5
Evaluating Hearing Ability in Persons with Cochlear Implants with Single-Sided Deafness or Asymmetric Hearing Loss
This chapter will address item 4 from the Statement of Task, which directs the committee to:
Examine the special considerations inherent in evaluating hearing ability in persons with single-sided deafness or asymmetric hearing loss receiving a cochlear implant and to describe the following:
- Any special considerations in the testing and treatment of persons with bilateral but unequal hearing loss;
- Whether there is a correlation between the presence and degree of hearing loss in the less-affected ear and the recovery time or treatment for individuals with single-sided deafness or asymmetric hearing loss receiving a cochlear implant in their more-affected ear;
- Whether there is a level of hearing ability in the less-affected ear which would render cochlear implantation in the more-affected ear immaterial with respect to meeting the severity of hearing loss in the Listings (i.e., would not prevent an adult from engaging in any gainful activity nor a child from having “marked” limitations in two domains of functioning or an “extreme” limitation in one domain1);
- Whether the tests identified in task 3 remain appropriate for testing hearing ability in persons with single-sided deafness or asymmetric
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1 See 20 Code of Federal Regulations 416.926a and DI (disability insurance) 25225.030, DI 25225.035, DI 25225.040, DI 25225.045, DI 25225.050, and DI 25225.055.
- hearing loss receiving a cochlear implant and why, and if there are any differences in how the tests should be administered or interpreted; and
- Whether the equivalent scores identified in task 3 remain accurate proxies for the HINT word recognition scores when assessing persons with single-sided deafness or asymmetric hearing loss receiving a cochlear implant.
The chapter begins with background information and challenges for the U.S. Social Security Administration (SSA) in regard to single-sided deafness (SSD) and asymmetric hearing loss (AHL) in individuals with cochlear implants. The chapter also provides an overview of special considerations inherent in evaluating hearing ability in patients with SSD or AHL who receive a cochlear implant. Finally, the committee responds to each of the items, in the order in which they appear, in the Statement of Task.
INTRODUCTION
Hearing loss can be classified as bilateral hearing loss, unilateral hearing loss (UHL), or AHL on the basis of its lateral differentiation and degree of severity. Bilateral hearing loss is a general term for hearing loss in both ears, regardless of severity. UHL is a general term for hearing loss in only one ear, regardless of severity. AHL is defined as hearing loss in both ears, with a difference in pure tone averages (PTAs)2 between the two ears. The exact criteria for difference in PTA varies in the literature (Liu et al., 2020). SSD is UHL in which hearing loss in the impaired ear is severe to profound, most often caused by sudden sensorineural hearing loss (Giardina et al., 2014). There is some disagreement in the literature on the specific definition of SSD, and some authors categorize some forms of SSD as a type of AHL rather than UHL (Liu et al., 2020). With regard to cochlear implantation, the U.S. Food and Drug Administration (FDA) currently defines AHL as a profound sensorineural hearing loss in one ear and mild to moderately severe sensorineural hearing loss in the other ear, with a difference of at least 15 decibels (dB) in PTAs between ears (FDA, 2020). It defines SSD as a profound sensorineural hearing loss in one ear and normal hearing or mild sensorineural hearing loss in the other ear (FDA, 2020).
The prevalence of UHL in adult Americans has been estimated to be 7.2 percent, with 1.5 percent experiencing moderate or severe UHL (i.e., SSD) (Golub et al., 2018). The prevalence of UHL in children has been estimated at approximately 1 congenital UHL per 1,000 births, increasing
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2 The average of hearing threshold levels at a set of specified frequencies (e.g., 0.5, 1, 2, and 4 kHz).
to an estimated 14 percent when one includes delayed-onset congenital UHL and acquired etiologies among adolescents ages 12–19 years (Lieu, 2018). Hassepass et al. (2013) estimated an SSD prevalence of 2–5 percent in children and teenagers. A recent study estimated AHL prevalence in the United States using data from the National Health and Nutrition Examination Survey and two definitions of AHL (Suen et al., 2021). Using the American Academy of Otolaryngology—Head and Neck Surgery definition of AHL as a PTA difference of greater than 15 dB, the researchers found an overall AHL prevalence of 2.77 and 9.46 percent when calculating the PTA with 0.5–4 kHz and 4–8 kHz, respectively. In contrast, using the U.S. Department of Veterans Affairs definition of AHL as a difference greater than/equal to 20 dB across two contiguous frequencies or 10 dB across three contiguous frequencies, the authors calculated an overall prevalence of 25.05 percent across 0.5–8 kHz (Suen et al., 2021).
