Cochlear Implants
(Re)habilitation
* Long-term process for children * Emphasis on auditory training (Iearning to recognize and understand speech) * Typically followup (after first 12 months) is every 6 months and then annually * Adjustments are made if/when needed (monitor children's behavior / auditory responsiveness) * Administer questionnaires
CI Programming
* Mapping (process of PROGRAMMING speech processor) * Threshold (T-Levels, amount of electical stim to detect sound) * Comfort (C or M levels, max electrical stim before discomfort) * Dynamic Range (difference between T and C levels)
Pediatric CI Eval (Audiologic)
*Child may be as young as 3-4 months 1. Meet with family, educational specialist (discuss goals, review loss, genetics counseling, CI technology, realistic expectations, methodology [oral or ASL], mentor for support) 2. Behavioral Testing (VRA or Play, Unaided and aided) 3. Objective Measurements (ABR, OAEs, Tympanometry, ARTs) 4. Speech Perception Testing (goal is to determine if child is receiving enough benefit from HAs to develope spoken language, depending on age of child it can be done via speech perception testing or parent questionnaire)
How are CIs Different than HAs?
*HA 1. Amplify sounds and utlize existing acoustic hearing mech 2. Dependent on integrity of hair cells 3. Only has an external component 4. Surgery not necessary 5. For patients with hearing loss from mild to severe *CI 1. Designed to bypass the damaged structures and stimulate the nerve directly 2. Dependent on an intact neural pathway and auditory cortex 3. Have an external speech processor and internal device 4. Surgically implanted 5. Considered for pts with severe to profound loss
CI Candidacy for Children
- 12+ months - Bilateral, severe to profound SNHL - Limited benefit w/ HA - Lack of progress in auditory skills development - No medical contraindications - Realistic expectations and commitment to F/U - Family motivation
CI Candidacy for Adults
- Bilateral, severe to profound SNHL - Minimal HA benefit - No physical/medical contraindications - Realistic expectations and commitment to F/U - FDA Guidelines (50% or less correct on sentence rec in ear to be implanted, 60% or less in non-implanted ear) - Medicare Guidelines (40% of less correct on sentence recognition in best aided condition
3 Major Manufacturers in US
- Cochlear Corporation - Advanced Bionics - Med-EI Corp (wireless now) *All 3 use different numbers of channels and proprietary speech processing strategies
Surgery
- Day surgery (1 to 2 hours) - General Anesthesia (Mastoidectomy, opening created in cochlea, electrode introduced into basal trun of cochlea, round window sealed, electrode secured)
Goals for Initial Stimulation
- Determine if electrode stimulation produces an auditory senstation - Determine the least amount of curent necessary to produce auditory perception (TH) for each activated electrode - Determine the amount of current, which produces the appropriate perception of loudness (UCL) - Ensure that loudness perception is equal across all activated channels
What is a CI?
- Device that delivers sound to individuals with SEVERE to PROFOUND SNHL - Bypasses damaged structure of inner ear and provides electrical stim to hearing nerve fibers directly - Brain able to recognize this stimulation as sound (neural impulses sent to brain as if cochlea had been stimulated via acoustic input)
Why CI?
- HAs not beneficial for everyone - With little to no residual hearing, acoustic signal may not be recognized - Majority of SNHL is result of hair loss or damage - Typically auditory nerve and central function still intact
Post Operative Management
- Most often outpatient day surgery - Head wrapped but can be removed w/in 1 to 2 days - Healing of incision will take longest - 4 to 6 weeks average recup
Speech Processor Programming
- Sessions take longer with kids than adults - Often takes several appointments - Uses TH and UCL to determine dynamic range - Regular visits scheduled for first 6-12 months (varies)
Tonotopic Organization
-Cochlear implant interfaces with cochlea -Sound is divided in frequency bands -Delivers each frequency band to appropriate region of cochlea -HF sounds of electrode correspond to BASAL end of cochlea -LF sounds at APEX of cochlea
Cochlear Ossification
-Common w/ meningitis -Electrode may be partially inserted -Allows for implantation of some electrodes (maybe 50%) -Can lead to satisfactory results
Possible Complications
-Loss of residual hearing -Infection at implantation site -Fluid accumulation under incision site -Irritatin over site -Facial nerve paralysis -Post-op ME infection -Pain in area of implant site -Facial nerve stim during programming -Risks of anesthesia and surgery -Leakage of perilymph -Risk of meningitis
Benefit May Be Delayed
-Many CI users continue to see steady improvement up to 3 years after implementation -Just because someone did well w/ HA does not mean they will do well w/ a CI -Pre-lingually deafened adults may not improve open-set scores w/ implantation
Why the lack of consistency?
-Perhaps related to bilogical and cognitive factors -Physiologic factors (auditory nerve and central auditory system deficits) may cause poorer performance -Intact systmes may correlate w/ better performance
Recipients
-Post-lingually deafened adults and hcildren -Congenitally (pre-lingually) or early-deafened children -Category may affect outcome
Post-Op Evals
-Same pre-op evals should be readministered post-op -Warble tones in soundfield to determine TH -Closed and open-set speech perception testing -Eval of speechreading abilities
Which Ear?
-Surgical process of implantation can be destructive to the structures of the cochlea -May eliminate any residual hearing or benefit from HA (except hybrid implantations or electro-acoustic stim) -Conventional wisdom is to implant the poorer ear -However, better ear may to better w/ CI due to more surviving hair cells/established neural pathways and connections
Successful CI Users
-Wear device consistently -Have realistic expectations and are satisfied w/ the device -Device helps to monitor the volume of their own voice -CI enables user to detect and recognize enviro sounds -Increases sence of security -Continue to develop improved speech perception
Who is Involved in the Process?
