Australasian Science: Australia's authority on science since 1938

Spin doctors: Identifying and treating human balance disorders

By Shane Huntington

Neurologist Dr David Szmulewicz describes the human balance system, and what’s going on in our brains and ears when we experience vertigo.

SHANE HUNTINGTON
I'm Dr Shane Huntington. Thanks for joining us. Most of us at some stage in our lives attempted to achieve the difficult task of taking a doll or action figure and standing it upright. At first glance, it would seem that these simple miniatures of the human form should stand as easily as we do but sadly they too easily topple over. Of course the reason for this poor performance is because these replicas lack something that we possess, namely a sophisticated balance system. The human body and that of many other animals has evolved a system of balance that is more sophisticated than anything we are yet able to model or reconstruct in the lab. Our balance system enables us to manage extraordinary acrobatic acts and, on a simpler scale, safely perform the necessary movements of day to day life.
But what happens when this system fails? How do we react to a lack of balance and what can we do to resolve problems of this type? To discuss the balance system of the human body, the problems that can arise and the treatments that have been developed we are joined today on Up Close by Dr David Szmulewicz, a neurologist at the Royal Victorian Eye and Ear Hospital here in Melbourne, Australia.
Welcome to Up Close, David.

DAVID SZMULEWICZ:
Thank you, Shane.

SHANE HUNTINGTON
Before we discuss the way in which the human body actually generates this perception of balance, I want to start with a description of dizziness and vertigo. These terms are often used interchangeably. Do they mean the same thing?

DAVID SZMULEWICZ:
Not to us. So in the area of balance medicine, dizziness is a much more general term, far more inclusive whereas to us vertigo is quite specific. The broad definition of vertigo is an illusion of movement, however most commonly it's an illusion of rotatory movement such that a patient might describe spinning as if on a merry-go-round.

SHANE HUNTINGTON:
In terms of our bodies, what systems are involved in us having this perception of balance?

DAVID SZMULEWICZ:
It's a joint effort really. As you mentioned in your introduction, it's a combination of systems. The first one is the inner ear balance mechanism or vestibular system, the brain in general but particularly the cerebellum or coordination centre of the brain as well as our vision so we're constantly receiving visual cues from our environment.

SHANE HUNTINGTON:
Let's go through these one by one and start with perhaps our vision. How does our vision give us the balance perception that we all feel?

DAVID SZMULEWICZ:
We're constantly looking at our environment, we're getting horizontal and vertical cues from our environment such that if our brain perceives that we're moving, for example, to one side relative to a vertical line, for example the outline of a window, then there are mechanisms that will right us straight away without us knowing.

SHANE HUNTINGTON:
You mentioned the brain. This obviously has a separate role to play, separate to the eyes and the ear. How is that working?

DAVID SZMULEWICZ:
The brain really is the master controller in all this so it's receiving an enormous amount of input not only from vision, not only from the inner ear, not only from the cerebellum or coordination centre but also from our joints, for example, which have small spindle-like receptors and are able to inform our brain, if you like, of the position of that joint in space. Furthermore, the sense of touch is important so we're constantly receiving information on where the ground is relative to our feet, which is very important.

SHANE HUNTINGTON:
What happens when we go and we see a three dimensional film, for example, and there's a lot of motion so our eyes are being stimulated but the rest of these balance sensors are not? How does the brain deal with that situation?

DAVID SZMULEWICZ:
The answer is variably. Certainly the picture makers are very clever and manage to trick our brains into perceiving motion that clearly is not there. We all sit on a continuum in terms of our sensitivity to visual motion and so while some people sit there and think it's great fun, those people who perhaps have a predisposition to imbalance can feel very yuk and that's because some of us are very visually sensitive to motion.

SHANE HUNTINGTON:
How do the ears play the role of providing us with balance?

DAVID SZMULEWICZ:
The ears are often synonymous with hearing because hearing is a sense that we're all aware of constantly. Balance is something that we're not usually aware of until it goes wrong and then we're acutely aware of it. Deep in the inner ear which sits under the brain within a thick portion of skull is the cochlear which is the snail-looking part of the inner ear which most people will know is associated with hearing perception but it has a couple of neighbours and one of the neighbours are three semi-circular canals, which perceive angular motion and they're orthogonally arranged such that motion in any plane will be perceived. The other neighbours are the otolith organs which sense linear motion.