The committee notes that when cochlear implants were first approved, they were intended for use with adults and children with bilateral profound sensorineural hearing loss. Over the years, the safety and efficacy of cochlear implants have been well established, and their approval for use has been expanded to include patients with greater amounts of hearing. FDA approved cochlear implants for use in patients with SSD and AHL (FDA, 2019a). As a result, many insurers now cover the cost of cochlear implants for patients with SSD and AHL and will consider approving cochlear implants for patients who do not meet FDA-approved indications but who have been determined by a medical professional to be suitable to receive a device (a practice referred to as “off-label use” of a medical device) (FDA, 2020).
Those changes in practice regarding who receives a cochlear implant pose special challenges for SSA for several reasons. First, current indications for disability due to hearing loss not treated with cochlear implantation (SSA Listing 2.10) base eligibility on the hearing in the better hearing ear; individuals will qualify for disability if they have an average air conduction hearing threshold of 90 dB or greater in the better ear and an average bone conduction hearing threshold of 60 dB or greater in the better ear (2.00B2c) or if they have a word recognition score of 40 percent correct or less in the better ear determined using a standardized list of phonetically balanced monosyllabic words (2.00B2e). Presently, SSA considers an individual who receives a cochlear implant to be under a disability for 1 year after initial implantation or, if more than 1 year after implantation, a word recognition score of 60 percent correct or less determined using the Hearing in Noise Test (HINT) (2.00B2b). It is evident that those guidelines were based on the underlying assumption that cochlear implants were primarily being used by individuals who demonstrated a significant and impactful bilateral sensorineural hearing loss. However, that is no longer the case.
The presence of normal or near-normal hearing in one ear, which is the case for individuals with SSD or AHL who receive a cochlear implant, has complicated the determination of disability due to hearing loss. Historically, professionals have assumed that the presence of normal hearing in one ear provides sufficient auditory input to result in a relatively normal hearing experience (Giardina et al., 2014). Thus, SSD and AHL often went untreated. Recent research has identified several difficulties that patients with UHL or AHL face, including difficulty hearing in complex or noisy environments and an inability to identify the location or laterality of sounds (Kamal et al., 2012) as well as an increased prevalence of tinnitus (Liu et al., 2018). The presence of SSD or AHL can be particularly impactful for children and has been found to result in delays in auditory behavior (Kishon-Rabin et al., 2015); reduced communication, motor skills, and adaptive behavior (Vohr et al., 2012); delays in the development of speech and language (Fischer and Lieu, 2014; Lieu et al., 2013; Sangen et al., 2017); a higher incidence of behavior issues (Lieu et al., 2012); and a reduction in self-reported quality of life (Rachakonda et al., 2014; Umansky et al., 2011). Because these difficulties have been noted, professionals are now more likely to recommend intervention for SSD and AHL in both children and adults than in the past.
The safety and efficacy of treating SSD and AHL with a cochlear implant has been demonstrated in both children and adults (FDA, 2019b). However, due to changes regarding who is considered to be a candidate for a cochlear implant, it is necessary to re-examine the disability coverage related to cochlear implantation. It needs to be determined whether patients with SSD and AHL who receive a cochlear implant and possess normal or near-normal hearing in one ear should automatically be covered under disability for a period of 1 year after they receive the cochlear implant.
SPECIAL CONSIDERATION IN THE TESTING AND TREATMENT OF PERSONS WITH BILATERAL BUT UNEQUAL HEARING LOSS
Hearing Testing
Hearing can be measured unilaterally (one ear at a time), bilaterally (each ear separately), or binaurally (both ears tested together at the same time). Additionally, hearing testing can be performed in either an unaided or aided condition. Unaided testing provides a measure of hearing sensitivity without the use of hearing technology and is typically performed using insert earphones and a bone conduction oscillator. The results of such testing provide information regarding the type and severity of the hearing loss. When testing is done in an aided condition, the patient uses hearing assistance, such as a hearing aid or cochlear implant. For patients who use
hearing technology, this testing is often used to investigate the patient’s typical hearing situation, and a comparison of unaided and aided responses can be used to estimate the amount of benefit a patient will receive from the hearing technology.
When hearing testing reveals the presence of hearing loss, the loss can be unilateral (present in only one ear) or bilateral (present in both ears). In unilateral hearing loss, the severity of the hearing loss in the affected ear can range from mild to profound while the non-affected ear typically has normal hearing.
There are special considerations that need to be addressed when testing the hearing of individuals with unequal hearing in the two ears. During testing the examiner needs to ensure that steps are taken to control for the possibility that sound presented to one ear (the test ear) may cross over and be heard by the other (non-test) ear. Such steps should be applied to signals delivered via air conduction, via bone conduction, and during speech recognition testing, and they should be taken during both unaided and aided testing.
