Auris Repletus by Dr. Tom Goyne

Newborn Hearing Screenings

Several times a week, a mother will bring her toddler into my office for a hearing test.  Typically, the mother, nor I, are expecting to find a hearing loss.  By the same token, extraneous circumstances such as a slight delay in speech development dictate that we make sure.

While gathering a case history, the parents will invariably mention to me that, "He/She passed her hearing screening at birth, but we always wondered, how can they tell?  It's not as if he/she was able to respond at just a few days old!"

It's true, other than a startle reflex to very loud sounds, newborns can't respond to sound in a way that we can detect.  But through the application of signal averaging, we can use objective, non-invasive physiologic measures such as otoacoustic emissions (OAE) and auditory evoked potentials (AEP) to determine with relative certainty whether a newborn -- or any other patient incapable of voluntarily responding to stimuli -- has normal hearing or not.

In the case of OAE's sounds are presented to the newborn's ear and if the cochlea is normal sounds will resonate back out.  We record these resonances and if they are a pitch and intensity (right around 0 dB) we expect, we assume normal hearing is present.

AEP's are used more often for newborn screenings because OAE's require the testing to be performed in a quiet setting, and if you have ever been in a hospital's newborn nursery, you know it is not a quiet place.  AEP's on the other hand can be recorded with a fair amount of ambient noise present.  Headphones and sensors are placed on the newborn and electrical signals are painlessly recorded through the newborn's skin [see below].

While these tests are not meant to be a substitute for a comprehensive audiologic examination, performed in a sound-proof booth with a responsive patient, they are reliable and are very good at identifying patients with greater than a mild hearing loss.

Below is a list of states that require newborn hearing screenings, according to the Centers for Disease Control:

Relation Found Between SIDS and Hearing Acuity

It is estimated that for every 1,000 infants in the world, one dies as a result of Sudden Infant Death Syndrome (SIDS), making it is the leading cause of death among infants.

Up until now, warning signs as to which children are at greater risk for SIDS have been few and far between.  But researchers at Seattle's Children's Hospital may have discovered a screening for SIDS, and best of all, it is a test that is already in place in most of the fifty United States -- newborn hearing screenings.

From the press release:

One of the greatest medical mysteries of our time has taken a leap forward in medical understanding with new study results announced by Dr. Daniel D. Rubens of Children’s Hospital and Regional Medical Center in Seattle. Rubens’ study published in July, 2007 in Early Human Development found all babies in a Rhode Island study group who died of Sudden Infant Death Syndrome (SIDS) universally shared the same distinctive difference in their newborn hearing test results for the right inner ear, when compared to infants who did not have SIDS. This is the first time doctors might be able to identify newborns at risk for SIDS by a simple, affordable and routine hearing test administered shortly after birth. In the study, medical records and hearing tests of 31 babies who died from SIDS in Rhode Island were examined and compared to healthy babies. Rhode Island has a particularly robust database of newborn hearing test data.

The next step in research is to find out exactly why there is a link (the study's authors suggest that sensory cells in the inner ear also serve to measure carbon dioxide levels in the body, besides their role in hearing), which will hopefully lead to even better understanding and greater prevention of SIDS.

Improved Performance Leads to Increased Acceptance of Amplification

In recent weeks, the advertising campaigns of a leading hearing aid manufacturer have received a significant amount of attention, both positive and negative (examples: 1, 2, 3).

While discussing the merits of the campaigns -- you can decide for yourself if they will be effective or not -- Phonak CEO Valentin Chapero tells Business Week, "It's very difficult when you are making a product that actually nobody wants."

It's true, there is very little demand for hearing aids, despite the fact that over 30 million Americans have some form of hearing loss.  But, there is reason to think that is going to change, and it has nothing whatsoever to do with a schnazzy ad campaign or catchy slogan.  It has everything to do with improved performance.  Several times a day, patients tell me that they are pleasantly surprised to find they have none of the complaints about hearing aids that their parents, aunts and uncles had about amplification.

The fact of the matter is, for decades hearing aids were incapable of processing sound in the manner that most patients with hearing loss need it to be processed.  They did not treat loudness growth differently across pitch ranges, something that is absolutely necessary for improved clarity along with loudness comfort.  It wasn't until the arrival of multi-channel devices in the early 1990's that this was possible, and it is only in the last five to seven years that the industry has gotten pretty good at designing devices that do it quite well (for more, read here).  It wasn't for lack of trying however, for many years we did not fully understand the nature of the ear and cochlear hearing loss and even if we did, the technology did not exist to engineer the devices anyway.

As time goes by and the success stories with hearing aids that people tell over a card game begin to finally outnumber the negative experiences recounted over the years at those same card games and family gatherings, gradually, people will become much more accepting of amplification.

