Cochlear Implants: Q & A

I have received several emails recently from parents of children newly diagnosed with hearing loss. I love the fact that this blog has allowed us to connect with other families all across the country (well, the world, really) that are going through similar experiences. Some of the questions I have received may be on the minds of others, so I thought I would post all of my answers here:

What genetic testing should I have run on my child now that he has been diagnosed with hearing loss? Do the genetic testing results have any relevance in regard to the treatment options? Did you see a geneticist or can an ENT order genetic testing?

While I am sure genetic testing varies from one hospital to the next, our genetic testing was ordered by Drew's ENT. He ordered the test after our initial meeting as a result of Drew's hearing loss. Drew's testing was run when he was about six weeks old. The genetic test is called a "Comprehensive Hearing Panel" and consists of testing for Connexin 26, Connexin 30 and a specific gene mutation. These are the most common, non-syndromic causes of hearing loss that can be tested and are genetic.

Many people never find a cause of their child's hearing loss. It is believed that there are many genetic causes of hearing loss that have not yet been discovered, so if these tests come back negative, that does not mean that your child's hearing loss was not a genetic cause, just not anything they can test for. I would however strongly recommend having this test run because if your child's hearing loss was caused by one of these genetic causes, you can rule out other causes, some of which are syndromic.

In addition to the initial genetic testing, your ENT will order a CT scan or an MRI to check the anatomy of the child's' ears. After the CT scan or MRI, the ENT may elect to run further genetic testing. If it is found that the child has enlarged vestibular aqueducts, malformation of the inner ear or other anatomical abnormalities, there are specific genetic tests that can be run for syndromes that have these abnormalities, such as Pendred Syndrome. This is just one of many syndrome's associated with hearing loss.

The genetic testing has no relevance in your actual CI candidacy. The only thing it can give you is an idea of how well your child may do with a CI. Children with hearing loss caused by Connexin 26 are known to do very well with cochlear implants because they don't have any other known problems, such as with thier balance, kidneys, eyes, just to name a few. So you might get an understanding of the possible outcomes with a cochlear implant. For instance, if a child has Mondini or EVS, all electrodes might not go in the cochlea, so results can vary. Ultimately, the success of the child is in the hands of the parents. The surgeon and audiologist can only do so much. Without parent support, intervention and therapy, the child will never perform to his maximum potential.

What made you so sure about having Drew simultaneously implanted? Furthermore, what made you feel that Drew needed two implants?

There were several reasons:

First, bilateral cochlear implants are proven to help with sound localization and with hearing in noisy situations, two areas we felt were vitally important for children. Drew can hear what direction a car horn is coming from if he is playing in the street. Also, for children in noisy situations - classrooms, play grounds, Chuck E Cheese - they can hear much better. For example, we were having dinner at Roosters the other night and I was talking to the waitress, who is an audiology major at Ohio State, about Drew's cochlear implants. I was listing all of the words he can say and he was repeating them! He was sitting on the other side of the table, I was turned talking to the waitress and he could hear everything I was saying. I don't think this would happen with just one cochlear implant.

Second, we did not see the need to put Drew through two surgeries when we already knew we wanted Drew to have bilateral implants.

Third, if you do sequential implantation, meaning one ear after the other 3-6 months, or more, apart, there is a "big" ear and a "baby" ear. The new ear has to catch up. You have to do specific therapy to catch up that second ear because it has gone longer without auditory stimulation to the brain. We didn't want to do that. It is important to know that many parents did not have this option when their children were first implanted, as research into bilateral implants has only been around for about two years. When Drew was diagnosed we received mixed reviews on the medical necessity of bilateral implants. The whole concept was very new. Drew is only the second child in Ohio to receive bilateral implants. I have a feeling that many families would have chosen simultaneous implants if it would have been a choice at the time.

We have also, over the last eight months, run into other reasons why there is a significant advantage to bilateral cochlear implants.

What made you decide to have Drew implanted at such a young age?

Drew got zero, and I mean zero, benefit from his hearing aids. He never responded to anything with his hearing aids! Seriously, we got one response in the testing booth in over six months time. We never saw him respond to any environmental sounds at home (phone ringing, dog barking, doorbell). Every day that went by was one more day that Drew was not getting any auditory stimulation and one more day further behind in his development. Had Drew shown even the slightest benefit with his hearing aids we probably would not have pushed as hard as we did. (Although, seeing the results, I can't imagine not getting him implanted as young as possible). Once a child is 6 months old the complications of surgery reduce considerably, as the risk of anesthetic declines.