SHANE HUNTINGTON:
It seems quite extraordinary that the evolution of the body was such that hearing and balance ended up being essentially done by many of the same components.

DAVID SZMULEWICZ:
Absolutely and they share a nerve so the electrical pathway or highway if you like back into the brain is shared. Clearly these two very basic senses evolved to be absolutely mandatory for survival quite early on and the vestibular system is very well conserved from an evolutionary point of view.

SHANE HUNTINGTON:
Now we're getting all of this information coming into our brain from these multiple sources throughout our body, also our eyes and the system in our ear. How does the brain know what to prioritise in order to give us a sensible sense of balance?

DAVID SZMULEWICZ:
The integration occurs at multiple levels but I think there are a couple of important processes and one really is in terms of a gate or a filter through the hypothalamus and thalamus such that we're not if you like overwhelmed by all this sensory input. So at that level there's already quite a bit of if you like prioritising and discounting. Then there's a kind of linking or joining up of various bits of information and when our balance systems are working normally things are then again discounted or discarded where there's some degree of mismatch if you like.

SHANE HUNTINGTON:
The way you describe the inner ear sounds more like a mechanical structure as opposed to a more biological structure. Is that a fair statement?

DAVID SZMULEWICZ:
Yes, I think that's right. I think it is a very physical or mechanical structure whereby gravity acts on certain physical structures which move within those inner ear vestibular organs and the movement or deflection of certain structures then generates different patterns of sensory information going up into the brain.

SHANE HUNTINGTON:
Do you find it surprising that the human body is capable of still dealing with sensory inputs of these types when we're under extreme conditions, fighter pilots, gymnasts and so forth? It seems as though the inputs are extraordinary rapid and detailed for some of those people.

DAVID SZMULEWICZ:
Absolutely and if like me you're a fan of the theory of evolution then it makes a lot of good sense because under those very situations when we're probably at most threat and really things have to be automatic or a reflex if you like, because if you think about the savannah back in Africa, if the lion comes after you, you need to move very quickly, there's no room for conscious thought.

SHANE HUNTINGTON:
David, when you describe the various parts of our balance system, in some people of course these parts are non-functioning so we have people who have lost their sight or are born without sight, similarly for hearing. What is occurring for them in terms of establishing a sense of balance and how is it different for a person who has been born with this condition versus someone who acquires it through accident or disease or otherwise?

DAVID SZMULEWICZ:
There's a significant difference really. In children who are born without fully functioning senses such as balance or eyesight or who lose it at a young age the brain is quite amazing. The term that we use is plasticity so really it's able to reroute, redesign, rebuild its information pathways such that there is often negligible impact. We see this in some of our children who are implanted with a cochlear implant and, for instance, they might be born with a very abnormal inner ear affecting both their hearing and balance and yet these kids are running around, jumping normally. The one caveat on that is certainly in a dark room they suffer. So again these children are much more visually dependent.

In adults who have compromised senses such as the inner ear balance mechanism, again the process of compensation is much less perfect. It varies. It often needs coaxing and for this really probably the most evidence-based medicine if you like is specific vestibular physiotherapy or rehabilitation.

SHANE HUNTINGTON:
I'm Shane Huntington and you're listening to Up Close. In this episode we're talking about the phenomenon of vertigo with neurologist Dr David Szmulewicz.

David, as a neurologist specialising in balance disorders, what kind of patients actually get referred to you?

DAVID SZMULEWICZ:
A range of patients. Given that we're in a subspecialty hospital so the Royal Victorian Eye and Ear Hospital in Melbourne, Australia, we tend to see quite a large subgroup of patients who have presented diagnostic dilemmas to their doctors. So we do see the more complex and if you like fancy conditions but we also see a lot of the basic or garden variety dizzy disorders coming from either general practitioners or family physicians, physiotherapists or physical therapists as well as from within the hospital itself.

SHANE HUNTINGTON:
How common are these sorts of balance disorders in the general population?

DAVID SZMULEWICZ:
Very common. The first comment to make is that the collection of epidemiological data or how often these disorders occur is fraught for a number of reasons and not the least of which is that it's thought that the more common conditions are significantly underreported and under-recognised in general practice. But the Germans in 2005 put together some data based on around 5000 patients and the lifetime prevalence there was about 30 per cent.

SHANE HUNTINGTON:
That's quite extraordinary and these are people who go untreated, a large portion of them, presumably?

DAVID SZMULEWICZ:
Yes, quite right.

