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 deﬁnite 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 gunﬁre or explosions is also likely to develop some hearing impairment: service personnel, for example.
Conductive hearing impairment is the other main classiﬁcation. 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 inﬂammation 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 eﬀusion (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 ﬁt behind the ear with the sound transmitted to the ear via a mould in the external ear. Smaller hearing aids are available which ﬁt 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 ﬁttings 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 ﬁtted 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 eﬀusion (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 diﬀerence 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.