HELP FOR THE HEARING IMPAIRED
| INNOVATIVE APPROACHES TO AUDITORY REHABILITATION —Robert Sweetow, PhD, Professor of Otolaryngology
and Director of Audiology, University of California, San Francisco, School of Medicine
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| Problems with modern hearing aids: inability to resolve impaired frequency and temporal resolution; inability to resolve
maladaptive listening strategies (eg, bluffing, asking for repeats rather than rephrases, social isolation) developed
by patients before fitting for hearing aid (usually 7 yr from first noticing hearing loss to seeking help); inability
to reverse neuroplastic effects of years of peripheral attenuation
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| Effects of older age: decreased speed of processing; decreased auditory working memory (ie, not listening in real-
time; use memory of what was just said, real-time hearing for what is being said, and knowledge of linguistics and
context to predict what will be said next; listening in past and future); susceptibility to distraction from external
stimuli (eg, noise, visual, emotional) due to decreased executive control, (ability to decide immediately what to attend
to); even without hearing loss (HL), older people require higher signal-to-noise ratio (SNR)
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| Listening: while hearing is access to acoustic information, listening requires hearing, attention, and intention; moving
from listening to comprehension requires acoustic and linguistic knowledge; communication bidirectional and
involves manipulation of environment; only 20% of people with hearing loss wear hearing aids
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| Listening and Communication Enhancement (LACE): program developed by speaker; inexpensive; practical;
easily accessible; conducted in patient’s home; interactive and at patient’s pace; difficult enough to keep patient’s
interest, but not so difficult that patient becomes fatigued; trains near learning threshold; integrated with
repair strategies (to manipulate environment); gives feedback to patient about progress; can be verified remotely
via Health Insurance Portability and Accountability Act (HIPAA)-compliant Web site; makes patient responsible;
4 areas of training —degraded and competing speech (eg, background noise, 1 competing speaker); compressed
speech; cognitive (eg, auditory memory, speed of processing); context and linguistics to fill in gaps; interactive
communication strategies; all designed to enhance listening and improve confidence
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| LACE training: individualized based on patient need (eg, listening in noise, fast speech); patient chooses topic because
general understanding of topic helps communication; patient hears sentence; screen shows sentence and asks
patient if understood correctly; feedback provided; if answered correctly, next sentence more difficult (adjusting
SNR by few decibels [dB]); if answer wrong, next sentence easier; training in patient’s comfort zone; degraded speech
—patient hears at rapid, compressed pace; correct answer increases pace in next example; if incorrect, next example
slower; feedback provided; cognitive skills — enhance auditory memory; target words and sentences; asked
which word precedes target word; if correct, target word first, then sentences; target words increased; missing word
—score based on correct answer and speed of answer; helpful hints interspersed in training; sessions last 30 min
daily, 5 days/wk for 4 wk; at end of each session, patient shown graph depicting progress on each task for each day;
audiologist logs on to computer and can alter task, based on patient’s progress, and provide feedback
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| LACE multisite study: reported in Journal of the American Academy of Audiology; determined differences between procedural
(task) learning and perceptual learning; significant improvement in each training area; does this generalize to real
world? outcome measures include QuickSin, Hearing In Noise Test (HINT), and subjective Hearing Handicap Inventory
for the Elderly (HHIE); lasts “beautifully” for 2 mo; some groups start to fade at 6 mo; booster training implemented
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| Other online training programs: one using melodies; some used for cochlear implant patients; LACE translated
into other languages; adapting LACE for cochlear implant patients; costs <$100 per patient, sometimes free; other
programs (involving pressing buttons) for cochlear implant patients; program incorporating speech reading and auditory
training in early stages of development
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| Conclusion: best training parameters still not known; patients become better listeners; training generalizes beyond training
tasks; lasts over extended period for some patients; substantially affected return of hearing aids for credit; training provided
to patients who cannot hear in noisy environment; majority of patients do not comply; hearing aid patients benefit
from listening enhancement training; recommended by audiologists; program available from www.lacecentral.com
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| IMPLANTABLE HEARING AIDS — Lawrence R. Lustig, MD, Associate Professor of Otolaryngology, Department
of Otolaryngology – Head and Neck Surgery, University of California, San Francisco, School of Medicine
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| Hearing aids: advances — analog to digital; nonprogrammable to programmable; advantages — noninvasive, replaceable,
