What is a cochlear implant?
A cochlear implant is a small, complex electronic device that can help to provide a sense of sound to a person who is profoundly deaf or severely hard-of hearing. The implant consists of an external portion that sits behind the ear and a second portion that is surgically placed under the skin.
An implant has the following parts:
- A microphone, which picks up sound from the environment.
- A speech processor, which selects and arranges sounds picked up by the microphone.
- A transmitter and receiver/stimulator, which receive signals from the speech processor and convert them into electric impulses.
- An electrode array, which is a group of electrodes that collects the impulses from the stimulator and sends them to different regions of the auditory nerve. An implant does not restore normal hearing. Instead, it can give a deaf person a useful representation of sounds in the environment and help him or her to understand speech.
How does a cochlear implant work?
A cochlear implant is very different from a hearing aid. Hearing aids amplify sounds so they may be detected by damaged ears. Cochlear implants bypass damaged portions of the ear and directly stimulate the auditory nerve. Signals generated by the implant are sent by way of the auditory nerve to the brain, which recognizes the signals as sound. Hearing through a cochlear implant is different from normal hearing and takes time to learn or relearn. However, it allows many people to recognize warning signals, understand other sounds in the environment, and enjoy a conversation in person or by telephone.
What are the benefits of a cochlear implant?
- Hear better with a cochlear implant than with a hearing aid
- A previous study has shown that people with a cochlear implant achieve an average of 80% sentence understanding, compared with 10% sentence understanding for hearing aids.
- Can focus better when in noisy environments.
- Find it easier to have conversations with people across meeting tables, in restaurants and other crowded places.
- Reconnect with missed sounds that they could not hear before their cochlear implant.
- Feel safer in the world as they can hear alarms, people calling out and approaching vehicles.
- Talk and hear on the phone.
- Enjoy music.
What factors can affect these benefits?
The benefits of cochlear ear implants are often different for different individuals. These differences are often due to:
- how long they have had hearing loss before receiving a cochlear implant
- how severe their hearing loss is
- the condition of their cochlea (inner ear)
- the presence of other medical conditions
- how much practice they include in everyday life when using their cochlear implant system.
Evaluation of the candidates for cochlear implant surgery
An implant team consisting of otolaryngologist, audiologist, radiologist, pediatric neurologist, clinical psychologist and speech therapist does the clinical and other laboratory assessment. The otolaryngologist examines the middle and inner ear to ensure that no active infection or other abnormality precludes the implant surgery and assess the patient in detail for fitness of implant surgery. The audiologist performs hearing tests to find out the severity of hearing loss and also does pre-implant assessment and counseling for prospective implant client. High Resolution Computerized Tomography (HRCT) of temporal bone and Magnetic Resonance Imaging (MRI) scans of head with 3D reconstruction for the inner ear and the 7th and 8th nerve complex are done to assess the morphologic status of the ear and the brain. Anesthetists will do a complete physical examination and analysis of the laboratory investigations to identify any potential problems with the general anesthesia. We also take opinion from pediatric neurologist and clinical psychologist regarding fitness for cochlear implant surgery.
After the completion of abovementioned evaluation, the patient/parents will be explained what can reasonably expect after cochlear implant surgery. The complications of the implant surgery which include wound hematoma, infection, facial weakness etc will also be explained to the individual patient/relative/parent on his/her visit to the hospital.
Cochlear Implant Surgery
Implant surgery is performed under general anesthesia and lasts from two to three hours. An incision is made behind the ear to open the mastoid bone leading to the middle ear and then the inner ear is opened and implant electrodes are inserted. A well is created in the skull bone for the placement of the receiver-stimulating system. The procedure requires a stay in the hospital for 7 to 10 days. Antibiotics and other supportive medicines are given to such a patient.
Post operative switch-on, Mapping and training
The rehabilitation team, 3 to 4 weeks after surgery (when the surgical wound is well healed) activates the cochlear implant. During this “switch-on”, the patient’s implant is programmed using computer-based software. The impedance parameters of the electrodes are checked. The first MAP (a computer program that determines how sound signals will be converted to electrical signals) is created by determining the psychophysical parameters of threshold level, comfortable level for each active electrode and balancing the parameters for all the channels. Together, measures of the threshold level and comfortable loudness levels set the electrical dynamic range inside which all auditory signals will fall. The MAP is saved in the speech processor. It is very difficult to determine these behavioral parameters in younger prelingually deafened children. Objective assessment by Neural Response Telemetry (NRT) will be done in these patients. After the initial switch-on, the audiologist of the habilitation team will conduct the subsequent mapping sessions once or twice a week in the first month, then once a month for the first six months, then every three to six months as needed. This may differ according to individual children’s needs. The audiologist would do assessment tests such as speech perception tests at regular intervals and also offer ongoing technical support to the parents working with the child. The therapist works with the goal set for speech, language and listening. The therapist teaches the child to listen to the sound that is received from the cochlear implant and helps them in developing effective spoken communication. The therapist works closely with the parents to educate them about the stages of the development for speech and language and to counsel and inform them about realistic expectations about the cochlear implant
The parents and relatives are also made to actively participate in the training of the implantees. Parents are taught how to create a listening environment at home where the child can learn through play, daily routines and some planned listening activities. The parents are the main teachers and the language models, while the therapist is actually teaching the parents how to interact with their child at home. The parents need to have knowledge and confidence to effectively apply that role in their daily lives. Parents participation in the training is of paramount importance and one of the parent has to learn the therapy to train the child at home.
How to Contact:
If you are interested to know more/ perform the procedure then you can send to us at the email: firstname.lastname@example.org
You may also contact Dr. Biswajit Gogoi, MS (ENT) at mobile number 09435104443