From My Perspective: Merging Signals For some patients with single-sided deafness, cochlear implantation has proven benefits—especially for those who also have severe tinnitus. From My Perspective
From My Perspective  |   March 01, 2014
From My Perspective: Merging Signals
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Hearing Disorders / Hearing Aids, Cochlear Implants & Assistive Technology / From My Perspective
From My Perspective   |   March 01, 2014
From My Perspective: Merging Signals
The ASHA Leader, March 2014, Vol. 19, 6-8. doi:10.1044/leader.FMP.19032014.6
The ASHA Leader, March 2014, Vol. 19, 6-8. doi:10.1044/leader.FMP.19032014.6
“Marie” was the first patient to receive a cochlear implant for single-sided deafness at Denver Ear Associates. We performed the surgery at the end of 2012, when she was 9 years old. Her circumstances had been strongly influenced by her insurance company; it repeatedly denied requests for a bone-anchored hearing aid, but quickly approved a cochlear implant. Using this technology, we hoped to merge the implant’s signals with those of Marie’s unimpaired ear.
Some clinicians might question implantation when patients—especially children—appear to be doing well. But even Marie’s mother was unaware of the breadth of her child’s difficulties, to such an extent that she had trouble filling out pre-operative questionnaires. Only in hindsight—after Marie received the CI—could she recognize all the circumstances in which her child experienced significant difficulties. Until patients and their families know what benefits an implant can provide, they may continue to underestimate their current challenges.
That’s why using cochlear implants to treat patients with single-sided deafness is one of the most interesting and potentially challenging applications of cochlear implant technology since they were introduced, some 30 years ago. People with normal hearing in one ear often perform normally in a quiet listening environment, but are challenged by sound localization and hearing in noise. To help these patients recover the ability to function in challenging listening environments, we ideally consider a cochlear implant for the deafened ear.
But determining when the recommendation is appropriate, obtaining insurance coverage and doing all we can to ensure our patients’ successful outcomes are critical steps. These clinical opportunities did not exist two decades ago ... and clinicians currently have no clear evidence-based guidance to help them decide how best to implement this technology.
Ongoing controversy
Why would we hesitate to implant a unilaterally deafened patient? Historically, clinicians and researchers have questioned whether the two different signals—that is, normal hearing and prosthetic hearing—would merge in the brain to result in meaningful, beneficial hearing. When cochlear implants were first being used, clinicians were required to ensure that the patient did, in fact, show bilateral deafness and that the patient discontinued hearing aid use in the contralateral ear following surgery. Insurance criteria are still based on bilateral deafness only, although the application of cochlear implants is broadening.
Two decades later, the debate rages on as to when to allow a hearing aid in the non-implant (opposite) ear once the patient has a cochlear implant. There is strong documentation to indicate that patients who are allowed to use amplification in the non-implant ear do, in fact, benefit from it. However, many clinicians insist their patients learn to the use the new device more quickly by temporarily suspending hearing aid use in the non-implant ear. But given what we know from these bimodal patients, we should feel more confident that natural and prosthetic hearing will complement each other.
Among people with single-sided deafness, it is difficult—if not impossible—to deny the non-implant ear access to sound. Our clinic recommends a custom earplug in the non-implant ear as part of the patient’s rehabilitation. Patients wear the plug during most waking hours and during formal rehabilitation, although we need to conduct more research to determine if this practice has the desired impact on the patient’s long-term outcomes.
A colleague recently shared an early experience of implanting a patient with single-sided deafness, many years ago, and having her subsequently reject her device. These early experiences or anecdotal cases may lead to skepticism, but stand in stark contrast with current research—for example, a German study by Roland Jacob and colleagues, published in the May 2011 issue of the journal HNO—showing wide user acceptance.
This increased user acceptance may be related to advancing cochlear implant technology; current coding strategies able to represent fine timing and envelope cues in a rapid manner seem to have the greatest impact. Reports in the literature, such as a study published by Sally Kamal, Aaron Robinson and Rodney Diaz in the October 2012 Current Opinion in Otolaryngology & Head and Neck Surgery, show patients’ improvements in sound localization and speech perception in noise—thus improving patients’ quality of life.
Securing reimbursement
As more patients who are unilaterally deaf become implanted in the United States, the benefits that European clinics have already experienced are becoming evident to us, compelling more clinics to offer implantation as an option. But lack of approval and poor reimbursement by our health care system has significantly limited their use in the United States.
It is likely to be a while before insurers consider these patients to fall within criteria, but when the benefits are proven there will be a strong case to be made. As clinicians, it is imperative that we support one another by determining effective evaluation methods, sharing programming considerations, and helping obtain insurance coverage with documentation when possible. Because cochlear implantation is considered an off-label application for single-sided deafness, manufacturers are unable to make recommendations or offer support until after a patient has been implanted.
