sound thinking
Johnny Martinez can’t hear, but this 5-year-old can still make Bwwooooo! Bwwooooo! sounds like a trucker climbing the Grapevine.
He is learning sign language, with first things first: mine (a necessity when you have a little brother), McDonald’s (his favorite restaurant) and candy (self-explanatory).
On a wintry afternoon, he gleefully shakes his Etch-A-Sketch and insists others in the family’s Laguna Hills living room draw with him, communicating in finger-points, nods and grins.
He signs an X for Xena, the TV warrior princess, then shows off his newly learned signs for the alphabet.
He is joyfully oblivious to the fact that he is helping researchers study what may be a potential breakthrough in ear nerve problems, one that may change the way hearing disorders are treated.
UC Irvine neurologist Arnold Starr and Yvonne Sininger, audiologist and director of children’s research at the House Ear Institute in L.A., are examining and testing 10 patients--including Johnny, a Seattle college student, a 4-year-old San Fernando Valley boy and an Orange County man.
The three-year study is funded by the National Institutes of Health. Starr and Sininger’s initial research, published in June in the prestigious medical journal Brain, has shown a nerve problem between the ear and the brain stem called auditory neuropathy.
In this disorder, the ear receives sound, but that message is not delivered properly to the brain.
“We’re thinking it might be common; we just don’t know what causes it and why it happens,” Starr says.
“In this leg of the research,” Sininger says, “we hope to have some idea about the nature of the disorder in the nerve [itself], which may tell us a lot.”
The research team is seeking more subjects--as many people as possible--whose cochleae, home to the sound receptors, are in mint condition but who still cannot hear.
Because it suspects that the nerve damage might run in families, the team is also trying to find patients who have a relative with similar symptoms.
Some of the hearing-impaired patients were born deaf. Others, like Johnny Martinez, lost part or all of their hearing as a result of an illness or allergic reaction.
“I feel now a little edge of hope,” says Johnny’s mother, Angela Zaragoza, 25, “that maybe someone could do something for him in his lifetime. I was crying when I found out he could be in this research project.”
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Hearing aids are still a common treatment for hearing loss. They can be very effective for some people. But it’s also very common for a hearing-impaired person to report that the hearing aid doesn’t work. It is, they say, as ineffective as turning up the volume to make a radio station come in clearer: The static just gets louder.
Traditionally, hearing loss has been linked primarily to the sound receptors of the ear.
In conductive hearing loss, fluid buildup from an infection could prevent the eardrum from properly vibrating. Or disease might impair vibration of the smaller bones in the middle ear.
In sensory hearing loss, commonly found in deaf children and the elderly, hair cells critical to the hearing process don’t exist or have died away with time. Exposure to tremendous noise, for example, will destroy such hair cells.
These are probably still the two leading causes of hearing loss.
However, the ear team is finding that there may be other causes involving the nerve.
This is no small finding, given that there is no cure for deafness and an estimated 9% of the population--21 million nationally--has some form of hearing loss, if just temporary, according to the House Ear Institute and the Providence Speech and Hearing Center in Orange. One in three people over 65 suffers hearing loss, according to the center.
“I believe that the research is highly significant,” said Alison Grimes, director of audiology for Providence, a nonprofit organization affiliated with Children’s Hospital of Orange County.
“Sininger and Starr are highly respected researchers, and I believe auditory neuropathy is a rare phenomenon but probably more frequent than we have realized.”
Understanding how the ear works is necessary in understanding hearing disabilities.
Picture sound entering the ear as an invisible wave. The wave reaches the eardrum, triggering vibrations that travel through several small bones before reaching the cochlea. Inside the cochlea, which is coil-shaped, the same sound wave travels through fluids.
As the sound wave moves, it tickles minute hair cells, and that tickling triggers a chemical reaction. That reaction tells adjoining nerve fibers to send word to the brain stem that a sound wave has been received.
When problems occur, they are either because the hair cell doesn’t exist or function or because the nerve fibers are not working.
As the tickled hair cells sway, the contraction itself creates a sound inaudible to the person but detectable with equipment. This test, which uses highly sophisticated microphones, tells researchers if the hair cell is working. If it is, the person’s hearing loss is likely due to nerve damage.
