Sensorineural and Conductive Hearing Loss: Causes and Treatments
Guest: Dr. Judy Dubno – Otolaryngology/Head & Neck Surgery, MUSC
Host: Dr. Linda Austin – Psychiatry, MUSC
Dr. Linda Austin: Dr. Judy Dubno is Professor of Otolaryngology; Ear, Nose, and Throat. Dr. Dubno, you have just been very highly honored by being elected to Vice President-Elect of the Acoustical Society of America?
Dr. Judy Dubno: That’s correct.
Dr. Linda Austin: Well, congratulations.
Dr. Judy Dubno: Thank you.
Dr. Linda Austin: In this podcast, let’s talk about a real passion of yours, which is hearing loss. When somebody comes to you and says, I’m having problems with hearing, what are the first questions that come to your mind about what’s important to understand for that person?
Dr. Judy Dubno: Let me tell you a little bit about how common hearing loss is in the United States. It’s actually one of the leading public health concerns in the United States. Approximately 17 percent of Americans; about 36 million people, report some degree of hearing loss, so it’s a very common problem.
Dr. Linda Austin: And, actually, just to look at that number a little closer, if you’re to take people over the age of, say, 65, or some cutoff, it’s probably a much higher percentage, I would think.
Dr. Judy Dubno: It’s much higher. Actually, it’s the third most common chronic condition of aging, and number one among older males. So, it is a very common problem. And, as we all know, the population is aging, so there are going to be more and more people with hearing loss as the years go by. So this is a common problem now, and it’s becoming even more common. Among adults, the most common form of hearing loss is called sensory neural hearing loss, which means that the impairment affects the inner ear, the auditory nerve, or higher sensors of the auditory system.
Dr. Linda Austin: For those people listening who haven’t taken a course in anatomy lately, the inner ear consists of what?
Dr. Judy Dubno: The inner ear is mostly the cochlea. This is the area behind the tympanic membrane, or eardrum. So, this is not visible from the outside. This is inside the head, and it’s encased in bone, so it’s not something that’s visible to your ear doctor. And that’s actually one of the problems with inner ear hearing loss. It’s not usually treatable with surgery, or by drugs.
Let me also go through the most common causes of sensory neural hearing loss.
There are three major ones. One is exposure to noise for extended periods of time. That’s sometimes called noise-induced hearing loss. Another common cause is exposure to certain types of drugs. We call these ototoxic drugs because they are damaging to the auditory system.
Dr. Linda Austin: And what drugs are those?
Dr. Judy Dubno: The most common of these drugs are some anti-cancer drugs, like Cisplatin, and also, aminoglycoside antibiotics. There are certain forms of antibiotics; they’re not used commonly in the United States, but they are commonly used worldwide.
The third most common cause of sensory neural hearing loss is aging. That’s the area that our research program focuses on mostly; age-related hearing loss.
Dr. Linda Austin: Does age-related hearing loss run in families?
Dr. Judy Dubno: That’s a very good question that we don’t have the answer for. And one of the reasons is that there have not been enough studies of large numbers of older adults where, at the same time, we have good measures of hearing over a long period of time. And that’s one of the goals of our program; to collect that information and, at the same time, obtain, with our participants’ permission, DNA from which we can do an analysis of genes, and determine if there’s an association with their genes and how much age-related hearing loss they have over time.
Dr. Linda Austin: So, you mentioned that one form of hearing loss is sensory neural. That implies there’s another form of hearing loss, what is that?
Dr. Judy Dubno: The other most common kind of hearing loss is called conductive hearing loss. That form of hearing loss affects the external ear and the middle ear. The most common is otitis media, or middle ear fluid. Sometimes there are changes to the three little bones in the middle ear that effect hearing loss. The main difference between conductive hearing loss and sensory neural hearing loss is that, often, conductive hearing loss can be corrected with surgery.
As I discussed the three common causes of sensory neural hearing loss; exposure to noise, exposure to drugs, and aging, each of these results in damage to the delicate structures of the inner ear and the auditory nerve, which is not reversible. That is, once the damage to these structures occurs, it cannot be repaired or regenerated in humans. Therefore, prevention and treatment of hearing loss is very important and requires a clear understanding of how this damage occurs to the inner ear. Some of our basic science research is focused on answering some of these questions, to try to prevent damage to the inner ear and treat it once it occurs; because it is not reversible once it occurs.
Dr. Linda Austin: Can both of these types of hearing loss be helped with hearing aids?
Dr. Judy Dubno: The most common form of treatment for sensory neural hearing loss is a hearing aid. However, only about 20 percent of individuals who could benefit from hearing aids seek treatment in the form of hearing aids, or are successful users of hearing aids.
Dr. Linda Austin: Dr. Dubno, I see this in some of my elderly relatives, who are so darned resistant to even trying hearing aids. What is it about hearing aids that make them so difficult for people to accept?
Dr. Judy Dubno: There are lots of reasons. It’s a very complicated problem, for which some of our research is focused on. One of the problems is cost. Hearing aids, today, in the United States, are very expensive. They’re often not covered by insurance, and they’re not covered by Medicare.
Dr. Linda Austin: The range of cost is what?
Dr. Judy Dubno: I would say $500 to $6,000, depending on the features that the hearing aids have, and how many you have. Most people wear two hearing aids, so that doubles the cost. There’s also an ongoing cost for batteries. Hearing aids most often run on batteries that have to be replaced. Some of the new hearing aids run on solar batteries and are rechargeable, so that problem is being addressed. In addition to cost, there’s also some stigma related to using hearing aids. People feel that wearing a hearing aid makes them look older.
Dr. Linda Austin: Yes. My father, who is 85 years old, doesn’t want to look older by wearing a hearing aid, so, instead, he can’t hear a darn thing.
Dr. Judy Dubno: Yes, that is a very common problem. The other issue is that hearing aids work very well in certain areas. Their main function is to make speech louder. So, when we’re in a quiet room; like the room in which I’m speaking to you right now, a hearing aid would work very well, because it would amplify my voice, which would make it easier for you to hear me. Under those circumstances, in a quiet environment, hearing aids work very well.
Unfortunately, the most common problem for people with hearing loss is understanding speech in noisy environments, like a restaurant, or a cocktail party. These are the situations that people complain about most. And it’s in these situations that hearing aids don’t work very well. Not only do they amplify the person you’re speaking to, they amplify all the other noise in the room as well. So, you haven’t really improved the amount of speech that you hear; you’ve just made everything louder. People react to that by turning down the volume on the hearing aid. And then they’re back to the situation they’re in without a hearing aid.
So, there’s a lot of research going on; some of it at MUSC, which is trying to understand why people have difficulty in noisy environments, with the goal of improving technology to develop better hearing aids, and to develop better rehabilitative programs so that people can learn to use the new information they’re provided with the hearing aid. So, there is a lot of research going on. But hearing aids remain an underutilized form of treatment. And the main issues are cost, stigma, and the fact that hearing aids, in certain situations, do not work very well.
Dr. Linda Austin: Dr. Dubno, we have a lot more to talk about, but let’s save that for the next podcast. Thank you.
Dr. Judy Dubno: Thank you, Dr. Austin.
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