Tag Archives: Otoacoustic Emission

The Second Opinion

Bright and early this morning, Eliza and I made our way out to the Alpharetta location of Northside Pediatric Hospital to perform Fiona’s hearing retest. Different audiologist and different equipment, a qualified second opinion.

Rather then braving a 75 minute rush hour drive, we decided to stay the prior night at Grandma and Grandpa Underwood’s house. A wise choice, as our drive was now only 10 minutes.

Northside Pediatrics - Alpharetta

Northside Pediatrics – Alpharetta

If you recall from my earlier post about the Hearing Test, we had both the Otoacoustic Emission (OAE) Test as well as the Auditory Brainstem Response tests rerun today. This time we were much better prepared for the long stay: bouncy chairs, “boppy pillows”, pacifiers, you name it – we were pimped out.

The test ran about 3 hours, just like last time. For the most part Fiona was cooperative, thanks to the amazing rocking skills of Mom. Fiona had to remain very still, with electrodes on her head measuring the responses received from various sound pulses generated into a small earpiece. You can see her sporting some stylish head gear (with an intriguing “Mona Lisa” Eliza smile) in the pic below:

Auditory Brainstem Response Test

Auditory Brainstem Response Test

Unfortunately our small hopes of a miraculous misdiagnosis from the original test were quickly put to rest, as the results were consistent with profound loss. We didn’t really expect anything different, but you can’t help but have that small hope…

Over the 3 hours, the audiologist patiently ran through all the frequencies in both ears and recorded virtually identical results to before: severe to profound loss in both ears.

She also ran a pulse test through the skull that tests for conductive hearing loss (hearing loss that occurs due to obstructions in the outer ear canal or bones) versus sensorineural hearing loss (hearing loss that occurs due to damage in the inner ear/cochlea). Conductive loss is usually correctable through surgical means. Sensorineural loss is not currently correctable in itself by surgical means, and is instead treated with hearing aids or cochlear Implants. Fiona was confirmed with sensorineural loss, which was as we expected.

One interesting anomaly, though, was they found slight response to low level frequencies in her right ear…the exact opposite result we got last time (left ear). Because of this inconsistency, we unfortunately need to return next week for another retest to confirm consistency. Awesome.

All in all, though, this test ran much smoother since we knew what to expect. More importantly, though, we weren’t in an emotional shock, which allowed us to ask a lot of great questions. Some things I learned:

  • Hearing aids are still beneficial to babies with profound loss, even though they can not hear speech (see Fred Flintstone Teaches Us About Hearing Loss). Why? Because stimulation of the auditory nerve forestalls atrophy and readies the baby for the introduction of a signal from the Cochlear Implant.
  • Reading the chart from the ABR test (see Hearing Test post), we learned the x-axis charts latency of sound received. In other words, the quicker the baby hears a sound, the further to the left you will see a jump in the graph. The audiologist is looking for those jumps to occur within certain periods of time, depending on the volume.
  • Northside has done CI surgery on qualified infants less than 1 year old with great results. (1 year is the current FDA limit). The kicker is not all insurance companies cover prior to 1 year. We’ll need to check on that, but we definitely want asap so we can hit her speech centers early.
  • I asked if babies with the surgery done at 1 year old develop speech indecipherable from hearing children. The audiologist responded with an almost surprised “of course” response, which was extremely comforting. One of her patients even grew up to have a distinct southern accent, not sure how i feel about that :-).

Since we are returning next week for yet another retest, Fiona did not get fitted for hearing aids today, but that will be on the docket next week. (Recall she will first need to wear hearing aids for 3-6 months before candidacy for the CI, which is the path we expect).

While we didn’t receive any miracles today, we also didn’t receive any surprises, and left more informed and confident. I’ll call that a check in the plus column.

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The Hearing Test

If you’re like me, you probably have no clue how you could possibly test hearing on an infant who can’t even speak. What’s even more fascinating is that they can test infants a DAY AFTER they are born! Incredible.

How does it work?

