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Hearing Both Sides:
Research Clarifies Debate Over Groundbreaking Ear Surgery

Lincoln Gray and Erika Cole

Dr. Lincoln Gray and Erika Cole.

It turns out that two ears are better than one.

That may seem like an obvious conclusion to some. But among audiologists, a debate has been raging about the benefits of an extraordinary surgical procedure offered at the University of Virginia. The procedure essentially creates a new ear for patients suffering from aural atresia.

Working with U.Va. ear surgeon Dr. Bradley Kesser, James Madison University professor Lincoln Gray and graduate student Erika Cole ('09D) collaborated on a project to document the efficacy of the surgery.

"The issues are: Why do we need two ears? What's the role of early experience in perceptual development?" said Gray, who teaches in JMU's department of communication sciences and disorders.

Sufferers of unilateral aural atresia experience complete hearing loss in one ear due to undeveloped external ear canal and middle ear structures. Since patients who undergo the surgery have never experienced sound input from the blocked ear, they provide a unique population with which to study the role early experience plays in the development of hearing.

"It's not often you can investigate that with humans," Gray said. "And here we've got these friendly, helpful, verbal subjects. They're interested."

Binaural Squelch

Perhaps the most important evolutionary advantage to having two ears, Gray said, is the ability to distinguish a desired sound out of a background of other noise. In a phenomenon called "binaural squelch" the human brain is able to integrate separate sound signals from the two ears to pick the sound out of noise.  speaker icon Listen to Gray describe the phenomenon of binaural squelch.

But would patients who haven't had the benefit of early hearing experience due to aural atresia have the ability to conduct binaural squelch? That was the question the team wanted to answer.

"I certainly want to know whether the surgery is making a difference in the lives of my patients," U.Va.'s Kesser said. "It has both clinical as well as basic science implications as to how the brain processes binaural inputs. Our hope is that the research clarifies the importance of binaural hearing."

The results were mixed. The researchers found that the effectiveness of the surgery differed significantly among age groups. For both young children and older adults, the procedure was not as effective.

"After this surgery, it was possible [hearing in noise] could get worse, because now you have noise coming into that ear, whereas before there was none. It might also be that it would improve, because of this phenomenon called binaural squelch. With this new input, you now have the first opportunity for the patients to experience binaural squelch," Gray said.

Children ages five to eight showed little improvement, a fact Gray attributes to a probable lack of important cognitive development.  For adults ages 38 and older, little improvement was seen, Gray said, because by that age, the ear and mind have adjusted to having one ear for a long period of time and are no longer plastic enough to be able to process new sensory inputs.

Young adults, however, showed the ability to process new sound inputs better than others, with a peak around age 18.  speaker icon Listen to Gray describe one patient's successful hearing improvement.

"The question is that after this remarkable surgery, you could imagine that they would get worse, and you could imagine that they would get better. Interestingly enough, both things happened. Some patients got worse, some patients got better," Gray said.

Gray compared the findings to earlier research on critical periods and subjects' ability to multitask.

"Lots of people have researched critical periods for sensory development. There are lots of papers that say multitasking is easiest for people in their late teens or young adulthood, and it's harder for the youngsters and the oldsters," Gray said. "I ended the paper by interpreting this as something similar to multitasking. If you've never heard out of one ear, and suddenly you get these new inputs, I think it might take a skill similar to multitasking."

A Rooted Interest

In addition to patients with a deep interest in learning more about their recovery, both Gray and Cole's interest in the topic stems from their own challenges with sensory perception conditions.

Cole, now a clinical audiologist practicing in Maryland, has suffered from unilateral hearing loss since birth.

"My hearing loss was the catalyst for my pursuit into a career in audiology. When selecting the area of research for my doctoral dissertation, I was naturally drawn to the unilateral congenital aural atresia patients," Cole said. "They too were born with a unilateral hearing loss. I found the opportunity to participate in their experience of hearing binaurally for the first time without the use of a hearing aid to be both fascinating and an honor." 

Gray said he became interested in studying sensory perception due to his own struggle with congential anisometropia, a condition resulting in one of his eyes being larger than the other, which required him to wear contact lenses from an early age and still renders him unable to locate the position of an image using stereo cues. speaker icon Listen to Gray discuss his eye condition.

After earning his Ph.D., Gray completed a post-doctoral fellowship at the U.Va. with surgeon Dr. Robert A. Jahrsdoerfer, who pioneered the atresia surgery more than three decades ago. After collaborating with Jahrsdoerfer again at the University of Texas, Gray now works with Kesser, a protégé of Jahrsdoerfer.

Adding a Voice to the Debate

Studying at JMU put the researchers in an even rarer position, as the university's Doctor of Audiology program is one of few in the nation that require both a dissertation and clinical thesis for the Au.D.

The article, which appeared in International Journal of Pediatric Otorhinolarygnology, was the first JMU Au.D. dissertation to be published. Gray commended the effort and determination Cole took to complete this project that included making frequent one-hour trips from JMU to U.Va.

"It takes heroic efforts to test these patients and work with their schedules," said Gray. "It's a multi-institutional, multi-disciplinary project. We've got a physician and an audiologist and me, who's a basic scientist. We've got three very unique perspectives. It's a remarkable example of collaboration."

It's an effort that Gray hopes will help not only atresia sufferers and physicians make choices about treatment, but also help provide clarity to the larger debate over unilateral hearing loss.

"It's a hotly debated topic. It's debatable about how important it is to have a second ear. A lot of insurance companies wouldn't even pay for the surgery, because they said it was completely cosmetic, that one ear was as good as two," Gray said. "Well, it turns out, it isn't. There are important advantages to having two ears."

 

Published October 2009