COCHLEAR IMPLANTSPATIENT EVALUATION AND DEVICE SELECTION

DEPARTEMAN OF OTO-RHINOLARYNGOLOGY OF ISFAHAN MEDICAL UNIVERCITY

In the name of GODIn the name of GOD

What is a cochlear implant

A prostheses include external and internal hardware. The external equipment includes a microphone, a speech processor, and a transmission system. The internal device includes a receiver/stimulator and an electrode array.

Microphone Processor Antenna/Transmitter

Receiver/Stimulator Electrode Array

Components

Recommendations for AdultAdult Referral for Cochlear Implant Evaluation

Unaided thresholds of 70 dB HL or poorer at 1000 Hz and above in the better ear, even if hearing levels at 250 and 500 Hz are better.

Unaided word discrimination <70%.

Frustration on the part of the patient due to communication difficulties, even with appropriate hearing aid use.

Recommendations for PediatricPediatric Referral for Cochlear Implant Evaluation

Unaided thresholds of ≥90 dB HL at ≥ 2000 Hz in the better ear, even if hearing levels at 250 and 500 Hz are better.

Aided levels in the better ear >35 dB HL, especially at 4000 Hz.

No response for ABR testing in both ears or no response for one ear and responses at elevated levels in the other ear.

Parents are frustrated with their child's development of auditory and/or communication skills.

Evidence of severely impairing auditory neuropathy/dyssynchrony.

Audiologic Protocol

Auditory abilities using hearing aids to compared with the most recent average and range of cochlear implant performance, it can also reveal recruitment.

Assessment of ears in the best-aided condition, provides critical information for determining in which ear to place the implant for unilateral implantation.

ABR test and OAE in childrenchildren..

For too young childrenchildren to participate in speech perception measures, parent interview scales are administered.

Imaging; High-resolution temporal bone CT scans without contrast

In all candidates preoperatively for assessment of IAC, cochlea & vestibular aqueduct, position of fallopian canal.

Postoperatively for device dysfunction or an unexpectedly poor outcome.

Other Evaluations for Pediatric Cochlear Implant Candidates

Speech production assessments & language evaluations.

Psychological evaluation to assess the child's verbal and nonverbal intelligence, attention, and memory skills and his or her visual-motor integration.

Indications for Cochlear Implant in Adult

Severe to profound HL (≥70 dB with little or no benefit from hearing aids)

Use of appropriately fit hearing aids or a trial with amplification (1-3 m)

Aided scores on open-set sentence tests of <50%

No evidence of central auditory lesions or lack of an auditory nerve

Realistic expectations and willingness to follow-up procedures as defined by the center.

Indications for Cochlear Implant in Children

12 months - 17 years old

Profound SNHL (unaided PTA ≥ 90 dB)

Minimal benefit from at least 3-6 m use of hearing aids (< 20% - 30% on single-syllable word tests, or, for younger children, the lack of developmentally appropriate auditory milestones measured using parent report scales)

Surgical Contraindications*

Cochlear aplasia (ie,Michel).

Congenital or acquired narrow IAC afferent innervation may be lacking.

Hearing in contralateral ear,

Persistent chronic ear infection with otorrhea.

Pathologies that affect the auditory nerve, such as bilateral acoustic neuroma or neurofibromatosis type 2.

* Saunders technique textbook

Ear Selection in Cochlear Implant Candidates

Select the ear that is least likely to benefit from amplification because of using hearing aid in contralateral ear after implantation,

If neither ear can continue to use a hearing aid implantion of better ear.

If either ear can continue to use a hearing aid equally well implantation on the basis of handedness, patient preference, or other nonaudiologic reasons.

In children if all things being equal right ear to capture the possible advantage of contralateral left-hemisphere specialization for speech recognition.

Cochlear implantation in COM;

Two-stage surgery; radical mastoidectomy & obliteration with oversewing of the ear canal & implantation 2 to 6 months later.

One-stage surgery; oversewing the external auditory canal and cochlear implantation without obliteration.

Individualized strategy; (1) dry perforation myringoplasty then implantation in 3 months. (2) cholesteatoma or unstable mastoid radical mastoidectomy and

obliteration then implantation months later. (3) stable cavity one-stage surgery with obliteration and electrode

implantation.

Outcome Expectations for Adults

Average postoperative thresholds is 25 - 30 dB. Improvement in the high-frequency range is more significant.

Postlingually deafened adults demonstrate more significant improvements, often as early as 1 month after the implantation.

Older patients are enjoying relatively good health no upper age limit for cochlear implantation but preimplant central auditory assessment is warranted to ensure positive outcomes.

Outcome Expectations for children

2 years or younger communication skill development similar to normal-hearing peers.

< 4 years substantial improvement in speech perception.

4 - 5 years excellent closed-set performance and varied open-set abilities; reduced dependence on visual cues for communication.

> 6 years old or older improved auditory detection abilities; improvements in speech perception that entail good closed-set abilities but limited open-set skills.

Progressive or sudden onset hearing loss excellent progress and achievement of these skills with a shorter duration of cochlear implant use.

Current Trends That Affect Adult Cochlear Implant Candidacy

Combined Electrical and Acoustic Stimulation In patients with significant residual hearing in the lower frequencies but little measurable hearing at 1000 Hz and above.

Rehabilitation of Asymmetric Hearing Loss.

Binaural Cochlear Implants improves sound localization and listening in noise. Binaural summation effects have been reported in which performance is improved in the binaural condition as compared with either monaural condition when speech and noise are in the front.

Factors That Affect Adult Cochlear Implant Performance

Preimplant factors;

Hearing experience (residual hearing, length of profound hearing loss, hearing history for each ear), age of onset (particularly if before the age 3 years), age at implant (particularly if 75 years old or older), cognitive/central abilities and motivation to hear.

Postimplant factors; Length of cochlear implant use, stability of threshold and comfort

levels used for device programming and lifestyle.

Devices selection

Currently, there are three major cochlear implant devices for use.

Nucleus Contour

The magnet is removable/replaceable and allows for MRI studies with magnets up to 1.5 Tesla.

The stiffest electrode and, consequently, it is relatively easy to insert.

The greatest disadvantage is that, after the stylet has been removed, it cannot be replaced. This is problematic if the electrode insertion is difficult because of anatomic variations.

Has a second electrode design can be used for the implantation of severely ossified cochleas.

Bionics Hi-Res 90K

Has a removable magnet that has been approved by the FDA to allow for an MRI with a field strength of up to 1.5 Tesla.

Metal or Teflon insertion tube, metal tube provides greater stability.

If errors occur during electrode insertion, the electrode is easily reloaded into the insertion tube.

MED-EL C40+

Receiver/stimulator is housed in a ceramic case.

FDA approved for use with MRI at 0.2 Tesla, causing no additional risk to the patient or significant impact on the device or image quality except for the magnet-induced artifact surrounding the internal magnet.

three separate electrode designs. The standard electrode is the longest electrode available in the marketplace and has a tapered design. for partially or severely ossified cochleas, a compressed electrode is also available

Has a insertion test device .