What Starr and Sininger found six years ago with a patient was that her ear received the sound wave and carried it to the point that the chemical reaction was to occur. But the nerve impulse to the brain was either mottled or didn’t get transmitted at all.
This was a new wrinkle.
They wrote a paper in 1991 for Brain and kept a lookout for similar symptoms in other patients. But as time went on, the team concluded that it needed more patients to come to any solid conclusions.
So the team e-mailed computer chat rooms on the Internet, put up queries on hearing-related Web sites and sought prospective research subjects via organizations such as Providence.
Starr’s e-mail was spotted by Audrey Haug, an audiologist at Providence who was working with Johnny Martinez.
“I’ll never forget the day she called me about the research,” Angela Zaragoza recalled. “Everybody else before [Providence] had kind of shined me on. This made me think, ‘Well, even if Johnny doesn’t benefit, somebody can.’ ”
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As a result of losing his hearing just as he began learning to talk, Johnny Martinez speaks very little.
At 15 months old, he developed what was diagnosed as an ordinary ear infection, his mother said. She said the doctor prescribed Pediazole, which contains sulfa. The sulfa apparently caused an allergic reaction that developed into anguishing burn-like wounds all over his body.
Called the Stevens-Johnson syndrome, the miserable condition, Zaragoza believes, burned Johnny’s nerves and caused his hearing loss.
Starr and Sininger, new to the case, have tested Johnny and concluded that his ear’s cochlea “is perfectly normal,” Sininger said. “That is the distinguishing feature of this condition. Whereas in the majority of hearing loss, the receptor [the mass of hair cells] has been damaged.”
When the syndrome struck, Johnny had begun to speak a few single words. But because he was barely speaking at all by age 3, his family suspected he might have some kind of hearing problem.
He now visits a speech pathologist weekly. But he still communicates mostly through gestures and the sign language that he is learning at Taft Elementary School in Santa Ana, which has a program for hearing impaired students.
He’s a huggy, kissy kind of boy, Zaragoza said, but she knows what they are both missing.
“He’s not ever going to hear his mom say, with the emotion in my voice, that I love him. And that’s really disappointing. And I won’t ever hear him say that to me,” Zaragoza said. “But the hope of that, that’s what I hold onto.”
The research, Sininger said, will include ongoing hearing tests to answer questions about the nerve signal: “Is it the timing of the nerve impulse, which we think is the primary problem? We know the nerve impulse is there, it’s just that the timing is off, the synchrony, and that is why people can’t hear speech properly, because speech is a very precise timing information transmission to the brain.”
In adult patients whose symptoms suggest the possibility of a general nerve disorder, the team will do a biopsy of a section of nerve from the foot.
“We can’t look at the auditory nerve because it is buried in the skull,” Sininger explained. “But in some patients, we can take a piece of the nerve from the foot and biopsy it, and it may help to see what could be wrong with the nerves in general.”
The team can probably conclude that whatever nerve problem affects the foot is likely to be affecting the ear nerves, Starr explained.
The researchers and their subjects are hoping that the next three years together provide a breakthrough.
“The first paper we did on this was in 1991, based on one patient,” Starr said. “So we are just beginning to get into what to do for them.
“What we know we don’t want to do,” Starr added with a smile, “is give them another hearing aid.”
More information is available from Tammy Majeski at the House Ear Institute, (213) 353-7017, or with Arnold Starr, reachable via e-mail at AStarr@uci.edu
(BEGIN TEXT OF INFOBOX / INFOGRAPHIC)
How We Hear
Deafness usually is attributed to disease or fluid preventing sound from vibrating the eardrum. An absence of key hair cells also causes hearing loss. New research by doctors Arnold Starr and Yvonne Sininger suggests that nerve problems also may be a culprit. The ear receives sound, but nerve fibers don’t alert the brain. How we hear:
1. Sound wave enters ear, vibrates ear drum.
2. Vibration travels through set of small bones before arriving at cochlea.
3. Sound wave swirls through cochlea, stimulates minute hair cells.
4. Hair cells trigger nerve fibers, which transmit message to brain: Sound is received.
Sources: Drs.Arnold Starr and Yvonne Sininger; American Medical Assn. Encyclopedia of Medicine
