Welcome, everyone, to the webinar, Acoustic Reflex Testing, Methodology, Interpretation, and Clinical Uses. We're so glad that you could be here today to learn more about Acoustic Reflex Testing protocols. My name is Ted Annis. I am a Senior Marketing Specialist with the International Hearing Society, and I will be your moderator for today. Our expert presenter today is Ted Venema, Ph.D. Ted is a practicing audiologist and seasoned professor, having taught at several colleges and universities throughout Canada. Ted created Canada's fourth Hearing Instrument Practitioner Program while at Conestoga College in Kitchener, Ontario. He is a passionate speaker and continues to give presentations on hearing, hearing loss, and hearing aids across North America and beyond. Ted is also the author of the textbook, Compression for Clinicians, now in its second edition. We're very excited to have Ted as our presenter today, but before we get started, we have just a few housekeeping items. 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It is brief and your feedback will help us create valuable content for you moving forward. Today, we'll be covering the following topics. A quick review of tympanometry, acoustic reflexes, contralateral, and ipsilateral, and interpreting acoustic reflexes. At the end, we'll move on to a Q&A session. You can send us a question for credit any time by entering your question in the question box on your webinar dashboard, usually located to the right or the top of your webinar screen. We'll take as many questions as we can in the time we have available. And now, I'm going to turn it over to Ted, who will guide you through today's presentation. Take it away, Ted. Hey, thanks a lot. Thanks a lot, Ted. And I'm happy to be presenting once again in a webinar for IHS. I always enjoy doing these. And this one here, as we know, is on acoustic reflexes. And acoustic reflexes is actually one of the parts of tympanometry. So if I slide down here, and I'm going to see if I can move to my next slide, having a little bit of difficulty moving this guy. I don't know why. Are you able to advance the slides using your mouse button? Yeah, I can't. It's frozen. Here, I'll try this. Ah, thank you. That worked. And that worked. I don't know. It got stuck there for a sec. Here we go. A quick review of tympanometry. Ah, thank you, Ted. Tympanometry normally consists of four separate types of tests. And the first one that we are most familiar with, and we did this in a webinar in the past for IHS, was on tympanometry. And the most obvious of these is tympanogram types, A, B, and C. Now, that's already done with tympanometry, and it's a non-behavioral test, which means it does not require a voluntary response on the part of the client, which is great. Another part of tympanometry that automatically gets done is static compliance. You don't really do this, but the equipment tells you exactly what it is. The third is physical volume of the external auditory meatus, the air space. And then the last test is acoustic reflexes. Now, the function of the middle ear, when you're looking at this thing, you've got three things. You have a reason for having a middle ear. And that's what tympanometry is assessing, is the function of the middle ear. And I want to underline the importance of doing tympanometry and acoustic reflexes when you find an air bone gap. An air bone gap with pure tone testing is going to indicate some middle or outer ear pathology, because you've got a conductive hearing loss now. Why not back that up with tympanometry? A stool can't stand with fewer than three legs. We need to back up tests when we see them. So is tympanometry and acoustic reflexes within the scope of practice for the hearing instrument specialist? Absolutely. It's no more a diagnostic, in quotes, test, than pure tone testing by air conduction and bone conduction is. Looking at the function of the middle ear, it helps transmit sound to a fluid-filled cochlea. If you had your head under a swimming pool, and I'm talking to you from the edge of the pool, your head's underwater, you're not going to hear me. Airborne sound will bounce off that water. We need something to help airborne sound activate a fluid-filled cochlea, and that something is the middle ear, and it does so in three ways. Number one here, look at my cursor here. The eardrum is much larger in space than the footplate of the stapes. If you push with your hand against the side of your cheek really hard, you'll feel some pressure. But if you push with the same force against your fingertip against your cheek, you'll feel more pressure. Pressure is force over an area. Force over converged onto a smaller area like the footplate of the stapes has increased pressure. Number two, the manubrium of the malleus, the handle of the malleus is a little bit longer than the long process of the incus. That's why we give a child the advantage of the longer part of a seesaw or teeter-totter. It gives a leverage advantage, similar in the middle ear. It's the leverage advantage of the malleus compared to the incus increases pressure as well because the malleus is a little bit longer. The third is the buckling action of the eardrum itself. That also increases pressure. So you've got a 17-to-1 increase, a 1.3-to-1 increase, and a 2-to-1 increase. Putting it all together, 17, 1.3, 2-to-1 offers a 44-to-1 pressure increase. Remembering our decibels from hells, okay? A 10-fold pressure increase corresponds to a 20-decibel increase. A 100-fold pressure increase corresponds to a 40-decibel increase. Well, 44-to-1 is somewhere between 10 and 100, so that's going to offer somewhere between 20 and 40-decibel increase. And yup, it does, around 30-to-35-decibel increase of sound pressure. That's why you have a middle ear. It's likely why the dinosaurs couldn't catch the little mammals in the early days. The little mammals had middle ears. They could hear better. Anyway, the key concept behind tympanometry is that for the middle ear to be most efficient, air pressure has to be even-steven on both sides of the tympanic membrane. Here's your ear canal. There's