I was very persistent and direct with our ENTs on my expectation that Drew be implanted at eight months of age. I finally called each of the ENTs we were considering and asked them for a surgery date the first week of June for bilateral implants. One agreed, one did not. We would have gone to the end of the earth to get him implanted when we did. Travel distance to the implant center did not matter to us. We would have searched out skilled doctor after skilled doctor to have Drew implanted at that age.

What is the difference between Auditory Verbal and Auditory Oral philosophies? I know there is an Auditory Oral school near us - is that successful as well from what you have heard?

The line between AV and AO is blurring.

Traditionally, AV believes in not allowing the child to do any lipreading, mainstreaming from the beginning (meaning there are no AV schools because they believe in putting the child in a preschool with typical, hearing peers) and the process of catching up a child's hearing age to their actual age happens without any special needs schooling.

Traditionally, AO allows you to see the lips of the person talking. In fact, AO used to encourage the use of lipreading as a means of communication, although I think that idea is fading as amplification options become better and better. In addition, with AO, the idea is to give the child intensive therapy from the beginning, in a special needs setting, so that the child can mainstream in school by kindergarten, or when the child is ready.

We are doing a combination of both therapy methods with Drew. In his therapy sessions we use a lot of AV, where we don't allow Drew to see our lips, making him perform all tasks with auditory input only. But in everyday life, Drew can see our lips. We also strongly believe in sending Drew to an oral preschool that will focus on his specific needs and give him a head start to mainstreaming in kindergarten. I would not feel comfortable sending him to a mainstream preschool. To me, that would be like giving up precious years that we can use to educate him with intense auditory and speech therapy.

How old was Drew when he received hearing aids? Were you able to use loaner hearing aids? I'm thinking my child will be 3-4 months of age before he receives his hearing aids through our states loaner program.

Drew received his hearing aids when he was 10 weeks old. We did get loaner aids through our Regional Infant Hearing Program, because we knew that the hearing aids were likely not going to give Drew enough amplification to develop normal speech and hearing.

There is a mandatory hearing aid trial in order to develop candidacy for a cochlear implant, so the sooner your child receives hearing aids the sooner you can head down the CI path (if the aids aren't working). We had to wait 3 months from when we got the aids to begin down the path toward the cochlear implant, and this time frame may vary by program. We actually started the official cochlear implant process in March. We then had to do the candidacy process, which included meeting with a Social Worker, SLP, ENT and our audiologist. I had scheduled many of these appointments in advance to speed things up. The best advice I can give it to advocate for your child in order to move the process along. I went with the old saying, "The squeaky wheel gets the oil." I called the doctors office everyday to see if there were cancellations so that I could get Drew in for his evaluations sooner. I think that the receptionist got so sick of me calling everyday that she finally just gave me an earlier appointment.

What forums would you recommend I join?

There is a great Yahoo! Group: CI Circle. It is a group for parents with kids who have cochlear implants and for parents of kids in the cochlear implant process, although there are many professionals involved with the group as well. This group has been an excellent source of information for me throughout this entire process. This group was where I initially discovered that kids were being implanted under 12 months of age. They were also great with providing information on insurance companies that were providing coverage for bilaterals and for under 12 months of age.


If you have any recommendations or would like to expand on these questions, please leave a comment.

Genetics

I received the results of my genetic test today. I have the same mitochondrial abnormality found in Drew. This means that my daughter most likely carriers this abnormality, as well as my sister, brother, Mom, her siblings, my Maternal Grandma, and the list goes on and on. Your mitochondria is only passed from your mother, so the chain ends with every boy. Boys can be a carrier, but can not pass the abnormality to their children. While everyone in my family has normal hearing, it is important to know of this abnormality, because deafness could be induced immediately with the use of amnioglycoside antibiotics.

The doctor tried to explain all of the risks to me, but all of this biology stuff is a bit overwhelming and difficult to understand entirely. With a mitochondrial abnormality, the only test that can be performed is to see if you have the abnormality or not. It is a very black or white test. The testing can not confirm "how much" of your mitochondria is affected by the abnormality. While still in the research phase, it is believed that mitochondrial abnormalities affect only a percentage of mitochondria DNA. The more affected, the greater risk of exhibiting a hearing loss. In addition, some of these abnormalities are only exhibited when they are in conjunction with another factor, like the antibiotics, or potentially in Drew's case, with Connexin 26. It is hypothesized that in my family, the percentage of abnormality is small, since no one exhibits signs of hearing loss on that abnormality alone.

