The role of audiology in concussion diagnostics

This video provides an overview of concussion and how this type of brain injury sits in the field of vestibular audiology. The diagnostic considerations for concussion patients will be explored, with a discussion of the treatment and rehabilitation options available for these patients.

You can read the full transcript below.

Introduction

Today I am super excited because we're going to focus on rehabilitation. Specifically in a concussion patient population. This is definitely one of my interests. I am a vestibular audiologist and have seen a number of concussion patients through my clinic. And I wanted to talk and start the day with the role that an audiologist can play in concussion diagnostics.

We know that diagnostics is the basis for great rehabilitation. The more information you have going into a therapy plan, the better outcomes. For the patient.

So let's talk in specifics. To this concussion patient population.

What is a concussion?

Just to make sure we're all on the same page. A concussion is a type of traumatic brain injury or TBI that can be caused by either a direct hit to the head or by a hit to the body that causes the brain to rapidly move within the skull back and forth.

Prevalence of traumatic brain injuries (TBIs)

And traumatic brain injuries are actually quite common. We know that in 2020, about 42 million people were diagnosed with a concussion worldwide. And many of these head injuries can result in hospitalizations and even deaths.

Specifically in patients that we frequently see in our audiology clinic, those that are 75 years and older, they tend to have some of the highest rates of TBI-related hospitalizations and deaths.

Not only are these common, not only are they very impactful to our patients, but they can also come with a heavy medical financial burden to the patient and to the hospital system. This is a big health concern worldwide, that we want to be better at diagnosing and addressing so that patients aren’t out of work as much and are rehabilitating way faster.

Common causes of TBIs

There's a lot of different things that can cause traumatic brain injuries, everything from accidents in the car, sports, being in military or some form of combat type event or some sort of assault. And depending on the type of head injury, it can result in a variety of different symptoms.

Types of injuries

Now, the origins of the issue that's going on in the brain can be impacted by the type of injury because how you are hit affects how your brain. So there's really two different types of injuries that people discuss in the literature.

One is called deceleration. That's really where the brain just moves forward and backwards within the skull. You can have multiple sites of impact both on the frontal lobe and the central lobe, or it may just impact one of those sites.

The other type of injury is called a rotational injury. And this can honestly be one of the hardest injuries to rehab from and can result in much longer recovery times. But a rotational injury actually involves the shearing or tearing of axons or even the shearing or tearing of certain blood vessels that can cause hematomas.

And there can also be impacts of the brain on the skull. So it can result in multiple impact sites.

Pathophysiology of concussion

There's a lot of theories, of course, what's causing the pathophysiology behind the concussion? But really, it's all at the axon level.

So some describe it as a bio-mechanically-induced brain lesion in the absence of any anatomical lesion. So something that you wouldn't necessarily see on the MRI, there's no structural evidence of this injury, but you see functional changes to the brain.

And some describe it as a neuro-metabolic dysfunction because of these chemical changes that take place in the brain due to the axon damage.

Common concussion symptoms

Regardless of the type of injury that you have, most head injuries do result in some types of symptoms. Some of the most common that we hear are headaches, dizziness, and tinnitus. But there's actually quite a variety of symptoms that a patient can experience.

As an audiologist, I've heard patients describe:

• Dizziness
• Blurred vision
• Poor balance
• Tinnitus
• Noise sensitivity

We are used to hearing some of these things, symptoms. In fact, I told you, I've seen a number of concussion patients. There are many symptoms that a lot of my patients tend to disclose, and they tend to be in these four main realms:

• Dizziness
• Motor dysfunction
• Balance issues
• Auditory complaints

And you'll notice these are very common things we hear post head injury and they're also well within the scope of an audiologist and a vestibular audiologist to be able to address.

Challenges in concussion diagnosis

You can imagine after hearing all of these different types of symptoms that a patient experiences, everything from sleep to emotional changes to dizziness, it can be really challenging to determine whether a patient has actually had a concussion.