Think about it this way.  If the automobile industry had failed, despite their best efforts, to improve upon the first "horseless carriages" and they remained unreliable and uncomfortable, would there be more cars in Los Angeles today than people (there really are, look it up)?  No.  Cars would have remained a product with a small niche until significant and worthwhile developments actually came about.  History tells us that when technology actually catches up with the needs of consumers, it is almost always a success.

As a matter of fact, the quality of today's hearing aids has audiologists and researchers thinking less about audibility at the ear-level and more about processing in the brain.

Useful Communication Tips

Over the past few weeks, we've spent a considerable amount of time and energy discussing advancements in technology to help those with hearing loss.  However, there are some very "low-tech" tricks for better hearing that have been applicable since humans first started to vocalize to each other about what might be outside the cave.

• If you are speaking to someone with hearing loss, make sure that you have their attention first.  When someone has hearing loss, comprehending the spoken word is a matter of filling in the blanks, and so if they are focused on you, there is a better chance they will understand you.

• Get face to face.  Patients are always flabbergasted when I tell them they read lips, but the truth is, we learn to do it at a very young age, right when we begin to learn language.  Again, comprehending speech when you have a hearing loss is a matter of filling in the blanks, and having some visual cues (a "b" looks much different on the lips than a "t") to go along with the sounds that are getting through goes a long way to better comprehension.

• Rephrase something if it just isn't getting through.  Different sounds of speech have different pitches and if someone with hearing loss just can't catch what's being said no matter how many times or how loudly it's repeated, it is likely that a particular sound or two is just inaudible.  The solution is to rephrase the statement or question, which will in turn use slightly different pitches.

• Reduce the amount of background noise.  People with hearing loss have a difficulty time sorting out what they want to hear from what they would prefer to tune out.  By reducing the amount of background noise, there will be greater separation between the competing sounds that the desired signal.  For instance, if someone has normal hearing, they can correctly comprehend speech at a rate of 50% if the competing noise and the speaker are at the same level of intensity.  On the other hand, for someone with sensorineural hearing loss -- the most common type -- to perceive what the speaker is saying, the speaker must be at least 10 decibels louder than the competing noise.

• Speak slower.  Someone with hearing loss has to do twice the work to understand what is being said as someone with normal hearing.  Rapid speech makes it difficult for the person to keep up and fill in the blanks (think of Lucy and Ethel at the chocolate factory).  Slower speech, on the other hand, is easier for a person to decipher.
  

All of the above, when you think about it, are nothing more than common sense and are actually good advice for anyone, whether there is a hearing loss present or not.  Patients who use these tips in conjunction with hearing aids seen even greater improvement in their ability to communicate.

The Nature of Hearing Loss and the Fundamentals of Proper Amplification (Part IV)

For decades -- from the 1940's to the early 1990's -- the simple truth is that hearing aids were not capable of providing adequate benefit for most patients with the most common form of hearing loss in adults (sensorineural hearing loss).

For those fifty years or so, hearing instruments were only capable of making every sound louder, no matter what pitch or intensity that sound was.  Remember, as we discussed in earlier parts of this series, most patients with sensorineural hearing loss, which represent the largest bulk of patients with hearing loss by a very large margin, have normal to mildly reduced hearing in the lower pitches, while their hearing in the higher pitches is declining at a much greater rate.  Therefore, they would ideally receive more "help" from a hearing aid in the higher pitches than in the lower pitches, and even better, the hearing aid would treat loudness growth differently in those pitch ranges.

As an aside...
Several years ago, I was having a discussion with a leading executive in the hearing aid industry.  At the time, he was rather discouraged at the rate at which consumers were purchasing devices that he knew were clearly head-and-shoulders above previous generations of technology.  I was surprised at his outlook and I reminded him that you can't undo a reputation created by 50 years of poor performance in just a year or two.

Today, in my office, we are seeing much less reluctance on the part of patients to try amplification.  I'm convinced it is because finally, the majority of patients are reporting greater benefit than was possible just five years ago.

But unfortunately until the recent past, hearing aids were not up to that task and it is that reason that far too many of them spent more time in desk or bureau drawers than ears.

At an absolute bare minimum, if a patient with sensorineural hearing loss is intending to obtain amplification, the hearing aid must be able to process low pitches and high pitches independently.  Otherwise, the patient will experience a great deal of loudness without necessarily noticing improved clarity, which is the point of obtaining the device in the first place!

Fortunately, the majority of hearing aids offered today, even those that might be termed as "less-sophisticated" by today's standards are indeed capable of independent gain in the low and high pitches.  However, all too often, I meet people in my office or socially that did not obtain the proper device.