your middle ear space. The air pressure, if it's even on both sides, allows your middle ear to function at its best. Tympanometry is really a test of middle ear efficiency. You've got a probe jammed in the ear canal, airtight. You've got a speaker emitting a tone. The tone bounces off the eardrum and is picked up by the microphone, the second hole here. And the third hole in the probe is for air pressure changes. So when air pressure is equal on both sides of the eardrum, this creates the least stiffness of that middle ear, eardrum and middle ear ossicles. The least stiffness is consequent, of course, with the most compliance. So with greater middle ear compliance, i.e. least stiffness, the middle ear is the least stiff and it offers the least overall impedance to sound going through it. This means more sound will be able to go through the middle ear when it's least stiff and less sound will bounce back off of it. Tympanometry is a measure of this. A low pitch tone, 226 hertz, at around 70 dB SPL is emitted out of the speaker. That normally would bounce off the middle ear system, and it is supposed to. Lows don't go through stiff systems very easily. Stiffness resonates with high frequencies. Mass resonates with low frequencies. Sitting in our living room, the drums and the bass guitar from the people upstairs is what comes through the ceiling. The mass resonates with low frequencies. Stiffness resonates with highs. Well, with tympanometry, we are deliberately using a low pitch tone so that it will bounce off the stiff middle ear system. It's supposed to. That's what you want to happen. Otherwise, you're not going to have any sound bouncing back. To measure. That is why tympanometry uses a low pitch tone. The test number one, tympanogram, stages of otitis media, type A. Look at the pup tent here. High compliance, okay? The peak is over zero air pressure, which is what you want. The peak to be over zero. The slide is a little bit screwy here. Zero should be right underneath the peak, but no matter. Anyway, meaning that least sound bounced back at zero air pressure in the ear canal, okay? That must mean the air pressure behind the drum was also at room air pressure. Good. That's what you want. When air pressure is even on both sides of the eardrum, the middle ear is most efficient at passing sound through. If that 226 hertz tone was 70 dB SPL, maybe 65 dB bounced back, but about 5 dB went through. Whereas at negative air pressure, look here on the left, or positive air pressure, look on the right, that means all the sound bounced back. All the sound bounced back. All 70 bounced back. Because at negative and positive air pressure in the ear canal, you made the middle ear even more stiff. Now we know that beginning of otitis media, you've got negative air pressure behind the drum. So now you have to use negative air pressure in the ear canal itself to make those negative air pressures even-steven again. And there you're getting a peak at negative air pressure. Abnormal. Your peak should be at over zero, meaning that the air pressure behind the drum is also at zero. Well, type C early otitis media means you've got negative air pressure behind the drum. It turns into a type B, because now your middle ear is beginning to rebel, and it's exuding serous fluid, which will turn into pus. And now your eardrum is going to bulge. Those who indulge bulge. Anyway, look, now you've got a type B. That means no peak at any air pressure. You can change the air pressure in your ear canal until the cows come home, but air pressure is no competition for a fluid-filled, pus-filled middle ear space. Nice topic, eh? All right, test number two. Beyond the types of tympanograms is static compliance. And in English, this just simply means the height of your pup tent. How tall was the tent? With otosclerosis, you've got a stiff middle ear system. You haven't got any trouble with air pressure behind the drum, but your pup tent, your tympanogram, is abnormally squat. You don't have very much compliance at any air pressure. You do have the most at zero, but it's not as much compliance as normal. In other words, a lot of sound is still bouncing back off the drum. The middle ear system is fairly stiff, overly stiff, caused by a growth of bony tissue or soft bony tissue around the footplate of the stapes. AS, a type A, but it's stiff. On the other hand, maybe you've got disarticulated ossicles. So now your whole eardrum is abnormally flaccid, abnormally compliant, abnormally understiff. So now your pup tent is so tall it reads off the board. A type AD. So static compliance is just the height of the tympanogram. Various pathologies affect static compliance. So you can see how tympanometry is so useful to aid and abet the findings of an air bone gap. And I repeat, it is within our scope of practice. Test number three, the physical volume of the ear canal. What's the volume of air space? Look on the left. In between the probe and the eardrum. Normally it's about that of a sugar cube. About one to one and a half cubic centimeters. Well, if you've got a type B tympanogram an abnormally large physical volume could accompany that. You never know. Or maybe an abnormally small one will. Look, an abnormally large physical volume might indicate a perforated eardrum. Now you've got a hole in the drum, so now the air space in your ear canal is communicating with the air space in the middle ear. So it's abnormally large. A true type B tympanogram will have a normal physical volume of one to one and a half cubic centimeters. If the type B tympanogram arises with a tiny physical volume, maybe then your probe tip is jammed against your outer ear canal and you better do the test again. So you can see how tests back each other up. The type B tympanogram, look at the physical volume. Is it really a type B tympanogram or does the guy have a hole in his eardrum? And if you've got a hole in your eardrum, you'll have an abnormally large physical volume and you will have a type B tympanogram. You can't do a tympanogram unless the eardrum is intact. Should tell you something about tubes in the ear too. Not