Partial or complete loss of hearing in one or both ears. There two different types of deafness: sensorineural deafness, in which there is a failure in transmission of sounds to the brain; and conductive deafness, caused by faulty propagation of sound from the outer ear to the inner ear.
Sensorineural deafness can be present from birth. This type of deafness may result from a birth injury or damage resulting from maternal infection with rubella in early pregnancy. Damage to the inner ear may also arise soon after birth as the result of extreme neonatal jaundice.
In later life sensorineural deafness can be due to damage to the cochlea and/or labyrinth of the inner ear. It can result from prolonged exposure to loud noise or caused by Meniere’s disease, some viral infections or certain drugs. The cochlea and labyrinth also degenerate naturally with old age, which results in presbyacusis.
Sensorineural deafness due to injury of the acoustic nerve can be the result of an acoustic neuroma (non cancerous tumour that develops on the nerve).
The most commonly seen cause of conductive deafness in adults is ear wax. Otosclerosis a condition in which the stapes (small bone in the middle ear) loses its usual mobility, is a less common cause. In infants, conductive deafness is often due to otitis media (middle ear infection) or glue ear (accumulation of sticky fluid in middle ear). In uncommon cases, deafness results from a ruptured ear drum.
Symptoms and signs
A child or baby whom is congenitally deaf won’t respond to sounds, and although crying is usually normal, he or she doesn’t make the common baby noises that lead to speech. In an adult that has started to become deaf, sounds may be distorted and less clear and are heard a lot quieter.
Deafness can also be accompanied by vertigo (dizziness and loss of balance) and tinnitus (noises in the ear). Occasionally deafness can lead to depression and also confusion.
All newborn children are given a hearing test in the first couple of weeks of life to check for congenital deafness. For older children and adults examination of the ear with an otoscope (viewing instrument with a light attached) can show if the outer ear canal is blocked by wax, or if the eardrum is perforated, inflamed or has fluid behind it. After a physical examination, hearing tests can be performed; these tests then determine whether deafness is sensorineural or conductive.
The treatment will depend on the specific cause of the deafness. Removal of excess earwax cures conductive deafness in a lot of cases. Otosclerosis is usually treated by an operation called stapedectomy, in where the stapes are replaced with an artificial substitute. Glue can also be treated by surgery and by insertion of a grommet (a little tube that lets excess fluid drain out of the middle ear).
Most children that are born deaf do learn to communicate successfully, usually by means of sign language. Cochlear implants (electrodes implanted in the inner ear that can receive sound signals) can help profoundly deaf adults and children, but aren’t always suitable for everyone. Those who have sensorineural deafness typically need hearing-aids to increase the level of sound that is reaching the inner ear. Lip-reading is invaluable for those people who have trouble hearing, whatever the severity and type of their deafness. Many other aids, such as an amplifier for the earpiece of a telephone, are accessible to assist the deaf, perform everyday tasks.