Cochlear implant – Patient information sheet
A cochlear implant is an electronic device that restores partial hearing to the properly selected deaf. It is surgically implanted in the inner ear and activated by a device worn behind the ear. Unlike a traditional, which simply amplifies sound which is then heard in the normal way, a cochlear implant converts sound to electrical impulses which are then transmitted to the nerve of hearing that would normally carry the auditory signal to the brain. The device bypasses damaged parts of the auditory system and directly stimulates the nerve of hearing, allowing individuals who are profoundly hearing impaired to receive sound. Presently, cochlear implant is the only hope for these groups of patients for developing and learning linguistic ability for communication. Cochlear implant is now an accepted and established method of therapy for deafness in children and adults.
Prof. William House from House Ear Institute (USA-1961) first
described the successful outcome from a single channel 3-M House Implantation in
terms of making a deaf patient able to perceive sound as well as
improve lip-reading ability. Since then, there has been a large body of research
knowledge available to the clinicians and audiologists pertaining to the implant
technology and its clinical use in managing patients with bilateral deafness.
Professor Graeme Clark and his team consisting of engineers and other scientists
from university of Melbourne, Australia made
significant breakthrough in devising the multi-channeled Cochlear Implant and
demonstrating its superiority over the single channel- cochlear implant in terms
of providing open set recognition of language and speech following implant
surgery and supported by auditory –verbal habilitation therapy. Soon the
multi-channel Nucleus Implant (Cochlear make, Australia) made history in the
world, in successfully managing a deaf person. In 1984, Professor Clark
founded the Bionic Ear Institute which continues to lead research in
collaboration with Cochlear Limited in achieving significant improvements in the
device technology. Early in eighty’s this device was,
after clinical trials, approved by the FDA (Food and Drug Administration, USA)
as a safe and useful implantable device for use in adult post-linguistically
deafened patients and later in 1991 it was also approved for use in children.
Human ear consists of three parts—the external ear, middle ear, and inner ear. The mechanism of hearing involves two components. In the conductive component, sound travels along the external ear canal causing the eardrum to vibrate. Three small bones of the middle ear conduct this vibration from the eardrum to the cochlea (hearing organ) of the inner ear.
In the sensorineural component, the vibrations of the bones of the middle ear start waves of fluid in the cochlea, and these waves stimulate delicate hearing cells called hair cell. The movement of the hair cell generates an electrical current in the auditory nerve and it travels through interconnections to the brain area that recognizes it as sound.
Types of Deafness
There are two types of deafness
How does a cochlear implant work?
In cases of sensorineural deafness, the hair cells are damaged although many auditory nerve fibers may be intact. These nerve fibers are unresponsive because of hair cell damage. But these fibers can transmit electrical impulses to the brain on stimulation. Cochlear implants bypass damaged hair cells and convert speech and environmental sounds into electrical signals and send these signals through the hearing nerve to the brain.
Parts of cochlear implant:
Cochlear implant has external (outside) parts and internal (surgically implanted) parts.
The external parts include a microphone, a speech processor, and a transmitter. The microphone looks like a behind-the-ear hearing aid. It picks up sounds just like a microphone of the hearing aid and sends them to the speech processor.
The speech processor may be housed behind the ear with the microphone, or it may be worn on a belt or pocket. The speech processor analyzes and digitizes the sound signals and sends them to a transmitter worn on the head just behind the ear.
The transmitter sends the coded signals to an implanted receiver just under the skin.
The internal (implanted) parts include a receiver-stimulating system and electrodes. The receiver is surgically fixed to the skull bone behind the ear. The receiver takes the coded electrical signals from the transmitter and delivers them to the array of electrodes that have been inserted in the cochlea during surgery.The electrodes stimulate the fibers of the auditory nerve to send information to the brain where it is interpreted as meaningful sound and thus the implanted person starts learning language and speech communication skills.
Cochlear implant surgery in AIIMS:
The Cochlear Implant team which includes surgical team and rehabilitation team works under the leadership of Professor RC Deka.
1. Professor RC Deka
2. Dr Alok Thakar
3. Dr Rakesh Kumar
4. Dr C Venkatakarthikeyan
5. Dr. Kapil Sikka
6. Dr. Rajeev
Audiology & Speech Rehabilitation Team:
1. Ms Shivani Agarwal
2. Ms Pallavi Rani
3. Ms Bharti Berry
4. Mr Rakesh Kumar
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 they 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.
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.
Outcome of surgery
The outcome of cochlear implantation depends on the age of the patient at implantation, previous sound experience, motivation/active participation of the patient/parents and good post operative auditory verbal training.
