What is a Cochlear Implant?

What is a Cochlear Implant?

A cochlear implant (CI) is a surgically implanted device that can enhance hearing and auditory perception for children who are hearing impaired. To understand how a CI works, you need a basic understanding of how normal hearing works.

  • Sounds are transmitted as acoustic waves from the outer ear to the eardrum.
  • The sound waves cause the eardrum to vibrate, which set the bones in the middle ear in motion.
  • The motion of these bones causes the fluid within the inner ear (cochlea) to move. This fluid motion triggers sensory cells (hair cells) within the cochlea to bend and stimulate the auditory nerve.
  • The auditory nerve transmits the signal to the brain that interprets and processes the signal as a hearing sensation.

How Normal Hearing Works?

Most severe-profound hearing loss is sensorineural hearing loss (SNHL) in nature, which means that the outer ear and middle ear are intact and functioning but most commonly the hair cells in the inner ear—or cochlea—are damaged or absent. So, sound waves are lost or distorted and cannot be transmitted through the hearing nerve to the brain. Cochlear implants bypass the damaged hair cells by directly stimulating the auditory nerve.

The CI system consists of the externally worn sound processor and an internal implant.

  • Sounds are picked up by the microphone of the sound processor, which processes the sound and turns it into digital codes
  • coded signal is sent across the skin to the internal device where it is converted into electrical signals.
  • The electrical signals are sent down the electrode array which has been implanted inside the cochlea.
  • The signals from the array stimulate the nerve fibers of the auditory nerve directly and are recognized by the brain as sound.

Who will benefit from a Cochlear Implant?

  • Child has been diagnosed with Moderately Severe to Profound hearing loss of the Sensorineural variant (Meaning pathology in the inner ear and/or auditory nerve with no significant involvement of the outer and middle ear)
  • Child has been fitted with good quality amplification device but has not shown significant benefit and adequate progress in terms of audition and/or speech and language skills. (Your auditory habilitation specialist would be able to assess whether the progress shown is at an acceptable rate)
  • General health condition of the child is suitable for him to undergo surgery (Clearance to be taken from pediatrician and other medical professionals as advised)
  • Child is in the critical age period for learning language. (Critical age period refers to a restricted developmental period during which the nervous system is particularly sensitive to the effects of experience, owing to a property known as Neural Plasticity. For more information on Critical age visit (https://www.ponyrunning.com/en/news/window/91.html )
  • Understand (when able), along with their parents, their role in the successful use of cochlear implants
  • Have support from family and an educational program that will emphasize the development of auditory skills.

What is Cochlear Implant Mapping or Programming?

Mapping (or MAPping) is the term for programming a cochlear implant to the specifications and needs of its user or ‘recipient’. MAPs are programs that help to optimize the cochlear implant user’s access to sound by adjusting the input to the electrodes on the array that is implanted into the cochlea. While each cochlear implant company has different terminology, different programming strategies, and different capacities for various MAPs on their processors, the basic ideas behind MAPping hold true for almost all the devices.

Mapping is an ongoing process as the amount of input that can be given to and utilized by the user varies with more and more stimulation or use of the auditory nerve and auditory brain through the Cochlear Implant. These changes takes place rapidly in the initial few months after implantation, and gradually gets stabilized by around 12-16 months post activation (or ‘Switch-On’). Mapping plays a very important role in the child’s progress using a CI as it determines how much access to auditory information he is getting and how fast he is able to adapt to this new stimulation. A qualified Audiologist trained in Cochlear Implant Mapping should be able to optimize the MAPs based on the capacity and requirement of the child, which gives him/her the maximum language input while ensuring that the stimulations do not cause discomfort or pain.

What is AVT and why is it required?

Auditory-verbal therapy is a method for teaching children with hearing loss to listen and use verbal mode of communication with the help of appropriately fitted amplification devices such as hearing aids, FM devices, and cochlear implant. Auditory-verbal therapy emphasizes learning language through listening following natural developmental listening and language milestones.

The Auditory Verbal approach stimulates auditory brain development and is suitable for children who are within the critical age period which is up to 3 years of age. When children are older, brain’s neural plasticity is reduced and hence it’s difficult for them to follow normal developmental milestones. For such children we require a more structured method which relies on training the brain to listen and learn spoken language.

What can I expect if my child has a cochlear implant?

We cannot predict how well any child will progress with a cochlear implant. A child’s progress depends on many factors, including:

  • The age at which the child became deaf
  • The length of time in which the child has been deaf
  • Family and educational support
  • Family’s and child’s motivation
  • Child’s cognitive development and learning style
  • Child’s level of speech language development prior to implantation
  • Presence of a cochlear abnormality
  • Presence of additional social, behavioral or physiological issues that may interfere in the learning process through a Cochlear Implant (e.g. ASD, ADHD, Cerebral Palsy, Cognitive deficits, processing disorders, etc)