Cochlear Implants
Terms
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- Reasons that people do not like HAs?
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-poor benefit
-poor performance in background noise
-fit & comfort
-neg. side effects like infections, itching and wax buildup
-feedback problems
-stigma of wearing a hearing aid - Considered the standard of care is to have all unilateral CI recipients utilize___
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-a hearing aid on their non implanted ear if the residual hearing in that ear is capable of providing binaural advantage
-many CI users do not have enough residual hearing to make it worthwhile so the only way to provide effective binaural hearing is through bilateral cochlear implantation - The use of a prosthetic device implies...
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-that we are replacing function
- providing a device that will substitute for function
-In CIs the electrode goes into the cochlea but acts on the VIII nerve - Devices and types of HL that indicate them...
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BAHA = CHL, Mixed HL single sided deafness
MI IMPLANTS = SNHL (now mixed and conductive too)
CI/ABI = profound SNHL - What is a CI?
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An implantable electronic prosthetic device:
-for severe or profound HL
-to gain access to sound & improved speech perception
-via electrical stimulation of the auditory nerve -
Criteria for candidacy of CI is still???
The FDA requires what testing before implantation? -
Severe or profound SNHL
-but criteria is loosening up
HINT (hearing in noise test)
50% or less speech for implant - FMRI and PET scans are used in assessing candidacy why?
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to evaluate how auditory cortex exhibits plasticity in late-deafened adults and
-to determine if the degree of plasticity can be used to predict the surgical outcome of electrical stimulation via CIs - Non-predictive factors for CI success?
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-etiology of HL
-degree of HL
-intelligence
-oral communication vs use of ASL
- - How to decide which ear to implant?
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-conformance to criteria
-anatomical requirements
-may ony be able to insert electrode on 1 side
-surgeons handedness/preference
-patient preference
-current HA usage and percieved residual hearing - Predictive factors that may have an effect of whether or not CI will be successful...
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-length of deafness
-age of onset
-age of implantation (in children)
-recency of hearing aid use
-lip reading skill - Typical etiologies seen?
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-ototoxicity
-Meniere's complex
-sudden HL/autoimmune disease
-trauma (excluding temporal bone fractures that sever the VIII nerve)
-noise exposure
-infection , rubella syphilis, congenital hearing loss, including connexin 26 - Advantages post CI patients percieve
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-environmental sound perception
-psychological effects
-speech perception when speech reading cannot be used
-lifestyle & social effects
-speech production
-reduction of tinnitus
-enjoyment of music
-educational achievment
-improved employment opportunities - more possible benefits from CI?
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-benefit to lipreading/communication
-speech & language development
-changes in quality of life - Expanding domain of implantable hearing devices...
- BAHA - for cond losses where HAs not possible or mixed losses Vibrant sound Bridge -(middle ear implant) for sloping mild to severe SNHL when speech recog >50% CI - for sever to profound HL , severe cochlear damage but intact 8th nerve. Speech recognition
- Adult studies on Adult binaural implantation...
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-the more adverse the signal to noise,the greater the benefit
-subjects significant improvments in speech understanding in noise (mostly due to head shadow effect)
-subjects had significantly better speech understanding in quiet than unilateral patients(you always capture the better ear)
-binaural advantage
-all subjects demonstrated improved localization ability primarily due to detection of interaural intensity differences
-subjectively report significant improvements in performance with 2 cochlear implants - Catagories of audiologic assessment for fittings
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-unaided
-aided-soundfield sensitivity,speech recognition,
-assessment with competing technology
-phonemic information transfer
-sentence level
-performance in noise
-device simulator if possible
-Baha headband -
Head shadow effect is more pronounced for what frequencies?
when the lead is between the auditory signal & the good ear, the sound is attenuated by about... -
high frequencies.
10-16dB on the side of the impaired ear at 1000 Hz, by the time it reaches the good ear - Advantages of Binaural hearing?
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provides loudness summation
-provides elimination of head shadow effect
-sound localization
-improved speech intelligibility in noise
-spatial balance - What does transpositional technology do?
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-device selectively moves high frequency information into the lower frequency bandwidth, where residual hearing exists.
-usually training is needed - What is EAS
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Electric Acoustic Stimulation = CI plus HA in the other side with residual hearing.
-benefits of preserved residual low frequency hearing
-improved word understanding in noise
-music appreciation - What variables external to each individual patient may affect performance for CI?
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-electrode design & insertion
-speech processing strategy
-quantity & quality of auditory input - What variables internal to each individual patient may affect CI performance?
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-physiological factors like quality and quantity of neural survival
-central auditory processing ability
-cognitive ability
-motivation - Even the best available imaging cannot reliably provide a measure of the quantity of ____ ___ ____ in the cochlea, which are thought to be important for successful electrical stimulation
- spiral ganglion cells
- The available evidence indicates that implant benefit is achieved ____ over a ____ period of time
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slowly over a long period of time
-it is clear that functional experience with the implant contributes to the ultimate outcome.
