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Judith Lieu, MD, from the Department of Otolaryngology–Head and Neck Surgery at Washington University in St Louis, discusses the need for screening young children for hearing loss and the importance of treating hearing loss as early in life as is possible.
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Ed Livingston: Hearing loss in children is a very common phenomenon. And I think everybody knows that the technology for treating hearing loss has dramatically improved in the last decade or so. Cochlear implants are fairly common and are game changers for treating hearing loss in kids and even in adults. It's also very important to diagnose hearing loss in children at a young age because intervention at a young age will result in better outcomes for those kids. In today's JAMA Clinical Reviews, we cover the topic of hearing loss in children.
Intro: From the JAMA Network, this is JAMA Clinical Reviews, interviews and ideas about innovations in medicine, science, and clinical practice. Here's your host, Ed Livingston.
EL: In the December 1st, 2020 issue of JAMA, we published a review on hearing loss in children written by today's JAMA Clinical Reviews guest. Could you tell us who you are and where you work?
Judith Lieu: My name is Judith Lieu. I am a professor in otolaryngology and head/neck surgery at Washington University in Saint Louis.
EL: Let's start by talking about the importance of diagnosing hearing loss at an early age. One major part of your review is in encouraging clinicians to pursue earlier and earlier diagnosis in these kids. So why is that important?
JL: So there has been some very well-done research over the past 20, 25 years that has shown that the earlier we can identify children with hearing loss, get them fitted with hearing devices so they can hear closer to normal or near normal, their speech and language development improves quite a bit, to the point where we can even get it to close to that of normal hearing children. And this is in the background of knowing that if we waited just kind of for a natural history to identify children with hearing loss that many of these kids are very delayed in their speech and language communication. And in eons past, they would not really achieve the level of education and speech and language communication that we would like our children to achieve. And so the progress toward early identification has helped us to fit children with hearing loss earlier and, if needed, to place cochlear implants earlier so that, again, they can achieve more normal trajectories and so -- and all of the downstream consequences, or I actually should -- I should say the benefits of better speech and language -- that they can have better reading skills, better educational skills, and all the other cortical processes that allow them to do well in whatever they choose to do in their life.
EL: When we speak of early diagnosis, how early are we talking about?
JL: The earlier the better. [Laughter] So there are now nationwide hearing screening programs that are start at birth. So if a child is born in the hospital, then we want them to have a hearing screening performed before they're discharged, so at a day or two of life. For children who are born at a birthing center or perhaps even at home, we have the goal of having hearing screening done before they turn one month old, hopefully by their pediatricians. And this is a national initiative that started way back in 1993 and that over time has spread nationwide across the United States and really all over the globe. So that -- the intent is to identify children as soon as possible with hearing loss, hopefully get them confirmed with a problem by the time they're about three months of age and no later than six months of age, get them fitted with hearing aids so that we can start that habilitation process.
EL: How do you screen newborns or children less than a month old for hearing loss?
JL: Well, we have been very fortunate with technology that allows us to screen both babies in the newborn nursery as well as the neonatal ICUs. In the newborn nurseries, we use what's called otoacoustic emissions. And that is based on a response that the outer hair cells in the cochlea will make in response to a noise that is given to the ear in a child at birth. And so these can be measured objectively. And if they have a normal response, then they pass the screening. But if they don't have a normal response, then they're usually screened again. So these are looking at the cochlear hair cell health of babies. In the neonatal ICU, we have children who may have some neural issues, whether that's because of prematurity or internal problems or other insults that may have affected their neural development. And we use what's called an automated ABR, or auditory brainstem response, where it is a sound that is presented to the ear and the responses are measured at the brainstem.
So we're looking at the auditory nerve, the cochlear nerve, responses to that auditory stimulus.
EL: I didn't exactly follow how the auditory stimulus is measured in either technique that you just described. So could you tell us how that's done? I can't conceptualize that.
