Deafness or hearing impairment describes any inability or difficulty in perceiving or understanding sounds. It can have many causes and can be the result of several physical impairments.
- It can be congenital, generally due to a genetic cause although it can also be caused by exposure to certain toxins during pregnancy that damage the struture of the ear, the auditory nerve or the part of the brain that perceives sounds.
- It can be the result of disease, particularly at an early age. Almost all of the childhood diseases such as measles and mumps can cause nerve damage, but any severe infection can result in such damage.
- In older persons, it is usually the result of exposure to constant loud noise, typically those found in industrial facilities or airports, but often through voluntary exposure to things like loud music. However, deafness can also be caused by an extreme loud noise, such as an explosion.
- Trauma to the ear or brain can also result in total or partial hearing loss.
Deafness results from:
- Damage to the parts of the ear itself that perceive sound, such as the eardrum, small bones, or cochlea.
- Most commonly, damage to the auditory nerve.
- Less often, damage to the part of the brain that perceives and interprets sound.
Success of treatment often depends on the age of onset. If the individual loses hearing before starting to speak, learning to communicate verbally is far more difficult than if the individual has already started speaking. In addition, the use of hearing aids and cochlear implants should be made as quickly as possible to preserve what hearing remains and to allow the individual to adjust to the new sensation of hearing.
There is a great deal of controversy whether the deaf should be required to attempt to communicate verbally or to allow them to use non-verbal communication such as sign language. In most cases the approach has to be individualized. Although most persons raised non-verbally have great difficulty dealing with even written language (due to the lack of ability to translate letters into familiar sounds), many person have great difficulty with skills such as lip reading (which is inaccurate in any case) and never adjust to learning a spoken language, although all deaf people will pick up sign language if exposed to it at a young age the same way a hearing person will pick up a spoken language.