And there's actually been quite a bit of discussion in this realm about how it's so difficult to diagnose a concussion. And that's mainly due to a few things.

One, there's not just one test that exists to determine whether a concussion has occurred. And so most of the time we really rely on a multidisciplinary approach with many different professionals, many different tools and evaluations. Cross-checks and say all of these signs and symptoms are in place. We also have this objective data. It's likely that they have a concussion.

It's also been difficult to say whether concussion has occurred in many populations because no two concussions are the same. So depending on the type of injury, the force, whether it was a direct or indirect hit to the head, what symptoms they're presenting with, what preexisting medical conditions and other risk factors or in their path. All of these play a role in the clinical presentation of that patient.

Team-based evaluation of a concussion

So as I said, right now the status is relying on a team-based evaluation of a concussion. And so there's a lot of multidisciplinary concussion teams all across the nation and across the world that are utilizing a variety of different aspects.

Most of them have these core components:

• Neurocognitive evaluation
• Neurologic evaluation
• Imaging
• Symptom evaluation (computerized or oral)

So you may be wondering where it is an audiologist fit into this team-based evaluation. Audiologists are actually not new to the concussion world. There's been a significant amount of past research, more so on the auditory effects of a head injury.

But in the recent years we've seen an increase in research articles on the vestibular impacts that a head injury can have. So it's not new to our world, but it's a growing subfield of vestibular audiology.

Vestibular tests

We do have a lot of tests in our battery that we can utilize in patients that describe blurred vision, dizziness, or imbalance. And we know that many of these tests are sensitive to dysfunction that you can see post head injury, whether that's BPPV, labyrinthine dysfunctions, superior canal dehiscence. There's a lot of known injuries that can happen specifically to the inner ear post head injury.

But how do we know what tests to do or what tests are most sensitive? So today, we're going to go through two main realms of a vestibular evaluation: the ocular motor aspect and the vestibulo-ocular reflex evaluation aspect.

There are obviously many more tests we can do and depending on the patient that you're seeing in the clinic, it may necessitate different tests. Not every patient is the same.

Audiology goals

But regardless of what tests you specifically do when you see a patient post head injury, you typically have some of the same goals maybe that I have.

One you want to test their peripheral auditory and vestibular systems to see if there's any functional damage or functional changes that the patients experience, like a change in hearing, a change in how their eardrums are moving, or a change in their vestibular function.

You also want to evaluate the vestibular and ocular reflex pathways because we're looking for evidence of disruption. And really, this disruption or the abnormalities that you see in our testing can be really helpful to guide what recommendations are made or what types of intervention or therapy is needed for that patient in order to improve.

It's also helpful to establish objective baselines in order to measure and track recovery over time. So concussion patients can change quite rapidly. You know, day to day, their brain is in a state of healing and wants to get better. So these results change quite often and it's helpful to see where their starting point is very soon after the head injury, so you can measure the amount of recovery or change with different therapy types.

Oculomotor evaluation

So we're going to focus on those two main realms. First one is oculomotor evaluation, which is done by many different professionals on a concussion management team. Most of the time it is performed on a bedside aspect, and that's because maybe they're on the sideline of a soccer field or they're in an area where they don't have quick access to video goggles.

But the benefit of a vestibular audiologist or a physical therapist who utilizes video goggles is that you are providing a standardized stimulus every single time. So it's hard to tell how much change your patient has had if you can't ensure that your stimulus is exactly the same. Each appointment that you have with them.

So they're using video goggles to not only provide the standardized stimulus, but also to measure and record the exact changes in their eye. Movements can be very beneficial in this population.

In addition, I love being able to compare to age-based normative values. If I have a 55-year-old that comes into the clinic and says, I didn't hit my head, but I'm also just getting older, so I know this is part of it, I can utilize my age-based norms to say: You know what? I know you're sad, you're getting older, but you're performing lower than what I would expect for your age. So I think we can do some work, you know, in therapy to help. You feel a little bit better. So it's really helpful to have these objective measures in this patient population.