JL: Sure. So just like you would wear earbuds to hear this podcast, the acoustic signal is sent through like a little earbuds into the ear canal. And that's also measured that same way, with a little receiver. And it looks like a little handheld device, kind of like an ear thermometer, except that you put it right into the ear canal. People may have also had the experience of having had a tympanometry done in their ear. And it's not quite the same experience, but it's a similar setup. For an automated ABR, they'll again put little earbuds into the baby's ears, and they will present an acoustic signal through that earbud. But then the brain waves are measured at the skull base and at the forehead so that we have a sense of the neural integrity of that sound being picked up by the brain where it goes toward the auditory cortex.
EL: Are there guidelines suggesting that all children be screened at these very young ages?
JL: Oh, yes. This is something that the NIH, again, put out the first recommendations back in 1993 and has been administered through the CDC with the early detection of hearing impairment network. And there are national organizations that help to produce guidelines and publish benchmarks for hearing screening in babies. So the Joint Commission on Infant Hearing has been publishing these updated guidelines for -- well, since -- at least since 1994. So every state in the US now has some type of newborn hearing screening program. Now every state does it a little bit differently, but the idea is the same.
EL: And once a child is diagnosed with impaired hearing, what are the treatment options?
JL: Well, it depends on the severity of the hearing loss, but almost always, we start out with some type of hearing aid. And most of the time, it can be -- sound can be delivered through the ear canal. However, there are some babies who don't have an ear canal because of congenital deformity. And they -- the sound is delivered to them through the mastoid process. Nevertheless, the point is to try to amplify whatever sound that can be delivered to the ear so that a child can make use of it at the cortical level and then learn to make that magical transition from just hearing sounds to making sense of it, like in terms of words and music and other acoustic signals that we take for granted.
EL: Who gets cochlear implants?
JL: The children who get cochlear implants are those who have failed to achieve adequate benefit from hearing aids. And by the way, hearing aids have become much better than people may have recalled from 20, 30 years ago. They are now digital. They're -- they can be customized. They're -- the technology has improved immensely over the past 20 years or so. But cochlear implants are generally reserved for children who are not getting any usable hearing from the cochlear implants. And they're surgically implanted and are being done at earlier and earlier ages.
EL: Could you describe how they're put in? You know, what they are made of and how they're put in.
JL: So cochlear implants are basically electrodes that are implanted into the cochlea. So it's surgically implanted behind the ear, through the mastoid, and into the cochlea directly. And then they're hooked up to receivers and then to very complex signal processors that help to make sense of the sound that the child will hear through, again, a receiver then that goes straight to the cochlea and in -- up to the brain.
EL: One of the things that I've wondered is so you have this device that picks up the sound. It transmits it. It converts it to an electrical signal that goes into this fiber that stimulates the cochlea itself. Do those kids have to go through a learning process to how to translate those sounds into something interpretable for them? And do we know if those sounds sound the same to them as they do to us, or how does that work? I've always been curious about this.
JL: So yes, they definitely have to learn to process the electrical signals because they're obviously not quite the same as acoustic signals. And the electrodes are tonotopically placed in the cochlea. That is, you know, the cochlea has its frequency tuned and so that depending on the frequency of the acoustic signal, the different electrodes will take them to different parts of the cochlea and then stimulate the different areas of the brain. And yes, just like any baby infant needs to learn how to talk and to hear speech and understand it and then men to produce speech, children with hearing loss who receive cochlear implants have an intense habilitation process where most of them will go through intense speech and language therapy in order to learn to make use of their cochlear implants and do the speech and language learning and development that we assume that all babies would do otherwise.
EL: Is there anything you think we should talk about that we haven't covered already?
JL: Well, one of the things that I want to mention is that even though we're talking about newborn hearing screening and identifying children with hearing early, I think that process actually never ends, because children can lose hearing throughout their childhood. And there are some etiologies where hearing loss can happen anytime during their early childhood or even into adolescence. And so whenever a child has problems with hearing, it really behooves us to try to help them to hear better. We have learned over time that there is really no degree of hearing loss that is too small to ignore. That is, even a little bit of hearing loss, even in just one ear, can put a child at a disadvantage because it is really our brains that use the acoustic signals to hear and understand. And it's not just our ears. And so if we do not provide children the adequate signals to both ears so that they can process this, and critically, that they can have significant disadvantages from that.