advisable to do tympanometry when there's tubes in someone's ear. Anyway, we get to the topic now of today. Acoustic reflexes. Contralateral and ipsilateral. This is the fourth test that just immediately can follow in tympanometry. The acoustic reflex is caused by two different muscles. The stapedius muscle shown here which is attached to the neck of the stapes. It's also connected to the tensor tympani muscle which is connected to the manubrium of the malleus. Now these two muscles when a loud sound comes in the ear canal, these two muscles instantly contract. It's a reflex. What's defined reflex? Reflex means an involuntary reaction that you never took, you didn't think about and decide. It's like when you're at a doctor's office and your legs are crossed and she or he taps just below the kneecap with that little rubber hammer and it sticks out. Or when you touch a hot stove with your hand and instantly you pull your hand back. It's not that you didn't sit there thinking hmm, yes this might scald my skin and perhaps it would be a good idea for me to remove my hand. The message went up my arm to my spinal cord and right back to the muscles of my arm to contract. It was a reflex. When messages go to your spinal cord and back out again, that's a reflex. Now the brain actually has a tail called the spinal cord which goes all the way down your back. Your spinal cord inside your skull is called your brain stem. Once the spinal cord enters your skull, you're entering the brain area and that part is called the brain stem. Now the acoustic reflex You memorize this slide yet? Great! Look at the green arrows. That's the afferent route. That's the brain going route. Let's follow it. Loud sound in the ear canal through the middle ear, going through the cochlea, the hair cells of the cochlea. Which hair cells? The inner hair cells because they send sound to the brain. Message goes up the eighth nerve to the something called the CN. Doesn't stand for Canadian National. It means cochlear nucleus. It's a little gray area and from there down to what's called the SOC, superior olivary complexes. No, there's no pimento in those. Anyway, the message goes to those and now right back out. Look at the red arrows. Now you're efferent. You're leaving the brain and you're going back out and that's going to the fifth cranial nerve, the seventh cranial nerve and the fifth cranial nerve activates the tensor tympani muscle and the seventh cranial nerve activates the stapedius muscle. So it's a reflex. But now look on the other side. Because you had a loud sound in one ear canal, you also caused a reflex to happen on the opposite side. That's because of crossover in the brain stem. In the brain stem you've got neural crossover. A loud sound in one ear causes an acoustic reflex in both ears. That crossover has a name. It's called decussation. D-E-C-U-S-S- A-T-I-O-N. Decussation. At any rate, crossover. Why do we have acoustic reflexes? Have you ever listened to a recording of you? You're the only one who hates it. Everyone else thinks it sounds just like you. That's because for the first time you are hearing yourself by air conduction only when you're listening to a recording. Air conduction is how others hear you. But when you speak yourself you're hearing yourself by air conduction from your mouth to your ears, but also through the bone of your skull. So you're hearing yourself by air conduction and bone conduction. Your voice tone to yourself is a bit richer. It's a bit lower in pitch. It's also louder, which causes the acoustic reflex. By air conduction, normal speech is 65 dB SPL. By air conduction and bone conduction, your own voice is closer to 85, 80 to 85 dB SPL, and that's enough to cause an acoustic reflex. The purpose of reflexes is not to protect against noise-induced hearing loss. That's one of the fallacies we've been commonly led to believe. Acoustic reflexes actually occur while we speak. They kick in about 50 milliseconds just before you talk. That's a 20th of a second. Now you talk about weird. I mean, the ear is married to the voice. Notice your acoustic reflexes are strongest for the low frequencies. We will see this. And this is because our voices are louder for the vowels. So the acoustic reflexes reduce the loudness of our own voices while we are talking. They reduce the upward spread of masking. They allow us to hear better while we are speaking. You can hear the tiny snap of a twig behind you better with acoustic reflexes while you are talking because acoustic reflexes dull the loudness of your own voice while you speak. Acoustic reflexes are a low frequency phenomenon. Look at this picture here. We are looking at 85, 90, 95, 100, 105 increasing sound pressure levels. And we are looking at the drop in transmission through the middle ear due to the acoustic reflex. Notice on the bottom you've got frequency. Acoustic reflexes are strongest. In other words, they work the best with loud, low frequency sounds. They are not elicited. They do not react very much with intense, high frequency sounds. So this shows us how acoustic reflexes work with the voice and the vowels especially. The acoustic reflex and tympanometry. With acoustic reflexes you are still using tympanometry. You are still measuring how much of the 226 low frequency tone is bouncing off the eardrum. But while tympanometry changes middle ear compliance with different air pressures, acoustic reflexes, they change middle ear compliance with loud sounds. That's the distinction between the two. They are using the same equipment, but we are no longer changing the air pressure. In fact, you measure acoustic reflexes at whatever air pressure gave you the tallest tympanogram. Wherever your static compliance was, that's the air pressure where acoustic reflexes are tested. And if you've got a type C tympanogram where your peak is over negative air pressure, it's quite unlikely that you'll get acoustic reflexes. They usually only occur with relatively normal tympanograms. We'll just show this in just a little bit when we look at some cases. Acoustic reflexes are thus normally restricted for fairly normal tympanograms. Maybe some type C's you might be able to measure an acoustic reflex, but certainly not with a type B. The acoustic reflex causes a temporary reduction in static compliance. While the loud sound is coming in the ear canal, you'll have a slight drop in the height of your tympanogram for the duration of that noise, and that drop is the acoustic reflex. Look here. Acoustic reflexes are measured as temporary decreases in middle ear compliance. In other words, temporary increases in middle ear stiffness. And how is that measured? By the amount of the sound bouncing back off the drum, right? Think on the left here. Think of a temporary drop in the tympanogram peak. A temporary drop in static compliance while the loud acoustic reflex stimulus is presented. If it's presented at 80, 85, 90, 95. 