you have them stand with their feet sort of shoulder length apart, just normal stance. Their arms are now at their side. They're not making themselves as small as possible. Or, you can make the Romberg a little bit more challenging by having them put one foot in front of the other or cross their feet. I know that you're supposed to do that. I have never really found that helps more than anything other than it freaks everybody out that they're going to fall down.

For the Fukuda, they're very comfortable stance. Then you have them just march in place. You say to them, okay, when you're good and ready, and again, your arms are at either side, you ask them to close their eyes. If within about 15 to 20 seconds, if they turn, they are turning toward the weaker side, the strong side is pushing them. They will turn towards the weaker side. If they just sway, or if they just feel very off balance, it's just sort of an uncompensated vestibular dysfunction, but it doesn't tell you a side.

You can look at gait testing. One of the really good tests that we've incorporated from the physical therapy literature is something called the timed up-and-go test. What you do with that, it's a great test for falls risk. This is really important, as we're treating an older population and a population that's often on some sort of blood thinner. This is now later on in the course. This is not the acute phase.

Podcast Contributors

Dr. Sujana Chandrasekhar discusses Labyrinthitis Unpacked: Clinical Perspectives & Management on the BackTable 154 Podcast

Dr. Sujana Chandrasekhar

Dr. Sujana Chandrasekhar is an otologist / neurotologist practicing at ENT and Allergy Associates in New York City.

Dr. Ashley Agan discusses Labyrinthitis Unpacked: Clinical Perspectives & Management on the BackTable 154 Podcast

Dr. Ashley Agan

Dr. Ashley Agan is a practicing ENT and assistant professor at UT Southwestern Medical Center in Dallas, TX.

Cite This Podcast

BackTable, LLC (Producer). (2024, January 16). Ep. 154 – Labyrinthitis Unpacked: Clinical Perspectives & Management [Audio podcast]. Retrieved from https://www.backtable.com

Disclaimer: The Materials available on BackTable.com are for informational and educational purposes only and are not a substitute for the professional judgment of a healthcare professional in diagnosing and treating patients. The opinions expressed by participants of the BackTable Podcast belong solely to the participants, and do not necessarily reflect the views of BackTable.

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