SHANE HUNTINGTON:
Now I'm going to give you an acronym, you can explain what it means. BPPV is one of the areas that you work on quite extensively in your practice. What's happening in the inner ear in this particular case?

DAVID SZMULEWICZ:
Yes, BPPV or benign paroxysmal positional vertigo is the most common cause of vertigo and here in the horizontal semi-circular canals which I mentioned earlier as part of the vestibular system, there are quite dense calcium carbonate stones which are attached to sensory hair cells and so the idea is that the gravity acts on these dense ear rocks and that causes deflection of the hair cells and alters the firing rate of those neurons. What happens in BPPV is that these normally occurring yet attached ear rocks become displaced. They can then float freely in the fluid which is contained in the semi-circular canal and basically cause havoc. So what happens classically is you get episodic motion induced rotatory vertigo so the patient will describe rolling over in bed and a short period of the room spinning around.

SHANE HUNTINGTON:
Now presumably without these rocks attached to the hairs, the hairs are just sitting there and not doing anything, is that right? So they're not contributing to the balance system at that point?

DAVID SZMULEWICZ:
Well they're contributing far less than they would be. The point is though that there are very, very many and the vast majority will still have these dense ear rocks attached.

SHANE HUNTINGTON:
Now you can't diagnose a patient in this case by just looking into their ear and seeing these particular crystals or rocks. How do you go about determining if someone has this condition?

DAVID SZMULEWICZ:
Some patients find it quite perplexing that we don't look into their ear. We actually look into their eyes. The important thing here is that the vestibular system has significant input into vision. If you think about the fact that we're intensely visual beings, we rely on vision to navigate our environment, then it's very important that we're able to acquire and maintain a clear visual image. Given that we're sort of long tall beings with eyes up near the top of our heads, it's very important that despite the head and hence eyes are moving all the time that we maintain clear vision.

Part of how we do this is through the vestibular system and specifically a reflex called the vestibular ocular reflex or VOR, which very simply says that every time your head moves in one direction your eyes are driven an equal and opposite amount to cancel out any movement of the vision and hence we maintain a clear visual world. We rely on these eye movements particularly when there's something wrong with the function of the inner ear because the eye movements will be abnormal.

SHANE HUNTINGTON:
Does that mean that a person with this condition essentially feels a problem whenever they move their head?

DAVID SZMULEWICZ:
That is the classic presentation, yes.

SHANE HUNTINGTON:
It sounds like the rocks essentially have gotten into the wrong part of the ear. Is treatment as simple as getting them back and how do you go about that?

DAVID SZMULEWICZ:
Treatment is actually as simple as tipping them out of where they're causing havoc which is the semi-circular canal into an adjacent area where there isn't this sensory epithelium so they can float around and they don't cause havoc. Now in some people that occurs spontaneously so when they're asleep they'll roll over and just align the canal with gravity and the ear rock if you like or canalith will drop out.

In other cases it requires a manual manoeuvre and in the first instance we need to identify which of the three canals is involved and then based on our knowledge of the spatial orientation of the canal we can use gravity to help move the canalith out of the affected canal.

SHANE HUNTINGTON:
You must have been very good at those little maze games with the balls when you were a child I suspect to be able to do this. How do you go about determining which of those canals the problem is in?

DAVID SZMULEWICZ:
First of all we use probability so the posterior canal is affected about 90 per cent of the time. Then we know that there are specific manoeuvres which are more likely to stimulate certain canals and if the canalith is in that canal then there's a certain pattern of abnormal eye movement or nystagmus that we can see.

SHANE HUNTINGTON:
Now this is one indicator – BPPV – of the cause of vertigo that we've discussed. What others are there? Are there areas where you can take an impact or have a virus, other things that can give you the same kind of problem?

DAVID SZMULEWICZ:
Both of those. Certainly, while in most cases we don't understand why a patient has gotten BPPV, there is a small subset where it's post traumatic and the classic description might be a footballer takes a knee to the head during a match and at some time after that gets up and they're spinning. Presumably the physical force is actually causing the shedding of the otoconia or the ear rocks.

There is another condition which is less common called vestibular neuronitis or vestibular neuritis which is thought to be a viral infection of the inner ear usually with a herpes simplex virus and that then causes damage of the end organ so the vestibular system or the nerve, the vestibular nerve linking the vestibular system to the brain.

SHANE HUNTINGTON:
Many of these things almost sound like inconveniences for patients but how severe can this get?

