Rehabilitation of Hearing Loss

1. Hearing loss prevalent among the elderly, yet hearing aids are underutilized a. Affects 40%-45% of those over 65 years of age; >80% of those over 70 years of age (Cruickshanks et al., 1998) b. Only 20% obtain hearing aids (Kochkin & MarkeTrak, 1999) c. 46% of those wearing hearing aids at the time of testing failed screening (Smeeth et al., 2002) d. Only 60% of those who own a hearing aid use it regularly (Smeeth et al., 2002) 2. Importance of hearing aids to elderly a. Hearing aids reduce the perceived impact of the hearing loss in daily communication (Stark & Hickson, 2004) b. 31% of older users report benefit from hearing aids in noise (Kochkin & MarkeTrak, 2003) c. 76% of older users report overall benefit with their hearing aids (Kochkin & MarkeTrak, 2003) d. Hearing aids not only reduce hearing disability but also reverse social, emotional, and communication dysfunction (Vuorialho et al., 2006) 3. Factors that influence purchase and use of hearing aids (Southall et al., 2006) a. Recognition of hearing difficulties i. Progressive nature of presbycusis limits patient awareness of extent of handicap being experienced ii. 2- to 3-kHz region: if no hearing loss present in this range, patients tend not to accept hearing aids iii. Awareness develops as impact on valued activities (social or leisure) becomes more evident and complaints by family and friends increase iv. Hearing difficulties in adverse listening conditions (e.g., noisy and/or reverberant environments) b. Awareness of availability of technological solutions i. Expense can be a major prohibitive factor ii. A single programmable hearing aid with features that optimize function can cost about $2000 c. Seeking consultation for and acquisition of assistive devices d. Adaptation to device i. Positive attitude, influenced by self-esteem and confidence, important e. Realistic expectations i. Hearing aids may always restore full function, but can improve quality of life by increasing awareness of environmental sounds, facilitating directional hearing, etc. ii. Requires appropriate pre- and post-fitting counseling 4. Characteristics of hearing aid seekers (Cox et al., 2005) a. Pragmatic and routine-oriented b. Feel relatively more personally powerful in dealing with life’s challenges c. More trusting, less cynical d. Use social support coping strategies less frequently than their non-hearing- impaired peers e. More aware of impact of their impairment on family 5. Factors that elderly cite as reasons for not following physician recommendation to obtain hearing aids (Garstecki & Erler, 1998) a. Cost b. Relatively low value placed on effective communication c. Other factors include low self-esteem, depression, low locus of self-control d. Primary reasons cited by elderly for not routinely using hearing aids: poor benefit, particularly in noise, restaurants, and large groups (Kochkin & MarkeTrak, 2000) 6. Basic research - Implications for auditory rehabilitation (Chisolm et al., 2003) a. Complex interaction of biological aging in the peripheral and central auditory systems with peripheral pathology b. Plasticity — Changes in auditory input due to peripheral pathology result in hearing loss–induced plasticity in the central auditory system (e.g., regions previously responsive to high-frequency sounds become tuned to lower-frequency sounds with high-frequency hearing loss) i. Therefore, amplification of high-frequency sounds may not necessarily result in improved auditory function ii. On the other hand, amplification of lower-frequency sounds may improve function iii. Some evidence suggests that speech understanding in new hearing aid users improves over time (auditory acclimatization effect) — this is particularly true of sounds that were inaudible prior to use of amplification (Philibert et al., 2005) c. Auditory deprivation effect i. In monaurally aided individuals with bilateral sensorineural hearing loss, unaided ears display degraded suprathreshold speech recognition performance ii. Speech recognition improves after a hearing aid is fitted to the previously unaided ear iii. These findings are consistent with plasticity in the central auditory system iv. Implication: When possible, fit both ears with hearing aids d. Age-related sensorineural pathology may be modulated by use of amplification i. Animal studies suggest that an augmented acoustic environment can slow (not reverse) progressive sensorineural hearing loss ii. Implication: Start use of hearing aids earlier rather than later 7. Advantages of binaural hearing aids a. Provide binaural summation — hearing threshold improvement that occurs when listening with two ears as opposed to one ear b. Provide binaural squelch — ability to “tune out” unwanted noise c. Auditory deprivation effect — lack of amplification leads to decline in word recognition (Silverman et al., 2006; also see above) 8. Factors influencing hearing aid choice — complex and multifactorial; this section will highlight some