What is a Cochlear Implant?
A cochlear implant is an electronic device that restores partial hearing to the deaf (Figure 1). It is surgically implanted in the inner ear and stimulated by an external device worn outside the ear. In most cases of sensorineural deafness, the cause is the loss or damage of the organ of hearing (Organ of Corti). The cochlear implant bypasses the damaged part of the auditory system and directly stimulates the nerve of hearing (Cochlear Nerve), allowing patients with profound hearing loss to perceive sound.
(For more information, you may visit www.cochlear.com)
Who can benefit from an implant?
Cochlear implants are best designed for patients who do not receive any or little benefit from hearing aids. Children and adults (with postlingual deafness) with such severe deafness loss are suitable. Although the there is no ‘best’ age for the timing of surgery, children are most often implanted from age 1 to 3. Children over the age of 6 need careful assessment and the decision for cochlear implantation would be also dependent on other factors such as use of hearing aid, main mode of communication, social and educational background. Adults with prelingual deafness derive least benefit from a cochlear implant.
What does it involve?
Otolaryngologists (Ear, Nose & Throat specialists) perform the surgery though not all are trained to do this procedure. Before a cochlear implant is considered, a series of tests are necessary. They include;
Ear examination: To ensure that there are no abnormalities of the middle and inner ears that preclude surgery.
Hearing (Audiometric) evaluation: The audiologist performs a battery of tests to determine how much the patient can hear with and without a hearing aid.
Radiologic (X-ray) evaluation: A CT scan of the inner ear is performed to determine the anatomy of the inner ear.
Auditory Verbal Therapy (AVT) Assessment: An AV therapist will assess the child and his/her parental suitability for AVT after cochlear implantation.
About the Surgery
Cochlear implant surgery is performed under general anaesthesia and lasts from two to three hours. An incision is made just behind the ear to access the mastoid cavity that leads to the middle and inner ears. An x-ray is taken after surgery to confirm the position of the implant (Figure 2). Generally, the patient stays for one or two days after surgery.
About one month after surgery, the cochlear implant team will ‘switch on’ the implant. They will teach you how to look after the system. The patient will probably be asked to return for a few visits for regular checkups and readjustments (mapping) of the speech processor are needed.
What can I expect from an implant?
Cochlear implants do not restore normal hearing and benefits vary from one individual to another. There are many factors that contribute to the degree of benefit a user receives from a cochlear implant, including:
How long a patient has been deaf
The number of surviving auditory nerve fibres and
The patient’s and family’s motivation to learn to hear and speak.
What is Auditory Verbal Therapy (AVT)?
In children with prelingual deafness, having an implant will not result in spontaneous development of listening skills and speech. The process of speech acquisition and integration into mainstream education takes perseverance and patience. For this process, we adopt the Auditory Verbal approach. In general, patients are expected to attend AVT for 3 years after CI surgery although results can be seen much earlier.
How much does it cost?
The total cost of a cochlear implant including evaluation, surgery and the device excluding mapping sessions and therapy is around S$45000 – $50000 for Singaporeans and permanent residents. There are avenues to obtain funding for needy patients.
MBBS (S'pore), FRCS (Edin), FRCS (Glasg) Fellow, Otology / Neurotology (Can)
Child Team, NUH
Dr Chee with a recently implanted patient