And so that's what we have learned over the past 10 to 15 years for sure. And we're learning how best to utilize the devices and the technologies that we have currently to figure out "When should we recommend them?" At what point should we step from hearing aids to cochlear implants? Or is it better to retain an acoustic hearing through a hearing aid, even a -- even if a child is kind of borderline? There are lots of areas in which we don't have the definitive answers yet about what's best. But it is clear that hearing better is almost always better for the child.
EL: What are the causes of hearing loss? You know, we talked mostly about congenital hearing loss. But as kids age, you mention we should be cognizant that they could lose their hearing and need intervention. So what does cause hearing loss as kids grow up?
JL: Well, there are a lot of causes. Some of them include infections. Thankfully we don't see as many children with pneumococcal meningitis as we used to, but that was certainly a -- an important cause of hearing loss in the past. Children can have trauma. Trauma is certainly a big reason. Any kind of head trauma can cause hearing loss. It is very common also for children who have received, say, chemotherapy or radiation therapy for childhood cancers, especially to the head, to have experienced hearing loss. Other ototoxic medications, such as some types of antibiotics, such as gentamicin or furosemide for -- again, for children who have been treated with other problems are at risk for hearing loss. And, you know, there are genetic causes that come up with hearing loss later in life. So, for instance, Alport's is a reason for hearing loss that happens later.
Usher syndrome is the most common reason for both deafness and blindness, and that usually happens later in childhood. So there's a myriad number of etiologies that could potentially show up with hearing loss later in life.
EL: What about, you know, kids growing up now are all using earbuds, high-quality, powerful ear phones in numbers that didn't occur in previous generations. When you and I were growing up, we didn't have those things. And now they've always got something in their ears, and they're probably listening to things fairly loudly. Does that contribute to hearing loss, and is that a problem that we need to worry about?
JL: That's an excellent question. And I don't think we've come to a resolution yet as to a definitive answer. There is no doubt that noise-induced hearing loss can cause hearing loss over time, especially in adults. And so we even have occupational safety thresholds and standards for hearing of noise exposures in the workplace. However, it's been challenging to show definitively that children who are wearing earbuds are at higher risk for noise-induced hearing loss than in the past. But despite that not being able to find it, I think we are all concerned, as you mentioned -- is that if they're using earbuds and turning up the volume that we're all concerned that that can eventually lead to downstream adult-onset noise-induced hearing loss. So at least in my clinic, and I know just about in every pediatric otolaryngologist practice, you know, we recommend that kids turn down the earbuds so that it's not loud.
And, you know, I use one very rough measure that if a parent can hear it off the earbuds, then it's too loud. But it's an question that we haven't quite answered yet.
EL: What should we be telling parents about hearing loss in children, and especially if their understanding is that mild degrees of hearing loss or unilateral hearing loss aren't important?
JL: I think that there is a ton more research that is being done. And I think one of the areas that perplexes many of us is how to counsel parents when maybe we don't always have the evidence that doing something to help hearing is better. But -- and so I think one of the issues that I would like to bring up is I have heard over and over again where, you know, based on prior research or prior studies that discounted, you know, mild forms of hearing loss or hearing loss in just one ear as being not a problem. I would encourage, you know, all physicians and anyone who's listening to this, you know, consider that any hearing loss can be a problem for children as they develop and grow and not discount the possibility that even what appears to be a little bit of hearing loss can be a problem.
EL: I'd like to thank Dr. Judith Lieu from Washington University for speaking with us today in the JAMA Clinical Reviews podcast and especially for writing the review on pediatric hearing loss that appeared in the December 1st, 2020 issue of JAMA. We learned a lot today. We learned that children should be screened for hearing loss from the day they're born and that we should always be cognizant of them developing hearing loss throughout the time that they're growing up. It's now well-established that early intervention in hearing loss can result in better functional outcomes for children. So it's something that we need to pay attention to. The technology that's been applied for treating hearing loss is just amazing and has vastly proved our belief to treat children with hearing loss. This episode was produced by Daniel Morrow. Our audio team here at the JAMA Network includes Jesse McQuarters, Shelly Stephens, Maylyn Martinez from the University of Chicago, Lisa Hardin, and Mike Berkwits, the deputy editor for electronic media here at the JAMA Network. I am Ed Livingston, deputy editor for clinical reviews and education at JAMA. Thanks for listening.
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