Hearing loss is the total or partial inability to hear sound in one or both ears.

See also: Hearing loss of aging   

Minor decreases in hearing are frequent after age 20. Hearing problems usually come on gradually, and rarely end in complete deafness.

There are many causes of hearing loss. They can be divided into two main categories:

• Conductive hearing loss (CHL) occurs because of some mechanical problem in the external or middle ear. The three tiny bones of the ear (ossicles) may fail to conduct sound to the cochlea, or the eardrum may fail to vibrate in response to sound. Fluid in the middle ear can cause CHL.
• Sensorineural hearing loss (SNHL) results from a dysfunction of the inner ear. It most often occurs when the tiny hair cells (nerve endings) that transmit sound through the ear are injured. This type of hearing loss is sometimes called "nerve damage," although this is not accurate.

CHL is often reversible -- SNHL is not. People who have both forms of hearing loss are said to have mixed hearing loss.

Screening for hearing loss is now recommended for all newborns. In children, hearing problems may cause speech to develop slowly.

Ear infections are the most common cause of temporary hearing loss in children. Fluid may linger in the ear following an ear infection. Although this fluid can go unnoticed, it can cause significant hearing problems in children. Any fluid that stays longer than 8 - 12 weeks is cause for concern.

Preventing hearing loss is more effective than treating it after "the damage is done."

Genetic:

• Bjorn pili torti and deafness syndrome
• Cockayne syndrome
• Fronto-metaphyseal dysplasia syndrome
• Hereditary nephritis
• Hunter syndrome
• Hurler syndrome
• Kartagener syndrome
• Leopard syndrome (multiple lentigines)
• Mohr syndrome
• Morquio syndrome
• Multiple lentigines syndrome
• Multiple synostosis syndrome
• Osteogenesis imperfecta
• Otosclerosis
• Robinson type ectodermal dysplasia
• Stickler syndrome
• Taybi oto-palato-digital syndrome
• Treacher Collins syndrome
• Trisomy 13
• Waardenburg syndrome

Congenital:

• Congenital atresia of the external auditory canal
• Congenital cytomegalovirus
• Congenital perilymphatic fistula
• Fetal iodine deficiency effects
• Fetal methyl mercury effects
• Rubella syndrome

Infectious:

• Ear infection (otitis media)
• Measles
• Meningitis
• Mumps
• Scarlet fever

Traumatic:

• Acoustic trauma such as from explosions, fireworks, gunfire, rock concerts, and earphones
• Barotrauma (differences in pressure)
• Skull fracture (temporal bone)
• Traumatic perforation of the eardrum

Toxic:

• Aminoglycoside antibiotics
• Aspirin
• Chloroquine
• Ethacrynic acid - oral
• Quinidine

Age-related:

• Age-related hearing loss (presbycusis)

Occupational:

• Any occupation with exposure to loud noises on a continuous day-to-day basis can result in hearing loss due to nerve end damage. Increased attention to conditions in the work environment has markedly decreased the likelihood of work-related hearing loss. See occupational hearing loss.

Other:

• Acoustic neuroma
• Meniere's disease

Temporary hearing loss can be caused by:

• Allergy
• Blocked Eustachian tubes
• Build-up of wax in the ear canal
• Ear infections (chronic otitis externa, chronic otitis media, malignant otitis externa)
• Foreign body lodged in the ear canal
• Injury to the head
• Reaction to medication such as aminoglycosides, chloroquine, quinidine
• Scarred or perforated eardrum