Deafness

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.)