Definition and Overview
A cochlear implant is a small device placed in the inner ear to facilitate the transmission of sound to significantly improving hearing.
The implant, which is composed of different parts that are found either in the outer or inner ear, works like this: the microphone picks up the sounds in the environment and sends it to the processor, which then converts them into electrical codes. The codes then pass through the coil and into a stimulator, which changes the codes into electric impulses. These impulses are gathered by the electrodes that stimulate the auditory nerves of the cochlea, which deliver the impulses to the brain for interpretation.
Because it works directly with the auditory nerves, this hearing aid implant works differently from the other types of hearing aids, which mainly magnify the loudness of the sound they perceive. The implant can produce electrical impulses without passing through the damaged parts of the ear.
Who Should Undergo and Expected Results
The hearing aid implant is recommended for:
- Patients with severe hearing disability that can no longer be addressed by regular hearing aids
- Those who can hear normally in one ear
A cochlear implant can be used by people of all ages, although the Food and Drug Administration allows its use in children who are at least 12 months old.
Cochlear implants cannot store normal hearing. But although the overall hearing quality remains different from normal hearing, this device can promise a person a better quality of life. This is because the implant allows the person to communicate more clearly and become more efficient in responding to warning signals or sounds, among others. Also, children with hearing disabilities who wear implants early on tend to learn to speak as normally as those who have good hearing.
However, these implants take a lot of time getting used to. Children, for example, have to undergo more than a year of therapy to use the device efficiently.
How Does the Procedure Work?
Before the device is implanted, the patient is subjected to a thorough evaluation where his ears and hearing are assessed.
Patients with hearing problems are typically referred to a nose, throat, and eye specialist (ENT), a medical professional who can diagnose auditory problems including possible underlying conditions like otitis media. If the patient is diagnosed with a certain degree of hearing loss, he will be referred to an audiologist who will conduct various tests to assess the extent of the problem. If the patient is cleared for implantation, the surgeon may require imaging tests to help him plan the procedure.
The implantation of the cochlear device is done in a hospital setting under general anaesthesia. The surgeon shaves a part of the hair to fully expose the ear. An incision is then made behind the ear, and using surgical tools, the inner ear is exposed by removing a bone. The implant is then secured, ensuring that the eardrums and the ear canal are kept safe.
The surgeon then locates the cochlea, makes an incision to open it, and places the electrodes. The muscles and skin are returned to their original position, and the incision is sutured and dressed.
The procedure usually takes at least 2 hours while the patient stays in the hospital for the remainder of the day or overnight. The next day, the dressing can already be removed.
The patient needs to wait about 2 to 3 weeks before the processor can be attached. This is to give time for the incision to heal completely. While the processor and stimulator are not yet attached, the patient will still not hear even with the implant. During the follow-up, the audiologist attaches the external parts, and the device is adjusted according to the profile of the patient.
Possible Risks and Complications
The patient may feel pain and discomfort in the incision site. There may also be swelling or bleeding. In certain cases, the site may develop an infection, which can be treated with antibiotics.
Brown KD, Balkany TJ. Benefits of bilateral cochlear implantation: a review. Curr Opin Otolaryngol Head Neck Surg. 2007;15:315-18. PMID: 17823546 www.ncbi.nlm.nih.gov/pubmed/17823546.
Limb CJ, Francis HW, Niparko JK. Cochlear implantation. In: Flint PW, Haughey BH, Lund LJ, et al, eds. Cummings Otolaryngology: Head & Neck Surgery. 6th ed. Philadelphia, PA: Elsevier Mosby; 2015:chap 160.
Sparreboom M, van Schoonhoven J, van Zanten BG, et al. The effectiveness of bilateral cochlear implants for severe-to-profound deafness in children: a systematic review. Otol Neurotol. 2010 Sep;31(7):1062-71. PMID: 20601922. www.ncbi.nlm.nih.gov/pubmed/20601922.