Deafness Health Dictionary

See: HEARING LOSS. 

Complete or partial loss of hearing in 1 or both ears. There are 2 types of deafness: conductive deafness, which results from faulty propagation of sound from the outer to the inner ear; and sensorineural deafness, in which there is a failure in transmission of sounds to the brain. Hearing tests can determine whether deafness is conductive or sensorineural.

The most common cause of conductive deafness in adults is earwax. Otosclerosis is a less common cause and is usually treated by an operation called stapedectomy, in which the stapes (a small bone in the middle ear) is replaced with an artificial substitute. In a child, conductive deafness usually results from otitis media or glue ear. This condition may be treated by surgery (see myringotomy). In rare cases, deafness results from a perforated 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 at an early stage of pregnancy. Inner-ear damage may also occur soon after birth as the result of severe jaundice. Deafness at birth is incurable. Many children who are born deaf can learn to communicate effectively, often by using sign language. Cochlear implants may help those children born profoundly deaf to learn speech.

In later life, sensorineural deafness can be due to damage to the cochlea and/or labyrinth. It may result from prolonged exposure to loud noise, to Ménière’s disease, to certain drugs, or to 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. Deafness may be accompanied by tinnitus and vertigo. Sometimes it can lead to depression.

People with sensorineural deafness usually need hearing-aids to increase the volume of sound reaching the inner ear. Lip-reading is invaluable for deaf people. Other aids, such as an amplifier for the earpiece of a telephone, are available. (See also ear; hearing.)

Impairment of hearing, which affects about 2 million adults in the UK. In infants, permanent deafness is much less common: about 1–2 per 1,000. It is essential, however, that deafness is picked up early so that appropriate treatment and support can be given to improve hearing and/or ensure that the child can learn to speak.

In most people, deafness is a result of sensorineural hearing impairment, commonly known as nerve deafness. This means that the abnormality is located in the inner ear (the cochlea), in the auditory nerve, or in the brain itself. The prevalence of this type of hearing impairment rises greatly in elderly people, to the extent that more than 50 per cent of the over-70s have a moderate hearing impairment. In most cases no de?nite cause can be found, but contributory factors include excessive exposure to noise, either at work (e.g. shipyards and steelworks) or at leisure (loud music). Anyone who is exposed to gun?re or explosions is also likely to develop some hearing impairment: service personnel, for example.

Conductive hearing impairment is the other main classi?cation. Here there is an abnormality of the external or middle ear, preventing the normal transmission of sound waves to the inner ear. This is most commonly due to chronic otitis media where there is in?ammation of the middle ear, often with a perforation of the ear drum. It is thought that in the majority of cases this is a sequela of childhood middle-ear disease. Many preschool children suffer temporary hearing loss because of otitis media with e?usion (glue ear). Wax does not interfere with hearing unless it totally obstructs the ear canal or is impacted against the tympanic membrane. (See also EAR; EAR, DISEASES OF.)

Treatment Conductive hearing impairment can, in many cases, be treated by an operation on the middle ear or by the use of a hearing aid. Sensorineural hearing impairments can be treated only with a hearing aid. In the UK, hearing aids are available free on the NHS. Most NHS hearing aids are ear-level hearing aids – that is, they ?t behind the ear with the sound transmitted to the ear via a mould in the external ear. Smaller hearing aids are available which ?t within the ear itself, and people can wear such aids in both ears. The use of certain types of hearing aid may be augmented by ?ttings incorporated into the aid which pick up sound directly from television sets or from telephones, and from wire loop systems in halls, lecture theatres and classrooms. More recently, bone-anchored hearing aids have been developed where the hearing aid is attached directly to the bones of the skull using a titanium screw. This type of hearing aid is particularly useful in children with abnormal or absent ear canals who cannot therefore wear conventional hearing aids. People with hearing impairment should seek audiological or medical advice before purchasing any of the many types of hearing aid available commercially. Those people with a hearing impairment which is so profound (‘stone deaf’) that they cannot be helped by a hearing aid can sometimes now be ?tted with an electrical implant in their inner ear (a cochlear implant).

Congenital hearing loss accounts for a very small proportion of the hearing-impaired population. It is important to detect at an early stage as, if undetected and unaided, it may lead to delayed or absent development of speech. Otitis media with e?usion (glue ear) usually resolves spontaneously, although if it persists, surgical intervention has been the traditional treatment involving insertion of a ventilation tube (see GROMMET) into the ear drum, often combined with removal of the adenoids (see NOSE, DISORDERS OF). Recent studies, however, suggest that in many children these operations may provide only transient relief and make no di?erence to long-term outcome.

Advice and information on deafness and hearing aids may be obtained from the Royal National Institute for Deaf People and other organisations.

n. partial or total loss of hearing in one or both ears, now becoming more commonly called hearing loss. Conductive deafness is due to a defect in the conduction of sound from the external ear to the inner ear. This may be due to perforations of the eardrum, fluid or infection in the middle ear (see glue ear; otitis), or disorders of the small bones in the middle ear (*ossicles). Sensorineural (or perceptive) deafness may be due to a lesion of the *cochlea in the inner ear, the cochlear nerve, or the auditory centres in the brain. It may be present from birth (for example if the mother was affected with German measles during pregnancy). In adults it may be brought on by injury, disease (e.g. *Ménière’s disease), or prolonged exposure to loud noise; progressive sensorineural deafness (presbyacusis) is common with advancing age. Some forms of deafness have both conductive and sensorineural components, in which case it is called a mixed hearing loss.

The type of deafness can be diagnosed by various hearing tests (see Rinne’s test; Weber’s test; audiogram), and the treatment depends on the cause. See also cochlear implant; hearing aid; hearing therapy.