DAVID SZMULEWICZ:
The answer is very severe. These conditions at their worst render patients unable to move in bed, feeling very unwell, nauseous, vomiting and often unable to carry out even basic daily activities.

SHANE HUNTINGTON:
David, many of our listeners will have had the experience that you describe about loss of balance often self-induced due to alcohol. What's happening with our balance system in that case?

DAVID SZMULEWICZ:
In a sense alcohol is really replicating some of the pathology that we see in balance disorders. You may remember that I referred to the semi-circular canals and these are filled with fluid and the specific gravity, if you like the heaviness of this fluid is altered significantly by alcohol. Now why is that important? That's important because within this fluid are the special sensory apparatus, the hairlike cells which have the heavy ear rocks in them, and their dynamics if you like, the way that they move around and dance as our heads move alter significantly if you have thinner rather than thicker ear fluid.
Sometimes patients are sort of quite hesitant about mentioning to me that their dizziness somewhat resembles their previous drunkenness but this actually gives us a really good hint as to what's happening.

SHANE HUNTINGTON:
Having been a patient in your balance lab some time ago, I recall a number of devices that, and I'll be very polite, modified my balance. Can you tell us what some of these are and what sort of information they give us, in particular the sort of spinning chair, the blowing of air into the ears? How do they tell you what's going on with the patient?

DAVID SZMULEWICZ:
These specific tests that we do are an extension of the examination that we carry out at the bedside; a lot of these examinations and investigations are aimed at precipitating the abnormal eye movements because the pattern of abnormal eye movements often helps us diagnose the condition.
In the case of what's called bi-thermal caloric testing or we refer to it as the calorics, cold and warm air or water is placed into the ear canal. It sets up a thermal current and actually stimulates the activity of the inner ear such that we can record the abnormal eye movements and often gives us the ability to estimate the degree of underactivity of the vestibular system.
The spinning chair that you make reference to or the rotatory chair similarly moves the patient at various speeds in various directions stimulating again the inner ear balance mechanism and we are able to gauge whether the response is that that we'd expect physiologically or whether it's abnormal either under- or over-active.
Probably the newest iteration of these tests which was developed by a Sydney research group, and particularly a researcher Dr Hamish MacDougall at the University of Sydney in Australia, is called the video head impulse test and so it's a very lightweight set of goggles with a high speed infrared camera which is able to track these very brief rapid eye movements and then translate them into graphical data such that a doctor at the bedside can make an objective measurement of the inner ear balance function.

SHANE HUNTINGTON:
I'm Shane Huntington and my guest today is neurologist David Szmulewicz. We're talking about balance disorders and how to treat them here on Up Close.

David, you have a particular interest in a disorder called CANVAS. What does CANVAS stand for and can you describe the condition?

DAVID SZMULEWICZ:
CANVAS stands for cerebellar ataxia with neuropathy and vestibular areflexia syndrome so CANVAS is very easy and basically CANVAS is a degenerative neurological condition which affects three of the core balance mechanisms that we've discussed. The cerebellar ataxia relates to impairment of the coordination centre of the brain. The neuropathy refers to an impairment of the ability of the feelings or sensation if you like in the periphery such as the feet or the ankle joints being able to travel to the spine and up into the brain. The vestibular areflexia refers to a hypo-functioning or underactive inner ear balance mechanism.

SHANE HUNTINGTON:
When you have a patient with all three of their systems being affected, what sort of symptoms do they have and how do they contrast with some of the other conditions that we've discussed?

DAVID SZMULEWICZ:
The condition contrasts with others in that it tends to be constant, so unlike BPPV which tends to be episodic and motion induced, it tends to be slowly progressive. It's a degenerative condition so patients will often present with a long months or years history of slowly progressive imbalance. In particular the patients will note that their balance is significantly worse in poorly lit situations and this is because, going back to one of our earlier questions, these patients are intensely visually dependent. They are relying constantly on these visual cues in their environment because their brain is strangled if you like of many of the other normal inputs.

One of the other instances that these patients note that their balance is poor will be on uneven surfaces because again when you have a normally functioning nervous system you're not aware of the fact that you're constantly receiving inputs from the soles of your feet which is telling you that there's a cobblestone here, don't twist your ankle, move that way whereas these people find it intensely challenging to walk on an uneven surface because they're again deficient of a lot of this input.