At this point I know that I could potentially lose my hearing with the use of certain antibiotics. The same would be true for my daughter, sister, brother, others in my family, although to be certain they carry this abnormality, each individual could have a blood test run. But given that I am a carrier, it is believed that this mutation runs in our family, and was not just a brand new mutation in Drew.

I will be looking into medical alert bands for myself and my daughter, for use if we are in an accident to prevent any hearing loss we could have from the use of these antibiotics. If you would like information on how to have yourself tested through Cincinnati Children's, please click here.

One Step Closer

We were in Cincinnati today for another round of appointments and are now one step closer to having Drew receive his cochlear implants. Today's appointments included a CI consult for Drew with Dr. Daniel Choo and follow up on the genetic testing results.

On the CI front, Drew is moving toward candidacy. Dr. Choo is confidant that hearing aids are not going to benefit Drew enough to develop his listening and speech, and he is confidant that given Drew's cognitive abilities, he will perform optimally once he is implanted. From here, we will be having an MRI run in early June. His cat scan, scheduled for March 14th, has been cancelled. Dr. Choo is certain that Drew's cochlea is formed correctly, given the genetic testing results, and does not feel that the structural scan is as important as the neurological scan with the MRI. Then we will move toward insurance approval and we all hope to have the surgery performed when Drew is around 10 to 11 months of age.

We discussed for some time the surgical risks and limitations following the implant. There are minimal risks to balance and taste, but nothing that would prevent us from having Drew implanted. Drew's Dad was happy to hear that football is not out of the question! Although Dr. Choo does not actively promote football, lacrosse, rugby or hockey, there is no risk to Drew's overall health by playing full contact sports. The only risk is that the head to head contact could break the internal device, which would then have to be surgically replaced. Dr. Choo told us that one of his paitents is playing football as a freshman in college this year! We'll have to cross that bridge when we come to it, but for now, all things are possible. Maybe he will be the first MLB player or PGA golfer with an implant? Who knows?!

On the genetic testing front, we made tremendous progress. I had a hearing test today, which showed no hearing loss, and had my blood drawn for the mitochondrial abnormality test. From these DNA test results, we will know the risk of aminoglycoside induced deafness for myself and our daughter. Dr. Choo also explained that following my results we will know the exact path to take for testing others in my family, primarily my sister. We can expect the results in about six weeks.

Additionally, our daughters hearing was screened today. Given the genetic link for Drew's hearing loss, her hearing will be screened yearly until she reaches six years of age. She did have a mild hearing loss today in her left ear, which was attributed to fluid from her cold. Her tympanogram scores were indicative of fluid in both of her ears (even with the fluid, she was able to hear with her right ear). We will have a follow up test run, but Dr. Choo and the audiologist were both very confidant that she has no hearing loss at this time. As her parents, we are confidant too, especially since her language is developing ahead of schedule. She put four different word phrases together just today!

While we do get very anxious at times trying to move this process along, we are making progress. We know that Drew is in great hands with the team at Cincinnati Children's and we are so excited that we can take the journey with him. Even though the road is a little longer than we would like, all good things are worth waiting for!

Genetic Testing Road Block

I had thought that I would be able to have my genetic testing done through my OB/GYN's office this week for the mitochondrial abnormality that was found in Drew. I thought when they told me their lab ran this test it was too good to be true, as it is a very rare abnormality. It turns out that I was right. Their laboratory will only run the test for the connexin 26 abnormality, which I already know I carry. It is the testing for the mitochondrial abnormality that is crucial for me to know in order to understand my risk and my daughters risk of aminoglycoside induced deafness.

At this point, I am very frustrated. It seems to me that it should be easier to have this testing run. And it seems that I am the only one concerned about getting results, maybe because it is my hearing at risk. I do not know what else to do at this point. I have contacted Dr. Choo's office on several occasions regarding this testing, and his nurses tell me that in order for Cincinnati Children's to run the test I will have to have an audiogram test. They referred me to my primary physicians. Now I know that they do not have the capability to run these tests, my only option may be to have the testing run in Cincinnati.

I am going to talk with Dr. Choo about this at our CI consult on January 22nd, since he is the one that told me I needed to be tested. My hope is that he will order the test that day or refer me to a geneticist for further evaluation.

