The causes of hearing impairment can be divided into two main groups, namely genetic (inherited) causes and acquired causes.
Most hearing impairment is inherited. Of all types of inherited deafness only one third is present at birth. Another third starts during childhood and the other third only manifests in adulthood.
There are many ways in which people acquire hearing loss.
Causes before birth
During the first 28 days of pregnancy it is of utmost importance that the mother does not get an infection, especially German measles and cytomegalovirus.
If the mother gets German measles during the first eight weeks of pregnancy there is an 86% chance that her baby will be hearing impaired.
German measles appears to be dangerous throughout pregnancy. Any contact with a person with this illness is therefore potentially dangerous.
Other factors which can play a role in hearing impairment include Rhesus incompatibility as well as metabolic illnesses such as diabetes and thyroid problems.
Causes during and just after birth
The most common causes of hearing impairment at this stage are birth injuries, jaundice and a lack of oxygen.
Causes after birth
These causes include:
- viral and bacterial infections such as meningitis
- drug toxicity
- excessive noise exposure
- middle ear infection
- head trauma
Ear infections are painful and should be treated in time. If not, infection can cause lasting damage. Many conductive hearing losses can be eliminated or substantially improved by medical treatment.
Outer ear infection (otitis externa):
Infection can be caused by an object in the external ear canal, for example excessive ear wax. Foreign objects include peas, a piece of prestik and small insects.
Adults should not attempt to remove the object unless it can be done easily. Children should be taught that the only thing they are allowed to put into their ears is their elbow.
Rough cleaning can scratch the delicate skin in the ear canal and it may become infected.
Chlorine in swimming pools (and bacteria in dirty swimming pools) can irritate the ear canal.
If a child has earache or a discharge from his ear, he could have an outer ear infection. Ask the child to open his mouth wide, then gently pull the ear lobe back. If this is very painful, there could be an ear infection.
Middle ear infection (otitis media):
This is the most common source of conductive hearing loss. It is an inflammation and/or infection of the middle ear. Infections can be caused by a build-up of fluid in the middle ear.
Otitis media is common in children under five years, particularly those under two years. This might be because the eustachian tube connecting the throat with the ear is short. This allows bacteria and viruses to move quickly from the nose and throat to the middle ear.
Enlarged adenoids block the entrance to the eustachian tube, preventing mucous from draining into the throat. This could also cause infection.
Children prone to hayfever and those with a cleft palate are particularly at risk.
Written by Liesel Van Niekerk, speech and hearing teacher and author of Listening and Language Home Programme, updated February 2008
Types of hearing loss
When hearing becomes difficult
Hearing impairment identified too late