SHANE HUNTINGTON:
What do we know about the causes of this particular condition? It's something that is obviously affecting all three of these centres at the same time.

DAVID SZMULEWICZ:
Initially when we described this condition we didn't have an inkling of the fact that it is most likely to be genetic. There are now approximately 10 families that have CANVAS. The mode of inheritance is unclear. We're currently engaged in searching for the causative gene or genes but it's certainly not going to be an obvious or easily found mode of inheritance. By this in part I mean the families are quite shallow. There's often only one generation that is affected.

The other thing is that there are many patients who appear to be sporadic so they have no affected relatives. Possible explanations for this include that the pattern of genetic inheritance is such that it may only affect one patient in a family or that we're dealing with more than one condition. A term that's sometimes used for these is phenocopies where the phenotype or the expressed if you like complexion of the disorder is copied by another condition which is not necessarily inherited.

SHANE HUNTINGTON:
Is there currently a treatment in place for patients with CANVAS?

DAVID SZMULEWICZ:
There are certainly management strategies. There's no cure although that is the Holy Grail and often it's about maintaining a person's lifestyle as best as possible. In CANVAS really the two things I get most concerned about are patients who fall, so keeping patients on their feet. Another aspect of that really is making sure that if they fall they fall onto the strongest possible bones. The other issue with CANVAS is that some patients develop a problem with swallowing and at risk to their health is the possibility they might aspirate or breathe in part of their food.

There is evidence that's come to light in the last couple of years that suggested that conditions that affect the cerebellum or coordination part of the brain may benefit from intensive neurological physiotherapy. A couple of trials showed that an intensive course of neurological physiotherapy for one month confers a benefit out to at least a year.

The question that we have is in our patients who have more than the cerebellum involved, will this work and that's an avenue of enquiry for us at the moment.

SHANE HUNTINGTON:
David, what sorts of physiotherapy are there for various balance disorders?

DAVID SZMULEWICZ:
Principally there are two very important types of physiotherapy for our balance disorder patients. One is neurological physiotherapy and the other is vestibular physiotherapy. If I deal with vestibular physiotherapy first, the overall aim of vestibular physiotherapy is to help the patient recover from an insult to their inner ear balance mechanism. Often it's a case of encouraging or coaxing the brain to compensate or deal with the fact that the messages that it's now getting from one or more ear have altered and usually for the worse.

Whilst some individuals and certainly young children will adapt and compensate very well, some of us, particularly adults, can struggle with this and often exercises that specifically strain or challenge the balance centres of the brain will stimulate a rerouting if you like of the normal neurological information.

In the case of neurological physiotherapy it's much more varied because there are many more neurological conditions than vestibular conditions. One way I tend to think of it for example with the cerebellar diseases is that it's somewhat akin to the musculoskeletal or standard athletes type of physiotherapy in that it's trying to strengthen one part of the body to compensate for a weakness in the other.

SHANE HUNTINGTON:
With all these particular balance problems and how prolific it is in our society to find these problems, it's interesting that our standard sort of health checks and so forth that we undergo in our daily working lives and so forth do not include aspects of balance. Should this be something that becomes the norm given we're talking about upwards of 30 per cent of our population having problems?

DAVID SZMULEWICZ:
Absolutely. I think this needs to be a routine avenue of enquiry because often these conditions can be picked up and helped quite early on. The unfortunate thing for doctors like me is we often see the patients far down the track when they've visited many other doctors and it's become obvious that there is something going on that's affecting their balance.

I think the other issue, and this is a bug bear of mine, is that medical training is quite limited when it comes to balance and so I think a step before incorporating balance assessment into regular health checks is really making sure that the average doctor is aware of balance conditions and how they might be helped.

SHANE HUNTINGTON:
David, we've focused our attention on human patients but are we unique in terms of our balance performance or are there many other animals that have similar capabilities to humans?

DAVID SZMULEWICZ:
We're not at all unique and I think that's probably quite confronting for some of us but most of our balance mechanism in an evolutionary sense has been very well conserved. In fact there are many other animals that have at least as good if not better balance than ours and it certainly helps if you have four feet on the ground.

SHANE HUNTINGTON:
David Szmulewicz, neurologist at the Royal Victorian Eye and Ear Hospital here in Melbourne, thank you for being our guest on Up Close today and talking with us about balance disorders.

DAVID SZMULEWICZ:
My pleasure. Thank you, Shane.

University of Melbourne