Unaided Testing
During unaided testing, masking noise is typically delivered to the non-test ear via insert earphones, and the level of masking is determined by several factors, including the air and bone conduction thresholds of the non-test ear, the air conduction threshold of the test ear, and the level of presentation of the signal in the test ear. The masking level is also influenced by such factors as interaural attenuation (IA), a reduction in intensity of the stimulus as sound is transmitted from one ear to the other across the listener’s head. IA will vary depending on the equipment used to deliver the stimulus and is typically estimated to be a minimum of 40 dB for supra-aural headphones, 50 dB for insert earphones, and 0 dB for bone conduction. When presenting a masking stimulus, the examiner must be careful not to provide too much masking noise to the non-test ear as doing so may cause the masking noise to cross over to the test ear and affect the results (overmasking).
Aided Testing
It is also important to control for possible perception of the test signal by the non-test ear when testing patients with unequal hearing in an aided condition. Typically, the purpose of such testing is to determine the efficacy of the intervention and the benefit it provides when tested alone, without the influence of the other ear, and to determine the benefit that use of the
technology provides when tested in a binaural listening condition (which more likely represents the patient’s everyday listening situation). Techniques that can be used during aided testing to isolate the affected ear and block perception of the signal by the non-test ear include removal of the hearing aid or cochlear implant from the non-test ear, plugging of the non-test ear, plugging and muffling of the non-test ear, the delivery of masking noise to the non-test ear, and the use of direct connection to the hearing technology of the test ear. Those techniques may be used in isolation or in combination with one another depending on the amount of hearing present in the non-test and test ears and the level of signal being presented to the test ear. The above-mentioned signal control methods are typically used when evaluating speech understanding in quiet or in noise. Other measures used to evaluate the efficacy of devices include questionnaires that examine quality of life and tinnitus (Van de Heyning et al., 2017).
Treatment Options
Treatment options for patients with UHL and AHL are determined by the type and severity of the loss in the affected ear. Patients with mild to severe UHL (i.e., SSD) may choose to use a hearing aid in the affected ear or may choose to deny or defer treatment of the affected ear. The affected ear is often left untreated as some believe that the presence of normal hearing in at least one ear is sufficient for daily hearing function. Recent research, however, has shed additional light on this topic, and currently most professionals believe that treatment of mild to severe UHL (i.e., SSD) is warranted. The ability to successfully treat hearing loss in the affected ear will depend on the type and severity of the hearing loss as well as on the speech recognition skills of the affected ear. Additionally, a decision to treat an ear may be affected by other factors, such as the presence of tinnitus or balance issues in the affected ear. Possible treatment options for UHL include hearing aids (either air conduction or bone conduction), surgical treatment in the case of conductive or mixed losses, or the surgical insertion of a cochlear implant.
Because of the significant nature of the hearing loss in the affected ear, patients with SSD or AHL pose special treatment challenges because the affected ear typically cannot receive benefit from traditional technologies, such as an air conduction hearing aid. Thus, treatment options for such patients include use of devices that pick up sound on the side of the affected ear and transmit it to the ear with normal hearing, such as a Contralateral Routing of Signal (CROS) hearing aid. CROS aids place a microphone on the affected ear that picks up sound and transmits it to the ear with normal hearing via an air-conducted signal. In cases of AHL, if an aidable loss is present in the better-hearing ear, the patient may be fit
with a bilateral CROS. This is similar to a CROS, but the hearing aid used to provide sound to the better hearing ear is amplified. Alternatively, the surgical or non-surgical placement of a bone conduction device can be used to provide sound awareness on the side of the head with the hearing loss. Like the CROS, bone conduction devices pick up sound on the side of the affected ear and transmit it to the ear with normal hearing. However, the transmission of the signal is done via use of a bone-conducted, rather than an air-conducted, signal. Because these devices route the signal from both sides of the head to the ear with normal hearing, they are not considered binaural solutions.
The only treatment option that provides truly binaural hearing for SSD patients or patients with an AHL with an ear that has profound hearing loss is a cochlear implant. As has been explained previously, cochlear implants include surgical placement of an electrode array into the cochlea of the affected ear, with the patient using an externally worn sound processor that picks up sound from the environment and sends the signal to the implanted electrode array, which stimulates the inner ear and provides sound information to the brain. Cochlear implants received FDA approval for use in patients aged 5 years and older with AHL or SSD in 2018 (FDA, 2019a).