Till now (July, 2008), we have performed 216 cochlear implant surgeries in adults and children. 169 cases were prelingually deaf children and 47 were postlingually deaf adults. Habilitation with auditory verbal training and speech therapy is done by our audiologists and speech therapists in the cochlear implant Lab of our Department. Many of them also got training in their places by another speech therapist and they were coming to us at regular interval for follow up at AIIMS. After cochlear implantation, all postlingually deafened adults had significant improvement in the audiological perception, clarity of speech, performance in day to day activities and social interaction. Based on the age at implantation the prelingually deafened patients can be divided into 3 categories.
This consists of children of age less than 5 years. This was the group with the
best results. The linguistic development was significantly seen and 80% of the
children are going to normal schools. Their access to mainstream education is
reportedly successful. They used fewer school support services according to
available information from the parents. AIIMS now recommends cochlear implant
more for this group of patients as they are our target group.
2. Category B: This group consists of children with age between 5 to10 years. This category of patients also developed significantly notable lip reading capabilities and audiological perception. They are acquiring linguistic development with auditory verbal training, but when compared to Category A children, they lag behind them. These children also required special support services for improvement in the academic performances.
3. Category C: This group consists of children of age more than 10 years. The result of cochlear implantation in this group was comparatively less notable in respect to language and speech learning processes. However improvement in the lip-reading abilities was observed especially in those children who had sound experience in early life and those who had used hearing aid with some limited acquisition of linguistic ability.
All candidates irrespective of age required good postoperative auditory verbal training by audiologist, speech therapist as well as by parents to achieve significant and notable results.
Types of Cochlear implants
Currently there are three FDA (Food and Drug Administration, USA) approved cochlear implants available in the Indian market namely
1. Nucleus (Cochlear-Australian make)
2. Advanced Bionic (American)
3. Med El (Austrian make)
For details, one can visit the following websites.
At present AIIMS has the infrastructural facility for the Nucleus (Cochlear make) types of implants in RUAS (rehabilitation Unit of Audiology and Speech Pathology) laboratory Nucleus type is technically better than the other FDA approved implants available in the market because of its large number of channels, titanium casing (which has the property of Osseo integration), NRT facility and a better speech processor. It also has better service centers, located in Delhi and in other major cities of India for the repair/replacement/service of the wearable components, which include wires, microphone, speech processors and any other accessories like magnetic coil. Above all Nucleus 24 (Straight) is popularly used world wide and also decided upon by our Indian patients since it has the lowest price in Indian market (present price Rs.5.12 lakhs). All other FDA approved implants are costlier than this. AIIMS is following the selection procedure based on the purchase practice of cochlear implant made by the Directorate of AFMS, Defense Ministry, Govt of India for their cochlear implant programs in R&R Hospital, New Delhi, AFMC, Pune, and also Ashwani Hospital, Mumbai. They fully funded the cochlear implants but in AIIMS it is not funded.
The budget estimate based on the current price of the three types of Nucleus cochlear implants is as follows: (Prices are based on national prices declared by the Indian dealers /company)
1 (a) Price of the Nucleus 24 (Straight) cochlear implant system
(Most popular and widely used one) = Rs. 5.12 Lakhs.
(b) Price of CI-Nucleus-24 (contour) Cochlear implant system
(Hugging variety) = Rs. 7.00 Lakhs.
(c) Price of CI- Nucleus Freedom Contour Advanced
(Latest and state of art implant) = Rs. 9.50 Lakhs
Latest and state of art implant)
2. Post operative programming and tuning of the system in our rehabilitation unit is free
3. Hospital Expenditure: Minimal but for certain essential medicines, disposables if they are not available may cost about Rs. 5,000/-
Once it is decided by individual patient/relative/parent to undergo cochlear implant surgery, they have to decide the Once it is decided by individual patient/relative/parent to undergo cochlear implant surgery, they have to decide the type of implant based on their budget capacities. They have to generate funds for that particular implant from their own sources. In AIIMS, the process of procurement of cochlear implant will be through rate contract basis. It is under process and likely to be completed soon. As of now, AIIMS does not provide any implant. Patient/relative/parent can purchase the Nucleus implant from the authorized local Indian dealer, PIKA Medical Pvt Ltd, 201, A-285, Defense Colony, New Delhi- 110024 Ph: +91 11 24338080, Fax: +91 11 24338090 (Head Office , Bangalore). But if they needs assistance in procuring the implant, AIIMS helps him/her to procure the implant on his/her behalf on payment of the required amount in the form of a bank draft in favor of “The Director, AIIMS” (payable in Delhi). It processes the procurement on behalf of the individual patient/relative/parent and for the individual patient through Store Officer as per existing store purchase procedures approved by the competent authority (Director /DDA) since 1996.The ENT department assists this process of procurement for patient facilitation. The process is done by the AIIMS accounts and stores section for patient facilitation without any charges