Facts about Cochlear Implant
Deafness is the loss of ability to hear normally. There are two types of deafness - conductive and sensori-neural. These occur separately or together when it is called mixed loss .One (unilateral) or both ears (bilateral) may be involved. All degrees of hearing loss, from mild to profound, may occur. Conductive deafness is due to interference with the conduction of sound across the middle ear to the inner ear. Sensori-neural deafness is due to reduced function of the inner ear (cochlea) or the nerve fibers leading to the brain.
- Conductive hearing: sound travels along the ear canal of the external ear causing the ear drum to vibrate. Three small bones of the middle ear conduct these vibrations from the ear drum to the cochlea (auditory chamber) of the inner ear.
- Sensori-neural hearing: when the three small bones move, they start waves of fluid in the cochlea, and these waves stimulate more than 10,000 delicate hearing cells (hair cells). As these hair cells move, they generate an electrical current in the auditory nerve. It travels through inter-connections to the brain area that recognizes it as sound.
- Ear anatomy - The ear is made up of three different parts, including: Outer ear: includes the part you see outside. Its shape helps to collect sound waves which are then lead to a tube( external auditory canal) which directs it inward, towards the eardrum.
- Middle ear: Separated from the outer ear by the eardrum. The middle ear contains three tiny bones called the malleus (hammer bone), the incus (anvil bone) and the stapes (stirrup bone). These bones amplify the movement of the eardrum produced by sound waves. The Eustachian tube attaches the middle ear to the back of the throat and helps to equalize air pressure on both sides of the ear drum.
- Inner ear: sound waves are picked up by a little spiral shaped organ called the cochlea. It senses the vibrations and pass the message – interpreted into electrical impulses - to the brain via the cochlear nerve. The Cochlea therefore acts like a Transducer.
Conductive deafness is caused by the failure of the ear drum & the three tiny bones inside the middle ear to pass sound waves to the inner ear. A build-up of was in the outer canal or fluid in the middle ear could hamper the movement of the eardrum. In many cases , treatment is available for conductive deafness and normal hearing can be restored.
Nerve deafness is caused by disease, trauma (Head Injury) targeting the cochlea and the cochlear nerve. The rest of the ear – including the tiny bones and eardrum - may be working, but the electrical impulses aren't able to reach the brain. In other cases, the problem is in the brain itself, which can't translate the messages from the cochlear nerve. Most cases of nerve deafness don't respond to treatment and may only be helped with hearing Aids or Cochlear Implants, according to the severity of hearing loss.
Causes of temporary deafness–some of the causes of temporary deafness include:
- Wax: the ear canal secretes cerumen, a waxy substance that helps to protect and lubricate the tissues. A build up of wax can block the ear canal, leading to short term conductive deafness.
- Foreign object: similar to ear wax, a foreign object stuck inside the ear canal (such as the tip of the cotton bud) can temporarily cause hearing loss.
- Excess mucus: the common cold, a bout of flu, hay fever or other allergies can cause an excess of mucus that may block the Eustachian tubes of the ear.
- Ear infections: including otitis externa (infection of the external ear) and otitis media (infection of the middle ear). Fluid and pus don't allow the full conduction of sound to be transmitted properly.
- Drugs: (Certain Drugs, Including Aspirin, amino -glycosides, chloroquine, etc. can cause temporary deafness in susceptible people.
Causes of hearing loss
Some of the many causes of deafness include:
- Hereditary disorders: some types of deafness are hereditary, which means parents pass on flawed genes to their children. In most cases, hereditary deafness Is caused by malformations of the inner ear.
- Genetic disorders: genetic mutations may happen: for example, at the moment of conception when the father's sperm joins with the mother's egg. Some of the many genetic disorders that can cause deafness include osteogenesis imperfecta, Trisomy 13 S and multiple lentigines syndrome.
- Prenatal exposure to diseases: a baby will be born deaf or with hearing problems if they are exposed to certain diseases in utero, including rubella (German measles), influenza and mumps. Other factors that are thought to cause congenital deafness include exposure to drugs such as quinine.
- Noise: loud noises (such as gun shots, firecrackers, explosions and rock concerts) can damage the delicate mechanisms inside the ear.
- Trauma: such as perforation of the eardrum, fractured skull or changes in air pressure( barotrauma)
- Disease: certain diseases can cause deafness including meningitis, mumps, cytomegalovirus and chicken pox. A severe case of jaundice is also known to cause deafness.
- Other causes: other causes of deafness include Meniere's disease and exposure to certain chemicals.
Age related hearing loss
Our hearing gradually becomes less acute as we age. This is normal, and rarely leads to deafness. Age-related hearing loss (presbyacusis) typically begins with the loss of higher frequencies, so that certain speech sounds-such as 's', 'f' and 't' –end up sounding very similar. This means the older person can hear, but not always understand. For example, the words 'see' and 'tea' might sound the same.
Tinnitus is often associated with deafness
Tinnitus means a sensation of ringing in the ears. Some of the causes of tinnitus include middle ear infections and damage to the ear from loud noises. Tinnitus may occur on its own or in conjunction with hearing loss.
Things to remember
- Deafness can range from mild to profound and is caused by many different events including injury, disease and genetic defects.
- Deafness at birth is known as congenital deafness, while deafness that occurs after birth is called acquired deafness.
