Worlds of David Darling
Encyclopedia of Science
   
Home > Encyclopedia of Science

deafness





Failing of hearing may have many causes. Conductive deafness is due to disease of the outer ear or middle ear, while perceptive deafness is due to disease of the inner ear or nerves of hearing.

Common physical causes of conductive deafness are obstruction with wax or foreign bodies and injury to the eardrum (tympanic membrane). Middle ear disease (see otitis media) is an important cause: in acute otitis, common in children, the ears are painful, with deafness, fever, and discharge; in secretory otitis or glue ear, also in children, deafness and discomfort result from poor Eustachian tube drainage; chronic otitis, in any age group, leads to a deaf discharging ear, with drum perforation. Antibiotics in adequate courses are crucial in acute otitis, while glue ear is relieved by tubes or "grommets" passed through the drum to drain the middle ear. In both, the adenoids may need removal to relieve Eustachian obstruction. In chronic otitis, keeping the ears clean and dry is important and antibiotics are used for secondary infection, while surgery, including reconstitution of the drum, may be needed to restore hearing. Ostosclerosis is a common familial disease of middle age in which fusion or ankylosis of the small bones of the ear cause deafness. Early operation can prevent irreversible changes and improve hearing.

Perceptive deafness may follow infections in pregnancy (e.g., rubella) or be hereditary. Acute virus infection and trauma to the inner ear (e.g., blast injuries or chronic occupational noise exposure) are important causes. Damage to the ear blood supply or the auditory nerve by drugs, tumor, or multiple sclerosis may lead to perceptive deafness, as may the later stages of Ménière's disease.

Deafness of old age, or presbycusis, is of gradual onset, mainly due to the loss of nerve cells. Early recognition of deafness in children is particularly important as it may otherwise impair learning and speech development. Hearing aids are valuable in most cases of conductive and some of perceptive deafness. Cochlear implants can provide a significant level of hearing in some cases of perceptive deafness. Lip-reading, in which the deaf person understands speech by the interpretation of lip movements, and sign language are useful in severe cases.


Related category

   • HEALTH AND DISEASE