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The preceding was part of A four part series at Auris Repletus entitled, "The Nature of Hearing Loss and the Fundamentals of Proper Amplification"

- Part I; Part II; Part III; Part IV

The Nature of Hearing Loss and the Fundamentals of Proper Amplification (Part III)

In Parts I and II of this series, we discussed the symptoms of sensorineural hearing loss and the reasons behind those symptoms.  For Part III, we’ll take a look at why these symptoms are associated with sensorineural hearing loss – also known as “nerve deafness”, which you will soon see, is a bit of a misnomer.

Our ears have three parts:  the Outer, the Middle, and the Inner.  Sensorineural hearing loss, the most common type of hearing loss in adults, is caused by pathologies in the inner ear.  The inner ear is shaped very similar to a snail shell, wound in a circle.  Inside the “shell” is a membrane that runs the length of the inner ear, or cochlea.  On this membrane are thousands upon thousands of microscopic sensory cells, sometimes nicknamed “hair cells” due to the tiny cilia perched on top of them.

Any particular point on the membrane inside the cochlea is tuned to a particular pitch. When a sound enters the Inner ear after passing through the Outer and Middle ears, it vibrates the membrane, which in turn stimulates the sensory or hair cells [at right, click to enlarge].  When these cells are stimulated, they convert the acoustic signal into an electrical signal, which travels up the auditory nerve fibers they are attached to, all the way to the brainstem and auditory cortex in the brain.

It is these loss of sensory cells in the inner ear that are the greatest contributor to sensorineural hearing loss (for this reason, "nerve deafness" is a very misunderstood term) and the cells nestled on the portion of the membrane tuned to higher pitches are the first to go.

To conclude this series, Part IV will cover the basics of proper amplification because contrary to what you may have been told, hearing aids can and do help patients with "nerve deafness".  As a matter of fact, proper amplification benefits millions of people every day.

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The preceding was part of A four part series at Auris Repletus entitled, "The Nature of Hearing Loss and the Fundamentals of Proper Amplification"

- Part I
- Part II
- Part III
- Part IV

The Nature of Hearing Loss and the Fundamentals of Proper Amplification (Part II)

In Part I, we discussed the typical symptoms of the most common form of hearing loss, sensorineural hearing loss.  As you may recall, in most cases, but not all, vowels (a, e, i, o, and u) remain audible to the patient, but consonants (s, f, t, v, etc.) become inaudible.  This is because those two types of sounds of speech have different pitch ranges.

Vowels are predominantly strong and low-pitched, while consonants are usually weaker and higher in pitch.  Also, consonants are the sounds that give speech its clarity, while vowels give speech its rhythm, quality, tone, and inflection.

Here’s where the irony comes in…  When a person suffers from sensorineural hearing loss, it typically affects the higher pitches of their hearing range more than the lower pitches.  To the right is a diagram [click to enlarge] of a hypothetical patient’s hearing thresholds by frequency or pitch (x-axis) and intensity (y-axis).  It’s also possible to plot other environmental or speech sounds on the graph and so anything above the red and blue line is theoretically inaudible to the hypothetical patient, while anything below is audible.  This is why patients will often observe that they can hear nearly everyone, but yet understanding what is being said is another story altogether.

In Part III, we’ll discuss why the higher pitches of someone’s hearing are affected more than lower pitches and in Part IV, the basics of proper amplification.

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The preceding was part of A four part series at Auris Repletus entitled, "The Nature of Hearing Loss and the Fundamentals of Proper Amplification"

- Part I
- Part II
- Part III
- Part IV

The Nature of Hearing Loss and the Fundamentals of Proper Amplification (Part I)

Take a poll of audiologists about the observation or complaint they most often receive from patients and I’m willing to wager that the hands-down, clear-and-away, favorite would be something to the effect of “I hear just fine, but speech isn’t clear.”  Variations would include “Everyone mumbles” and “I just can’t make out the words”.

There’s a reason for all of this perceived mumbling, and that is the nature of sensorineural hearing loss, the most common form of hearing loss and often referred to as nerve deafness.  Sensorineural hearing loss occurs in the inner ear, the cochlea, and is typically non-reversible by medicine or surgery.  The causes are varied, but the leading ones are presbycusis (age-related), ototoxicity (drug interactions), or excessive noise exposure.

However, no matter what the cause of sensorineural hearing loss, the effect is often the same – the vowels of speech remain audible [a, e, i, o, u], while the consonants of speech [s, f, t, b, etc.] become inaudible.

To use a real life example of how this can affect one’s daily conversations, imagine printed text without many of the consonants.  For instance, try and decipher the following question:

"Wi__ __e __illie_ wi_ __e Wor__ _erie_ __i_ _ea_?"

Before I reveal the true identity of that sentence, let me demonstrate what context can do to help someone with hearing loss “fill in the blanks” on an auditory perception level.  Let’s say I showed you these two images before giving you the sentence: