Akademik

General term for inability to hear.

- central d. d. due to disorder of the auditory system of the brainstem or cerebral cortex.

- cortical d. d. resulting from bilateral lesions of the primary receptive area of the temporal lobe.

- hereditary d. See hereditary hearing impairment.

- nerve d., neural d. former terms for sensorineural hearing loss.

- postlingual d. hearing impairment occurring after speech and language skills have been developed.

- prelingual d. hearing impairment occurring before development of speech and language skills.

- sudden d. a profound sensory hearing loss that develops in 24 hrs or less; generally thought to be due to a viral infection in the inner ear.

- word d. SYN: auditory aphasia.

partial or total loss of hearing in one or both ears. 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 (ossicle). Sensorineural (or perceptive) deafness may be due to a lesion of the cochlea in the inner ear, the auditory 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.

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.