removable, programmable; improved technology; binaural; however, used by only 1 in 8 eligible adults;
disadvantages — cost (up to $3000 to $4000 per aid); inadequate loudness without distortion; inability to distinguish
voices in crowd; feedback; social stigma (decreasing); occlusion effect (less problematic with newer aids); incompatible
with some underlying medical problems (eg, recurrent otitis media [OM] or otitis externa [OE]); ongoing expense
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| Middle ear implantable hearing aids (MEHAs): design elements — microphone; signal processor; differ in sound
transduction (piezoelectric or electromechanical) and attachment to hearing mechanism (coupled to incus or stapes);
St. Croix Envoy — speaker’s favorite design; uses malleus as sensor, ie, takes advantage of sound processing by ear
canal before sending sound to processor that sends it to stapes; incus must be removed; Symphonix Vibrant SoundBridge
— couples floating mass transducer directly to incus; no need to remove ossicles; theoretically removable if
patient does not like device; Middle Ear Transducer (MET) — US trials on hold; enters through mastoid, couples
transducer into incus; powerful amplification; device companies — most no longer in business; surgeons must think
of company viability before inserting device; advantages of MEHAs — tolerated longer than conventional maximum
amplification behind-the-ear aids; have larger gains; no occlusion effect; no feedback; better perceived sound quality;
disadvantages —expensive; not covered by insurance; surgical risks, eg, ossicular disruption; gains not impressive
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Bone Anchored Hearing Aid (BAHA)
| Candidates: patients unable to tolerate conventional hearing aid because of large mastoid bowl, chronic OM, OE,
or otorrhea; patients with otosclerosis, tympanosclerosis, or atresia in whom surgical repair contraindicated (results
as good or better than surgery); patients who need closure of ear canal for skull base lesions
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| Advantages: simple and easily incorporated into practice; reduced pain, headache, and skin irritation
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| Hakansson study: 10 yr; if bone conduction threshold <45 dB, 89% of patients had significant hearing improvement
(best candidates); if threshold 45 to 60 dB, ≈60% improvement (intermediate candidates); if threshold >60 dB, 20%
improvement; need good cochlear reserve; larger device (Cordell) broadens criteria by giving more amplification;
advantage for for aural atresia — closes air-bone gap; combined with prosthetic device, BAHA creates functional
hearing with almost no surgical risk; alternative for atresia patients unwilling to undergo surgery; for implant to
work, needs direct contact with bone and surrounding tissue
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| Surgical principles: aim for result similar to skin over fingernail, ie, skin over bone with no intervening soft tissue;
limits skin motion and irritation at cutaneous-implant junction; operation takes 30 min; single implant for
BAHA; 3 surgeries with prosthetic ear; meticulous, gentle insertion with no bone damage
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 | Creating flap: done by hand or dermatome; elevate flap; critical to get skin “extraordinarily thin,” similar to full thickness
skin graft; speaker leaves periosteum down; thin skin through soft tissue and subcutaneous fat until hair follicles
seen; flap should be semi-translucent and follicle-free
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| Implantation of BAHA: undermine soft tissue in 1- to 1.5-cm surrounding; do not want large stepoff between flap
and surrounding tissue; for drilling hole, use copious irrigation and 3-mm burr, then 4-mm burr if enough bone
left over; countersink must be same size as central post of implant; remove extra bone; irrigate well to avoid thermal
damage; implant single stage with abutment attached to implant; drill at low torque; automated, straightforward
procedure; tap and screw implant at same point; drill automatically stops at appropriate tightness; speaker
performs tap test at end to ensure tightness (one eighth to one fourth turn), listens for “ping”; do not overtighten
(can fracture thin bone threads); snap coupling and implant now single unit; close incision
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| BAHA results: 40 patients; 32 dB average improvement; almost complete closure of air-bone gap (10 dB in 80%, 5
dB in 60%, overclosure in one third of patients); results excellent, regardless of pathology; few complications, eg,
small reaction at cutaneous-implant junction
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| Unilateral sensorineural HL (SNHL): limited soundfield; inability to localize sound; reduced speech understanding
in noise; previous options — Contralateral Routing of Offside Signal (CROS) hearing aid; deep canal aid; Audiant
(similar to BAHA) used with limited success; 2003 study — 10 patients; vestibular schwannoma, sudden HL, meningitis
or chronic OM with HL; normal hearing in contralateral ear; biggest gain with hearing in noise; BAHA provided
advantage over hearing with unaided ear or CROS aid in noisy background; patients preferred BAHA over
CROS aid; most patients still unable to localize sound; evidence that some patients able to localize some sounds after
≈6 mo
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| Cochlear Implants — Nikolas H. Blevins, MD, Assistant Professor, Department of Otolaryngology – Head and Neck
