What is a Cochlear Implant : Who is a Candidate?
Bilateral Severe-to-Profound Sensorineural Hearing Loss
Individuals with audiometric thresholds within the blue region of the audiogram are considered for assessment.
Aided thresholds
The basis for determining cochlear implant candidature is whether a patient will benefit more from a cochlear implant than acoustic hearing aids.
A useful indication of benefit from hearing aids is given by the aided sound field thresholds.
Individuals who cannot access the speech spectrum (blue region) with optimally fitted hearing aids are considered for cochlear implant.
Speech Perception
Candidature cannot be determined on the basis of an audiogram alone. Functional benefit from hearing-aids is evaluated from speech perception tests, anecdotal evidence and questionnaires. Patients must demonstrate that they have used hearing aids for an adequate period of time (for children this must be in an appropriate rehabilitation setting).
For adult patients, sentence tests are used to measure their ability to perceive speech. Sentences are presented at 70dB and the accuracy of which the respondent reports the content words is measured. Individuals who score between 0% and 30% on BKB Sentences are considered for implant. Results from other speech perception tests are also taken into consideration (e.g. VCVs, AB words, CUNY, CID & IHR sentences).
Spoken Language
Children with little or no spoken language should be <5 years old at time of implant surgery. There should be evidence of pre-verbal communication skills.
Older congenitally deaf children (5 years+) will be considered for cochlear implant if they have developed good spoken language skills through consistent use of acoustic hearing aids.
Congenitally deafened adults are considered for cochlear implant if they have developed good functional spoken language.
Speech Intelligibility
For adults and older children (5 years+) speech should be intelligible to listeners with experience of deaf speech.
Age at time of surgery
No upper age limit per se, so long as the individual is medically fit for surgery and general anaesthesia.
Lower age limit of 12 months (unless exceptional circumstances).
Otology
Tympanic membrane intact. No active middle ear disease.
Satisfactory Imaging
Patent cochlea and satisfactory imaging of the inner ear.
Integrity of Auditory System
No central or retro-cochlear problems.
Support
Appropriate support from family, local professionals and friends. A strong oral / aural emphasis is essential.
Long-term Commitment
Commitment to long-term follow-up: looking after/wearing equipment, keeping appointments and active parental involvement in encouraging the development of spoken language skills.
Expectations
Realistic expectations and a good understanding of the cochlear implant process.
No contraindications
No other contraindications that would prevent the patient from using the device or developing spoken language.