- Deafness due to congenital causes leads to Pre Lingual Deafness. Deafness acquired after acquiring speech is called Post Lingual deafness.
- The most common cause of acquired deafness is noise, which accounts for over one quarter of people affected by hearing loss.
Treatment involved for deafness
The specialist takes a history and carries out an examination. A hearing test and other tests, including blood examination and x-ray or magnetic scans, may be required. It may be necessary to have repeated hearing tests. Depending on the results and the type of deafness diagnosed, different treatments are suggested. For most patients with sensori-neural deafness the main treatment is the provision of a Hearing Aid.
With today's technology & instruments available (OAE, BERA & ASSR) hearing loss can be diagnosed in a child, as early as 1 day old.
Hearing levels are measured in decibels. If hearing level is say, 30 decibels (30db), then 30% of hearing may have been lost. At this level quiet conversation will be missed. If the hearing loss is at 30decibels or greater, then the use of a hearing aid is usually considered. Modern hearing aids are much lighter and smaller and better. They can be worn behind your ear and easily covered by the hair. Even smaller aids can be purchased to wear in the ear. All hearing aids consist of a microphone, an amplifier and a receiver. The microphone picks up the sound, the amplifier makes it louder and the receiver is a small loudspeaker. Sometimes, making sounds louder does not help the patient understand better. This is because the ear has lost the ability to discriminate what the sounds mean.
During treatment for deafness
Depending on the cause, some cases of deafness may respond to treatment with drugs, including antibiotics. The medicines must be taken as instructed and side-effects watched for. If a hearing aid has been prescribed, one should be aware how to use it and how to look after it. The hearing aid dispenser should be asked about other aids for the hard of hearing. Various devices are available, including loop systems and plug-in to the television amplifiers and warning lights may also be used in telephones.
Is deafness is left untreated?
Deafness in children interferes with the social and educational development of the child. It may be mistaken for backwardness. All young children must be screened to avoid these problems. Delayed speech and problems with behavior are common in deaf children. Adults who become deaf may not be able to do their jobs properly and they may have society problems. They may annoy their neighbors with radios, TV sets and hi-fi sets, keeping them too loud. Many of these problems may be helped by using hearing aids.
What is cochlear implant?
A cochlear implant is a small, complex electronic device that can help to provide a sense of sound to a person who is profoundly deaf or severely hard-of-hearing. The implant consists of an external portion that sits behind ear and a second portion that is surgically placed under the skin.
An implant has the following parts;
- A microphone, which picks up sound from the environment.
- A speech processor, which selects and arranges sounds picked up by the microphone.
- A transmitter and receiver/stimulator, which receive signals from the speech processor and converts them into electronic impulses.
- An electrode array, which is a group of electrodes that collects the impulses from the stimulator and sends then to different regions of the auditory nerve.
An implant does not restore normal hearing. Instead, it can give a deaf person a useful representation of sound in the environment and help him or her to understand speech.
How does a cochlear implant work?
A cochlear implant is very different from a hearing aid. Hearing aids amplify sounds so they may damage ears. Cochlear implants bypass damaged portions of the ear and directly stimulate the auditory nerve. Signals generated by the implant are sent by way of the auditory nerve to the brain, which recognizes the signals as sound. Hearing through a cochlear implant is different from normal hearing and takes time to learn or relearn. However, done at different ages it allows people to recognize warning signals, understand other sounds in the environment, and enjoy a conversation in person or by telephone.
Parts of the cochlear implant:
The implant is surgically placed under the skin behind the ear. The basic parts of the device include:
- A microphone.
- A speech processor, which selectively filters sound to priorities audible speech and sends the electrical sound signals through a thin cable to the transmitter.
- A transmitter, which is a magnetic pad placed behind the external ear, and transmits the processed sound signals to the internal device by electromagnetic induction.
- A receiver and stimulator secured in bone beneath the skin, which converts the signals into electronic impulses and sends them through an internal cable to electrodes,
- An array up to 24 electrodes wound through the cochlea, which sends the impulses directly into the brain.
Who gets cochlear implants?
Children and adults who are deaf or severely hard-of-hearing can be fitted for cochlear implants.
Adults who have lost all or most of their hearing later in life often can benefit from cochlear implants. This may help then to understand speech without visual clues or systems such as lip reading or sign language.
Cochlear implants, coupled with intensive post implantation therapy, can help young children to acquire speech, language, development, and social skills. Most children who receive implants are between two and ten years old. Early implantation provides exposure to sounds that can be helpful during the critical period when children learn speech and language skills.
How does someone receive cochlear implants?
Use of a cochlear implant requires both a surgical procedure and significant therapy to learn or relearn the sense of hearing. Not everyone performs at the same level with this device. The decision to receive an implant should involve discussions with medical specialists, including an experienced cochlear-implant surgeon. The process can be expensive. Surgical implantations are almost always safe, although complications are a risk factor, just as with an implant. This process takes time and practice. Speech-language pathologists and audiologist are frequently involved in this learning process. Prior to implantation, all of these factors need to be considered
Costs of implants
More expensive than a hearing aid, the total cost of a cochlear implant including evaluation, surgery, the device and rehabilitation is around 7 lacs to 13 lacs at our clinic.