Well actually there are 2 different kinds of tests. The first test, conducted 1 day after Fiona’s birth and again a week later as a retest was called the Otoacoustic Emission (OAE) Test. In my layman’s non-medical understanding, what they basically did was insert a small probe into her ear that generates sounds and captures the “echo” back from that sound. They can then measure if that echo looks normal or not. Its pretty quick and non-invasive, provided the baby can stay quiet for 15 minutes.

All new infants receive this test today, but it is not uncommon to fail due to ear blockage from the birth. This is why we were not too concerned when Fiona failed her first (and even second) tests.

So after failing the first 2 tests, they pulled out the big guns 1 month after her birth. This was a test called the Auditory Brainstem Response (ABR) test. Basically it measures how sound introduced into the baby’s ear translates into electrical responses received by the brain. Here’s a great  explanation from MedicineNet.com.

The test is performed by placing four to five electrodes on the infant’s head, after which a variety of sounds is presented to the infant through small earphones. As the hearing nerve fires, the sound stimulus travels up to the brain. This electrical activity generated by the nerve can be recorded by the electrodes and is represented as waveforms on a computer screen. The audiologist can then present different loudness levels of each sound and determine the softest levels at which the infant can hear. For infant-screening purposes, only one sound is used to test the hearing, commonly referred to as a “click.” The click is a grouping of several sounds to test a wider area of the hearing organ at one time. The click is typically presented at a loud level and a soft one. If a healthy response is recorded, then the infant has “passed” the hearing screen.

Here’s what the equipment looks like (stock picture, not Fiona). As you can guess, “Fiona was not impressed” with this setup:

Screen Shot 2013-06-09 at 11.12.46 AM

ABR Response Test Equipment

Sitting through this test was not pleasant – it took about 3 hours to run, while you’re sitting there in darkness and silence watching the audiologist fidgeting with various graphs on a screen, all the while having little clue if the graphs are “good” or “bad”. In addition, the baby needs to remain quiet and still, which is an immensely taxing chore, especially for mom.

The screen the audiologist is looking at looks something like this:

Screen Shot 2013-06-09 at 11.30.13 AM

I don’t pretend to understand 1/100th of how this works, but I’ll tell you what I learned: they test each ear individually, measuring responses to different frequencies at different volumes (dB levels). Low frequencies (like the booming of a subwoofer) are easier to hear while higher frequencies (breaking of glass) are harder. This is why you can hear the ground booming when walking up to a concert well before you hear the singer, especially annoying teeny-boppers like Bieber…

During this test they are basically measuring 3 different variables:

  1. The frequency: can the infant hear some frequencies (base drums) better then others (glass breaking)?
  2. The volume (dBs): are some frequencies just “quieter” then others and can be amplified?
  3. The ear: is the left different then the right?

Each different graph captures a different combination of the above 3. I don’t know how to read those graphs beyond saying “the bigger the peaks and drops the better”. If the line is essentially flat, that means no response at all.

Most infants have various responses at various frequencies and volume levels. Some may look just fine, while others can be corrected by “turning up the volume”, which is basically what hearing aids do.

Fiona was flat at all frequencies and all volumes, in both ears. This means “profound” hearing loss, and something that is likely not correctable by hearing aids. (to be fair there was one low frequency in one ear that got a small result at very high volume level, but that could be an artifact of the testing precision. We’ll know more in a later retest).

The good news is there are now options (beyond sign language, which is also awesome) for profound hearing loss in the form of cochlear implants. I’ll talk more about that in a future post, but we’re very excited there.

Hearing loss is the most common birth defect today. I had no clue. Apparently 3 out of 100 babies have some level of hearing deficiency. This is why they test so early now – and it is true wisdom. Babies begin learning language within their first 6 months. As you can imagine, hearing is a huge component of this, and the earlier you are aware of the problem, the sooner you can act on it to help speech develop normally.

In this regard we feel truly fortunate. Knowing for sure within 1 month (1 month!) after birth has set us on a course NOW that we’d likely not have otherwise started until 1-2 years old, well past the start of language learning. This makes me much more optimistic in our ability to educate her well in these early stages.