-Whether reflected in speech perception, expressive language or speech production, the trajectory of change follows at a time course that may not reach an asymptote until 3 or more years post implantation - capabilities of CI processors
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-interface with computers with proprietary software for programming
-multiple programs
-either through software or hard wired switches
-telephone compatible
-inputs available for accessories such as ALDs - Surgical risks of Cochlear implant surgery
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-takes 2-4 hours
-facial paralysis
-dizziness
-tinnitus
-loss of residual hearing (if any)
-no improvement in hearing (if it doesn't work)
-risks attributable to general anesthesia - Vaccines recommended when implanted...
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under 2 yrs = Prevnar, Pneumovax at 2 yrs
Prevnar for 2-4 with phneumovax if not fully vaccinated
5 to adult Pneumovax
over 65 a second dose of Pneumovax
- Measurements being done in the background by audiologist during surgery.
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-verification of the integrity of the electrode
-determination of "open circuits", may reflect breaks in the electrodes
-sometime air bubbles can cause this transient effect or could be failure to communicate with electrode in OR
NEURAL RESPONSE TELEMETRY used - What is considered a good implant electrode? (in surgery)
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-modiolar proximity
-channel selectivity
-reduced current requirements
-deep insertion
-cochlear patency
-minimal insertion trauma - Adult Cochlear Implant Candidacy criteria
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(18 or older)
-Moderate to profound SNHL bilaterally
-50% or less sentence recognition (in ear to be implanted)
-60% or less sentence recognition in opposite ear or binaurally
-pro or post linguistic onset of moderate to profound SNHL
-no medical contraindications
-a desire to be in the hearing world. - More criteria for Adults for CIs
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-Demonstrated lack of benefit from conventional HAs
-radiological evidence that it is feasible to insert the electrode
- Reasons to implant children
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-many profoundly deaf children acquire spoken language with CIs, an accomplishment realized by few deaf children who use conventional HAs
-Children with CI often function as well as children with less severe hearing impairments, allowing them to acquire spoken language through incidental learing
-consequently, deaf children with implants are educated in less restrictive environments and may require fewer educational special support services than their peers with HAs - CI selection criteria for infants
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12-24 months
-profound SNHL
-lack of progress in auditory skills using conventional HA:
babbling, localization, speech stimulability
-radiological evidence that it is feasible to insert electrode
- Infant criteria cont.
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-medically able to undergo surgery
-etiology consistant with cochlear damage
-Intact VIII nerve -radiological evidence of IAC with contents
-parents psychologically able to understand the risks, benefits and options
-parental realistic expectations - CI selection Criteria for Children
- 25mos to 17yrs 11 mos - severe or profound SNHL -demonstrated lack of benefit from conventional HAs -MLNT scores < or = 30% for 25 mths to 4yr11mos (best aided condition) LNT scores < or = 30% for 5 yrs to 17yr ll mos (best aided condition) -lack of progress in auditory skill development -radiological evidence that it is feasible to insert electrode -medically able to undergo surgery -etiology consistent with cochlear damage if known -intact VIII nerve, radiologic evidence of IAC with contents -Parents psychologically able to understand risks, benefits, and options. -parental realistic expectations
- Goal of cochlear implant pre-evaluation?
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-to determine if a child will gain more benefit from a CI than from HAs
-so except for instances "post meningitis" a HA trial is recommended prior to implantation - Objective test procedures to confirm presence of non-organic element of HL?
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-ABR, click or TB
-ASSR - can differentiate between severe & profound HL (90-110 dBHL)
-OAEs - objective measure of OHC function - usually not recordable in ears with HL > 30dB
[children with auditory neuropathy have been successfully implanted suggesting that neuropathy is a misnomer but perhaps a malfunction of another part of the aud. system ie IHCs] - Protocol for implant team
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-identify candidates/non candidates - counsel them
-post implantation planning - may need psychological counseling. additional vestibular therapy
-protocol is very formalized (check off list)
-genetic evaluation on many teams is a std procedure - Children being evaluated for CI should have thresholds in the sever to profound range therefore will not have OAEs but OAEs are included in the test battery to rule out....
- auditory neuropathy
- Current practice of unilateral cochlear implantation presents the assessment team with a dilemma; which ear is likely to give better listening performance post operatively. 2 main prognostic factors?
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1. a shorter duration of deafness in the ear to be implanted
2. greater residual speech discrimination ability pre-operatively
- the supposition in both cases relates to a presumably higher proportion of spiral ganglion cells likely to be preserved
selection should use one or both factors - Steps in Initial Stimulation session
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-first assessment of integrity of electrode and measurements of electrode impedances
-values of impedances that are too high may reflect break or electrode location at margin or outside the cochlea
- high impedance locations are generally eliminated from mapping process - CI programming
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Initial stimulation
-assessing electrode impedances
-verifying that no adverse response occurs with stimulation
obtaining (via implant) psychoelectric responses - threshold, maximum comfortable loudness, pitch ranking
-attempting to see which available strategy is most adventageous - When programming children, to set comfort level do what?
