PAGE 2 WHITEPAPER 2016 – BIMODAL HEARING AID FITTING GUIDELINES More than half of those receiving a cochlear implant have aidable hearing in the non-implanted ear 1 . If these recipients are fitted with a hearing aid in the non-implanted ear, access to bilateral and binaural cues (such as those arising from head shadow and redundancy) as well as complementary acoustic cues (such as fundamental frequency) may enhance cochlear implant performance. In this guideline, bimodal stimulation refers to the use of a cochlear implant in one ear and a hearing aid in the opposite ear and bimodal benefit refers to performance improvement with the hearing aid over performance with the cochlear implant alone. Even recipients with significant hearing loss in the non-implanted ear demonstrate bimodal benefit 2–4. For those who do not obtain bimodal benefit for speech recognition in noise 5, other benefits such as enhanced music and pitch perception may still occur 6–9. In addition, many studies have documented more natural sound quality and improved ease of listening with bimodal stimulation 3,10–15. Finally, bimodal stimulation can facilitate spoken language and literary skills in young children who subsequently receive a second side cochlear implant 16–18. The provision of bilateral hearing is considered the standard of care for cochlear implant recipients 19,20 . Therefore, all unilateral cochlear implant recipients who have some degree of aidable residual hearing in the contralateral ear should be considered candidates for bimodal stimulation. Candidates for bimodal fitting: If further optimization of the bimodal fitting is to be undertaken, it has been recommended that this be completed once the cochlear implant program is stable 23,24. However, clinical judgment may dictate that this be completed sooner (as long as the cochlear implant is set at a comfortable level) because it may take several months to arrive at a stable program. Unfortunately, studies have found that many bimodal users have hearing aids that are fit sub-optimally (i.e., set below targets) 25,26. It is beyond the scope of this paper to outline the standard hearing aid fitting process, but at a minimum, recommended guidelines for proper selection and verification of amplification should be followed to ensure maximum audibility and comfort of sounds of varying input levels 27,28 . How to fit the hearing aid for bimodal patients: Not a “one-size-fits-all” procedure. The approach that provides the greatest benefit will likely vary among patients It has been suggested that optimizing the hearing aid fitting for bimodal use (by considering frequency response and loudness balance) may result in greater benefit over standard hearing aid fitting 2,3,29,30. However, there is currently no single approach to bimodal fitting that is universally accepted 21,22. Additionally, there is conflicting evidence that indicates that further optimization of the hearing aid for bimodal use beyond fitting to target using proper verification methods does not result in superior outcomes 31. Nevertheless, certain fitting strategies may be considered and explored for bimodal recipients as the literature suggests these approaches have the potential for improving outcomes. It should be noted that the approach that provides the greatest benefit or that subjectively provides the most satisfactory sound will likely vary among recipients 32. Fitting a hearing aid in the nonimplanted ear gives acoustic cues that may enhance CI performance When to fit the hearing aid: The recommended time between activation of the cochlear implant and bimodal stimulation varies for different clinics 21,22. Some argue that delaying bimodal stimulation can facilitate the adjustment to the cochlear implant. However, cessation of hearing aid use or delaying the hearing aid fitting has not been shown to improve long-term outcomes. Many cochlear implant candidates are already fitted with bilateral amplification so continued use of the contralateral hearing aid after implantation will allow for continued bilateral stimulation. Immediate hearing aid use will allow the user to obtain the benefits associated with bimodal stimulation sooner rather than later. Continued use of amplification may also facilitate the patient’s adjustment to the cochlear implant. There may be isolated cases where this approach would not be appropriate, but in general, bimodal fitting is recommended as soon as possible. The accompanying Bimodal Fitting Flowchart was developed to serve as a guide for the bimodal hearing aid fitting process. This is not intended to be a “one-size-fits-all” procedure that is applicable to every bimodal listener. The cochlear implant population is extremely diverse and clinical judgment may warrant that a different approach be taken for a particular patient or patient population. For Bimodal decision-making flowchart:
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