A cochlea is a part of the human ear, shaped liked a tube and it is hollow and usually coiled in the form of a shell of a snail. The cochlea contains the Organ of Corti, which is the sensory organ of hearing. Therefore the cochlea is an integral part of the human ear that coordinates the nerve cells within the ear to help the human hear. When a person’s cochlea is damaged and she/he is unable to hear almost nothing or absolutely nothing, then that person is given a device to make her/his cochlea work. This process is known as a cochlear implant.
A cochlear implant is a small yet complex electronic device that helps a person to hear who is basically deaf or almost nearly deaf. The device has two portions – an internal and an external one. While the former is surgically placed under the skin, the latter sits behind the ear. A cochlear implant doesn’t restore normal hearing, but it can give a deaf person a proper form of sounds that are there in the environment and help that person to hear sounds and decipher them.
A cochlear implant consists of various parts. There is a microphone to pick sound for the external environment. This sound picked by the microphone is selected and arranged accordingly by a speech processor. A transmitter and receiver are there that received sound signals from the processor and convert them into electric impulses. Lastly, there is an electrode array consisting of a group of electrodes whose function is to collect impulses from the stimulator and sending them to different parts of the auditory nerve.
A cochlear implant helps to bypass damaged portions of an ear and directly stimulate the auditory nerve. Signals generated by the machine are sent to the brain via the auditory nerve, and the brain in turn recognises those signals as sounds. Hearing with the aid of this device is quite different from ordinary hearing and requires time to get used to it. But is allows people to hear speeches over the phone, understand sounds in the external environment and recognise warning signals.
A cochlear implant is generally done under the influence if anaesthesia. The procedure used most commonly to implant a mechanical cochlea into a human ear is called mastoidectomy with facial recess approach (MFRA). This is done by removal of the mastoid cells. There are various types of this surgery: Radical mastoidectomy, Canal Wall Down Mastoidectomy, Canal Wall Up Mastoidectomy, Cortical Mastoidectomy and Modified Radical Mastoidectomy. All the different types of mastoidectomy are done by removal of one or more parts of the mastoid bone in order to get the part of the cochlea where the device needs to be implanted.
This surgery takes about two hours, but may also extend up to three hours at a stretch. Before the surgery is done, the audiologist and the physician decide which ear to operate and a thin line of hair is shaved along the incision line. The operator creates cuts a section of the skull behind the ear to accept an internal receiver. Under a surgical microscope, a meticulous drilling in the mastoid bone provided access to the cochlea. A small cavity in the round window membrane allows insertion of the electrode array. The electrode array is tested previously before putting it into the purpose of hearing
Generally the ear with better understanding of speech is recommended for this surgery as residual hearing predicts better post implant performance.
Irrespective of their age or social and economic background, any person who is partially or totally deaf is eligible to take this surgery. It has been approved that even children aged 12 months are also approved to go under cochlear implantation. It is very common these days to find children with hearing problems, who after undergoing this surgery, are able to hear well and clear.
A person, who is not having any hearing problem, does not need to go under this operation. Only, a person who is severely or fully unable to hear is recommended to go for cochlear implantation.
Various types of surgery may involve certain risks during the surgery. There can be infections during the time of surgery, which is quite common in many cases. Extrusion of the implant where the scalp overlies the implant may break down and thus exposes the implant. Further surgery to cover the implant with new tissue or removal of the implant may be necessary in that situation. Also taste disturbance, mouth dryness, numbness of the ear, weakness of the face, dizziness, hematoma, meningitis or anaesthesia can occur after the surgery is performed.
Post treatment guidelines involve learning and re-learning the use of the device, as it is very different from the normal hearing aids. This may take time and would involve patience of the person who has undergone cochlear implant surgery. A person has to practice getting used to the device. Speech-language pathologists and audiologists are there to help people get into practising hearing with the aid of this implant.
It doesn’t take much time to recover from this surgery – about 1 or 2 days are enough to stay at the hospital after the process is done. As soon as the surgery is performed under the supervision of a medical personnel who is specialised in this particular field, the person suffering from hearing problems would be able to hear every sound clearly. He/she only needs some amount of time to get used to this device, and no other problem would exist any further.
The cost of cochlear implant in India starts from Rs. 5.12 lakhs and may vary according to the nature of the surgery. It may rise till Rs. 9.5 lakhs in certain cases.
The effect of the cochlear implantation is permanent. Once the surgery is performed, the people who initially suffered from this problem would get healed and no other problem regarding hearing would be faced by them in the future.
Certain people use hearing aids instead of this surgery. The surgery is quite expensive, and therefore those who cannot afford this surgery, can alternatively use the affordable hearing aids if they suffer from hearing impairment. This doesn’t require much practice to get accustomed to and many people use it.