80 here, there's no drop in compliance. 85, a little bit of a drop. 90, a bigger drop. 95, a larger one until it sort of plateaus. The bottom part of this graph shows the same thing. Your baseline height of your tympanogram, your baseline static compliance. Some people call it admittance. Doesn't matter. And here's the drop in static compliance when the loud sound was presented at 90, when the loud sound is presented at 95, and 100, and so on. The results here are shown for a 1,000 hertz tone that was presented for one second. Now, contralateral acoustic reflexes were the first to be developed. Look at this weird picture I drew. My sisters are artists. You can tell I'm not. Anyway, this is a guy's head, okay, with two ears. And the tympanogram probe is inserted into one ear canal, and a headphone is placed over the other ear. Now, the acoustic reflex stimuli is usually 500 and 1,000 hertz tones. Usually those are the best, and they're presented at any level from about 85 to 110, 115 dBHL. Your acoustic reflex is calibrated. The tones and acoustic reflexes are calibrated usually in dBHL. At any rate, these tones would be presented through a headphone. So follow the black arrow here into the headphone. In the opposite ear, there's a loud, or I shouldn't say a loud, a 70 dB SPL, 226 hertz tone. You can see the ongoing 226 hertz tone in the probe ear. It's just going on, and then suddenly, a loud sound is presented to the opposite ear. And was there a change? Look at the green arrows. Was there a change in the amount of low frequency sound that bounced back as a result? Now, isn't that weird? Loud sound in one ear. Remember, it causes an acoustic reflex in both. So now you've got the acoustic reflex in the opposite ear, emitting a constant, or the probe in the opposite ear. You've got an ongoing 226 hertz tone at 70 dB SPL, and a loud sound in the opposite ear. Did that cause a change in the amount of sound bouncing back off the drum? Ipsilateral acoustic reflexes came later. Probes stuck now in one ear, and so the tone is presented in the same ear as the probe is in. So everything is done in the same ear. So the black arrow indicates the loud 500 hertz or 1,000 hertz acoustic reflex stimulus tone. And at the same time, you have this ongoing 226 hertz tone. It is emitted at 70 dB SPL. And when a loud was made, was there a change in the amount of the low pitch tone that bounced back off the ear? You can see why ipsilateral ARs came later, because they had to figure out a way to make the stimulus tone and the ongoing probe tone not interact with each other in terms of phase and all that. But they figured it out. So basically, the acoustic reflex is always reported according to the ear that got the stimulus. So if your stimulus and probe are in the right ear, that's a right ear ipsilateral reflex. If your stimulus is put in the left ear and your probe is in the opposite ear, you've got a left ear contralateral reflex. You always label your acoustic reflexes according to the ear that got the loud sound. Stimulus in the right ear, probe in the left ear would be a right ear contralateral reflex on the bottom left ear. Left ear ipsilateral reflex means the sound is presented in that left ear and the probe tone is in that left ear. So four possible sets of reflexes. Right ear contralateral, right ear ipsilateral, left ear contralateral, left ear ipsilateral. Well, interpreting this, let's look at this. I wrote HA on the left side of the slide. This is a slide taken out of Martin, Introduction to Audiology. And you'll see four rather quizzical heads across the top, indicating the four sets of reflexes we just talked about. And then you're going to look at conditions from A down to K. Now, look closely here. A through F are all talking about conductive loss, sensorineural loss, or normal hearing. In other words, A through F are all looking at the peripheral ear. A, normal hearing in both ears, you should have present acoustic reflexes in all ears. Normal hearing in one ear, conductive loss in one ear, okay, blah, blah, blah, blah. Conductive loss in both ears, absent, absent, absent, okay. Normal hearing in one ear, mild to moderate loss in the other ear, sensorineural. I like the word sensorineural. Sensory refers to outer hair cells. Neural refers to inner hair cells. You ever think about that? That's the best way for me to categorize it. Anyway, looking at E, cochlear hearing loss, mild to moderate, cochlear hearing loss, mild to moderate in both ears, outer hair cell pathology. Okay, look at F, severe hearing loss in both ears, absent. Remember we said the inner hair cells are part of that acoustic reflex arc, that loop, that afferent loop we showed you on that previous slide. Going outer ear, middle ear, inner ear, eighth nerve to the brain stem and then back out the fifth and seventh cranial nerves to the tensor tympani and the stapedius muscles. Well, that acoustic reflex arc covers a lot of territory, doesn't it? Okay, and of the cochlea, what hair cells does it involve? Inners. And when inner, outer hair cell pathology usually occurs before inner hair cell pathology. So if you've got outer hair cell pathology, you should still get acoustic reflexes. Okay, but once your hearing loss gets severe, now you've got inner hair cell involvement as well. So that's why acoustic reflexes