Clinicians have been successfully implanting “out-of-criteria” patients, but qualifying them via antiquated insurance guidelines has been challenging. For some patients, maximizing competing noise and using the most acoustically and phonetically complex text materials to evaluate the person’s ability to function in real-life listening situations has helped to demonstrate need. Patients with single-sided deafness are a uniquely challenging population to test, because we are accustomed to testing in the sound field—but in these cases, we have to take extra measures to isolate the test ear. Earplugs or earmuffs don’t offer enough isolation to show what the cochlear-implant side alone is capable of, and only one of the three cochlear implant manufacturers has software, with limited availability, capable of testing the patient directly connected through the computer, even for tasks such as localization.
How best to test these patients is being decided—with little consistency—across clinics. Our clinic is testing these patients in the spatially separated noise condition as if you were testing for a bone-anchored hearing aid; we present noise at the good ear and speech at the bad ear on standard clinical tests in various signal-to-noise ratios meant to simulate real-word listening conditions. Questionnaires assessing quality of life and hearing difficulties can also help determine the treatment’s effectiveness on the patient’s ability to function.
We confirm the patient’s current signal-to-noise ratio loss with either the Quick-SIN or BKB-SIN test. Our implanted patients demonstrate an average pre-operative SNR loss of 9.5 dB, with one patient’s three-month post-operative improvement to 3 dB. Some research has shown hearing in background noise with the CI to be superior than that obtained with a CROS [contralateral routing of offside signals] hearing aid and bone-anchored hearing aid. Ideally, testing should include a sound localization task, but typical sound booths found at most clinics do not provide this type of testing.
Our clinic reports all of these findings to a patient’s insurance company in support of a cochlear implant recommendation. In 2013, cochlear implant manufacturer MedEl obtained European Medicine Agency approval to implant patients of all ages for single-sided deafness. An attempt to gain approval from the U.S. Food and Drug Administration may be next.
More options, tinnitus benefits
I’ve been thrilled to watch Marie’s progress with her device, but in light of all of the available marketed technology I still have unanswered questions about when best to implement it for single-sided deafness. There are many options—including CROS and bone conduction—for routing the signal to the poorer ear. So how do we determine for each case whether to use that patient’s damaged cochlea or bypass it? Obviously, we would look for an intact cochlea and viable cochlear nerve.
In addition to patient reports of difficulty in real-life listening situations, clinicians must also consider the presence of accompanying tinnitus. Not all unilaterally deafened patients have tinnitus, but a 2013 Chinese study by H. Zheng and colleagues showed the prevalence of tinnitus with sudden, severe deafness to be as high as 92 percent. Although patient reports of tinnitus may or may not qualify as severe, cochlear implants have been shown to reduce its negative impact. A German study by Griet Mertens and colleagues, published in the June 2013 issue of Otology & Neurotology, showed that significant tinnitus originating from the deaf ear further impairs a normal-hearing ear’s ability to understand speech. This documentation offers strong support for cochlear implant consideration when the deafened ear also has significant tinnitus.
Some U.S. clinics involved in this research have placed a 10-year limit on length of deafness in the implanted ear. This limitation seems sensible for a study, given how much the auditory system can change when underused. However, with research showing that the age of primary ear implantation contributes to better outcomes than age of the secondary implant, one wonders if there is a valid age limit for this procedure, especially when the patient has a normally functioning auditory system. More research is required in these areas.
But for the time being, cochlear implantation should be a top consideration for a patient with deafness in one ear who wants to hear better in background noise and localize sound more precisely. Further, any patient known to have an intact cochlea and cochlear nerve with accompanying severe tinnitus should be considered for cochlear implantation.
As for Marie, this past winter marked her one-year anniversary. She excels with her implant, rarely missing information in the most challenging listening situations. Many patients implanted at Denver Ear Associates have had similar results, which is highly rewarding for them and also for us as clinicians. Decidedly, implantation will continue to be my go-to recommendation for patients with single-sided deafness.

Electric-Acoustic Stimulation: Headed for Mainstreaming?

An emerging topic in cochlear implants is the use of both a hearing aid and cochlear implant in the same ear—electric-acoustic stimulation. The hearing aid amplifies the low frequencies and the cochlear implant transmits the higher ones. We may well see this method mainstreamed for U.S. commercial use within the year, leaving clinicians to wonder when an EAS device may be more beneficial than, for example, a frequency compression hearing aid.

EAS devices are under investigation in the United States, but with the release of new electrode designs—as well as doctors adopting “soft” surgical techniques—we are getting closer to being able to control the outcomes for hearing preservation. Clinicians feel that if they preserve hearing in the implanted ear, it may benefit the patient to offer acoustic stimulation in the lower frequencies, where they can better represent pitch and timing cues than with a cochlear implant alone.

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March 2014
Volume 19, Issue 3