Genetic Testing Progress

It has been a bit of a struggle over the last week as I have been trying to secure the genetic testing I need to have run. With the results of Drew's genetic testing showing a mitochondrial abnormality, I need to find out if I have the same abnormality. By knowing this information, I will know my risk of aminoglycoside induced deafness, and I will know the potential risk that my daughter may carry this abnormality as well.

I could have the testing run through Cincinnati Children's, where Drew's was done, but they require an audiogram and I would have to drive to Cincinnati to have my blood drawn. So, I contacted my OB/GYN's office. I learned that their lab will run certain genetic tests, and fortunately this is one of the ones they perform. In addition, they contacted my insurance company for me and found that the testing is covered. They told me that I can expect the results in four to six weeks.

Pending the results of the test, others in my family may need to be tested. If I do not carry this abnormality, meaning that it is a new mutation in Drew, my daughter will be the only one tested for the mutation. It is possible, although unlikely, that she received the mutation and deafness will only ensue with aminoglycoside antibiotics. Because this mutation is generally passed to all children of an affected mother, knowing that I do carry the mutation will additionally require testing for my sister and mother, so we can determine their risks for deafness, as well as my sisters risk for passing this abnormality on to her children.

All of this genetic testing is a new road for us, and I am learning more about it everyday. I will let you know when we receive the results and what our next steps will be.

More Genetic Testing

The past week has been a whirlwind, as I am trying to understand Drew's genetic test results, and determine where to go from here. I have learned a lot about both his connexin 26 and mitochondrial abnormalities. As I have discussed before, the mitochondrial abnormality is the most worrisome, as it can affect others in my family. Here are some of the steps we will be taking in the immediate future:

1. I will be having a DNA test run in the next week or so to see if I carry the same mitochondrial abnormality as Drew. If I do, I am at risk for hearing loss. In some, the hearing loss is apparent at birth (like Drew), and in others it is only induced by certain aminoglycoside antibiotics. I have read that I have a 100% chance of losing my hearing by the time I am 60 years old if I carry this mitochondrial abnormality and have ever had one of these antibiotics. There is a possibility, however, that this mitochondrial mutation popped up "de novo" in Drew and that I do not carry this mutation.

2. We will be having our daughter's hearing screened. As a result of the genetic testing, there is now hereditary hearing loss. It is recommended that all children in families with genetic hearing loss be evaluated yearly until they are six years old. Our audiologist will set a benchmark with our daughters' hearing, and then evaluate it each year to see if she has any loss. We will know more about any risk for her after my DNA test results. If I do in fact carry the mitochondrial mutation, it is very likely that she carries the mutation as well. Generally the mutation is passed to all children of an affected mother. That being said, she would be at risk for hearing loss from the aminoglycoside antibiotics. Knowing this information could prevent deafness in both of us.

3. Our daughter will also have a DNA test run to see if she carries the connexin 26 gene recessively and if she has the mitochondrial mutation. Even if I do not carry the mutation, I could have passed it on to her. Again, the more information we have, the better we will be at preventing hearing loss in her. Knowing if carries the connexin abnormality will help her in the future to know her possibility of having a child with hearing loss.

4. Pending the results of my DNA test for the mitochondrial abnormality, my sister will be tested for these abnormalities. If I carry the mutation, she most likely does as well, since it likely would have been passed to both of us from our mother. (This mutation would not affect my brother's children, since it is only passed from the mother. He would, however, be at risk for the amnioglycoside deafness. He may be tested for this at a later date). This will allow my sister to know if there is any possibility of passing this mitochondrial mutation to her children. She would only be at risk of having a connexin baby if her husband also carries the connexin 26 gene recessively. Since only three out of every 100 people carry this abnormality, it is highly unlikely.

Again, if you have any questions regarding testing for genetic hearing loss, please feel free to email me. Or, you can get information on testing for genetic hearing loss from Cincinnati Children's Hospital.

Biology 101

I wish I would have paid more attention in my 10th grade biology class, or that I would not have avoided taking biology in college like I did. The genetic studies would really come in handy now, as I struggle to understand Drew's genetic results for his hearing loss.

I understand the connexin abnormality. I carry one abnormal copy of connexin 26, passed to me from one of my parents. My husband carries one abnormal copy of his connexin 26 gene, passed to him from one of his parents. In Drew these two abnormal copies met up, causing his hearing loss.

What I can not understand - and what I am most worried about - is the mitochondrial abnormality that I passed to Drew. This is a very rare genetic disorder, so I contacted Dr. Choo with several questions regarding this abnormality, primarily because of the conflicting information I am finding in my Internet research.

