|By Cheryl Heppner 6/27/11
Dr. John Niparko wears many hats at Johns Hopkins Medical – or should that we say he wears many surgical masks or coats? He is the Interim Director of the Department of Otolaryngology-Head and Neck Surgery and George T. Nager Professor, as well as Director of the Division of Otology, Audiology, Neurotology, and Skull Base Surgery, and Director of the Listening Center. Long-time attendees of NVRC’s educational programs will remember his highly-acclaimed workshops at NVRC in past years.
Every new presentation by Dr. Niparko brings exciting information, and his workshop “New Options in Auditory Rehabilition” on Friday, June 17, 2011 at the convention was no exception.
Setting the backdrop for his program, Dr. Niparko emphasized the importance of the spoken word, which connects us to one another and maximizes our communication. He called the importance of the cochlea to our hearing akin to flipping a switch to turn on a light fixture. The hair cells in the cochlea are some of the body’s smartest cells, and they have a very complex structure. Atop them are tufts of cilia; if they fail to beat, or fall off, or die, we get hearing loss.
The importance of speech sounds
There are 45 different sounds in English spoken by a native speaker. Each has its own sound signature. That sound signature is very different in a non-native speaker. The brain learns these sounds from the time you are born. The sounds have three dimension – intensity which comes from loudness of the speech, frequency which comes from pitch, and timing which is determined by the onset and duration of the speech. There are regional differences and dialects. As an example, people from the Midwest hold their vowels longer.
Dr. Niparko quipped that the 45 speech sounds for male listeners have a hole for the spouse’s voice, and this is a problem he can’t solve.
We tend to tail off frequency at the end of a word. A change in frequency information aids in localization, which is the ability of our ears to zone in and choose the voice of the person we want to listen to. When there are multiple speakers, we zone in with their specific pitch cues.
The effect of hearing loss
The effect of aging on hearing is one of the things we can do the least about. Hair cells are fragile, particularly for men. A 60 year old male will typically have much higher hearing loss than a female of the same age. Trauma is another cause of hearing loss. It could come from damage due to noise. We now start to see signs of hearing loss in young adults. An estimated 8.5% of those aged 20-29 have a hearing loss. In the future there is hope we can see continued steps to avoid the onset of hearing loss.
Sensorineural hearing loss is almost completely absent on Easter Island. Here in the U.S., something genetic may be the cause of the higher rate. We now also know that medications can cause hearing loss and that some people are more sensitive to the effects of noise than others.
The impact of hearing loss
The symptoms of hearing loss are not just reduced ability to hear. There is reduced sensitivity to sound and impaired pitch resolution. There can be loudness recruitment, which causes painful or almost painful surges of loudness. Tinnitus continues to be an issue, although advances which can mask or suppress it have helped. Some individuals were helped by putting sound that is just below the level of the tinnitus in the ear, such as music.
Understanding speech in noise is a great problem in sensorineural hearing loss. With this form of hearing loss, the ear is being swamped by noise and recruitment. Speech is remarkably resistant to corruption. We are born with the ability to use it well, but it can be difficult or impossible to understand speech when there are multiple speakers, especially in a large room where sound is being reflected from hard surfaces. These are factors that modify the pitch and timing structure of the speech signals and create a masking effect.
Perceptions about hearing rehabilitation have been varied. A recent MarkeTrak survey found that seniors with hearing loss often reported “I hear well enough and don’t mind it,” thus marginalizing themselves. As a result, they often tend to adopt a less communication-filled lifestyle and reduce their social connections. Sensorineural hearing loss has long been associated with social withdrawal, which frequently brings consequences such as decreased general health and impaired immunity.
Recent research has also shown that hearing loss could be associated with increased risk of dementia. With severe hearing loss, an individual’s chance of getting clinically significant dementia is 70% if left untreated. Getting a cochlear implant can significantly mitigate the effect, and use of hearing aids on a consistent basis also helps. It is essential that we bring hearing aids and cochlear implants into the treatment picture.
Current predictions show that the percent of people with dementia will double in 20 years, and by 2050 it could affect 1 in 30 Americans.
Newer hearing aids are a step in the right direction. They look better, are more comfortable, and more of them are able to provide directionality (ability to identify direction of sound) and provide noise reduction. They also increase the naturalness of speech and its fidelity. But they still are not the same as normal hearing and require adjustment.
Cochlear implant electrodes in the inner ear stimulate the auditory nerve through responsiveness to electrical signals. Modern digital technology has helped us to increase the speed of sound processing; in the early years cochlear implant users said sound had a robotic or cartoonish quality.
We have now been able to achieve preservation of healthy hair cells in the ear and stimulate the rest of the cochlea with a cochlear implant. It is possible to wear a hearing aid in the same ear and preserve hearing while getting a more natural sound. This has worked very well for selective patients.
Questions and answers
Q: Which comes first, the hearing loss or dementia?
Dr. Niparko: Someone could have reduced speech understanding due to dementia, but data in many cases showed that hearing loss preceded the dementia. Data is also beginning to show us the importance of social connections.
Q: If someone is already exhibiting symptoms of dementia, is it too late for a cochlear implant?
A: Based on data we have now, a hearing aid is probably much more helpful.
Q: What are the experiences of cochlear implant users who have had chemotherapy?
A: Several patients went through chemotherapy with a cochlear implant in place. The implant may not be stable in many cases due to the neurotoxic effect chemotherapy can have on nerves, but it hasn’t seemed to have a permanent effect.
Q: How good are the results with partial insertion implants?
A: A lot of music comes into the ear through the low tones, which helps pick up the beat/rhythm and bass. Research is still open on this. Some people with the partial implants were not happy and came back to get implants with full insertion. One individual has done well. This person had hearing loss that started in high school and got an implant 30 years later. Hear hearing aids in both ears are supplemented with a cochlear implant. She calls it “trimodal hearing”.
Q: What about auditory neuropathy?
A: We are seeing this more frequently. It is a result of the brain mechanisms not putting information together well.
Q: What are the primary predictors of a cochlear implant?
A: An auditory foundation.
Q: What resources are there to help learn speech understanding with a cochlear implant?
A: All of the cochlear implant companies have online resources, and there is a web product called LACE.
Q: What will be the impact on bilateral cochlear implants if I have carotid surgery?
A: Today the only concern about surgery is if it involves the head, not the neck or anything below it.
Q: What cochlear implants make it possible to have MRIs?
A: We now have a way to perform MRIs on patients who have cochlear implants without having to remove the magnet. A binding procedure is used. The important thing to know Is that we can do the scan but we can’t keep you comfortable. It will hurt for about 10 minutes afterward because the magnets are moving around. We couldn’t find an MRI with a Tesla (measurement of strength) of less than 1.0, so the research has used one with a Tesla of 1.5.
Dr. Niparko showed a short video from his famous 2005 study with David Ryugo where deaf cats were implanted for three months with a 6-channel cochlear implant that used human speech processing programs. The cats responded to environmental sounds and their auditory nerve fibers showed some recovery. Food conditioning was used, and the cats could differentiate the sound of music by Bach from the sound of music by Beethoven.