Cochlear ImplantWhat is it -?
Cochlear Implant
(Bionic Ear) is an artificial
electronic hearing device designed to produce useful hearing sensations by stimulating Cochlear nerve inside the Inner Ear.It transforms the mechanical energy of sound into electrical energy which directly excites the remaining auditory fibers.
Historical Background
* In 1751 Benjamin Franklin first suggested that Electricity could produce hearing sensation in the Deaf.
* Alessandro Volta (1800) placed metal rods into both his Ears and connected them to a source of Electricity. Before he lost consciousness apparently he heard the sound of bubbling water.
* At the end of 19th century, Many famous Otologists including Politzer, Ritter and Gradenigo were interested by the finding that passing an alternating current through electrodes applied around the ear produced sound.
* In 1934, Andreed, Gersuni and Volkhov published their report entitled,`Electrical stimulation of the hearing organ` where an electrode was placed near the round window and described various hearing sensations. Similar finding was reported by Jones,Stevens and Lurie in 1940. William F. House began thinking about & working on possibility of CIs in 1956.
* First CI was reported in France by Djurno and Eyries in 1957.The report was on two subjects and both claimed that the devices helped them greatly with lip reading. According to Zollner and Keidel(1963),the Implants in Djurno’s patients were still functioning 4-5 years later and the auditory sensations remained unchanged.
* This was a remarkable report which stimulated further research particularly by two groups in USA; Blair Simmons and his group in San Francisco and William F.House and his group in Los Angeles.
* Due to some untoward effects noticed in subjects implanted by House(1961) and Simmons et al (1964) leading specialists urged not to do further Implants until much more basic animal research had been completed. This effectively stopped further clinical work for several years although much work continued in laboratory.
* In 1968 Michelson showed that intracochlear electrodes could be maintained safely in cats and would function over long periods of time.
* In 1969 human studies began again when House implanted a further patient. It was a bold move when House used a six-electrode system designed by Jack Urban which were Hardwired. The patient was tested extensively for two years in the laboratory as, a wearable external stimulator was not available until 1972. The Result was sufficiently encouraging and then further 10 patients were Implanted in 1973 and finally despite much criticism the CI was established as a means of alleviating Total Deafness. Similar clinical works were carried out in San Francisco (Merzenich-1975), France (Chouard et al-1984),Germany (Benfai et al-1984) and in Austria(Burian et al-1984) during this period.
* In July 1983 , American Medical Association Recommended CI for postlingually Deaf patients. Initially it could enhance lip reading ability and bring awareness of environmental sounds which give benefit to the deaf. William F. House produced 1st practical CI in 1984 in conjunction with the House Ear Inst. & the 3M corporation. With recent Multichannel Devices it is expected that a Deaf Child who can Hear with CI will have the same educational outcome and employment prospects as a Hearing Child.
* Prof.Graeme Clark of U M is creator & developer of World’s first M-C Implant & considered father of CI.
* Now a days in some developed countries CIs become a routine clinical procedure both in Pre and Postlingually Deaf Patients.
* More Recently, Multichannel Auditory Brain Stem Implant (ABI) has been developed based on CI technology. It is indicated in patients having Bilateral Total Deafness not suitable for CI (e.g;Bilateral Skull base fracture, Ossified Cochleas). Here Electrodes are placed in the entrance of the 4th Ventricle to stimulate the Auditory Pathway on the level of 2nd Neuron, the Cochlear Nucleus Complex. Patients having ABI have measurable benefits and reported improvements of life quality.
How cochlear Implant works?
1. Sounds and speech are detected by the microphone.
2. The information from the microphone is sent to the speech processor.
3. The speech processor analyses the information and converts it into an electrical code.
4. The coded signal travels via a cable to the transmitting coil in the headset. Radio waves from the transmitter coil carry the coded signal through the skin to the implant inside.
5. The implant package decodes the signal. The signal contains information that determines how much electrical current will be sent to the different electrodes.
6. The appropriate amount of electrical current passes down the appropriate lead wires to the chosen electrodes.
7. The position of the stimulating electrodes within the cochlea will determine the frequency or pitch of the sounds. The amount of electrical current will determine the loudness of the sounds.