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-use electrophysiologic data to estimate uncomfortable level
-increase intensity and watch childs response
-mcl is substantially below acoustic reflex responses - The cornerstone of CI evaluation testing is?
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CNC
Consonant Nucleus Consonant
test - can get credit for # of phonemes correct and the whold word correct - HINT =
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Hearing in Noise Test
- administered at a single level of 50dBHL
-scored for words correct
-minimum of 2 lists per condition due to variability of lists
-presented in different signal/noise
-5 to 7 word sentences
-compare to pre-implantaton levels - CID sentences
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-scored on key words
-sentences are too easy now to be used in testing CI patients
-if pt gets key words they get the full score - Mac testing for?
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identification of environmental sounds such as male vs female voice
-most appropriate if person never had hearing or early onset of HL - Causes of facial stimulation in CI users
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-electrode outside cochlea
-dehiscent cochlea (fluid leakage)
-programming variables such as intense stimulation levels, pulse widths inopportune, stimulation speec -
New trends in Implantations
expanding indications -
-residual hearing
-younger children
-bilateral implants
estimate = 750,000 potential CI candidates.
only 70,000 have received them so far - Why is cholesteatoma life threatening?
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-it can spread through the mastoid bone and cause meningitis,
-meningitis can get into the meninges
-cholesteatoma can wrap around the facial nerve -surgeon won't touch that
-should never wear an ear mold if you have this because moisture can cause greater risk of spreading infection - complications of meningitis with regarg to implantation
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-inflammation of the meninges, has central potental impact
-causes new bone growth in cochlea
-thus there is time pressure to implant after meningitis
-sometimes electrode insertion requires a drill out - What is a MEHD
- - Any surgically implanted device that converts acoustic energy to mechanical energy and delivers it to a vibratory structure in the middle ear
- IMEHD (implantable middle ear hearing device) summary
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-Ideally no change in bone conduction
-air conduction within 10 dB of preoperative levels
-appropriate gain achieved with varying degrees of hearing loss
-subjectively patients are happy with quality of sound
-better cosmesis
-precludes occlusion effect
-improves sound fidelity
-avoidance of feedback
-increase in high frequency gain - Intent of IMEHDs
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-simplify a 3 steps process to a 2 steps process
-direct drivers of the ossicular chain
-transduction of amplified electrical to acoustic then to vibrational energy
-trandsuction from electrical directly to vibrational energy - General risks of IMEHDs
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-compared to stapes surgery
-long term injury to ossicular chain
-risks to facial nerve
-general anesthesia risks
-possiblity of total loss of hearing
-multiple surgeries to replace battery
-not MRI compatible - International consensus on MEIs 2004
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-must act on an intact ME
-must be reversable w/no alteration of ME or IN function
devices & surgical procedures should be designed for replacement w/o hearing loss int the future due to device malfunction or availabilility of new technology
-anchoring system must be easy and safe to affix to ossicular chain
-must keep EAM clear
-dynamic range -accomodate HL w/o distortion, measureable
-should be adaptable
- Disadvantages of MEI
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-high cost
-possible requirement for revision surgery
-inability to try different types
-precludes MRIs - Candidacy for Otologics MET
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-18 yrs of age or older
-bilaterally symmetrical (w/20dB)moderate to severe SNHL within the audiogram range
-high freq pure tone avg 40-80dBHL or 40dBSL in ear to be implanted
-post linguistic HL
-non fluctuating, stable HL
-normal ear anatomy
-trial with conventional HA first
-English speaking
-realistic expectations - Otologic MET exclusion criteria
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-vestibular disorders including Menieres
-Osteodegenerative disorders including Pagets
ME pathology including recurrent OM
-conductive or mixed HL
-non organic HL
-retrocochlear HL
-pre linguistic onset of HL
-medical contraindications - Originally BAHAs were intended for what type of HL?
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-persons with atresia (conductive)
-expanded to mixed HL
-now also unilateral SNHL - BAHA can be used for :
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Bilateral conductive or mixed HL, includes such pathologies as:
-congenital aural atresia
-draining mastoid cavities
-recurring otitis externa
-individual patient review may make unilateral HL a good candidate - BAHA candidate criteria
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-adults & children over 5 yrs
-BC threshold cannot exceed 45dBHL for BAHA classic , cannot exceed 65dB for Cordelle II
practical considerations
-manual dexterity, range of motion of arm, availability of assistance with visual inspection
-support resources
-realistic expectations
-absence of psychological or social contraindications - 3 parts of the BAHA
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-processor (external)
-abutment (external)
-implant (titanium screw) - After BAHA implantation how long before loading?
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3 months for adults
6 months for kids
Wazwen found
6 wks for adults
4 mths for children -
MAIS = meaningful Auditory Integration survey
ESP= early speech perception (closed set)
MLNT = Multisyllable lexical neighborhood test (open set)
LNT = Lexical Neighborhood Test (open set) -
PSI = pediatric Speech intelligibility (closed set
CID
MAC
SPIN= Speech perception in noise
MTS= monosyllable Trochee Spondee Test
PIPSL = performance inventory for profound & severe loss -self perception