Hearing complications are mostly seen in children and elderly people. Few complications occur due to any major injury or infections. These could lead to Cochlear Diseases if neglected. Cochlear Diseases are pathological diseases of the inner ear that involves nervous tissue, blood vessels and endolymph. Cochlear disease research has been linked to vestibular diseases, sensorineural hearing loss, complete hearing loss and other hearing issues. Few other Cochlear diseases include acoustic neuroma and Meniere’s disease. In a few cases, the hearing loss can be rectified by using Cochlear Implants.
MedPiper Technologies and JournoMed had conducted a webinar in association with IRIA Kerala- Raksha, Shakti and Social Wings on 16th June 2022 where the speaker, Dr. George Kuruvilla, addressed the importance of Cochlear Implants and how they help with hearing complications. Dr George Kuruvilla is a Pediatric ENT Surgeon at Lourdes Hospital. He is well versed in specialized branches of ENT like Cochlear Pathology and Cochlear Implant.
What is a Cochlear Implant?
The Cochlear Implant is a prosthetic device used as a stand in for the inner ear (cochlea) and is appropriate for adults and children who receive minimal to nil benefit from a conventional hearing aid. Cochlear implants can help people with severe or profound hearing loss as they help process sound and hence, speech effectively. While they are standards for treating severe hearing loss, cochlear implants don’t restore a person’s hearing.
Mechanism of Hearing
To understand how the cochlear implant works, it is necessary to understand the basic mechanism of hearing. The sound waves move towards the eardrum which causes the eardrum to vibrate which in turn passes on these vibrations to three bones: malleus, incus and stapes. Due to the vibration of these bones, there is an oscillation in the middle ear. The stapes pushes the sound into the cochlea causing vibrations in the cochlear fluid.
The cochlea is filled with fluid (perilymph and endolymph) and is divided into three chambers: Scala vestibuli, Scala tympani and Scala media. The first two fluid-filled chambers sense the pressure changes and the third chamber contains organ of Corti, the cochlear duct and the basilar membrane. The organ of Corti, the receptor organ for hearing, consists of auditory receptor cells (hair cells) which stimulates the nerves and a system of supporting cells holding them in place. There are two types of hair cells: the inner and the outer hair cells. When the sound moves through the cochlear fluid, the sound energy is converted into electrical impulses. These electrical impulses travel through the cochlear nerve and reach the brain.
Even if a child or an adult loses or has no hair cells, the rest of the structures remain the same. The cochlear fluid would vibrate and since there are no hair cells, there is no conversion of sound energy to electrical impulses. Hence, there is no impulse transmission to the brain and the person is unable to hear.
The Cochlear Implant System
The Cochlear Implant is an implanted hearing device that bypasses the damaged part of the ear and stimulates the auditory nerve directly. There are two components of a cochlear implant:
- An internal implant placed just beneath the skin, behind the ear.
- An external speech processor.
How does a cochlear implant work?
In cochlear implant surgery, an incision is made in the back of the pinna (the only visible part of the ear) and the implant is inserted inside. .
The surgeon will make a small window in the cochlea to insert the electrode. This electrode winds around the cochlea once inserted. The structural arrangement of the cochlea is such that the bottom of the cochlea helps in processing high-frequency sounds and the cochlea apex is responsible for low-frequency sounds.
The external speech processor picks up environmental sounds through its mics and codes it.
The coded sounds are then transmitted via radio frequency through the skin and into the
underlying implant. The electrode, which winds around the cochlea, is able to stimulate
different parts of the cochlea based on various frequencies. This in-turn helps with more
coherent, understandable speech.
How to use the Speech Processor?
The Speech processors translate the acoustic signals of the microphone into one that fits electrostimulation of the auditory system. In multiple steps, the signal has to be analyzed and processed to fit the demands of electrical stimulation. Speech processors are widely used for voice identification, speech enhancement, audio signal processing, effective telecommunication and translation.
Who are the suitable candidates for Cochlear implants?
Cochlear implants are only suitable for patients who have limited or no benefit from standard
hearing aids. Children who are born with severe to profound hearing loss may be greatly
benefitted from the cochlear implant surgery, if done early. Post lingual adult patients who do
not benefit with hearing aids, but have reasonably good speech, may also benefit with
cochlear implant surgery.
Risks involved in the Surgery
There are minimal risks involved in this surgery and the surgical procedure can be performed within a short span of 2-3 hours.
Would be hearing aid be appropriate for patients?
Hearing aids help a lot of children with hearing loss. However, they are not suitable for everyone as hearing aids simply make sounds louder and on many occasions the sounds can’t be heard properly. In such situations, cochlear implants are preferred. In case of bilateral cochlear implant surgery or if a cochlear implant is required to completely learn a new language, the implant that is inserted surgically lasts for a long time.
There are several hospitals which provide implants to patients either through Government or Private Schemes. Most hospitals provide implants to patients following the central government scheme. If patients need to purchase implants from private hospitals, the cost would range around 6-15 lakhs, depending upon the technology used, per ear.
Cochlear implants improve the communication ability of most adults with severe or profound hearing loss. According to a 2019 study, cochlear implants are the most beneficial hearing interventions among acceptable candidates. In recent times, hearing aids have become more affordable to people across India. Hearing aids can make a huge difference in one’s life and now they are no longer the chunky plastic pieces around the ear. They come in new ways as “new rechargeable hearing aids” that are invisible.