Many of you probably already perform some sort of remote evaluation every single day on your vestibular patients. And although many things may look the same in the concussion profile, there's a lot of new or different types of oculomotor tests that you may want to consider.

We're going to focus today on convergence, smooth pursuit neck torsion, and saccadometry.

Near-point convergence

So near-point convergence, maybe something you've heard of or maybe it's something that you already frequently do in the clinic. But if it's new to you, it’s the ability to focus your eyes on an object really close to your face without it doubling, i.e. the ability to convert your eyes.

So you'll see in our little graphic here with our eyes, what do you have? Normal convergence. That means you can clearly read and focus on an object pretty close to your face. If you have the inability to do this, you're actually going to see double vision when things are close to your face, whether you're reading or scrolling on your phone, you're going to start to see all of those things in double.

This convergence insufficiency idea where you have to have things further from your face in order to see that clearly is actually really common post head injury. And it's been probably one of the most well documented oculomotor abnormalities, post head injury. It's pretty easy to measure.

There are some tools that can help you be really exact with screening for convergence, but it's quite easy to add to your oculomotor battery in order to see if your patient may have experienced dysfunction post head injury. And this has been well documented in the TBI literature in a number of different populations, everything from adult and children to military and sports.

And I love that most concussion research includes a variety of different types of injuries and different populations because we know that even just the origin of how they experience their head injury may result in different manifestations of their dysfunction.

So we can see that up to 50% of people experience convergence in severe insufficiency post head injury. So this is a very easy thing to screen for and very effective in order for identifying post head injury abnormalities. Many of your patients who have convergence insufficiency may complain of blurred vision, difficulty reading, or anything double vision when they're looking at their phone or scrolling, something's up close.

Smooth pursuit neck torsion test

The next test you may not do with all of your patients is something called smooth pursuit neck torsion. So we're familiar with the pursuit test, where a patient is smoothly following a target as it moves across the screen. This takes that pursuit test and adds a component to it.

So we're starting to get a lot smarter beyond just looking at the eyes in isolation. Technology is moving towards looking where the head is, where the neck is looking, where the body is, because all of these aspects play a role in how our eyes move.

If I am looking at something while my head is turned, I'm getting different information to the brain that may affect how my eyes are moving. And especially after a head injury, those individuals are known to have neck related impacts.

So the basis of the smooth pursuit next gen test is you're looking at how well a patient does pursuit when their neck is in a neutral position and also when their neck is turned 45 degrees to the right or left.

So you actually turn their body, turn the head back, towards the screen and have them do pursuit again. And ultimately, you're comparing how closely did they follow the target in neutral versus these extended positions.

This test originally gained a lot of momentum in the early nineties and is now regaining momentum due to its sensitivity towards identifying cervical disorders, which are very common in this post-concussion population.

What you'll see in their pursuit findings when they are in a neck extended position, you'll see the increase in psychotic intrusion, so their eyes start to get a lot jumpier as they're trying to follow the target. Or maybe they have reduced gain where they can't even follow the target as well.

There's also been, I'd say, more information coming out in whiplash, idiopathic neck pain patients that has shown that the smooth pursuit neck torsion, that difference between neutral and extended actually has pretty darn good sensitivity and specificity for identifying those whiplash and idiopathic neck pain patients.

An older study found that there was really no significant difference between chronic neck pain and healthy controls. But this test is showing a lot of different potential for certain types of neck injuries and how that may impact oculomotor function.

It's important we keep the neck in mind as we're looking at this patient population because again, the neck plays a vital role in how our eyes move as well. So we have to make sure we're evaluating everything that's contributing to ocular dysfunction.

Saccadometry

If you were here on day one, we spent significant amount of time talking about saccadometry. We know that this is an advanced oculomotor test that has pretty good sensitivity to identifying dysfunction post-concussion.

