Hearing Loss Determining Eligibility for Social Security Benefits (2005) / Chapter Skim
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5 Sensory Aids, Devices, and Prosthesis
5 Sensory Aids, Devices, and Prosthesis
Pages 140-162
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This chapter reviews the variety of devices that typically are used to ameliorate the effects of hearing loss. Wearable personal devices include hearing aids and cochlear implants, as well as auditory brainstem implants.
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Most hearing aids also modify sounds somewhat to attempt to compensate for specific features of the individual hearing loss. It is typical to shape the frequency response to provide more amplification for frequencies for which the hearing loss is greater: this is called selective amplification.
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Use of hearing aids and cochlear implants by children with hearing loss is considered in Chapter 7. For adults with hearing loss, hearing aids can be useful when hearing thresholds in the better ear are poorer than about 25 dB HL.
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Issues such as high cost, low perceived benefit, stigma associated with hearing loss, and denial of hearing problems may contribute to the low acceptance rate of hearing aids. As a result of these complicating factors, many individuals do not have or use amplification despite having pure-tone thresholds that suggest that they are hearing aid candidates.
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For many clients, this probably contributes to a lessthan-optimal long-term outcome. Problems Not Solved by Hearing Aids Even when hearing aids are fitted competently, hearing aid wearers often continue to experience a variety of problems.
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For many hearing aid wearers who have sensorineural hearing loss, the major concern is an inability to understand speech in a situation when background noise is present. This is generally agreed to be a physiological problem resulting from hair cell loss.
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Real-life problems associated with hearing loss are complicated by such contextual issues as personality, lifestyle, environment, and family dynamics, and these play an important part in the ultimate success of a hearing aid fitting. Numerous studies have shown that measures of technical merit are not strongly predictive of real-life effectiveness of hearing aid fitting (e.g., Souza, Yueh, Sarubbi, and Loovis, 2000; Walden, Surr, Cord, Edwards, and Olsen, 2000)
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It is likely that individuals who seek Social Security disability benefits would have more severe hearing losses than these groups. The literature yields relatively few data reflecting the performance of people with severe and profound hearing loss who have been fitted with appropriate hearing aids.
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Thus, some individuals with significant hearing loss are able to perform quite well in situations requiring speech communication, while others with similar pure-tone thresholds are almost completely unsuccessful. COCHLEAR IMPLANTS Profound neurosensory hearing loss is one of the most significant impediments to an individual's ability to successfully communicate with other human beings using audition and spoken language.
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The indications and results for children are discussed in Chapter 7. Cochlear Implant Devices Cochlear implants attempt to replace the transducer function of damaged inner ear hair cells.
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The basic components of a cochlear implant (shown in Figure 5-1) include: · a microphone to pick up auditory information from the environment, · a speech processor that changes the mechanical acoustic sound energy into electrical signals, · a headpiece with transmitter coil to send the information via radio frequency through the skin, · an implanted receiver/stimulator that interprets the electrical signal sent by the speech processor, and · an intracochlear electrode array that distributes the electrically processed speech information to the auditory nerves.
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Most cochlear implants today employ a band-pass filter system to separate the acoustic signal into discrete frequency bands that can be delivered to the appropriate frequency regions of the cochlea, providing spectral information about the speech signal. Temporal and intensity cues are delivered by varying the rate of stimulation and the amount of stimulating current.
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Prelingually deafened adults who use sign language have not been able to obtain much benefit from the devices. Cochlear implantation is also limited to individuals with bilateral moderate to profound sensorineural hearing loss in the low frequencies and profound loss in the high frequencies.
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, a series of speech perception tests are performed, bilaterally aided in a sound field at 70 dB SPL. Candidates unable to detect speech in a sound field with the assistance of appropriately fitted hearing aids are considered audiological candidates for an implant.
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Case reports indicate that these ears perform similarly to implants in prelingually deafened adults, in that a sensation of sound may not be perceived in a prelingually deafened ear. Other Considerations The characteristics of an individual cochlear implant user play a large role in the communication outcomes he or she achieves (Wilson, Lawson, Finley, and Wolford, 1993)
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Initial prospective randomized clinical trials using the four-channel Ineraid cochlear implant and the Nucleus CI-22 (feature extraction, F0F1F2 coding) implant demonstrated an average open-set sentence score of 30
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. Multiple speech coding strategies are available in most cochlear implants.
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Stimulation The improved speech perception scores achieved by an increasing number of individuals implanted with multichannel cochlear implants,
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The cochlear implant has been shown to be safe and effective in providing significant improvements in speech perception skills for postlingually deaf adults. The results with cochlear implants are encouraging and have continued to improve as indications for implantation expand and software and hardware advances become clinically available.
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. OTHER ASSISTIVE LISTENING DEVICES In addition to conventional hearing aids and cochlear implants, there is a category of technologies called ALDs.
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It is difficult to achieve this in an inconspicuous, flexible manner that does not inconvenience communication partners in the work setting. This presumption has been supported in two studies that have compared hearing aids and ALDs in fairly large groups of persons with hearing loss.
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Research Recommendation 5-1. There is very limited information about the efficacy and effectiveness1 of modern high-technology wearable hearing aids in adults with severe or profound hearing loss.
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Because many of them are less costly to purchase, adjust, and maintain and less individually specialized than either hearing aids or cochlear implants, they could provide a cost-effective approach to facilitating integration of some persons with hearing loss into the workforce. The committee recommends that SSA support research directed toward determining the benefits and cost-effectiveness of ALDs in the workplace.
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