BPPV: An Introduction (1/3)

This video is part 1 of 3 of the Interacoustics Webinar "Beyond 2D eye recordings - The importance of measuring torsion and dynamic head movements in the diagnosis and treatment of BPPV” In the first part of this webinar, Darren Whelan provides an introductory overview to BPPV, its diagnosis and treatment, as well as the challenges facing clinicians and recent technological advances in the field of BPPV.

Read the full transcript below.

Welcome to this webinar: Beyond 2D eye recordings: The importance of measuring torsion and dynamic head movements in the diagnosis and treatment of BPPV. My name is Darren Whelan. I have the pleasure of opening this webinar today before handing over to my expert colleague Dr. Michelle Petrak to examine some case studies. And then summarizing towards the end, I'll be back.

So let me just quickly recap what the objectives are for today's webinar. We're going to have a look at the benefits of using an accelerometer to detect head position during a BPPV assessment also. Then looking at the benefits of a torsional algorithm to identify the affected canal in BPPV and looking at torsional eye movements in general when we look at positioning and positional assessments.

And then finally, at the very end, we'll come back and just take a moment to look at the benefits of pairing these torsional eye movements, these 3D eye movement recordings, with a repositioning chair such as the TRV Chair.

History of BPPV

So whilst this webinar is not a deep dive into the pathophysiology and the fundamental properties of benign paroxysmal positional vertigo, I think it always is nice to take a moment just to take a quick glimpse into the history of where we are at with that particular condition because it sometimes illustrates and highlights where we currently sit in terms of our understanding of where the technology is being incorporated into both the assessment and the treatment.

So if we take a moment to step back a little bit in time really. Some of the first descriptions of BPPV, certainly in the medical literature and there are some further back in literature in general, but in the medical literature are attributed to Adler in 1897. But really, it's Robert Bárány who probably made the first descriptor of this paroxysmal element of vertigo and the cause of this being potentially from the utricular system.

And then we move a little bit further in time in the 20th century and we come across what now has become very familiar terminology to us in our field. Margaret Dix and Charles Hallpike, who were working together in Queens Square in London, England did really the first in-depth analysis of 100 patients who they were seeing with this condition of benign paroxysmal positional vertigo.

And they devised the provoking maneuver, actually the 'Lagerungs' maneuver as described within their literature that then became the gold standard test for BPPV, particularly the posterior canal. And that we now call the Dix-Hallpike test.

But even then, the pathophysiology, the actual process behind how this condition was affecting the peripheral vestibular semicircular canals in particular, wasn't really fully understood. And the first highlight to that was Schuknecht in 1969 actually doing some histology of temporal bone examinations and came with the theory of cupulolithiasis.

So the idea that these otoconia were in the semicircular canal and were potentially resting on the cupula making it much heavier and gravity sensitive. And if you like some nice reading, there's a very detailed paper by Dix and Hallpike from 1952, looking at three different groups of patients with vestibular conditions of which the hundred patients with BPPV are described.

Moving a little bit further forward into the 20th century, we really got the two further names that join us in terms of both the assessment and the treatment of BPPV, which were Alan Semont, a physical therapist in France, who also came across a provoking and treatment option for BPPV, the Semont maneuver, and the side-lying test being part of that, in 1988.

And then the movement in understanding some of the pathophysiology of BPPV and canalithiasis was proposed by John Epley. And certainly by the latter end of the 1980s and early 1990s, a group of medical specialists came up with the treatment option then of the Epley maneuver, which we now see as being much the common treatment option for posterior canal BPPV that we utilize today in clinic.

What is BPPV?

So let's take a moment just then to consider with that information, what we're referring to when we collectively talk about BPPV, this benign paroxysmal positional vertigo disorder. So, let's take a moment and consider what we're actually referring to in terms of the process of what's happening in BPPV.

So essentially, what we're referring to is this condition where otoconia becomes displaced from the utricular system and makes its way into the semicircular canals. And, as we've just mentioned, there are two processes that we see commonly.

Canalithiasis, which we think 90% of BPPV is attributed to, which is the displacement of these otoconia that are free floating within the endolymph of the semicircular canal.

And cupulolithiasis, which is the Schuknecht theory, where the otoconia is actually adhered to the cupula itself making it heavier and gravity dependent.

So essentially, BPPV is characterized by these brief episodes of vertigo, more commonly referred to as spinning dizziness. But it can be referred to by different descriptors induced by a change in head position.

