Cochlear Implants

Cochlear Implant Overview

A cochlear implant (CI) is an electronic medical device which is surgically implanted and functions by energizing cells of the auditory spiral core (inside inner ear) to deliver sound (in the form of electrical signal to brain) to a person who is severely hard of hearing or completely or profoundly deaf. The implant directly stimulates the hearing nerve (auditory nerve), which carries sound from the cochlea to the brain, using electrical signals. Cochlear implants may assist hearing in patients who lost hearing because of damage to sensory hair cells in their cochlea. The sound which comes through Cochlear Implant is different than the normal sound and it takes some time before getting used to the sound.

Cochlear implant is consists of following parts:

1. Speech Processor

Speech processor is an external device which look likes a hearing aid and has in built microphones which picks up sound from the surroundings.The little computer chip inside speech processor selects and manipulates sounds compiled up by the microphone based on the hearing profile (requirement) of the wearer.

Cochlear Implant (CI) System
Fig 1: Cochlear Implant System

2. Transmitter Coil

Transmitter coil is attached to the speech processor and it sends the electrical signals to implant via skin. Transmitter coil has a magnet which align itself to the implant inside the head.

3. Implant

Implant (receiver & stimulator) gathers signals from the speech processor and change them into electric impulses. It send the electric impulses to electrode array. Electrode array is a bunch of electrodes that compile the electrical impulses from the stimulator and sends them to different regions of the auditory nerve.

Cochlear implant does not bring back normal hearing; instead it can give a deaf person a beneficial understanding of sounds in the environment and help him or her to appreciate speech.

Working Principle

A cochlear implants works by transmitting sound directly to inner ear via following steps:

How Cochlear Implant (CI) Works
Fig 2: How Cochlear Implant Works

  • Sound is received by the microphone of the speech processor.
  • The sound is digitized, analysed and transformed into coded signals.
  • Coded signals are sent to the transmitter.
  • The transmitter relays the signals via the skin to the internal implant where it is converted to electric signals.
  • Internal implant send the electric signals to the electrode array whic stimulate auditory nerve fibres inside cochlea.
  • Signals travel to the brain, carrying information about sound.

Who will benefit from Cochlear Implant?

CI devices are helpful for the people with sensorineural and mixed hearing loss, for whom conventional hearing aids provide little or no benefit. This includes people with:

  • People with little or no hearing and or little conductive component to the loss
  • Who receive little or no benefit from a hearing aid.
  • Implants seem to work best in adults who had overall relatively good hearing in the past before becoming profoundly deaf, and who developed good language.
  • Children who are young enough to develop language through an implant.

Getting a Cochlear Implant

The process involved in getting a cochlear implant involve 3 key steps:

1. Assessment

A cochlear implant candidate need to go through a number of tests to make sure a cochlear implant is the right solution. These steps include:

  • Audiology tests such as hearing levels with and without hearing aids, speech understanding, and auditory nerve function.
  • Medical tests and MRI scans to determine general health, evaluate the cause of the hearing loss and assess the hearing anatomy.
  • Psychological tests to confirm your ability to cope with surgery and participate in follow-up.
  • Speech and language testing, as a benchmark for ongoing assessment of speech and language development.

2. Surgery

The cochlear implant procedure is considered to be a low risk surgery and usually takes between 1 and 3 hours. Thousands of cochlear implant surgeries are performed each year. Your surgeon can give you more information about the surgery.

3. Activation

Within a few weeks of surgery, audiologists activate the cochlear implant for the patient. They program the device to suit the unique hearing needs and hearing loss of patient. They also fine tune the settings over a few follow-up sessions.

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