are usually affected by inner hair cell pathology. Look at cases G through K. Those all refer to retrocochlear pathology. Eighth nerve and brain stem. Now, we don't use acoustic reflex anymore really to assess retrocochlear pathology. You know why? Because we've got CAT scans and MRIs to do that. We've got way more sensitive tests, tests that pick up retrocochlear pathology better and they're also more specific. In other words, they let you go if you don't have the pathology. So retrocochlear pathology is best assessed, of course, by CAT scans and MRIs. We don't rely on the acoustic reflexes to assess for retrocochlear pathology as much. Seriously though, the previous slide highlights why we don't often do both ipsilateral and contralateral acoustic reflexes anymore. We basically flip a coin and choose which one you're going to use. Why? Because cases A through F show conductive hearing loss or sensory neural loss. And note, if you can't get ipsilateral acoustic reflexes, you won't get contralaterals. Similarly, in those cases, if you couldn't get contras, you won't get ipsis. And that's why for these cases, just run either ipsi or contras. Cases G through K show retrocochlear pathology and note very different ipsilateral and contralateral acoustic reflex patterns. Here, it would make sense to run both. That, however, was yesterday. This is today. If you suspect retrocochlear pathology, well, how would you? HIS, asymmetrical sensory neural loss, tinnitus in one ear, vestibular problems, anything like that, poor speech discrimination in one ear, all this kind of stuff. Refer to an audiologist who will run an ABR, an auditory brain stem response, electrophysiological brain wave test, to look for retrocochlear pathology or refer to a physician who will get a CT scan or an MRI to look for the same. Acoustic reflexes are reported in sensation level. Acoustic reflexes are tested in DBHL. Remember we said the tympanometer is calibrated in DBHL. ARs are found normally between 80 to 100 DBHL. They are reported in DBSL. That's relative to your own threshold. Read with me. Acoustic reflexes can be tested at 5, 1, 2, or 4,000 Hz. We usually confine our testing to 5 and 100 because those are the lower frequencies. Normal and mild to moderate sensory neural hearing loss. They may very well have acoustic reflexes at, let's say, 100 DBHL, but the sensation levels for each will be very different. In other words, read at the bottom. For example, normal hearing loss and flat 50 DB sensory neural loss may both have acoustic reflexes occurring at 100 DB, but the normal hearing person, their sensation level will be 100 DBSL. The sensory neural loss that has a 50 DB threshold, his acoustic reflexes is reported at a reduced sensation level of 50 DBS sensation level. So, they're both present, one's just present at reduced sensation levels. Do you get it? Sensation level is the difference between the presentation level and your threshold. So, it doesn't matter. If they're reported at low sensation levels, who cares? That's a good finding. Nothing wrong with that. Conductive hearing loss tends to obliterate the acoustic reflexes. Read with me. Case of unilateral conductive loss. Unilateral. Look at the right ear. Normal. Left ear. Mild conductive air bone gap. Now, look at the tympanogram on the right. The right ear tympanogram is normal. The left is a flat type B tympanogram. Now, read with me on the top. Contralateral acoustic reflexes with a loud sound to the bad ear. So, look at this top head, headphone over the left ear. The hearing loss in that bad ear is going to prevent the intensity required to cause an acoustic reflex in the opposite ear. Okay? So, left ear contralateral is going to be either absent or elevated, usually absent. The right ear, ipsilateral reflex. The good ear, normal. It will be present. It will be normal. Now, let's switch things around. Let's put the probe in the bad ear and the headphone in the good ear. Right contra, loud sound in the good ear will still be absent. Read with the second black heading here. Contralateral acoustic reflexes with the loud stimulus to the good ear, well, they'll still be absent because the mechanical middle ear problems in the left ear will still prevent an acoustic reflex. Of course, ipsilateral acoustic reflex will also be absent in the left ear, as you can see on the bottom. So, look at the black ear. Left ear contra, absent. Right ear contra, absent. Left ear ipsi, absent. The only one present. Right ear, ipsilateral. And again, I like the reasons why. In the bad ear with the stimulus, the hearing loss prevents the sound from being loud enough to cause an acoustic reflex. Put the loud sound in the good ear, well, the mechanical problem of the middle ear in the left ear is going to prevent an acoustic reflex from occurring in that left ear. So, conductive hearing loss tends to obliterate ARs. No kidding. Bilateral conductive hearing loss. As you can see here, two flat tympanograms and no response. Okay? Nada. Acoustic reflexes and sensorineural loss. Look at this. Notice that the degree of sensorineural loss as it increases along the bottom. And now look at the sensation level of acoustic reflexes. And now read on the left. The sensation level for acoustic reflexes tends to decrease linearly as the degree of sensorineural hearing loss increases. And this really occurs up to about 60. Look at this. As the loss gets worse, the sensation level also gets worse. Okay? So, normal hearing, 80 to 100 dB sensation level. 60 dB loss, maybe a 40 dB sensation level. You see that? Each of these dots or circles is a case, is a person. These are called scatter plots. Okay? So, with growing degrees of sensorineural loss, outer hair cell pathology now, folks. Okay? 60 dB or less. Because outer hair cells help inner hair cells pick up sounds below 60. Okay? That's what their purpose is. That's why presbycusis, death to outer hair cells, is usually a moderate degree of loss, outer hair cell pathology. Look again at this slide. Same thing, showing the same trajectory. Increases in sensorineural loss, sensory especially, outer hair cell pathology, reduction of sensation level. 