Now commonly, this would be laying down or turning over in bed. But certainly, we may see that by tipping our head back or tipping our head forward, if we were reaching up for something off a shelf or closing a curtain for example.

So it's the mechanical displacement of that otoconia from the utricular system, the otolith organ, into the semicircular canals that makes an angular sensor, which is what our semicircular canals are, gravity sensitive.

And that's where we get this conflict within the sensory systems providing information to the brain that doesn't correspond to the actual head or body movement that we have undertaken.

So when we see BPPV in the clinic, actually what we're seeing is patients that frequently are experiencing an unexplained sensitivity to movement of which then we need to identify what might be causing that condition.

And we have some great guidance and documentation that enables us to really adhere to the diagnostic criteria to separate out BPPV, thinking of this as a benign treatable condition from other things that would be a red flag, maybe requiring different medical management and investigation.

And one here that we've referred to is the Bárány criteria, the benign paroxysmal positional vertigo diagnostic criteria, by the Bárány Society published in 2015.

So what remains a challenge, even looking at the descriptors for the diagnostic criteria, is how do we locate or how do we ascertain where these otoconia have become displaced? Because as we know, the vestibular end organ and the inner ear itself are within the bony labyrinth.

So therefore, it's not possible for us to access it and look at it in a way in which where we could observe what was happening at that level. We really then need to look at some of the interactions of the reflexes.

And that then becomes key in terms of both diagnosing the location of the otoconia that's floating around in the semicircular, but also which process is occurring. Is it cupulolithiasis or is it a canalithiasis BPPV that's causing these alterations? And that's really where eye movements become key and important.

As we know when examining BPPV in a patient and using the provoking assessment procedure, whether that's the Dix-Hallpike procedure or the Semont side-lying procedure, it's really those eye movements and the activation of the VOR response that's giving us a location of where the rogue signaling is coming from the peripheral end organ.

Prevalence of BPPV

Now, BPPV itself is often reported as occurring spontaneously in the population, certainly as we become older adults of the 50- to 70-year-old group. And some of the statistics do show different levels of prevalence.

And I think part of that depends on which clinic you're counting your data from, whether it's an ENT or a neurology or a primary care clinic. But also which age range is in your data sample.

But typically, what we're expecting to see is that of patients that report dizziness, up to 30% and certainly on average 25% may have BPPV as part and parcel of their reported symptoms.

And that could be an idiopathic BPPV as we describe something that just has literally occurred spontaneously. And we think that may be from an aging utricular system not holding on to the otoconia quite as well as it would have done when it was younger.

Or it could be as a secondary issue related to other vestibular lesions that's affected the peripheral end organ, where BPPV becomes a secondary concern after that lesion has occurred.

BPPV evidence base

So what about the evidence base with BPPV? Well, there's a growing evidence base of the interest of looking at three-dimensional analysis of the nystagmus. Because typically up to this point in time, when we've looked at BPPV and we're looking for the characteristic torsion of the eye movement created by the location of the otoconia, we're doing that under direct observation whether we've recorded that or whether we're looking at that through a Frenzel goggle or actually just observing the eyes. We're looking at the direction of the eye movement.

If we've been under VNG goggle recording, then we've got horizontal and vertical channels being represented. But up to now, not really a clinical application of being able to capture the torsional element of the eye movement.

And the clinical practice guidelines show interest into locating the area of concern for BPPV by examining the eye movement and suggesting that certainly moving towards video-oculography or VNG recording of eye movement is becoming much more preferential in being more precise about identifying BPPV and separating it out from pseudo BPPV or non-benign BPPV.

Now, for those that have a little bit more interest in BPPV and want to understand a bit of the history and the pathophysiology, office treatment, and future directions, I can certainly make a recommendation of a paper that we have here by Dr Jeremy Hornibrook that gives a great overview and whets your appetite in terms of where BPPV has been developed and our understanding over time.

2D eye movements

Let's get back to the topic of today's webinar now that we've set the scene and look at eye movements. So the clinical challenge that we have, whether we're doing it under direct observation, a Frenzel goggle, or VNG, is what direction is the eye actually moving?

Now we've said that in BPPV, these are generally quite short latency, so quick eye movement responses. And their duration can be quite short. But the patient does experience quite a violent sense of dizziness.

