Listen to the Implant
Adult cochlear implantation is proving a boon for patients that are unable to listen with hearing aids
By: Dr. Sheelu Srinivas
Technological advances never cease to amaze. One such latest addition to the list is of adult cochlear implants. Something that the surgeons all over the industry are excited about.
Cochlear implants (CI) are designed for individuals with hearing impairment to compensate for moderately-severe to profound sensorineural or mixed hearing losses, if there is limited or no benefit from hearing aids.
CIs bypass the non-functioning part of the auditory system in order to deliver electrical signals directly to the auditory nerve.
Take into account the broad cognitive, social & physical functioning outcomes that are likely detrimentally impacted by hearing loss. This can be overcome by cochlear implantation in the right patient group followed by dedicated rehabilitation
How does it work
A cochlear implant consists of two parts, an external and an internal component. Internally, the implant consists of a receiver-stimulator, which contains the electronics, the receiving antenna and a magnet that holds the coil in place behind the ear, and the electrode array. Externally, the device consists of a sound processor that is generally worn behind the ear and consists of a microphone, which picks up sound, a processing unit that processes and converts sound into a radio frequency signal, and a transmitting coil through which the information is transmitted through the skin to the internal components of the implant. The sound processor also includes manual controls and batteries.
Cochlear implantation only works well in those who have developed language before their deafness or in those who receive their implant at a very young age.
Implantation requires an operation and comes at a high cost. Also, there is a requirement of post implantation auditory and language therapy for 3-4 years in children born with profound deafness. There are about 25000 CI done in India and this has increased exponentially in the last 5 years. About 10 state governments are sponsoring CI in children below 5 years and there are about 300 independent clinics in India running a multidisciplinary CI program. All these programs are mainly concentrating on children and the adult deaf population is not aware of CI option available to them.
However, we have a large young and elderly deaf population who could benefit from this technology. As per Census 2011, in India, out of the 121 cr population, about 2.68 cr persons are 'disabled', which is 2.21% of the total population. The Census 2011 revealed that of this disabled population, 19% are with disability in hearing. If we refer to the age group statistics, out of the total disabled in the age group 0-59 years, 18% are having disability in hearing. The impact of hearing loss in the elderly effecting their quality of life and cognition is already well known.
Hearing loss in adulthood is linked to a greater likelihood of unemployment, as well as an increased risk of poor health, depression and other conditions, including dementia. Despite this, there is little recognition of the impact of hearing loss or of the latest hearing technologies, which could improve hearing in the adult age group in India. This failure to address the consequences of hearing loss is exemplified, above all, by the low level of awareness and provision of cochlear implantation for adults.
The selection criteria
Age of onset of hearing loss has a big influence on the selection criteria for cochlear implantation. People who are born with profound sensorineural hearing loss are prelingual deaf. This group should get a cochlear implant within 3-5 years of birth. The second group is the post lingual deaf population who were born with normal hearing and lost hearing later in life due to following causes:
• Ear infections and surgeries
• Tumour and lesions of nerve of hearing
• Meneires disease damaging hearing
• Trauma and ototoxic medications
• Progressive hearing loss of any etiology
People who are born with normal or mild to moderate hearing loss and later progress to profound deafness are called progressive hearing loss group. This group should be fitted with appropriate hearing aids and regularly monitored for hearing and speech. The absolute contraindication for CI is complete absence of inner ear or absent nerve. Also, as it involves general anesthesia-sometimes a high-risk medical condition can become a risk for CI.
In our program, we have a strict selection criterion for adult CI. The factors commonly influencing decisions are age of onset of hearing loss, use of hearing aids, duration between hearing loss and CI and also cause of hearing loss. The etiology in adult can be so varied, it needs careful planning and different surgical technique tailored to each of them.
Hearing with CI is not automatic. After the implant is switched on, the recipient is likely to hear sounds right away. But it can take months or years of hard work to interpret these sounds and give meaning to them. Rehabilitation, regular mapping, family support and setting appropriate expectation is the key to success of a CI program.
Adult population form 50% of the CI we have performed in our program and that is due to the awareness we have created and also the rehabilitation support. Our deafness rehabilitation team patiently works with age groups of 6 months to 65 years who are using hearing aids or cochlear implants. We recently offered CI to a 63-year-old Mrs Savitri and her husband had some genuine feedbacks.
Till we start thinking of benefit beyond hearing and speech, we will not be able to convince families or governments for an adult CI program. We need to take into account the broad cognitive, social, and physical functioning outcomes that are likely detrimentally impacted by hearing loss. This can be overcome by cochlear implantation in the right patient group followed by dedicated rehabilitation.