What is a cochlear implant and how does it work?
A cochlear implant is a surgically placed device comprising an internal and external component. It is capable of receiving sound and transmitting the resulting electrical signals to electrodes implanted in the cochlea of the ear. The external component of this device consists of a microphone, sound processer and transmitter system that is held in place by a magnet connecting it to the internal part consisting of the implanted receiver and electrode system. The speech processor picks up sound produced by the microphone to analyse and convert it into digital code. This signal is then sent to the headpiece and distributed to the electrode array inserted into the cochlea. Electrical impulses produced by these electrodes stimulate the auditory nerve, allowing the implant to bypass the damaged or non-functioning ear. The entire process is quick and produces no noticeable delays.
Candidacy
The age limit for getting a cochlear implant may vary based on a number of factors. To qualify, candidates must be 18 years or older, have moderate to profound sensorineural hearing loss, not benefit from hearing aids, and possess a sentence recognition ability of 50% or less. Children aged 12 months and above with severe to profound hearing loss, showing no auditory development even after 3 to 6 months of hearing aid use can be referred for a cochlear implant. Older children having long standing hearing loss with limited benefit from hearing aids can also be considered. In every child’s case however, realistic goals and expectations need to be discussed with parents in detail prior to the surgery.
Pre-implant evaluation
Prior to surgery, a thorough audiological evaluation is necessary to determine the candidacy. This is carried out by a multi-disciplinary team, including (but not limited to) ENT surgeon, nurse, audiologist, speech language pathologist and pediatrician. A thorough medical examination is also required to rule out medical contraindications and prevent possible surgical risks.
Contraindications
Contraindications can include ongoing chronic otitis media or mastoiditis, complete absence of the cochlea or the auditory nerve, very narrow internal auditory canal, severe developmental delays or intellectual disabilities where management of a surgically implantable device may be difficult.
