How is hearing loss diagnosed?

04-01-2020 | ENT & DENTAL CENTRE

Hearing loss can be diagnosed within a few days of birth. Tests such as BERA, ASSR, Impedance audiometry, OAE and BOA (behavioural observation audiometry) can all be carried out and a complete diagnosis made. These tests will confirm the presence of any hearing loss and tell us the degree/severity of hearing loss also. Most of the time the exact site of damage can also be ascertained.

What is the impact of hearing loss on a child?
Reduced listening skills
Lifelong language deficits
Lifelong communication deficits
Poor basic reading skills
Poor ability to learn to write
Compromised academic career
Behaviour, self esteem, mental health & social skills are also affected.

Is it important to diagnose hearing loss early?
Early diagnosis is very important in the management of hearing loss. This is why most developed countries have Universal Hearing Screening Program's in which all new born babies are tested for hearing loss immediately after birth.

A child's brain is very plastic and can learn new tasks easily, such as hearing. As the child hears, new pathways develop in the brain and the child learns to understand speech and language. With time, the child learns to speak and express himself. If the diagnosis is delayed, then the child starts hearing sound late in life. By the age of 6-7 years, the child's brain has lost it's plasticity. That means that the child will find it difficult to learn new tasks at this age.

This is the reason that children who are diagnosed early and who receive either hearing aids or cochlear implants at an early age (depending on the severity of hearing loss) tend to do very well compared to older children.

Hearing aids are beneficial upto what degree of hearing loss?
Hearing aids are beneficial in children and adults who have a hearing loss between 25-70 decibels (mild to moderately severe hearing loss). Anyone with a hearing loss of more than 70decibel needs to be fitted with a cochlear implant.

How does a hearing aid work?
Hearing aids are simply amplifiers of sound. Some are very sophisticated in terms of technology, but they all have a limitation in that they do not provide benefit to someone with a hearing loss greater than 70db (decibels).

What is a cochlear implant and how does it work?
A cochlear implant is an electronic device that provides hearing sensation to those with severe to profound hearing loss. This device consists of two parts. One is the internal part that is placed under the skin behind the ear by a surgical procedure. The other part is the external part called the processor that is used behind the ear like a hearing aid. This processor collects the sound with the help of microphones and digitises it into FM radio waves. These waves pass across the skin to the internal implant where they are converted into electrical impulses. These impulses then reach the cochlea thru the electrode and they stimulate the hearing nerve fibres directly. Hence, the implantee hears sound.

How successful are cochlear implants?
Cochlear implants are a modern medical miracle. They have helped lakhs of children and adults hear sound, learn speech and language. Since the first implant in a child in 1985, they have helped children go to normal schools and colleges and develop near normal hearing, speech and language. These children are now socially useful and productive members of society.

What is the process to get a cochlear implant?
Once the hearing (audiological) tests have confirmed that there is a severe hearing loss, the decision is made to implant the child. A CT and MRI scan of the inner ear and hearing nerves is conducted to confirm that the anatomy of the cochlea is grossly normal and that the patient can be implanted. Then some basic blood and urine tests are carried out. After this a cochlear implant surgery can be performed. This procedure usually takes between 1-2 hours.

How early can a child be implanted?
My youngest child is 8 months old, but children as young as 6 months are being routinely implanted in some centres in the world.

Can an adult be implanted?
Cochlear implants are very effective in adults who lose their hearing at any stage in their lives. This may be due to age-related hearing loss, accidents, infections and many other reasons. My oldest patient is over 87 years old.

How common is severe hearing loss in India?
An estimated 50,000 babies are born in India every year with severe to profound hearing loss. Most of them need a cochlear implant. However at the moment, only an estimated 1,500 children in India under the age of 4 have a cochlear implant!