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Central Neural Auditory Prosthesis

Central Neural Auditory Prosthesis. Chp . 161 Irene Kim. Auditory Brainstem Implant (ABI). Effective partial hearing restoration in patients with NF2 Most common indication for ABI is NF2 In US, criteria is for postlingual NF2 patients 12 yrs or older F irst or second side vestibular

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Central Neural Auditory Prosthesis

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  1. Central Neural Auditory Prosthesis Chp. 161 Irene Kim

  2. Auditory Brainstem Implant (ABI) • Effective partial hearing restoration in patients with NF2 • Most common indication for ABI is NF2 • In US, criteria is for postlingual NF2 patients 12 yrs or older • First or second side vestibular schwannoma removal

  3. ABI in Non-NF2 Patients • Patients who have failed CI • Loss of 8th CN integrity 2/2 skull base fx, traumatic avulsion • Severe post-meningitic cochlear ossification • Possible in cochlear dysplasia or cochlear nerve aplasia • Hearing outcomes SIGNIFICANTLY BETTER than in NF2 patients

  4. http://www.youtube.com/watch?v=kcCRmFNpoxI

  5. ABI Benefits • Limited to environmental sound perception and aid to lip reading • Rarely, open set speech understanding • Definitely POORER hearing than with cochlear implant

  6. Current ABI • 21-electrode array • Stimulated similar to a cochlear implant • Transcutaneous radiofrequency transmitter and receiver

  7. Timing of ABI Placement • Usually placed at time of 2nd vestibular schwannoma removal • Can place at time of first side tumor removal (“sleeper”) • Second stage procedure after previous vestibular schwannoma surgery • Advantages/Disadvantages

  8. Surgical Approach • Translabyrinthine • Favored by most surgeons for ABI placement in NF2 patients • More lateral view of brainstem • Cerebellar retraction reduced or avoided • Retrosigmoid

  9. Surgical Approach

  10. Auditory Performance • Useful auditory perception • Hearing level much less compared to CI • Loss of peripheral tonotopic stimulation • Improvement in auditory sensation • Rare significant open set speech understanding (telephone use)

  11. Penetrating Auditory Brainstem Implant • Two generations (combo of penetrating and surface arrays) • Electode inserted into cochlear nucleus • Outcomes are not better than surface electrode ABI

  12. Penetrating Auditory Midbrain Implant • Stimulate auditory midbrain proximal to damaged cochlear nucleus • Dorsal surface of inferior colliculus • Penetrating electrode array • Access tonotopic orientation of inferior colliculus

  13. Complications • Cerebrospinal fluid fistula through the wound and risk of infx in presence of ABI • Possible hydrocephalus • Displacement of electrode array • Nonauditory/somatic sensations • Ipsilateral facial tingling/throat discomfort

  14. TAKE HOME POINTS • 1. Effective method of partial hearing restoration in patients with NF2 • 2. Provides environmental sound awareness • 3. Open set speech perception achieved only rarely. • 4. Trials of penetrating ABI and AMI have not shown improved hearing • 5. Better speech perception in patients w/o NF2

  15. Hearing Aids: Strategies of Amplification Chp. 162 Irene Kim

  16. General • HA predominantly for: • SNHL with flat or sloping hearing loss • Patient is candidate for HA depending on: • 1. Degree of hearing loss • 2. Extent of communication disorder resulting from loss • 3. Motivation of patient/attitude towards hearing aid use

  17. Hearing Aid Technology • Component miniaturization • Programmability • Wireless connectivity • Permits communication from one hearing aid to another • From hearing aids to other electronic devices and signal sources • FM radio, phones, computers

  18. Hearing Aid • Microphone, amplifier, receiver • Microphone: converts acoustic energy into electric energy • Amplifier: adds gain to level of electric signal • Receiver: receives amplified electric signal and converts it back to acoustic energy • Telecoil or t-coil • Allows HA to receive electromagnetic signals directly, bypassing microphone • Classroom setting

  19. Electroacoustic Characteristics • Frequency gain • Input-output • Linear • Non-linear • Output limiting

  20. Nonlinear Amplification • Designed to address major problem with SNHL • Reduced dynamic range • Normal hearing: Range is 0 to 100 dB • Patient w/ SNHL: Range is reduced • Compression circuitry • Peak clipping

  21. Hearing Aid Features • Directionality • Directional microphone • Noise reduction • Feedback reduction • Program management • Automatic adaptivity • Data logging

  22. Hearing Aid Styles • Behind-the-ear (BTE) • Microphone and amplifier behind the ear • Receiver may be in the canal or behind ear • Potential for feedback lowest • In-the-ear (ITE) • In-the-canal (ITC) • Completely-in-canal (CIC) • Reduction of wind nose, ease of phone/stethoscope use

  23. Hearing Assistive Technology • Assistive listening devices (ALDs) • Personal amplifiers, FM systems • Enhances acoustic signal over background noise • Uses remote microphone • Closed captioning of TV shows

  24. HA Fitting • Fitting • Verification (objective measurements) • Real-ear unaided response or gain (REUR/G) • Real aided response or gain (REAR/G) • REAG-REUG = real insertion gain (REIG)

  25. Outcome Measurement • Self-assessment scales • Assessment by spouses • Hearing Handicap Inventory for Elderly (HHIE) • Other Quality of Life measures

  26. Hearing Aids in Children • Always fitted w/ binaural hearing aids • Children grow quickly; hearing aids often adjusted • Usually BTE • Maximize audibility • Can remake ear mold of BTE as ear canal grows

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