20 dB hearing loss, you might have 65 dB sensation level. Well, 20 and 65 is 85. You had an acoustic reflex at 85 dBHL. You have a 20 dB hearing loss. Your sensation level will be at about 65. As your sensorineural hearing loss gets worse, notice how it's like the 45-degree angle. It's an inverse linear slope. Okay? Sensation level, we read on the left, decreases in almost exact proportion to the degree of sensorineural loss. Absent acoustic reflexes and sensorineural loss. Here you've got four different frequencies. Who cares? Just look at the general trajectory here. Note the absence of acoustic reflexes increases dramatically with sensorineural loss of 60 dB or more. Da-dee-da-dee-da. Soon as you get past this, now you're entering the realm of inner hair cell pathology, and now your acoustic reflexes are highly absent. Bilateral sensorineural loss, mild to moderate. Here's Mrs. McGillicuddy. Typical sensorineural presbycusis. Okay? Tympanograms, normal. No air bone gap. Acoustic reflexes, look where they are. 85, 95, 90. That is what you call normal as normal can be. The sensation levels will likely be reduced. Doesn't matter. Okay? They're present. That's a normal finding. And this person will likely have good speech discrimination. It'll be fair. You know why? Because her inner hair cells are intact. This hearing loss is due to outer hair cell pathology. Outers help inners sense sounds below 50 or 60. Inner hair cell pathology means a garbled message is sent up to the brain. Your speech discrimination plummets. That's why severe hearing loss almost always presents with worse speech discrimination. Here's a case of unilateral sensorineural loss caused by an eighth nerve tumor. Normal right ear, left ear asymmetrical loss. Note the tympanograms are normal for both ears because there's nothing wrong with the middle ear. Nothing wrong with the ear pressure. But look at the reflexes. Right ear contra, normal, 85, 85, 85. Left or right ear ipsilateral, normal, normal, 80, 80, 80. Left ear contralateral, highly elevated or no response. Left ear ipsilateral, gone. You should have acoustic reflexes here in the low frequencies because the loss is only mild. I can understand where they'd be gone here. But where the frequencies are close to just a mild hearing loss, you should still have acoustic reflexes. Albeit at reduced sensation levels, but you should still have them. Here they're not. Remember, though, we don't measure mostly ipsy and contra-acoustic reflexes to assess retrocochlear pathology anymore. Some places do, but it's really been replaced by tests that are more sensitive, better at catching the disease, and tests that are more specific, passing people that don't have the disease. And those tests that are very good at that are like gold standards. Those would be CAT scans and MRIs, especially MRIs. Normal contra- and ipsy-acoustic reflexes, I should say abnormal, in a person with an intraaxial brainstem lesion, meaning a tumor inside the brainstem, deep inside, not along the surface. The contralaterals maybe are highly elevated and the ipsies are all there. Hmm, weird. Well, a deep brainstem is going to affect crossover, so you're going to get that sensory neural loss happening in both ears, fairly symmetrical. Normal middle ear. And the ipsilateral reflexes don't involve the crossover so much. It's the contras that do. So the contras are absent while the ipsies are present. But again, we don't use the combination of ipsy and contra reflexes to assess for eighth nerve and brainstem pathology so much anymore. It's a bit dated, but it just shows you, you know, that when a sensory neural loss appears, look at the tympanogram is normal, isn't it? I'll bet the static compliance is normal, the physical volume is normal. Here it's the acoustic reflexes that were abnormal. Now, here's hearing level increasings, and this is talking about percent of absent reflexes with cochlear sensory neural loss. Look at how around 60, now the incidence of absent acoustic reflexes increases dramatically. Look at conductive loss, how almost any degree of conductive loss obliterates acoustic reflexes. And look at when you have an eighth nerve tumor, cochlear nerve, eighth nerve. I don't know why they put CN there, but at any rate, as your hearing loss gets to be anything due to an eighth nerve tumor, absent acoustic reflexes. Acoustic reflexes and speech discrimination. Acoustic reflex deals with the inner hair cells, the acoustic reflex arc. Inner hair cells send aferent brain-going information to the eighth nerve, and so inner hair cells are a critical part of that aferent-eferent loop. Autoacoustic emissions deal with outer hair cells. The cochlea, outer hair cells receive information from the brain to help the inner hair cells pick up sounds below 50 to 60. Outer hair cells are not involved with the acoustic reflex arc. Two people with the same moderate sensory neural loss may have very different speech discrimination, right? Look at when we're dealing in clinic. Two people with the same degree of sensory neural loss, very different speech discrimination. The one with good speech discrimination probably has acoustic reflexes at reduced sensation levels. Bet you dollars to donuts, the one with poor speech discrimination likely has absent acoustic reflexes. And we're talking with mild to moderate sensory neural loss. Acoustic reflexes involve inner hair cells. They are a unique test underused today. Autoacoustic emissions, on the other hand, involve outer hair cells. Now read this carefully. Both are non-behavioral. Acoustic reflex, autoacoustic emissions. Both are obliterated by middle ear pathology. They therefore make great cross-tests. With one, you're assessing inner hair cell situations. With autoacoustic emissions, you're assessing outer hair cell health or whatever. You know, the situation with outers. And you're not even going near the cochlea. Non-behavioral cross-tests involving inner versus outer hair cells. And by the way, this would be a great segue for a next webinar. Maybe we'll do the next webinar on autoacoustic