causes of Deafness
The Deafness - Complete or partial loss of hearing in one or both ears. There are two types of deafness: conductive deafness, which is caused by faulty propagation of sound from the outer to the inner ear; and sensorineural deafness, in which there is a failure in the transmission of sounds to the brain.

The most common cause of conductive deafness in adults is earwax. Otosclerosis, a condition in which the stapes (a small bone in the middle ear) loses its normal mobility, is a less common cause. In children, conductive deafness is usually due to otitis media (middle-ear infection) or glue ear (accumulation of sticky fluid in the middle ear). In rare cases, deafness results from a ruptured eardrum (see eardrum, perforated).

Sensorineural deafness may 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 occur soon after birth as the result of severe neonatal jaundice.

In later life, sensorineural deafness can be due to damage to the cochlea and/or labyrinth of the inner ear. It may result from prolonged exposure to loud noise, or be caused by Ménière’s disease, certain drugs, or some viral infections. The cochlea and labyrinth also degenerate naturally with old age, resulting in presbyacusis. Sensorineural deafness due to damage to the acoustic nerve may be the result of an acoustic neuroma (a noncancerous tumour that develops on the nerve).

A baby who is congenitally deaf fails to respond to sounds, and, although crying is often normal, he or she does not babble or make the usual baby noises that lead to speech. In an adult who has started to become deaf, sounds heard are not only quieter than before, but may be distorted and less clear.

Deafness may be accompanied by tinnitus (noises in the ear) and vertigo (dizziness and loss of balance). Sometimes deafness can lead to confusion and sometimes to depression.

Examination of the ear with an otoscope (a viewing instrument with a light attached) can show if the outer-ear canal is blocked by wax, or if the eardrum is inflamed, perforated, or has fluid behind it. After a physical examination, hearing tests may be performed; these tests can determine whether deafness is conductive or sensorineural.

The treatment depends on the exact cause of the deafness. Removal of excess earwax remedies conductive deafness in many cases. Otosclerosis is generally treated by an operation known as stapedectomy, in which the stapes is replaced with an artificial substitute. Glue ear may also be treated by surgery (see myringotomy) and by the insertion of a grommet (a small tube that allows fluid to drain away from the middle ear).

Many children who are born deaf can learn to communicate effectively, often by using sign language. Cochlear implants (electrodes implanted in the inner ear that can receive sound signals) may help profoundly deaf adults and children, but they are not suitable for everyone. People who have sensorineural deafness usually need hearingaids to increase the volume of sound reaching the inner ear. Lip-reading is invaluable for people who have difficulty hearing, whatever the type and
severity of their deafness. Other aids, such as an amplifier for the earpiece of a telephone, are available to help deaf people perform everyday tasks. (See also ear; hearing.)


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