It should be noted that patients with SSD often experience tinnitus in the affected ear. In some instances the tinnitus is debilitating. Because cochlear implants frequently help reduce tinnitus (Arts et al., 2012; Servais et al., 2017), the presence of severe tinnitus in the affected ear may provide additional support for a recommendation for a cochlear implant. Many insurers recognize the value of hearing from both ears and provide coverage for both bone conduction devices and cochlear implants as treatments for SSD.
CORRELATION BETWEEN HEARING LOSS IN THE LESS-AFFECTED EAR AND RECOVERY TIME OR TREATMENT IN THE MORE-AFFECTED EAR
This section discusses whether there is a correlation between the presence and degree of hearing loss in the less-affected ear and the recovery time or treatment of individuals with SSD or AHL receiving a cochlear implant in their more-affected ear.
Surgery and Recovery Time
Cochlear implantation involves the surgical placement of an electrode array into the cochlea. Typically, cochlear implant surgery lasts about 2–3 hours and is performed under general anesthesia. A few investigators have reported success performing cochlear implant surgeries under local
anesthesia and sedation (Connors et al., 2021). The recovery time following surgery can be influenced by several factors, including the patient’s reaction to anesthesia, the need for medication for pain reduction, and swelling at the incision site. In most instances, adults and children return to their normal routine when they feel well enough to do so, often within a few days of surgery. Patients are typically seen by their surgeon either in the clinic or virtually via telemedicine for an inspection of the incision about 1 week following surgery. In most clinics, the external device is activated 2–4 weeks after surgery and in some cases has been reported as early as 1 day following surgery (Hagr et al., 2015).
Activating a cochlear implant involves several different steps, including impedance telemetry, setting the levels of the electrodes, adjusting the levels when the patient is exposed to live speech, and downloading of the programs to the sound processor. Patients are typically provided with successively louder programs to use over the coming few weeks as they adjust to the overall loudness of the electric signal. In most clinics adults return 1, 3, 6, and 12 months post-activation for follow-up (Dunn, 2018), while children return slightly more often. During these appointments, the clinician reassesses the levels of the electrodes, reviews device use and care with the patient and his or her parent(s), and evaluates performance with the device.
How well an individual adjusts to the sound quality of the device varies greatly among those who receive a cochlear implant. Adjustment can be difficult for some patients, and that may affect both their device use and the amount of benefit they receive from the device. Children frequently participate in weekly therapy provided by a speech–language pathologist that helps them learn to use the speech information provided by the cochlear implant. Adults also might participate in such therapy, but recommendations for such therapy are less prevalent in the adult population.
When adults and children (ages 5 years and older) with SSD or AHL receive a cochlear implant, they typically participate in the same number and type of post-operative appointments as traditional cochlear implant recipients. The adjustment to sound quality and ability to recognize speech with the device is similar to the adjustment that takes place with traditional recipients and will vary among individuals. The presence of reduced speech recognition in the implanted ear soon after receiving a cochlear implant is somewhat common. However, reduced speech recognition with the cochlear implant is not as detrimental or as difficult for adult or pediatric patients with SSD or AHL as they are able to rely on the hearing ability of their normal hearing or near-normal hearing ear to communicate. The presence of good hearing in at least one ear will likely prevent an adult from meeting the indication of “being unable to engage in any gainful activity” and will likely also prevent a child from meeting the indication of “having marked limitations in two domains of functioning or an extreme limitation in one domain.”
SINGLE-SIDED DEAFNESS, ASYMMETRIC HEARING LOSS, AND SOCIAL SECURITY DISABILITY
This section will discuss whether there is a level of hearing ability in the less-affected ear that would render cochlear implantation in the more-affected ear immaterial with respect to meeting the severity of hearing loss in the Listing of Impairments (the Listings) (i.e., would not prevent an adult from engaging in any gainful activity nor a child from having “marked” limitations in two domains of functioning or an “extreme” limitation in one domain).
Historically, indications to qualify for a cochlear implant and indications to qualify for disability due to hearing loss have required patients to have a significant bilateral hearing loss. With cochlear implants, this was a decision made in early clinical trials when the safety and efficacy of cochlear implants were not yet proven. The decision to provide cochlear implants to patients with significant SSD or AHL was made only recently, when FDA approved cochlear implants for adults and children (ages 5 and up) with SSD and AHL (FDA, 2019a). This decision was based on research demonstrating that most individuals with SSD or AHL demonstrated improvements in word and sentence recognition in quiet in the implanted ear, improvements in sentence recognition in noise when noise was presented to the better hearing ear, improvements in sound localization, and improvements in self-perceived quality of hearing (FDA, 2019b).