Surgery, Stanford University School of Medicine, Palo Alto, CA
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| Candidates: eligibility changed; was >80 to 90 dB pure tone average and almost no speech or word recognition;
over last 10 yr, shift to 70 dB pure tone threshold and up to 50% in HINT testing; “moving down pyramid”; opening
technology to more patients, from no hearing to severe loss to hybrid devices for moderate loss; results improve
safety and environmental awareness, speech reading cues, and understanding speech; improvement needed in hearing
in noise and music enjoyment
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| Factors affecting performance: external — development of new technology; way sound delivered; signal processing;
patient — etiology of HL; neural survival (important for getting cochlear implant signal to brain); processing;
age of onset of deafness; duration; language development prior to HL; patient’s motivation and expectations;
auditory skills decline with time, as neural degeneration occurs; timing of implantation critical for pediatric patients
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| Animal studies: good functional connections in auditory pathway at birth, even in deaf animals (pathways later lost);
protection of auditory pathway occurs at cellular level
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| Human studies: Scharma — studies on cortical potentials; P1 potential (occurs at 100 msec); end point in measurement
of auditory electrical pathway; present in neonates; shortening over time indicative of normal myelinization
and maturation of central auditory pathway; patients implanted early (<3 yr of age) comparable to normal-hearing
individuals, and this continues through maturity; latency shortens, ie, central pathways protected; patients who received
implant after 7 yr of age do not fall into normal range, with few exceptions; patients implanted at 3.5 to 6 yr
of age in between
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| Clinical perspective: studies show earlier implantation allows better language development; categories of auditory performance
(CAP) measure of language development in prelingual children; children — if implanted at 1 yr of age, track
with peers who hear normally; if implanted at 2 to 3 yr of age, catch up but takes longer; for children implanted between
3 and 4 yr of age, slope of curve never catches up; children identified at birth implanted at 1 yr of age, earlier in
cases of meningitis and risk for labyrinthitis ossificans; geriatric patients — consider changes in central nervous system
processing, length of deafness (affects outcome), and longer rehabilitation process; patients 80 to 90 yr of age can
receive implants; marginal populations — eg, prelingual teens and adults with no hearing using American Sign Language
(ASL) and manual communication can benefit from implantation; must be informed of expectations; will not be
“star performers,” compared to those with spoken language; some may gain sensation, not hearing, but benefits significant
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| Coding strategies: ways to deliver sound to auditory nerve (external factors); traditional implants — presented information
in amplitude-modulated (AM) form, taking envelope of maximal energy of sound wave and matching energy
with pulses of varying strengths; discarded frequency information (FM) that goes into complex auditory signal; new
mechanisms — combining AM and FM to change amplitude and frequency of pulses entering inner ear; better appreciation
of fine structure of sound; improves hearing in noise and discernment of subtleties in music; beneficial for individuals
with contralateral hearing aid; improves hearing in background noise and appreciation of music; current
steering (virtual electrodes) — each electrode stimulates neural elements immediately next to it; by varying degrees of
stimulation on adjacent electrodes, can reach neuron population in discrete intervals between electrodes; results in
greater spatial resolution along basilar membrane or organ of Corti and hits greater frequency-specific neuron populations;
Advanced Bionics device will have 120 virtual electrodes
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| Implantation: not clear which ear better for placement of implant; speaker now using worse ear, assuming benefit from
hearing aid in better ear (augments information coming in from implant); anatomic and surgical considerations; bilateral
implantation performed in 1600 children and 1200 adults worldwide; shown beneficial in well-selected patients; guarantees
implantation of better ear; patients report subjective improvement (sounds more natural); in children, implant at
same time or within 18 mo; weigh against potential downside of vestibular effects and future therapies
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| New technologies: electroacoustic hybrid devices — in clinical trials; most losses high frequency at basal turn of
cochlea and surgically accessible to short arrays; possible to place short arrays in basal turn of cochlea and preserve
apical portions for acoustic hearing; improvement over hearing aid at 3 and 6 mo, compared to traditional implant
at corresponding time; speaker’s research — applying visualization (direct guidance) of inner ear navigation and
intervention through microendoscopy; eventually tailoring information to specific patient needs
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Suggested Reading
Backous DD, Duke W: Implantable middle ear hearing devices: current state of technology and market challenges.
