Cochlear Implants Flashcards

cochlear implant
Terms Definitions
Reasons that people do not like HAs?
-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___
-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...
-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...
BAHA = CHL, Mixed HL single sided deafnessMI IMPLANTS = SNHL (now mixed and conductive too)CI/ABI = profound SNHL
What is a CI?
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 upHINT (hearing in noise test)50% or less speech for implant
FMRI and PET scans are used in assessing candidacy why?
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?
-etiology of HL-degree of HL-intelligence-oral communication vs use of ASL-
How to decide which ear to implant?
-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...
-length of deafness-age of onset-age of implantation (in children)-recency of hearing aid use-lip reading skill
Typical etiologies seen?
-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
-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?
-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 lossesVibrant 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...
-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
-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?
provides loudness summation-provides elimination of head shadow effect-sound localization-improved speech intelligibility in noise-spatial balance
What does transpositional technology do?
-device selectively moves high frequency information into the lower frequency bandwidth, where residual hearing exists. -usually training is needed
What is EAS
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?
-electrode design & insertion-speech processing strategy-quantity & quality of auditory input
What variables internal to each individual patient may affect CI performance?
-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
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
-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
-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...
under 2 yrs = Prevnar, Pneumovax at 2 yrsPrevnar for 2-4 with phneumovax if not fully vaccinated5 to adult Pneumovaxover 65 a second dose of Pneumovax
Measurements being done in the background by audiologist during surgery.
-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 ORNEURAL RESPONSE TELEMETRY used
What is considered a good implant electrode? (in surgery)
-modiolar proximity-channel selectivity-reduced current requirements-deep insertion-cochlear patency-minimal insertion trauma
Adult Cochlear Implant Candidacy criteria
(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
-Demonstrated lack of benefit from conventional HAs-radiological evidence that it is feasible to insert the electrode
Reasons to implant children
-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
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.
-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
Goal of cochlear implant pre-evaluation?
-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?
-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
-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?
1. a shorter duration of deafness in the ear to be implanted2. 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 preservedselection should use one or both factors
Steps in Initial Stimulation session
-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
Initial stimulation-assessing electrode impedances-verifying that no adverse response occurs with stimulationobtaining (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?
-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?
CNC Consonant Nucleus Consonanttest - can get credit for # of phonemes correct and the whold word correct
HINT =
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
-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?
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
-electrode outside cochlea-dehiscent cochlea (fluid leakage)-programming variables such as intense stimulation levels, pulse widths inopportune, stimulation speec
New trends in Implantationsexpanding indications
-residual hearing-younger children-bilateral implantsestimate = 750,000 potential CI candidates. only 70,000 have received them so far
Why is cholesteatoma life threatening?
-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
-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
-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
-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
-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
-must act on an intact ME-must be reversable w/no alteration of ME or IN functiondevices & 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
-high cost-possible requirement for revision surgery-inability to try different types-precludes MRIs
Candidacy for Otologics MET
-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
-vestibular disorders including Menieres-Osteodegenerative disorders including PagetsME 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?
-persons with atresia (conductive)-expanded to mixed HL-now also unilateral SNHL
BAHA can be used for :
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
-adults & children over 5 yrs-BC threshold cannot exceed 45dBHL for BAHA classic , cannot exceed 65dB for Cordelle IIpractical 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
-processor (external)-abutment (external)-implant (titanium screw)
After BAHA implantation how long before loading?
3 months for adults6 months for kidsWazwen found6 wks for adults4 mths for children
MAIS = meaningful Auditory Integration surveyESP= early speech perception (closed set)MLNT = Multisyllable lexical neighborhood test (open set)LNT = Lexical Neighborhood Test (open set)
PSI = pediatric Speech intelligibility (closed setCIDMACSPIN= Speech perception in noiseMTS= monosyllable Trochee Spondee TestPIPSL = performance inventory for profound & severe loss -self perception
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