key factors; see Johnson et al., 2001 and Hanratty & Lawlor, 2000 for more complete overviews. In general, individual factors have to be taken into account to determine the right type of hearing aid for that individual (not “one size fits all”): a. Patient factors i. Hearing 1. Pure tone audiogram 2. Dynamic range 3. Loudness levels — most comfortable and uncomfortable 4. Speech recognition threshold 5. Word recognition ii. Physical 1. Manual dexterity, fine motor skills, ability to raise arm to level of ears (i.e., consider severity of arthritis), and visual status 2. Outer ear: shape, external canal length, mobility in outer 1/3 of canal, TMJ problems, exostoses/osteomas, mastoid bowl, canal eczema/otitis external, cerumen impaction iii. Psychosocial 1. Attitude, motivation, cognitive impairment, depression, social support and demands 9. Prescriptive rules (e.g., half-gain rule) a. Techniques used by audiologist in decision making b. Use loudness levels that are most comfortable/uncomfortable to calculate amplification needed c. Optimize understanding of conversational speech by using amplification levels that can be tolerated by the patient 10. Hearing aid types a. Vary from adjustable analog to programmable multi-microphone digital i. In general, the programmable digital aid offers greater flexibility and improved patient satisfaction; however, cost is significantly higher 1. Particularly suitable for patients with unusual audiometric configuration (take advantage of multiple frequency bands for matching targets and manipulating compression parameters) and also patients residing in reverberant, noisy environments b. Behind-the-ear (BTE), in-the ear (ITE), and completely-in-canal (CIC) i. BTE — for mild to profound losses, versatile (newer models are miniaturized, can be combined with open-fit molds) ii. ITE — for mild to severe losses 1. Feedback (sound leaking out of hearing aid getting amplified again, due to proximity of receiver and microphone) a problem for severe losses 2. “Occlusion effect” (good low-frequency hearing results in plugged-up effect and may make patient’s voice resonate) a. Reduced by use of vent hole iii. CIC — popular largely due to cosmetic appeal 1. Appropriate for hearing losses up to 60 dB HL in the low frequencies and up to 80 dB HL in middle to high frequencies 2. Special considerations for three types of hearing losses a. Flat or reverse-slope losses (out of CIC may not reach low-frequency targets); consider using two- channel digital programmable CIC aid b. Normal thresholds up to 2000 Hz followed by sharply sloping losses i. “Occlusion effect” — consider “step microphones” that eliminate gain below 1500 Hz in a two-channel digital programmable CIC aid c. CIC aids do not offer adequate gain required for severe to profound hearing losses 11. Hearing aid features — e.g., Siemens Centra hearing aids a. SoundSmoothing™ technology — recognizes and reduces annoying noises like rustling paper, clanging dishes, and breaking glass, while preserving the sound of voices and conversations b. DataLearning™ — learns based on patient volume changes, and automatically adjusts itself to match patient preferences c. e2e wireless™ communication — keeps patient instruments properly balanced at all times, so patient can tell where sounds are coming from; also makes instruments easier to use by enabling patient to control the volume and program of both instruments at the same time d. Advanced Adaptive Feedback Cancellation — reduces or eliminates the high-pitched whistling common with many other hearing instruments e. eWindScreen — an electronic system that detects wind conditions and adapts automatically to reduce annoying wind noise f. Directional Microphone System — automatically adapts to patient listening environment and can reduce multiple noise sources, making it easier to focus on speech and conversations g. BTE housings are gold-plated from the inside to ensure disturbance-free operation with mobile phones h. AutoPhone feature — telecoils that are automatically engaged when the wearer uses a hearing instrument–compatible phone i. Of note: integration of frequency modulation (FM) systems into BTE systems can further improve listening in reverberant environments (Chisholm et al., 2004) 12. Cochlear implants a. Criteria i. Bilateral, severe to profound sensorineural hearing loss (i.e., 70 dB or greater pure-tone average at 500, 1000, and 2000 Hz) ii. Limited benefit from an adequately fitted binaural hearing aid iii. Sentence recognition score of 50% or less in the ear to be implanted and 60% or less in contralateral ear in best-aided conditions b. Patients over 60 years of age with cochlear implants demonstrate similar speech perception gains as younger patients with cochlear implants (Herzog et al., 2003; Monsier et al., 2004) i. However, older patients need more time to reach the same level of performance as that of younger patients after implantation (up to 3 years, or 4 years when signal-to-noise ratio was 15%)