COCHLEAR IMPLANT- How and Why
It is an electronic device that helps deaf people to hear partially. This surgical implant in the inner ear is activated by a device worn outside the ear. Unlike a hearing aid, it does not make sound to be heard louder or clearer. Instead, the device used bypasses, damaged parts of the auditory system and directly simulates the nerve of hearing, allowing individuals who are profoundly hearing impaired to perceive sound.
What is normal hearing?
The ear consists of three parts that play a vital role in hearing – the external ear, middle ear and the inner ear.
- Conductive hearing: Sound travels along the ear canal of the external ear causing the ear drum to vibrate. Three small bones of the middle ear conduct this vibration from the ear drum to the cochlea (auditory chamber) of the inner ear.
- Sensorineural hearing: When the three small bones move they start waves of the fluid in the cochlea, and these waves stimulate more than 16,000 delicate hearing cells (hair cells). As these hair cells move, they generate an electrical current in the auditory nerve. It travels through inter – connections to the brain area
Hearing is impaired how and why?
If there is disease or obstruction in the external or middle ear, your conductive transmission of hearing may be impaired. Medical or surgical treatment can probably correct this?
An inner ear problem; however, it can result in a sensorineural impairment or nerve deafness.In most cases the hair cells are damaged and they do not function. Although many auditory nerve fibers may be intact and it can transmit electrical impulses to the brain, these nerve fibers are unresponsive because of hair cell damage which prevents sounds from being transmitted.
The severe sensorineural hearing loss cannot be corrected with medicine and it can only be treated by using a cochlear implant
How do cochlear implants work?
These implants bypass damaged hair cells and it converts the speech and environmental sounds into electrical signals transmitting them to the hearing nerve directly.
- The implant consists of a small electronic device, which is surgically implanted under the skin behind the ear and an external speech processor, which is usually worn on a belt or in a pocket.
- A microphone is also worn outside the body as a headpiece behind the ear to capture incoming sound..
- The speech processor translates the sound into distinctive electrical signals. These ‘codes’ travel up a thin cable to the headpiece and are transmitted across the skin via radio waves to the implanted electrodes in the cochlea..
- The electrode signals stimulate the auditory nerve fibers to send information to the brain where it is interpreted as meaningful sound.
Who can benefit from an implant?
Implants are designed only with individuals who attain almost no benefit from a hearing aid. They must be one year of age or older.
ENT Specialists perform implant. The local doctor can refer you to an implant clinic for an evaluation. The evaluation will be done by an implant team who will perform a series of tests.
- Ear evaluation: The Doctor examines the middle and inner ear to ensure that no active infection or other abnormality precludes the implant surgery.
- Hearing evaluation: The audiologist performs an extensive hearing test to find out how much you can hear with or without hearing aid.
- X-Ray evaluation: X-Rays are taken, usually CT Scan or MRI Scans to evaluate the inner ear.
- Psychological evaluation: Some patients may need a psychological evaluation to determine if they can cope with implant.
Physical examination: The Doctor also does a physical examination to identify any potential problems that may be encountered during general anesthesia needed for the implant procedure.
Minimally invasive cochlear surgery. Advantages: Less pain and swelling, less infection changes and hence less complications. More cosmetic. Less operating time.
Implant Surgery:
This 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. The procedure may be done as an outpatient procedure, or it may require staying in the hospital, overnight or for few days, depending on the device used and the anatomy of the inner ear.
Cochlear implants restore normal hearing and benefits may vary from one to another on an individual basis. Most users find that these implants help them communicate better, and over half are able to discriminate speech without the use of visual cues.
The degree of benefit a user derives from an implant is determined by many factors. Most important among them are:
- How long a person has been deaf,
- The number of surviving auditory nerve fibers (Neurons).
- A Patients motivation to hear and learn.