Early Bionic Ears for Hearing Deprived

Dr Rajeev Nerurkar

It is estimated that 1 in 1000 newborns have severe to profound hearing impairment. Children with normal hearing develop spoken language by listening to and by imitating spoken language in their environment.

A child with hearing loss is denied this input. Consequently they have deficient receptive skills and expressive skills. As a result they tend to achieve lower academic results than their peers. The age of 6 months is the critical time in language development.

Children who receive hearing help around this age achieve significantly better language development than those for whom detection and intervention occur after 6 months.

Early intervention with optimally fitted hearing aids and/or cochlear implants(bionic ears) allows access to speech sounds and ensures that the developing child has access to a wide range of spoken language input.

This is how we hear

The Ear consists of 3 parts: External ear, Middle ear & the inner ear. All 3 parts work together to send sound to the brain. The External Ear picks up sound waves that causes the Tympanic membrane to vibrate. Via the middle ear ossicles(tiny bones) these vibrations are transmitted to the inner ear. The hair cells in the cochlea- which is the sensory organ for hearing perception - are set in a wavy motion due to this vibration. This motion sends electrical impulses to the brain via the hearing nerve fibers.

 

Types of Hearing loss

Broadly, hearing loss can be because of defective transmission of sound vibrations (This is corrected by surgery or due to a defect in the inner ear and the hearing nerve. It is this hearing loss that requires intervention in the form of hearing aids and/or cochlear implants.

If there is a loss of hair cells in the cochlea, hearing aids are going to be of little or no use as they only provide an amplification of incoming sounds and not frequency discrimination. Bionic ear provides the answer.

Bionic Ear - What is it?

A Cochlear Implant or a Bionic Ear is an electrical device intended to restore a level of auditory sensation via direct electrical stimulation of the hearing nerve to help profoundly deaf individuals who gain little or no benefit from hearing aids.

Environmental sounds are picked up by a microphone that is behind the ear, converted into an electrical signal and are passed through a speech processor, which codes it into a pattern of electrical pulses. Through a coil the speech processor then sends this code to the implant, which is surgically implanted under the scalp. The implant transmits this code to the electrodes implanted in the cochlea where the auditory nerve picks it up and passes it to the auditory cortex in the brain. The brain recognizes this code as sound.

A cochlear implant is surgically inserted in the cochlea through an ear surgery under general anaesthesia.

Common clinical situations for cochlear implant surgery include Hearing loss at or by birth, Post meningitis Hearing loss & Traumatic Hearing loss.

A Cochlear Implant Programme

A Cochlear Implant Programme involves a team of specialists in Audiology, Ear Surgery & Speech,Language and Hearing rehabilitation with experience in the assessment of the needs of profoundly deaf individuals.

A lifetime commitment is required from the implant team as well as the implantee family. Decision to implant a child is taken after a thorough clinical , audiological, psychological , radiological examination. A trial with an optimally fitted hearing aid for a period of 3-6 months is essential.

Mapping & Habilitation

The programming and mapping of the speech processor i.e tuning of the implant according to individual needs continues for a typical period of 4-8 weeks after the initial switch-on. Sessions of rehabilitation therapy are also initiated during the period.

The child is expected to hear first sounds via the implant at the time of the switch-on which is done typically 3 weeks after the surgery.

Sessions of intensive speech and language therapy may extend from 6 mths to 2 years.

To maximize the benefits of cochlear implants , a thorough habilitation is essential. Through consistent exposure to a meaningful sound experienced in regular daily activities, children learn to interpret the sound perceived through their implant. This is a new process for children who have had no or little experience with an auditory input.

An auditory based learning style(AuditoryVerbalTherapy ) develops faster listening and talking skills than using a total communication style.

Cochlear implants provide children with access to frequency discrimination in speech that contributes to the speech intelligibility.

Children who start using hearing aids or undergo cochlear implant surgery after the age of 4 yrs will not develop listening and language skills as their peers because the brain becomes less responsive to hearing inputs.

A cochlear implant is a proven and established mode of management for very young children with severe to profound hearing loss who do not benefit from best possible hearing aid and this option should be made available to them at an early age so that they can reach their full potential in life that is equivalent to their ability.

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