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Study May Hold Answers to Ear Nerve Problems

June 01, 1997|NANCY WRIDE | TIMES STAFF WRITER

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).

He gleefully shakes his Etch-A-Sketch and insists others in the family's Laguna Hills living room draw with him, communicating in gestures, 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 Los Angeles, are examining and testing 10 patients, including Johnny and a 5-year-old North Hollywood boy.

The three-year study is funded by the National Institutes of Health. Starr and Sininger's initial research, published last 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, 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 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, lost part or all of their hearing as a result of an illness or allergic reaction.

Alex Bitzer of North Hollywood was 2 1/2 when his new preschool teacher noticed something wrong. "They felt he didn't respond quickly, or sometimes at all," says his mother, Joanne Bitzer. "The principal said she would stand behind him and he would continue an activity," as though he had not heard her approach.

The teacher suggested hearing tests, and within a week, his parents had arranged for Alex to be seen at the House Ear Institute. Many months of testing followed before Sininger concluded that Alex's hearing loss was linked to nerve problems. A hearing aid won't help. Research, eventually, might.

*

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. But the 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 older than 65 suffers hearing loss, according to the center.

"I believe that the research is highly significant," says 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.

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