Patients with severe to profound hearing loss benefit from this surgery, which involves the use of a specialized and small electronic hearing device called Cochlear Implant. It is highly recommended for patients who do not gain from hearing aids.
Q1 How does the ear work in sensing sound or hearing?
A1 Sound is a stimulus which needs to be perceived by a receptor for hearing. Sound is in the form of sound waves and receptor is in the form of tiny hair cells in the cochlea. They are specialized receptors that are sensitive to sound waves.
The ear has three sections namely Outer, Middle and inner ear. They work in coordination to transmit sound to the brain. External or outer ear takes in the sound and pass it to the ear drum through auditory canal, in the form of waves, causing it to vibrate back and forth. The vibration thus produced is transmitted to the three little bones in the middle ear namely maleus, incus and stapes. Stapes, the last bone in the series, is attached to the oval window in the inner ear. Oval window is an opening which is covered by a membrane and communicate the vibrations that travelled through the three bones, to the cochlea in the inner ear. There is fluid in the cochlea that is set into motion due to the vibrations of the oval window to an extent that it reaches the tip of the cochlea and go back all the way towards the round window, not the oval window this time from where the vibrations entered the inner ear as these paths are separated by a membrane in the middle of the cochlea.
Round window is another membrane bound opening in the inner ear that vibrates too, causing the fluid in the cochlea to move back and forth and with it the hair like cells in the cochlea move, that are instrumental in perception of sound.
Cochlea is a snail like structure in the inner ear that has tiny hair like cells that change this vibration that caused them to move, into electrical impulses that transmit through the nerve fibres(Auditory nerve) and finally to the brain. Cochlea is a Greek word for "Snail".
This is how the sound is produced.
Q2 What are the types of hearing loss?
A2 There are three kinds of hearing loss namely
Neurosensory/Sensorineural or Nerve hearing loss
Mechanical or conductive Hearing Loss
Mixed Hearing Loss
Q3 What is sensorineural hearing loss?
A3 In sensorineural hearing loss, the hair like cells in cochlea, the organ of hearing, get damaged and do not convert the mechanical energy into electrical energy that can be transmitted by the nerve to the brain. It is often called nerve hearing loss although it has nothing to do with the auditory nerve. The most common cause of such type of hearing loss is increasing age and genetics. With increasing age, everyone experiences some loss of hearing which may vary from person to person in intensity. Other causes may be a viral infection, certain genetic disorders or rarely a benign tumor on the nerve called Acoustic Neuroma.
Q4 What is mechanical or conductive hearing loss?
A4 Hearing loss due to disorder of the mechanism of the conduction of sound is commonly referred to as mechanical hearing loss. It could be due to impacted ear wax, disorder of the ear drum or little bones in the middle ear, fluid in the middle ear.
Q5 Which is more alarming-hearing loss in one ear or both ears?
A5 Hearing loss in one ear(unilateral hearing loss) is more alarming than in that in both ears(Bilateral hearing loss). Hearing loss in one ear suggests a possibility of a benign tumor called Acoustic Neuroma.
Q6 How does Cochlear implant work?
A6 Cochlear implant is a small, specialized electronic hearing device surgically implanted in patients who suffer from severe hearing loss or are profoundly deaf and helps them in the restoration of hearing.
A cochlear implant has two components: Internally placed cochlear implant and a speech processor, placed externally. Speech processor consist of microphones that help to pick up the sound and transform them into digital signals. These signals are then delivered to the transmitter and finally into the internal implant through the skin. Internal implant convert those coded signals into electrical impulses and delivers them to electrodes. Nerve fibres in the cochlea get stimulated through electrodes bypassing the damaged hair cells in the cochlea and the signals are perceived as sound by the brain.
Q7. Who is a suitable candidate for Cochlear Implant surgery?
A7. The patient is thoroughly evaluated by the ENT surgeon by means of clinical examination, running some medical tests and audiological assessments in order to determine if he or she is a suitable candidate for cochlear implant surgery. Usually, the following norm is followed:
Severe sensori-neural hearing loss or nerve deafness, bilaterally.i.e., both ears
Hearing aids have not helped
Potential recipient of the cochlear implant is devoid of infection in both ears.
Medically fit to undergo surgery
Inner ear is well formed
Q8 What is the difference between hearing aids and cochlear implant?
A8 Hearing aids versus Cochlear implant
Worn externally, either behind the ear or in the ear, hidden in the external auditory meatus or auditory canal.
Recommended for mild to moderate hearing loss.
It amplifies sound from the environment, in order to make it better to hear for the damaged ear. In other words, the damaged ear is being provided with better sound experience. However, if the cochlea is damaged, the sound through the hearing aid tends to get distorted.
Offers control to the user since they are placed externally, hence flexibility. The user can conveniently remove, replace, adjust or get it repaired, if need be.
Hearing aids are thought to perform remarkably better in case of hearing low frequency sounds.
Are associated with problem of "whistling" which is caused due to leakage of the amplified sound through the ear canal and the leaked sound again gets amplified through the hearing aids. it usually happens when the person eats, talks or chews gum.
Surgically placed under the skin, behind the ear
Recommended for severe hearing loss or profoundly deaf persons.
It does not amplify sound rather it helps stimulate the auditory nerve directly by changing the coded signals into electrical energy, bypassing the damaged part of the cochlea.
More costly as compared to the cost of the hearing aids.
Reduced flexibility to the user since half of it is surgically placed inside.
Cochlear implant are not as good as hearing aids in perception of low frequency sounds.However, they outshine hearing aids in perception of mid to high frequency sounds.
Patients with Cochlear implant do not face the problem of "whistling".
Dr Sanjay Sachdeva
Director, ENT, Head and Neck Surgery & Cochlear Implant
Max Super Specialty Hospital, Saket, Delhi
Dr K.K Handa
MBBS, MS(ENT), DNB
Director and Head, Dept. of ENT & Head and Neck Surgery
Medanta The Medicity Hospital, Gurugram, Delhi-NCR
Dr Ameet Kishore
MBBS, FRCS(Glas),FRCS(Edin), FRCS-ORL(UK)
Indraprastha Apollo Hospital, Delhi
Saket, New Delhi
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