Curr Opin Otolaryngol Head Neck Surg 14:314, 2006; Bauer PW et al: Central auditory development in children with
bilateral cochlear implants. Arch Otolaryngol Head Neck Surg 132:1133, 2006; Chang JE et al: Unintelligible low-frequency
sound enhances simulated cochlear-implant speech recognition in noise. IEEE Trans Biomed Eng 53:2598,
2006; Clark GM: The multiple-channel cochlear implant: the interface between sound and the central nervous system
for hearing, speech, and language in deaf people-a personal perspective. Philos Trans R Soc Lond B Biol Sci 29:791,
2006; Davids T et al: Bone-anchored hearing AIDS in infants and children younger than 5 years. Arch Otolaryngol
Head Neck Surg 133:51, 2007; Evans AK, Kazahaya K: Canal atresia: "Surgery or implantable hearing devices? The
expert's question is revisited". Int J Pediatr Otorhinolaryngol 71:367, 2007; Hakansson et al: The bone anchored hearing
aid: principle, design, and audiometric results. Ear Nose Throat J 73:670, 1994; Hickson L et al: Measuring outcomes
of a communication program for older people with hearing impairment using the International Outcome
Inventory. Int J Audiol 45:238, 2006; Kiefer J et al: Round window stimulation with an implantable hearing aid
(Soundbridge) combined with autogenous reconstruction of the auricle — a new approach. ORL J Otorhinolaryngol
Relat Spec 68:378, 2006; Kramer SE et al: A home education program for older adults with hearing impairment and
their significant others: a randomized trial evaluating short- and long-term effects. Int J Audiol 44:255, 2005; Lin LM
et al: Amplification in the rehabilitation of unilateral deafness: speech in noise and directional hearing effects with
bone-anchored hearing and contralateral routing of signal amplification. Otol Neurotol 27:172, 2006; Neuman AC:
Central auditory system plasticity and aural rehabilitation of adults. J Rehabil Res Dev 42:169, 2005; Pichora-Fuller
MK, Singh G: Effects of age on auditory and cognitive processing: implications for hearing aid fitting and audiologic
rehabilitation. Trends Amplif 10:29, 2006; Schmuziger N et al: Long-term assessment after implantation of the Vibrant
Soundbridge device. Otol Neurotol 27:183, 2006; Sharma A et al: Rapid development of cortical auditory evoked potentials
after early cochlear implantation. Neuroreport 19:1365, 2002; Siegert R et al: Fully implantable hearing aids in
patients with congenital auricular atresia. Laryngoscope 117:336, 2007; Sweetow RW et al: The need for and development
of an adaptive Listening and Communication Enhancement (LACE) Program. J Am Acad Audiol 17:538, 2006.
Educational Objectives
The purpose of this program is to improve the management of hearing impaired patients. After hearing and assimilating
this program, the clinician will be better able to:
| 1. Discuss the attributes and problems associated with different types of hearing aids.
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| 2. Summarize the components of the Listening and Communication Enhancement (LACE) program.
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| 3. Review the surgical principles involved in implanting a bone anchored hearing aid.
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| 4. Summarize the factors affecting performance of cochlear implants.
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| 5. Discuss when cochlear implants should be inserted.
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Faculty Disclosure
In adherence to ACCME guidelines, the Audio-Digest Foundation requests all lecturers to disclose any significant financial
relationship with the manufacturer or provider of any commercial product or service discussed. For this issue,
Dr. Sweetow has disclosed that he is a stockholder in Neurotone.
Acknowledgements
Drs. Sweetow, Lustig, and Blevins addressed the Stanford Otology and Neurotology Update 2006, held November 2-4,
2006, in San Francisco, CA, and sponsored by the Department of Otolaryngology – Head and Neck Surgery, Stanford
University School of Medicine, Palo Alto, CA. The Audio-Digest Foundation thanks the speakers, and Stanford University
School of Medicine for their cooperation in the production of this program.
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