1. AuD 2. Auditory Rehab Specialist 3. SLP 4. Clinical Psychologist 5. Surgeon 6. EI specialists 7. Familiy
Adult CI Eval
1. Audiologic Eval (Air/bone conduction, SRT, aided pure tones, aided baseline speech perception testing [done w/ HAs] 2. OAEs 3. Immittance Testing (Tymp, ARTs)
CI Eval - Device Testing
1. Device Counseling (available devices and diffferences) 2. Review how an implant works 3. Counseling regarding realistic expectations 4. Discussion of timeline for activiatino and F/Us
Internal Components
1. Internal Receiver - Receives signal - Transmits signal to elecrode array 2. Electrode array - Small wire inserted into cochlea usually through the round window - Current passes along the electrodes - Elecrodes stimulate auditory nerve fibers
Ped CI Eval
1. Medical Eval w/ Otologist (MRI/ CT) 2. Development Evaluation - Psychologist (Global Development, Adaptive, Parent Stress) 3. Communication Assessment - SLP
Medical Contraindications
1. Michel Deformity (missing cochlea) 2. Small internal auditory canal syndrome 3. Congenitally absent cochlear nerve 4. Any medical reason for not being able to go under general 5. Preferable if etiology of HL is known
Psychological Assessment
1. Motivation and expectation 2. Parental expectations and attitudes 3. Personality traits that may make program completion unlikely should be identified 4. Psychopathology should be identified and discussed
Medical Assessment
1. Otological case history and physical exam (check for middle ear disease) 2. CT scan of cochlea 3. MRI provides better resolution of soft tissue structures and should supplement the CT scan
To Review:
1. Parents contact CI program 2. AuD counsels parents 3. Eval hearing, auditory skills, HA benefit, and communication 4. Med eval and clearance obtained 5. Schedule and perform surgery 6. Conduct initial CI fitting (mapping) 7. Schedule regular f/u visits 8. Initiate AR program
How does it work?
1. Sounds are picked up by the micorphone of the speech processor, which analyzes sound and turns it into coded signals 2. Coded signal is sent across the skin to the internal device where it is converted into electrical signals 3. Electrical signals are sent down the electrode array which has been implanted inside the cochlea 4. Signlas from the array stimulate the nerve fibers of the auditory nerve directly and are recognized by the brain as sound *CI consists of BOTH surgically implanted components and an externally worn speech processor
External Components
1. Speech Processor - Worn on pinna - Processes and codes signal using speech processing strategy - Signal is digitized and filtered - Segmented to send different components to different electrodes in the array 2. Transmitter - Sends processed signal to internal receiver - Worn outside of the hea; held in place by a magnet
History of CIs
1790=Volta, metal rods in ears, 50 volts to head 1957=Djourno/eyries (france) electrode on auditory nerve 60-70s=House, research wearable device 80s= House, single channel device, current tech based on this 84=FDA approves implant for 18 years old and up 89=FDA approve implant for children 2+ years 2000=implant for children as young as 12 months
Predicting Success
Adult Considerations - Onset of deafness (sudden, progressive, etc) - Duration of deafness (how long w/out sound) - Mode of communication (spoken vs. sign) Ped Considerations - Age of child at implantation - Aural (re)habilitation - Family commitment
Audiological Assessment
Children: - ABR - OAE - Minimal Speech Perceptions (SAT) under best aided conditions - Sometimes VRA Adults: - Speech Discrimination - Pure tone THs - Aided speech discrimination - HINT
Improper Programming
Electrodes produce something other than an auditory sensation may result in: - Pain (ongoing stim) - Facial stimulation - Poor sound quality - Resistance to wearing implant *W/ children set VERY conservative maps
Setting Comfort Levels
If C levels are too HIGH: - Some sounds may be loud enough to be uncomfortable - Client may wear sensitivity (volume) turned down too low so cannot hear wide range of sounds If C levels are too LOW: - Speech will be too soft - Little variation in sounds (monotone) - Client may report echo sound quality
Setting THs
If THs are too HIGH - Background noise is artificially raised - May be too little variation in sound levels - Speech may have raspy / distorted quality If THs are too LOW - Soft sounds may be inaudible - Overall speech may seem too soft and mumbled - Pt may report inability to differentiate between speech and background noise
Loudness Balancing
Loudness Balancing: - Programming speech processor so stim follows loudness contour of incoming speech signal If electrodes are not balanced correctly: - Speech may have a popping or breaking-up quality - Speech may sound too tinny or boomy - Certain sounds may be unpleasant (keys, paper rustling, etc)
General Benefits for Adults
SOME adults may: -hear conversational and environmental sounds -demonstrate imporved detection of warning signals -improve speechreading skills -use the phone with limited ability (<50% of CI users)
General Benefits for Peds
SOME children may -detect environmental sounds at conversational level, including speech -distinguish speech patterns -identify sounds (enviro and speech sounds) -identify words (w/out lipreading/speechreading) -improve overall lipreading/speechreading -recognize speech w/out visual cues -imporve speech production skills after training and experience
Expanding Criteria
Since 1980s, criteria has expanded to include: -Younger children -Not only post-lingually deafened but pre-lingually deafened -Lesser degrees of HL -More benefit from HA
Clinical Results
WIDE RANGE -Some can communicate w/out lipreading -Some can communicate on phone -Others use CI primarily for enviro awareness and to enhance information from lipreading
