What is a Cochlear Implant ?
The cochlear implant is a unique implantable device that helps people with severe to profound hearing loss on both sides hear once again.
Figure 1 Cochlear implant internal devices
Figure 2 Normal anatomy of the auditory system
How the Device Works
This device stimulates the inner ear directly using electrical signals. This system does not use the ear canal and middle ear structures. These devices often work even when hearing aids do not because of its ability to stimulate the hearing nerves directly.
Figure 2 Electrode curls into the inner ear (cochlea)
Figure 3 Cochlear implant internal device
Figure 4 External device
Who May Benefit from the cochlear implant?
Hearing loss can be caused by many different problems. A conduction problem occurs if the sound pathway in the ear canal, eardrum, or middle ear is disrupted. These conditions are usually correctable with office procedures or surgery. Hearing aids can be used in these cases as well. A sensorineural hearing loss occurs when the inner ear or hearing nerve is damaged or becomes dysfunctional. Common causes of this type of hearing loss include age-related hearing loss (presbycusis), noise-induced hearing loss, hearing loss due to trauma or inherited disorders, and many others. These types of hearing loss in general cannot be corrected surgically, but hearing aids are a good option in many cases. There are some patients with hearing loss so severe on both sides that hearing aids are not useful. These patients can potentially be helped with the cochlear implant.
Adults and teenagers – The candidacy for cochlear implantation is based on lack of benefit from hearing aids and certain hearing criteria that are measured with special hearing tests. A CT or MRI is obtained to check for any anatomical problems that may prohibit implantation. The patient will need to be medically fit to undergo a 1 ½ hour outpatient surgery.
Children – The youngest age currently approved for implantation is 12 months. Kids can either be born with severe to profound hearing loss, or may acquire the hearing loss over time. It is critical that the hearing loss be diagnosed as soon as possible so the proper treatment can be started. Good hearing function is critical to a child’s language acquisition, and the hearing must be present at an early age for proper language development. Children with hearing loss that cannot be corrected otherwise can be fitted with hearing aids. Cochlear implantation can be considered for kids who do not develop their speaking and listening abilities in a timely manner.
What is the Evaluation Process?
Patients with hearing loss undergo a full ear, nose and throat evaluation in addition to testing such as audiogram and imaging such as MRI or CT. Based on the medical evaluation, the treatment options for the hearing loss will be presented to you. Those who are possible candidates for the cochlear implant undergo other special hearing testing to see if they are candidates for the procedure.
The procedure is an outpatient surgery that takes about an hour and a half. It is performed under general anesthesia. The surgery is performed through an incision behind the ear. The surgery consists of removing part of the mastoid bone and placing the cochlear implant.
After Surgery Care
The wound behind the ear usually heals very quickly and requires simple cleaning and application of antibiotic ointment. Regular activities are started the next day. Patients are typically seen 3 weeks after surgery to ensure proper healing of the wound.
The cochlear implant system contains a computer that processes the sound waves into electrical signals. There is an external part of the device that is worn behind the ear that contains this computer. The device needs to be programmed and customized for the patient for optimal results. The first programming session typically occurs 4 weeks after surgery and is called the initial “hook-up.” After this session, the patient will start to use the device for hearing. There will be several programming sessions over the first few months of implant use to adjust the implant programming so that the best hearing results are obtained.
Expectations of cochlear implant
Cochlear implants do not provide the same type of sensation as normal hearing. Cochlear implant users typically continue to hear “better” over time with continued use of the implant. The hearing function a year after the initial hook-up is usually much better than the hearing function initially. Patients who learned to speak and understand language prior to losing their hearing typically have better results than those who lost their hearing prior to language acquisition during childhood. In general, better performance is expected if the implantation is performed soon after the hearing loss occurs.
Adults and teenagers – Those patients who lost their hearing prior to language acquisition and are primarily using sign language usually do not benefit greatly from cochlear implantation. Patients who lost their hearing after language acquisition can typically be helped with the cochlear implant at any age, but the hearing function with the cochlear implant is better if the surgery is performed early after the hearing loss occurs.
Children – As in adults, kids who lost their hearing after language acquisition typically do very well with cochlear implantation. Children who were born with no significant hearing or lost their hearing at an earlier age can still obtain very good hearing and language results if the cochlear implantation is performed soon after the hearing loss occurs. Ideally, children who are born with little to no hearing are evaluated, diagnosed, and treated with hearing aids during the first year of life. Those who are candidates for the cochlear implant will be considered for the implantation at or soon after the age of 12 months. The goal for implanted children is to allow them to develop good listening and speaking skills so that they are able to attend regular schools. These kids often require speech education and other specialized education prior to K1-12 school to give them a “running start” on their education.