by Neil Bauman, Ph.D.
A concerned mother wrote:
Our son failed the newborn hearing test, and failed two repeat ABR tests. He has reverse slope hearing loss in both ears ranging from about 30 dB at 4000 Hz to 70 dB at 500 Hz. Our audiologist stated that reverse slope hearing loss is rare, and that he could have progressive hearing loss? Could you please explain a this to me? I read that you have reverse slope hearing loss as well.
Your audiologist is right. Reverse slope hearing losses (where you hear better in the higher frequencies than in the lower frequencies) are rare–particularly the extreme kind of reverse slope loss that I have. You son has a range of 40 dB between his best hearing frequency and his worst. My wife has a reverse slope loss, but her range is only about 20 dB. In extreme cases such as mine, this range is in the neighborhood of 100 dB.
Just as with the common high frequency hearing loss (typically called a “ski slope loss,” the impact of a 20 dB range versus a 100 dB range is very different.
My concern is that your son was tested in the lower frequencies, probably only up to 8,000 Hz. With a reverse slope loss, you really want to know how good his hearing is in the very high frequencies. Some reverse slope losses can result in incredible hearing in the very high frequencies. For example, my hearing didn’t cross the 0 dB threshold until 10,000 Hz and topped out at about -30 dB close to 20,000 Hz. This is incredible hearing! (-30 dB is 30 dB above the 0 dB line. 0 dB is considered the softest sound a perfect normal human ear can hear. This means that my hearing in the very high frequencies was far more acute than people with perfect hearing.)
In practical terms, having this extreme reverse slope hearing loss meant that I could hear people whispering from across a big school classroom because of my incredible high-frequency hearing, yet couldn’t hear the teacher talking just 4 feet in front of my face because my worst loss whas right at 1,000 Hz where a lot of speech occurs.
As far as reverse slope losses being progressive, I don’t think they are any more progressive than many other kinds of losses, but yes, reverse slope losses can indeed be progressive. For example, reverse slope hearing losses run in my family. For those affected family members, our hearing dropped rapidly from birth to about 5 years of age. After that, our hearing remains constant until we lose hearing from old age or from other causes.
In my family, reverse slope hearing loss is a dominant genetic condition. As such, each child has a 50% of being born with this loss. As a result, more or less half of us in each generation have this hearing loss. Also, reverse slope losses tend to be non-syndromic. This just means that there are no other “defects” associated with this kind of hearing loss.
This mother then asked:
Could you also tell me what if anything I could do to help him develop normally. Were you able to attend normal public schools?
Yes, way back then I attended normal public schools without hearing aids and without any accommodations apart from sitting at the front of the room. Not the ideal situation to be sure. Nowadays, with good hearing aids and FM systems and suchlike, it should be much easier. I depended a lot on my speechreading skills. In fact, I had to see a person’s mouth in order to know what they were saying. I still do for that matter, unless they are talking directly into one of my ears.
As for what he needs, treat him with love just like any other child, but make accommodations for his unique hearing needs. Be aware that if he has incredible hearing in the very high frequencies, sounds that you don’t even hear can be so loud they will hurt his ears–and you won’t have a clue these sounds exist.
Also, sounds that you would expect him to hear, he won’t hear. For example, I can’t hear cars and trucks approaching until they are almost on top of me, but I can hear certain insects chirping from several blocks away. I can’t hear the roar of a train bearing down on me, yet the screech of their wheels on the tracks as they go around a curve gives me an instant headache it is so loud. To most people, this is not even a loud sound, yet I can hear it from a considerable distance.
I can’t hear the hum of the furnace, fridge, washer, etc., so in order to know if they are running, I have to put my hand on them. What I am saying is that your son won’t hear low frequency sounds well if at all. Don’t expect him to.
On the other hand, higher frequency backgound sounds will mask speech and prevent him from hearing and understanding you. For example, I can’t hear a person talking over the sound of water running in the sink.
The big difference between people with reverse slope losses and people with the typical ski slope losses is that we need more amplification in the lower frequencies, whereas, they need the amplification in the highs. People with ski slope losses don’t want people to speak up, but speak slower and more clearly. In contrast, we need people to speak up! Therefore getting close to your son before speaking to him is very important, especially if he is not wearing hearing aids. Always let him get as close to the person speaking as he wants to be.
And on the plus side, people with extreme reverse slope losses all have perfect speech. They do not need any speech therapy. In fact, people will refuse to believe you have a hearing loss at all because of your perfect speech. That is one of the blessings of this rare kind of loss.
If you want to learn more about the rare reverse-slope hearing loss, read my article entitled “The Bizarre World of Extreme Reverse-Slope Hearing Loss.”