The presence of a bilateral profound hearing loss not treated with a cochlear implant will likely prevent adults from engaging in any gainful activity and will likely result in children having marked limitations in various domains of functioning. Currently, patients without a cochlear implant qualify for Listings-level disability if they demonstrate an average air conduction hearing threshold of 90 dB or greater in the better ear and an average bone conduction hearing threshold of 60 dB or greater in the better ear (2.10A) or if they demonstrate a word recognition score of 40 percent correct or less in the better ear determined using a standardized list of phonetically balanced monosyllabic words (2.10B). Thus, patients’ hearing loss must be bilateral and must have a significant impact on their ability to communicate. If an adult patient’s hearing loss has been treated with a cochlear implant, he or she is considered under disability for 1 year after initial implantation (2.11A). On occasion, adults and children will continue to demonstrate difficulty hearing even after receiving a cochlear implant. When this occurs, the individual can still qualify for disability by scoring 60 percent correct or less on word recognition using the HINT Sentences test (2.11B, 102.11).
Most adults and children with bilateral significant hearing loss who receive a cochlear implant derive benefit from the device, and the
improvements they receive often prevent them from qualifying for disability after 1 year of using the device. Buchman et al. (2020) recently reported post-operative sentence recognition scores for 96 adults with bilateral moderate to profound sensorineural hearing losses who received a cochlear implant and participated in a multicenter prospective clinical trial. The subjects demonstrated mean preoperative word scores of 14.6 and 28.8 percent for the implant ear and in a bimodal test condition, respectively. Six months post-implant the mean scores improved to 60.9 percent in the implant ear (range = 56.6 to 65.2) and 69.2 percent in the bimodal condition, meaning cochlear implant in one ear and hearing aid in the other ear (range = 65.4 to 73.1). Test stimuli were presented in quiet at a level of 60 dB SPL, which is softer (and more difficult) than the 60 dB HL presentation level currently used to determine disability under current SSA requirements. Thus, most of these patients would not have qualified for continuing disability under current SSA indications.
As indicated previously, cochlear implants were not yet approved by FDA for use in patients with SSD or AHL when the current SSA guidelines were developed. Prior to the approval of cochlear implants for SSD and AHL, indications for cochlear implants, like indications for disability, were based on the “best” hearing situation. Thus, most cochlear implant recipients who were implanted previously qualified for disability under both 2.10 and 2.11 prior to receiving a cochlear implant since they likely experienced significant hearing loss in each ear. This would not be the case for patients who currently receive a cochlear implant due to SSD or AHL because they possess normal or near-normal hearing in their better ear.
Under current SSA guidelines, patients with SSD or AHL automatically qualify for disability for a period of 1 year following cochlear implantation, with no consideration given to the hearing in their better ear. To remain consistent with the wording and rationale used in current guidelines for hearing loss not treated with cochlear implantation (2.10 and 102.10), it is reasonable to consider the hearing in the better ear when determining whether a patient with a cochlear implant qualifies for disability due to hearing loss after they receive a cochlear implant.
TESTING HEARING ABILITY IN PERSONS WITH SINGLE-SIDED DEAFNESS OR ASYMMETRIC HEARING LOSS RECEIVING A COCHLEAR IMPLANT
SSA asked the committee whether the tests identified in task 3 of the Statement of Task remain appropriate for testing hearing ability in persons with SSD or AHL receiving a cochlear implant and why and also if there are any differences in how the tests should be administered or interpreted. The committee finds that the same tests and testing parameters can be used,
with a few additional considerations. Testing for disability for hearing loss has typically focused on the test results obtained with the better ear. Thus, a patient who receives a cochlear implant due to SSD or AHL should be required to participate in testing that represents the listening situation that they use on a daily basis, which typically includes an un-occluded better ear and an ear using hearing technology. Alternatively, testing could be based on the individual being required to meet current requirements for hearing loss not treated with cochlear implantation in the ear that does not contain the device (2.10).
PROXIES FOR THE HEARING IN NOISE TEST FOR INDIVIDUALS WITH SINGLE-SIDED DEAFNESS OR ASYMMETRIC HEARING LOSS
The committee was asked to determine whether the equivalent scores identified in task 3 remain accurate proxies for the HINT word recognition scores when assessing persons with SSD or AHL receiving a cochlear implant. As indicated in Chapter 4, an accurate proxy for the HINT word recognition test does not currently exist. It should be noted, however, that the measures that will be proposed in Chapter 6 to determine disability for hearing loss treated with cochlear implants are applicable to individuals with SSD and AHL. Because such individuals typically use the cochlear implant in conjunction with the hearing in their normal or near-normal nonimplanted ear, testing should be performed while the individual uses the hearing in both ears (Sladen et al., 2017).
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