emissions for the hearing instrument specialist. Okay. Any questions? I'm done, but I'll certainly open up the floor for anybody with a question. Shoot. Go ahead. Thanks for listening. Thank you, Ted. Ted, we're so excited that we've had over 200 of your fellow colleagues that have joined us today on this webinar. As Ted said, we do have some time for questions. If you have a question for Ted, please enter it in the question box on your webinar dashboard. And, Ted, our questions are actually starting to come in, which is great. Our first question is from Jessica. And Jessica asks, so let's say you just tested the ipsilaterals. What would clue you in to a retrocochlear brain stem issue? That would probably, if you just did ipsilaterals, there's two answers to that question. Number one, we really aren't often looking for retrocochlear pathology by doing acoustic reflexes anymore. That's why we really don't, we're not using both ipsi and both contralateral reflexes to assess for retrocochlear pathology. But, to answer the second answer to your question is, if you had retrocochlear pathology, it's likely the ipsilateral reflex in the affected ear would be highly elevated or absent. Okay? Because the acoustic reflex involves the eighth nerve, and the eighth nerve is part of the acoustic reflex arc. So it's going to affect both contralateral and ipsilateral reflexes. So if you're just doing ipsis, those will be affected. Remember, it's only if you have a deep brain stem lesion per se, then your contras will be absent and your ipsis will be present. But in the case of usual eighth nerve pathology, it's good enough just to use either ipsi or contralateral reflexes, and likely the ipsilateral reflex would be absent in the ear that showed the retrocochlear pathology. Great. Thanks, Ted. Ted, our next question is from Nancy. Excuse me. And Nancy asks, what is the current thought on the use of acoustic reflex testing as part of the assessment battery for infants and toddlers? Can you tell me the youngest age in which reliable results can be obtained? Oh, yeah. A good question. Tympanometry can be done on an infant. I mean, acoustic reflexes can be tested on a newborn. Caution here, because many newborns have a bit of middle ear pathology. There's sticky gunk in there. You know, everything is brand new. The stapes is a little bit soft. It hasn't completely ossified yet. It's still cartilaginous to some degree. So that's why tympanometry and acoustic reflexes are not often and always used in infant screening programs. The ABR is brainstem response. Otoacoustic emissions is too, but that also can be faulty, because that also can be obliterated by middle ear pathology. But theoretically, yes, you can test tympanometry and acoustic reflexes on a baby. No problem. That's all the anatomy and physiology is there. A bit of caution, though, again, because some tympanometry is a little bit abnormal in newborns until they're a couple of weeks old. Thank you, Ted. Ted, our next question is for Mary, and Mary asks, How would you interpret testing that showed no acoustic reflexes but completely normal hearing? Could it mean damage to the tendons and or muscles of the reflex mechanism? That's a good question, too. You know, there are some people that just don't have acoustic reflexes. There are. You know, when nothing else is untoward. If a person has a normal tympanogram, no airborne gap, and has even normal hearing, there are some people who just don't have acoustic reflexes. There are few and far between, but there are some people like that. And it doesn't mean they're not nice people. If they don't have any particular other symptoms to report, okay, then probably they just happen to have, you know, like some people genetically can't curl their tongue. You know, they just can't do it. So sometimes these things just occur. It's not going to be too likely that a damage, like a muscle tendon isn't there, because, again, if the muscle tendon was damaged, the person would be talking about pain in the ear, would be having other symptoms. Do you know what I mean? So there are cases where some people just don't have them. Thanks, Ted. Ted, our next question is from Maria, and she asks, are upward deflecting reflexes indicative of anything? Can you read that one again? Can you read that one again, or upward? Say that again, upward? Are deflecting reflexes indicative of anything? Upward. Or is it just artifacts? I'm just not quite sure I understand the question. I apologize. I just can't figure. Read that one. Maybe the third time's the charm, Ted. Give it a try. Read it again to me. Maria, if you're listening, if you could expound on that a little bit, I can certainly re-ask that of Ted. Ted, our next question is from Elise, and she asks, when would you suggest performing acoustic reflex testing decay? Ah, good question. I would leave that to an audiologist to do that. I think that acoustic reflex decay means you're holding the tone steady for longer than a second. And you're trying to figure out, can the acoustic reflex hang on like you're doing a chin-up? Can you keep your chin above the bar? How long can you tolerate it? And they'll have that tone go for ten seconds. And if the acoustic reflex decays or gets weaker by 50% over that ten seconds, then it's said that, hmm, that's another positive sign for an eighth nerve tumor. Acoustic reflex should be able to hold its own. But, A, that's a painful test. It's loud. And, B, it's not always 100% sensitive or specific. But some audiologists do use it. As an HIS, I think I would probably leave that one alone. But your question is a good one. Acoustic reflex decay is a test done to assess eighth nerve pathology. It's a build-on additive to the acoustic reflex battery that we normally do. Thanks, Ted. Ted, our next question is for Martha. And Martha asks, what age would you transfer from high-frequency to low-frequency tympanometry? Ah, great question. Babies, I think babies like under six months to a year. Now, I'm not the best person to ask this. But very, very young children and infants, okay, babies and infants are often, their middle ear