I had thought after reading one site that the mitochondrial abnormality is X-Linked. I now know that is not the case. The mitochondrial abnormality is different, and generally is passed to each offspring of an affected mother. The concern I have is that if this mitochondrial abnormality did play a role in Drew's hearing loss, what concern should I have that my daughter will progressively lose her hearing?

From talking with Dr. Choo, he can not tell if the mitochondrial abnormality had any part in causing Drew's hearing loss. We know the connexin 26 abnormality certainly can cause profound hearing loss. In order to determine if the mitochondrial abnormality played a part in the hearing loss, Dr. Choo recommended that I have my DNA tested to see if I carry this abnormality. If I do, Dr. Choo believes that this abnormality in my families genetic make up does not cause hearing loss because I do not have hearing loss. If I do not carry it, it is possible, although very rare, that this mutation popped up "de novo," as a brand new genetic mutation in Drew. (The good news is that because the mitochondrial is only passed from mothers to their children, Drew will not be able to pass this on to his children.)

I am so thankful that I am working with Dr. Choo. Cincinnati Children's has a large research program on the genetics of hearing loss. I am confidant that with further testing, Dr. Choo will be able to locate the primary cause of Drew's hearing loss and will be able to tell me the risk factors for those in my immediate family.

With the genetic testing now complete, Dr. Choo has medical proof that the diagnostic hearing tests of Drew are accurate. He told me that this makes a Cochlear Implant medically necessary, and that it is very possible we will be able to have the surgery approved prior to him turning one year old. Finally, some wonderful news!

ER: Columbus Version

When I was pregnant with my first baby, I told myself that I was not going to be one of those neurotic parents that flips out about the smallest things, spending time in doctors offices, asking silly questions about nothing. And I did just that. She is rarely sick, usually happy, unless it's nap time, and I really don't worry about her overall health.

Pregnant with my second, I thought, "I have this down. It will be even easier the second time. I know what I'm doing." Not only was I telling myself this, but everyone around me was as well. Boy was I wrong, and so were other! I have been much more worried about Drew's health, spent more time at the doctor than I could have imagined. Wednesday night would be no different, as we found ourselves at Children's Hospital ER.

Drew started to show signs of having a cold on Monday night. It really didn't worry me too much, since his sister and father have had colds over the past few weeks. By Wednesday morning, however, it was getting worse, and he was wheezing, making eating difficult. By afternoon, he had hardly eaten all day, so I took him to the pediatrician. The doctor was concerned by the rate of Drew's breathing: over 80 breaths per minute, when normal is under 60. He did not feel comfortable sending us home, so he told me to take him to Children's ER.

His Dad and I arrived at the ER at 5:30 PM. It was packed, but, with an infant with a respiratory problem, we were called back right away. The nurse listed to his lungs and checked his oxygen level. He was wheezing, breathing too fast, but was maintaining a 98% oxygen level, which was really good. In addition, he did not have a fever, a good sign. As a result, we were sent back to the waiting room, to go in the normal order of patients.

At 7:30 PM we were finally called back to an exam room, where at 8:30 PM a nurse came in a took his vitals and suctioned out as much fluid as she could from his nose. He cried so hard and turned so red. We felt so bad for him, but after that, he was able to eat really well for the first time all day!

Finally, a little after 9 PM, the resident came in and looked at him. She listed to his lungs and checked his breathing rate, which had dropped to around 60 breaths a minute. She diagnosed brochiolitis, a fairly common viral infection for children. Drew was just having a little problem fighting it, probably due to his age. The doctor did order a chest X-Ray to rule out pneumonia, which came back clear. She also wanted the X-Ray so she could look at his heart, since sometimes respiratory problems can be related to a heart condition. That too was normal.

We finally were discharged from the hospital a little before midnight. Talking on the way home, we realized how much worrying we have done over Drew's health. It's not to say we were never worried about our daughter, but everything was just very natural and we never worried about her overall health. But with Drew having profound hearing loss, and now knowing it is genetic, we often worry that there are other problems we don't know about.

One bit of good news is that his ENT told us that by discovering the genetic abnormalities as a reason for Drew's hearing loss, we really can rule out the possibility of other problems. With all of the surprises we have had along the way, we are still worried.

Trying to Understand

It has been a difficult day. While I am relieved in some ways to know the reason for Drew's hearing loss, it has been emotionally draining trying to learn about genetic hearing loss and who in my family might be at risk.