8. Once the nerve endings in the cochlea are stimulated, the message is sent up to the brain along the hearing nerve. The brain can then try to interpret the stimulation as a meaningful sound.
How Hearing aid works?
Pre-operative selection procedures
Where does one receive a cochlear implant?
In Cochlear implant centers managed by a team .Team members include an audiologist, otologist/surgeon, medical specialists as needed, psychologist, counselors, speech-language pathologists, neurologists, social workers and educationalists.
What is the process?
Once a person is referred to the cochlear implant center extensive testing is done to determine the suitability of candidate. This evaluation usually includes extensive audiological testing, psychological testing, examination and tests performed by the surgeon, X-rays, CT scan, MRIs,physical examination, and counseling to assure suitability and motivation to participate in the process. It is important that the candidate/parents understand what the implant will and will not do and also understand the commitment required for care and follow-up services.
Who is best suited for a cochlear implant?
It is generally agreed that the best adult candidates are those who:
* Have severe to profound hearing loss in both ears
* Have had limited benefit from hearing aids
* Have developed verbal or pre-verbal communication skills
* Have ears free of infection
* Have inner ear properly formed
* Have auditory (hearing) nerve intact
* Have no other medical problems that would make the surgery risky
* Have a strong desire to be part of the hearing world and communicate through listening, speaking, and speech reading
Children can also be candidates for cochlear implants. Children as young as 14 months of age have received cochlear implants, and the potential exists for successful implantation at younger ages.
It is generally agreed that the best child candidates:
* Have profound hearing loss in both ears
* Have had little or no benefit from hearing aids
* Have developed verbal or pre-verbal communication skills
* Have ears free of infection
* Have inner ear properly formed
* Have auditory (hearing) nerve intact
* Have no other medical conditions that would make the surgery risky
* Are involved (when able), along with his or her parents, in all aspects of the informed consent process
* Understand (when able), along with his or her parents, their individual roles in successful use of cochlear implants
* Have (when able), along with his or her parents, realistic expectations for cochlear implant use
* Are willing to be involved in intensive rehabilitation services
* Have support from their educational program to emphasize the development of auditory skills
Cochlear Implant SurgerySurgical procedure is simple. Rarely there is a complication (Flap problems, Device migration/ Extrusion/ Failure, Facial palsy). The device is safe and reliable. Procedure to place the implant may soon become a distant memory. No mortality.
RESULT:
Vary individual to individual and depends on:
* Age at time of Deafness
* Duration of Deafness
* Age at Implant Surgery
* Status of Remaining Auditory Nerve Fibers
* Training etc.
Study Reports:
In a study Over 12000 Children and Adults all over the World received some degree of Sound perception as a result of CI. About 175000 Patients getting benefit from CI all over the world (Report on Nov.05, 2001) & only CHD have been implanted in 36000 people aged (5-92 yrs).
In a series of 150 congenitally profoundly deaf children who received CI, over 90% have acquired spoken language & attend a regular school with some special support. It is expected that a deaf child who can hear with CI will have the same educational outcome & employment prospects as a hearing child.
In a study, 60 patients were operated for removal of tumor (Neurofibromatosis type 2) from auditory nerve leading to severing/ cutting the nerve Implanted with ABI. 85% were able to hear and understand conversation with the aid of lip reading. 12% were able to well enough to use the phone. Failure in 15% due to misplacement/displacement of electrode.
Autopsy Study of Temporal bone after CI have already been done. Due to new bone formation R-S is firmly fixed in TB. Mastoid cavity is aerated showed no inflammatory reaction and lined by thin mucosa. Dacron mesh used for fixation of device is completely absorbed while fibrous tissue is noted in and around the remnant.
Usually electrode remain at the same sites where they had been fixed during operation. No inflammation is noted in Tympanic cavity, round window but RW is seen closed by some fibrous tissue.
Post-operative RehabilitationWhat Happens After Operation?
The purpose of the adult and children’s rehabilitation program is to help patients and their families assimilate the cochlear implant into their daily lifestyle. To achieve this, Team offer services that aim to optimize patients’ hearing, help developing listening and communication skills, promote speech and language acquisition and deal with medical issues.