So understandably, for those that have done many BPPVs, the eye movements are quite short. We're dealing with quite an anxious patient. Often, they're feeling dizzy. They may be seeing the room moving around them and they want to close their eyes, so it's a challenge.

How do we establish what the direction of the eye is moving to be accurate in terms of both separating out any red flag movements but also being able to then confirm the presence of the semicircular canal so we can carry out the correct repositioning maneuver?

As things stand presently, to carry out a Dix-Hallpike, we have the patient seated, we turn their head to 45 degrees to localize the side that we want to investigate. So in this illustration, we have the head turned a little bit to the right. We then lay them down.

Now, the head does need to be a little bit lower than the body, so extended somewhere between 20 to 30 degrees. So you can use the back of a table to do that or a cushion behind them. And then we can observe the eyes.

So as we said, the options for observing the eyes could be direct observation, a Frenzel observation. So we're trying to take away any points where the patient could fixate or certainly to take away some of the movement the patient might be seeing.

But what we would be proposing, as we've said in the guidance that's come before, is looking at the more direct observation, so video-oculography or videonystagmography (VNG). So being able to actually record the eyes whilst the patient is in the provoking position to establish an objective measurement, which we could then go back and re-examine without having to re-test.

Because those of us that are familiar with BPPV know that it can habituate as we do repeated testing. And also, the patient feels quite unwell if we keep testing them over and over again.

So we've got a record there of a video that we can review and even consult with our colleagues and obviously document what the severity is. So that's really covered up. So that's really brought us up to having a 2D recording of the eye, both in the vertical and the horizontal planes.

But so far, we haven't touched on the 3D element, the torsion. And that's where the movement towards an Advanced Dix-Hallpike comes into play.

3D head model

So when we're talking about the Advanced Dix-Hallpike, the first element that makes it a little bit more advanced is the application of a 3D head model. So what you can see here is the model within the VNG software of the orientation of the head relative to the position of the body and the semicircular canals.

Now, that allows us to position the head very precisely both into the testing and provoking conditions so we can correlate the localized semicircular canal that you can see here, Dix-Hallpike to the right, head extended.

And so we've got the position to the right, we've got the other bar telling us the position of the head is down, and we're getting a visual representation that the head is in the correct position for the test. So we can have a look at the eye movement.

The next thing to facilitate that head model is obviously the VNG software needs to know where the head is in position. So that is in the incorporation of an accelerometer on top of the VNG goggle to precisely orientate the calibrated system.

This gives us effective feedback through the model to make sure we're in the exact position to have the maximum stimulation for the identified semicircular canal. Let's look at that in a little bit more detail.

So at the very top screen here, you can see the right and left eyes being represented with almost what looks like a crosshair. We can see the model in a little bit more detail now. Moved the head to the right. We've laid the patient down. They're into the down position, head extended.

The model is indicating that and then we can see that characteristic eye movement being represented. So we've got objective recording of the torsional velocity on the bottom right but also the position in the horizontal plane as well. So we've got right to left clockwise and counterclockwise being represented.

Torsional eye tracking

Now, looking at the torsion tracking itself, we can see there's a lot of detail in here looking at both the horizontal, vertical, and torsional eye movement. And again, if we look, you can see in the time base as the recordings are being generated, we're able to quantify those and measure them in degrees per second of movement.

Now, this gives us a very clear objective measurement of the eye behavior. And it also allows us to separate out just pure torsional nystagmus from nystagmus that also is being influenced in the up or down positions.

Having the ability to record in 3D not only allows us to objectively measure those eye movements in the clockwise and counterclockwise directions and have a hard recording so we can review that with our peers, but it also gives us so much more data when looking at eye behavior.

Both in the provoking conditions but also then as we move through the repositioning, we can almost track how the behavior of the eye is being influenced by the otoconia moving through the semicircular canal.

But it also lends us a little bit more information. And we've alluded a little bit in this initial introduction towards the separation of benign paroxysmal positional vertigo from pseudo BPPV. So, non-benign conditions that may have torsion. So, central conditions.

And again, it's at this point that it gives me great pleasure to hand over to my colleague Dr. Michelle Petrak with her expertise in examining some cases to present to you on how the data may look different depending on what is the provoking pathology.

Watch or read next: BPPV: Case Studies (2/3)

Related courses

• Advances in BPPV
• BPPV: The importance of torsion and performing the maneuvers correctly