So the idea of anti-saccade testing in particular is that the patient is going to start with their eyes at the center target, but then they're going to look in the equal and opposite direction of where the stimulus target pops up.

And this is a much more complex cognitive evaluation. You've got two tests to focus on inhibiting, looking towards where the stimulus is going and creating your own imaginary visual target in the opposite direction.

In anti-saccade testing, which again, day one folks who are experts on this. But there's a number of things we evaluate. Many are similar to our saccade testing, but the one that you may not be as familiar with is directional error rate.

So that's how many times they really go in the wrong direction, which in anti-saccades means they're following the target instead of going in the opposite direction. In post-concussion cases, we're more likely to see that directional error rate and latency tend to be the most impacted measurement parameters in saccadometry.

And there have been studies to show that this is the case, you'll see that increase in error rate is quite high in acute concussion. And what's really cool about saccadometry is this is one of those tests that gets better over time.

So you'll see that their directional error rate starts to decrease throughout the recovery process. And you'll also see that latencies get shorter and shorter and getting back to that normative value. So it's a really nice tool in order to see how the patient is progressing.

VOR evaluation

Looking at the vestibulo-ocular reflex, there's a lot of different things that audiologists can do in order to evaluate the VOR. Everything from:

• Caloric testing
• Rotary chair testing
• Dynamic visual acuity
• Gaze stabilization
• Video head impulse testing

And this spans an entire spectrum of speeds of the VOR, which we know evaluating multiple speed is really important.

In the post head injury literature, it's mainly been focused on rotational chair testing and then also those high-frequency VOR tests.

The consensus from SHA testing, it's been kind of split depending on population, whether sinusoidal harmonic acceleration, where the rotary chair is just moving back and forth. We're looking at the VOR in the dark, whether that is sensitive or not to the TBI population. We've got many studies that show that it is and some studies that show that it isn't, which shows just the unique individualized nature of concussion research.

Same thing with VOR suppression. So when the patient is looking at a stimulus dot in their goggles while the chair is moving, do they have the ability to suppress their VOR? We've got split research and studies on that in the consensus. Maybe the differences are due to the type of injury or the population that's studied.

So if you are seeing concussion patients, it may be worthwhile to test this rotational chair testing because you may find something that is important for your particular patient.

Ultimately, with video head impulse testing, we found that most research does not find it to be a sensitive tool post-concussion, which is surprising because most concussion patients will complain of dizziness when their head is in motion. So you'd expect that vHIT may be a tool that is abnormal, but research has not indicated that.

What has been shown to be sensitive are some of the functions of your tests, like dynamic visual acuity and gaze stabilization testing. These are looking at how clearly a patient can see an object type on the screen while their head is in motion.

And it's helpful for an audiologist to be able to perform this to see what is the objective difference, which side is impacted, and at what speed does the VR break down? This is super useful data for physical therapy colleagues.

Audiology referrals for concussion

Ultimately, as a result of your evaluation an audiologist works with a variety of professionals. As we mentioned at the beginning, there's a multidisciplinary team that is necessary in order for us to best care for concussion patients.

One of my most frequent referrals is for vestibular rehabilitation therapy with a physical therapist, and that's really what the rest of the day is focused on, is what that process may look like after they receive a referral from an audiologist.

But there may also be a number of audiology and other colleagues that you work with for your particular patient.

General conclusions

Hopefully from this presentation you can see that an audiologist can play a vital role in assisting with the diagnosis post head injury, especially for those patients that are complaining of dizziness, balance issues, or visual changes after their head injuries.

And ultimately, referring to audiology earlier rather than later can really help speed up the recovery and direct therapy decisions. Especially if there is a peripheral vestibular involvement, it's helpful to know that earlier in the recovery process rather than discovering it later.

So, if you're an audiologist that's interested in this population, reach out to your concussion multidisciplinary team and talk about some of these benefits and where you can be of help in the diagnostics.