A child's speech depends on their hearing and carers should be on the look-out for problems, says Maggie Jones
Since it became known that babies can hear in the womb, expectant couples have sometimes been caught playing Mozart, jazz or other favourite music to their eagerly anticipated unborn. After birth, babies are able to recognise their mother's voice. From then on the ability to hear is vital for a child to imitate the sounds of speech and develop language.
Unfortunately, however, many children suffer from either temporary or permanent hearing loss. A total of 840 children are born every year with a permanent hearing impairment, and thousands more will experience temporary hearing loss from a number of causes, including ear infections and 'glue ear' (see below).
Childcare practitioners are in an ideal position to detect some of these problems, and it is important to do so as early as possible, because the development of normal speech can be affected by undiagnosed hearing problems.
How hearing works
Hearing involves the ear, part of the nervous system and the brain, which work together to receive sound and convert it into messages the brain can understand.
Sound waves enter the ear canal and cause the eardrum to vibrate. Vibrations pass through the middle ear through three tiny bones which act as levers and increase the strength of the vibrations before they pass through into the cochlea in the inner ear, via the oval window.
Inside the cochlea, shaped like a snail's shell, are thousands of tiny hairs called cilia, which are set in motion by the vibrations. These hair cells convert these movements into electrical impulses which travel along the auditory nerve to the brain, where they are interpreted and given meaning.
The ear also enables people to balance, a process which involves the semicircular canals in the inner ear.
What can go wrong
Conductive deafness is caused when sounds cannot pass through the outer and middle ear to the cochlea and auditory nerve. This can be caused by blockages such as wax in the ear or fluid in the middle ear (glue ear) (see below) or sometimes by some congenital abnormality of the bones in the middle ear.
Sensori-neural deafness, also known as nerve deafness, usually means the cochlea is not processing the sound effectively. This kind of deafness is often caused following infectious diseases such as rubella (German measles), mumps, measles, or meningitis. Sometimes shortage of oxygen at birth or other birth traumas can cause deafness, and premature babies are more likely to suffer from this kind of hearing impairment.
Mixed deafness occurs when a child has both types of deafness. Very few children, however, are totally deaf; most have some hearing at some frequencies and volumes.
Hearing tests
Because early intervention is vital for speech development, almost all babies will have regular hearing checks as part of developmental tests carried out by doctors and health visitors.
The first test is normally the distraction test, carried out by a health visitor at the age of seven to nine months. In this test, the child sits on their parent's lap and plays, while the health visitor moves behind the child and makes sounds likely to distract him. Another health visitor observes the child's reaction. The hearing child will normally turn to see where the sound is coming from. If there is any doubt about the result, the child will be referred for a more complex hearing test.
The otoacoustic emission test is very quick and reliable. A small probe is placed in the child's ear and a series of clicking sounds are sent down the ear canal. The instrument measures the strength and pattern of the echo coming back from the inner ear and can establish if some types of hearing loss are present.
A 1997 Medical Research Council report recommended that this test be made universally available for all babies to pick up hearing problems early, which would cost about 13 per child. At present an estimated 1,500 parents do not know their child is deaf because this test is not readily available.
For those children who need further investigation, the brainstem (evoked response) audiometry test can be carried out when the child is asleep.
Electrodes are placed on the child's head which record electrical activity in the brain when sound is relayed through a set of headphones.
With children aged two-and-a-half or more, tests involving toys and play as part of the assessment become more reliable and give a better understanding of the child's level of deafness. Pure-tone air conduction audiometry is often given to children when they enter school at the age of five. It involves the child in putting on a set of headphones and giving a signal when they have heard a sound. This test will show if hearing loss is present and helps the audiologist to find out the type of deafness.
The pure-tone bone conduction test involves tapping the child's skull to see whether the child can pick up the vibrations. This test bypasses the outer and middle ear and can detect whether the cochlea is functioning normally.
Hearing aids
If a child is suffering from hearing loss, a hearing aid can help the child hear better and thus develop more normal speech. Hearing aids act as amplifiers. They can be worn on the body, in or behind the ear, or even inside the ear.
Cochlea implants are a kind of hearing aid which send electrical signals to the brain, bypassing the damaged hair cells which cannot be stimulated by conventional hearing aids.
Sign language
If a child's hearing is poor and cannot be restored with surgical treatment or the use of a hearing aid, then sign language can be used to enable the child to communicate. Many children can lip-read effectively as well. The Makaton sign language can also be used with children who also have a learning disability.
Useful organisations
- The National Deaf Children's Society, 15 Dufferin Street, London EC1Y 8UR (020 7490 8586)
- The Hearing Research Trust,
330-332 Gray's Inn Road, London WC1X 8EE (020 7833 1733)
Facts about deafness
- Deafness tends to go undiagnosed for a long time. Half of all cases are not picked up until the children concerned are 18 months or older. A quarter of cases are not diagnosed until the children concerned are three- and-a-half.
- The overwhelming majority (90 per cent) of deaf children are born to parents who can hear normally and where there is no family history of hearing impairment.
Communication tips
To improve communication with children who have impaired hearing:
- Make sure you have the child's attention before you start talking.
- Make sure that you are in front of the child, fairly close, and at the same level.
- Keep background noise to a minimum.
- Make sure your face is well illuminated and that the child can see you clearly.
- Do not shout, as it will distort the mouth and acoustic patterns, making it harder for the child to understand.
- Speak clearly, a little more slowly than usual, but keeping the pattern of normal speech.
- Be aware of using unusual words and make sure the child understands any unusual word before moving on.
- Sentences are easier to understand than words on their own because it gives the child a context for what you are saying.
- Try to keep your hands free so you can gesture to support what you are saying.
- Always use the appropriate facial expression to show if you are pleased, angry, disappointed and so on.
- Consider using sign language as an additional method of communication. Your local authority will be able to provide you with a list of courses.
Glue ear
Colds, flu, and exposure to cigarette smoke can cause a child to suffer from glue ear. It is less common in children who have been breast-fed, and some carers find that cutting down on dairy products in the child's diet can reduce incidence. However, medical advice should always be sought before reducing foods which are such a valuable source of calcium.
Glue ear is caused by the build-up of mucus in the ear. For it to work properly, the middle ear needs to be full of air, which enters through the Eustachian tube, running from the back of the throat to the inner ear. In children this tube is not as straight or wide as in adults and gets blocked more easily. When this happens cells produce fluid which blocks the middle ear, making it harder for sounds to pass through.
The usual treatment for glue ear is grommets. These are tiny plastic tubes which are put in the eardrum after the fluid has been drained away to allow air to reach the middle ear and stop more fluid building up. Grommets usually remain in place for six to nine months and then simply fall out. If the fluid comes back, more grommets can be inserted.