system has more gunk in it, to you for any better word. Their stapes is larger because it's more cartilaginous. So their whole middle ear system is less stiff. It's more mass-dominated. And that's why they use a high-frequency tone, because highs will bounce off the mass, okay? Their middle ear systems are more mass-dominated than the normal middle ear, which is more stiffness-dominated. So that's why a stiffness-dominated middle ear, we use a low-pitched tone. And she's asking, a high-pitched tone would be used for a middle ear system that's more mass-dominated. That's usually found in infants. And when the exact age is, I sure wouldn't be the best person to answer this. I would say within a couple of months. Let's put it this way. If you did 226 hertz tympanometry and you didn't get, you got an abnormal finding, then do high-frequency, like 600 hertz or 1,000 hertz tympanometry, and find out what you got with that. That's the approach I would give. Thanks, Ted. Ted, our next question is from Robin. Robin asks, first she says, hi, Ted, and she would like to know, what would you say about tymps with positive MEP? With positive? MEP. Positive middle ear. Oh, what do I think of tympanometry with positive middle ear pressure? Hi, Robin. Positive middle ear pressure, you don't get that very often, but you will if you blow your nose really hard. Or if the baby's been screaming and screaming away, and then you do tympanometry, you might get a peak over positive air pressure. But having a peak over positive air pressure is really more self-induced. You can create that if you make an over amount of positive air pressure in your middle ears by blowing your nose really hard while you plug your nose. That can temporarily make your middle ear space a bit more positive air pressure, so then you're going to have to use positive air pressure in the ear canal to offset that, and then you'll have a peak over positive air pressure. But that's not very common. I have a feeling I didn't really answer your question, though. Did I? I don't know. Well, if you didn't, maybe we'll continue with you at the end of the presentation. Ted, our next question is from Margaret. And Margaret asks, why does the acoustic reflex show up best with a normal type A tympanogram? Because your acoustic reflex is measuring a slight reduction in the height of your tympanogram, a slight reduction in static compliance. Now, if you've got middle ear pathology, okay, like a type C or a type B tympanogram, well, your whole tympanogram is abnormal, so you can't really measure a reduction of the height or the reduction of static compliance in an abnormal tympanogram. Your middle ear has a pathology, and so your whole acoustic reflexes will likely be absent. If you've got like a vacuum in your middle ear space, you're going to have a tympanogram peak over negative air pressure in the ear canal. Your middle ear system is already overly stiff, do you see, because you've got a vacuum in the middle ear space. You've got negative air pressure. So because you've got negative air pressure, your type C tympanogram will likely not be as tall as the type A. It's going to be compromised already. Your middle ear system is already overly stiff, caused by the vacuum in your middle ear space. So a loud sound is going to be hard pressed to have an effect on that tympanogram that came about as a result of an already overly stiff middle ear. So that's why acoustic reflexes, likely if your peak is between positive 100 or negative 100, really that's going to be your range of air pressures. You can have slightly negative air pressure or slightly positive air pressure, but you can get an acoustic reflexes with those, because the middle ear is not compromised already. Thanks, Ted. Ted, we have time for one last question, and our last question is from Steven. Steven asks, why would the acoustic reflex not be nature's protection against noise-induced hearing loss? Well, I'll tell you this. What about a shot from a gun or a loud blast? That's going to happen so quickly that your acoustic reflex won't be able to kick in. And so you've got the hearing loss as it is. Another thing is the acoustic reflex is caused by loud low-frequency sounds. And if loud low-frequency sounds come in the ear, your acoustic reflex is strongest. So okay, already sudden loud sounds won't be dulled by the acoustic reflex. And secondly, only loud low-frequency sounds are going to be affected by the acoustic reflex. So when you think about it, what makes sense is it's working with the loudness of your own voice and the loudness of your own voice to you is sufficient to kick in an acoustic reflex. So upon retrospect, it seems that's a more plausible explanation for the reason why you have an acoustic reflex, because as I said, with a lot of noises, the acoustic reflex simply wouldn't help anyway. Great, thanks, Ted. Ted, I'd like to thank you for an excellent presentation today, and I'd like to thank everyone for joining us on the IHS webinar, Acoustic Reflex Testing, Methodology, Interpretation, and Clinical Uses. If you'd like to get in contact with Ted, you may email him at tvenema at conestogac.on.ca. Ted, it's tvenema at sha.ca. My apologies to you. I should have corrected that on the slide. tvenema at shaw.ca. Got it. Thanks, Ted. For more information about receiving a continuing education credit for this webinar, please visit the IHS website at ihsinfo.org. Click on the webinar banner or find more information on the webinar tab or the navigation menu. IHS members receive a substantial discount on CE credits, so if you're not already an IHS member, you will find more information on our website. Please keep an eye out for the feedback survey that you will receive tomorrow via email. We ask that you take just a moment to answer a few brief questions about the quality of today's presentation. Thank you again for being with us today, and we will see you at the next IHS webinar.

acoustic reflex testing

protocols

clinical uses

tympanometry test

middle ear

transmitting sound

contralateral reflexes

ipsilateral reflexes

retrocochlear pathology

webinar