All about cochlear implants
Updated: Oct 8, 2020
According to WHO, over 5% of the world’s population has disabling hearing loss. In the case of Pakistan, there are approximately 10.6 million people living with some degree of hearing loss. Two out of one thousand children in the country are profoundly deaf, meaning they have no sensitivity to sound. Even this ratio is just an estimation, seeing as no governmental research or data collection have been done on the lives and experiences of people with hearing loss. There are also no health programmes or initiatives that have been implemented to address this situation.
A neuroprosthetic technology, called a cochlear implant, has been created as the last option for people with severe to profound hearing loss to have their hearing sensation restored. It has been put to use around the world since the late 1970s, but the first time it was used in Pakistan was in 1998. As of today, more than 3,000 people have received cochlear implants in the country, of whom children make up the majority.
However, this process is generally expensive and unaffordable for a large number of the community. As a result of this inaccessibility, so many are unable to receive the hearing care they need and deserve.
We have prepared this comprehensive guide to give you a better understanding of what cochlear implants are, what are their working mechanism, and how you can use this information to help support those that may want to treat their hearing loss and hearing impairment.
What is a cochlear implant?
Cochlea is a snail-like, twisted tube inside the inner ear that is the main organ of hearing. The most important function of cochlea (auditory inner ear) is converting sound and vibration into a neural signal. When the cochlea is damaged, it can’t send proper electrical signals to the brain. If the proper signal is not sent, the sound may not be heard loud enough, and even if you hear the voice of the word, you may not be able to recognise the correct word. Hearing loss caused by problems to the eardrum or auditory ossicles may be improved by methods like surgery, even though there is no certainty to that. The function of a cochlea is difficult to recover through current medicine if it gets damaged.
The cochlear implant is a small electronic device that is used to convert sound into electrical signals, instead of the cochlea, and transmit it to the auditory nerve. It is one of the most common artificial organs in the world today.
It has two most important features:
Implant, which is a device that is surgically implanted in the body.
Sound processor, which is a device worn outside the body.
What is the difference between hearing aids and cochlear implants?
Hearing aids Cochlear implants
It is easy to mistake cochlear implants and hearings aids with each other at first glance, but they are two different hearing tools.
Hearing aids are removable devices, whereas cochlear implants are small and complex electronic devices.
The main difference between both instruments is that cochlear implants require surgery under the skin behind the ear to be implanted rather than being removable like hearing aids. Similar to the function of hearing aids, cochlear implants do improve sense of hearing and speech comprehension, but it is mainly recommended to people with severe to profound hearing loss. Unlike a cochlear implant that converts sound into an electrical signal that is transmitted to the auditory nerve, hearing aid is a device that makes the sound audible and louder and so, they are effective only when there is some sense of hearing left. A hearing aid is also considerably cheaper and more affordable than a cochlear implant surgery.
A hearing aid works best when fitted by an audiologist. A cochlear implant requires surgery and detailed rehabilitation afterwards to learn how to use it and understand how it works.
How does a cochlear implant work?
Sound travels from the ear to the brain in the following process:
The sound is picked up by the microphone and sent to the part that is embedded inside the ear;
The sound collected by the microphone is converted into an electrical signal by the voice-processing unit (called a sound processor);
The sound analysed by the sound processor is converted into electrical signals for the cochlear implant;
The signal passes through the cable and is sent to the receiving device embedded behind the pinna (external part of the ear) through the transmitting coil, which is a magnet that contacts the receiver through the scalp;
The signal transmitted to the receiving device is sent to the brain from the electrodes embedded in the cochlea through the auditory nerve and as a result, sound is recognised.
What is the procedure for wearing cochlear implants?
1. Preoperative examination:
An ear, nose and throat doctor (ENT doctor or otolaryngologist) is the concerned specialist to first test patients to see if they are potential candidates for cochlear implants.
If the doctor determines your hearing level is suitable for a cochlear implant, some medical tests are necessary to be followed through with.
Some most typical ones are:
Different hearing tests, such as an audiogram.
A trial of hearing aid use to evaluate if it is potentially beneficial for the patient.
A CT (Computerised Tomography) scan, which is a type of X-ray that evaluates external, middle and inner ear structures, also for signs of infection or abnormality.
MRI (Magnetic Resonance Imaging) scan.
A psychological examination to see if the patient can cope with the implant.
A physical exam to prepare for general anaesthesia.
The patient is under the influence of general anaesthesia when the surgery is performed. The operation commonly takes around a few hours. In some cases, the patient is able to move from the bed and even walk around the next day.
During surgery, the body of the cochlear implant is fixed to the temporal bone and the electrode. The doctor or other hospital staff may:
Insert some intravenous lines;
Shave or clean the scalp around the site of the implant;
Attach cables, monitors and patches to the patient’s skin to monitor vital signs;
Put a mask on the patient’s face to provide oxygen and anaesthetic gas;
Administer drugs through the I.V. and the face mask to cause sleep and general anaesthesia;
Awaken the patient in the operating room and take them to a recovery room until all the anaesthesia is gone.
3. The sound:
The external components of the cochlear implant will be adjusted about a week to a month after the operation, depending on the condition of the patient after the operation.
The sound processor is tailored to the need of the individual wearer. The first time you make adjustments and are able to sense sound, it is called “sounding”.
The sound that is heard for the first time through the cochlear implant after surgery is expressed differently by different individuals, and people with mild hearing loss often hear better than those with severe to profound hearing loss. It is most widely known to produce a mechanically synthesised sound.
Cochlear implant surgery does not improve hearing and speech listening right away.
In order to make the best use of the cochlear implant, it is necessary to continue regular rehabilitation at each facility for lasting hearing and language development.
For children, it is recommended to seek comprehensive rehabilitation by an expert speech therapist. Hospital guidelines are not the only thing that will cover everything. It is important to collaborate with nursery schools, nursing institutions, kindergartens, and such to improve the process. Parents and other medical institutions and hospitals need to work together in order to support the child’s full use of hearing.
Most adults have hearing loss after the acquisition of language, so their brains still have memory of words and syntax. After wearing the cochlear implant, you can improve your hearing little by little by comparing it with your past memory and new voice input. With good rehabilitation and family support, you will gradually become able to hear and understand the meaning of words. The most important thing is that the patient is willing to restore their sense of hearing.