Immediately following the operation (after 4-6 weeks) Device is activated. An adult would normally attend the clinic once a week for a period of 2 to 3 months. As they become more proficient in the use of the device, less programming (Mapping) of the speech processor is required, they would only need to visit the clinic every 6 or 12 months or when the need arises.
With children, regular listening, speech and language therapy would be maintained for as long as appropriate, which could be a number of years.
How is a person’s hearing optimized?
If a person who can hear any sounds before operation, they need to be given the speech processor and headset. These components transmit the sound up to the implant so they must worn whenever the person wants to hear. The Team will instruct the person in the use and care of the device.
The functioning of each person's auditory (hearing) pathway is different, so each speech processor needs to be programmed to output sounds that suit the wearer's hearing. The programming (Mapping) is done by the Team and it involves setting current levels that produce just audible sounds and comfortably loud sounds for each electrode in use.
For the implanted person, this means sitting next to a computer which will send signals to the speech processor and indicating which sounds are very soft and which sounds are loud.
The speech processor may need to be Re-Mapped frequently in the first few months as the ear takes time to adjust to the new form of stimulation. This can be very frustrating for the implanted person as it means the quality of the sound that they hear may be changing. As the person and their body adjust to the device, the need for Re-Mapping usually becomes less frequent.
How do people learn to listen with their implants?
It takes time and practice before people become comfortable in using the device, and thinking of the sounds they hear as their 'normal' sounds. The Team try to speed the process up by providing listening tasks at each session. These tasks involve listening to words, sentences and conversations, and practicing using different strategies to improve communication situations.
In the case of children who have limited speech and language abilities, regular therapy is offered to the children and parents, to help in promoting the development of these skills.
Another important aspect of the clinical program is counseling. Where patients are experiencing difficulties relating to the effect of device on their lifestyle, relationships and family, the clinic social worker is available to help.
Prospect of Cochlear Implant in BangladeshNormal hearing is an essential requirement for the development of speech and personality in children. It is also important for an individual to perform his / her activities at an optimum level. Any alteration in this norm might lead to disability.
Worldwide, approximately one person in a thousand (4/1000 in developing countries)is born deaf. Almost an equal number (10% of childrens under 10 yrs. Suffer from otitis media) of people born with hearing will develop deafness during their lifetime. About 13m people are suffering from variable degree of HL of which 3m are suffering from severe to profound HL leading to disability in Bangladesh.
A good number of patients really need Cochlear Implant in our country (In USA 500000-700000 could get benefit from CI). In the past we were not ready to accept the program in our country due to lack of initiative and high price of the program. Recently cost (Price of the device, evaluation, surgery, rehabilitation) of the program is getting down. Effort is going on for development of an affordable effective Implant for
developing countries. Very soon we will get a law-cost high-performance CI.
We have already done 10 Cochlear Implant Surgery in Dhaka Medical College and Sir Salimullah Medical College in the department of Otolaryngology in Bangladesh. A Cochlear Implant team from India and Uk help us to complete our dream project.
It is now true that deaf and dumb child will no longer disable and able to speak again after Surgery. This arrangement will help transferring high-tech technology development of manpower (ENT Surgeons) in Bangladesh.
On going program in BangladeshRecently on 13th December,2008 3rd time in Sir Salimullah Medical College&Mitford Hospital and 1st time in Dhaka Medical College hospital 5 Cochlear Implant surgery done successfully.All the patients are well enough and waiting for mapping.
Contact Us
Prof.(Dr.)Mohammad AbdullahFCPS,FICS
Professor of ENT
Dhaka Medical College
&Project Director
National Institute of Dhaka,Bangladesh
01819213359
862612-23Ext2374
Fax8125911,8117430
Email: mabdullahent@yahoo.com
http://www.nationalinstituteofent.webs.com/Dr.Zonaid RahimAssistant Professor of ENT
Mymensingh Medical College &Hospital
Mymensingh ,
Bangladesh
zonaidrahim@yahoo.com
+8801711144185
Posts
cochlear implant Bangladesh
View blog authorityMASLPDmegs Web DirectoryVote for Us: Dmegs Web DirectorySuperblog Directory