Mostly I am concerned about the mitochondria abnormality found in Drew. I have been doing a lot of research and believe that this is an X-Linked abnormality. I have learned the following:

X-linked inheritance refers to conditions or traits for which the gene is located on the X chromosome. Recall that females have two X chromosomes while males have only one X chromosome.
The majority of X-linked conditions are X-linked recessive, meaning that one normal (working) copy of the gene would compensate for a non-working copy. It is much more common for males to have X-linked recessive conditions than females, since males do not have a second copy of their X chromosome to compensate if their one copy has a mutation. There are some cases when females can be affected with an X-linked recessive condition, but this is much less common.
X-linked dominant inheritance is quite rare.
Females will only be affected with an X-linked recessive condition if both copies of the gene on their X chromosome have mutations (this is quite rare). If a female has a mutation in only one copy of the gene on their X chromosome, they will not have the condition. Males, on the other hand, will have the condition when the gene on their one X chromosome has a mutation, since they do not have a second copy to compensate
When a female is a carrier of an X-linked recessive condition (i.e. has a mutation in one copy of an X-linked gene), each of her offspring will have a 50% (1 in 2) chance of inheriting the working copy, and a 50% (1in 2) chance of inheriting the non-working copy. Thus, daughters of a female carrier have a 50% chance of being a carrier and a 50% chance of being a non-carrier, and sons have a 50% chance of being affected and a 50% chance of not being affected.
When a male has an X-linked condition, all of his daughters will be carriers (since all female offspring receive an X from their father), and none of his sons will be affected (since he will pass on his Y chromosome to all of his sons).

This information leaves me worried for my sister and for my daughter. My prayer is that my Mom passed this mutation only to me and I pray that I did not pass this mutation to my daughter. It is passed on to females 50% of the time, so I am praying that it was not passed to them. If it was passed to them, when they have children they will have a 50% chance of passing the mutation to thier daughter, and worse, they will have a 50% chance of having a son who is deaf.

After learning that this abnormality runs in my family, I have thanked God a lot today that my brother was not born deaf. He was very lucky to be born in the group of 50% of males that are not affected with the condition. It is still unbelievable to me that this runs in the family and yet we have no knowledge of anyone born with infant hearing loss.

Connexin 26

I received a call today from Dr. Choo (see previous post) with the results of Drew's genetic testing. While the results are surprising, I now have an answer to the "Why did this happen?" question.

Drew's genetic test came back with abnormalities in his connexin 26 gene. This is the most common gene for hearing loss. This means that both his father and I carry the recesive gene, and when Drew was conceived, he received two connexin 26 genes with hearing loss, causing him to be deaf. We learned that because we both carry this gene, we have a 25% chance of having a baby with profound hearing loss.

As a result, we now know that this runs somewhere in each of our families. If you would like to know if you carry the gene, please contact your local physician or click here for information on a genetic test for hearing loss. Dr. Choo said that Cincinnati Children's would run the test for anyone in our families wishing to know. Additionally, Dr. Choo said that he will send me some paperwork with the specific test to be run, so if you would like that information, please email me. Please know that you will only have a 25% chance of passing hearing loss on to your child if both you and your partner carry this gene.

In addition, Drew's mitochondrial tested abnormal. Here is some information on mitochondrial hearing loss:

Mitochondrial: Mitochondria are small organelles in our cells that have their own DNA, known as mtDNA. The number of mtDNA base pairs is only about 16,000, but there are many copies of mtDNA in each cell. We inherit all of our mtDNA from our mothers, so if the hearing loss is caused by a mutation in mtDNA, all the children of affected mothers (but none of the children of affected fathers) would be expected to have hearing loss. An mtDNA mutation, in which a G instead of an A is found at position 1555 (called A1555G), causes severe to profound sensorineural hearing loss. However, in some individuals with the A1555G mutation, the hearing loss does not occur until after exposure to aminoglycoside antibiotics. Thus, knowing this mutation is in the family can help to prevent aminoglycoside-induced deafness.

This information has me very concerned because it would mean that his older sister has the mutation, and could become hearing impaired by the use of certain IV antibiotics. We will be having her screened for this in the near future. In addition, it means that my sister could also be a carrier and pass hearing loss on to her children. I am doing a lot of research to learn more about the genetic causes of hearing loss, and will pass information on as I learn it.

For more information on the research being done at Cincinnati Children's hospital on genetic causes of hearing loss, please click here.