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

See also: Hearing loss of aging   

Decreased hearing; Deafness; Loss of hearing; Conductive hearing loss; Sensorineural hearing loss

Minor decreases in hearing are common after age 20.

Hearing problems usually come on gradually, and rarely end in complete deafness.

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

• Conductive hearing loss (CHL) occurs because of a mechanical problem in the outer or middle ear. The three tiny bones of the ear (ossicles) may not conduct sound properly, or the eardrum may not vibrate in response to sound. Fluid in the middle ear can cause this type of hearing loss.
• Sensorineural hearing loss (SNHL) results when there is a problem with the inner ear. It most often occurs when the tiny hair cells (nerve endings) that transmit sound through the ear are injured, diseased, do not function properly, or have prematurely died. 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.

HEARING LOSS IN CHILDREN

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 stay in the ear following an ear infection. The fluid can go unnoticed, or it can cause significant hearing problems in children. Any fluid that remains 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:

• Working around loud noises on a continuous day-to-day basis can damage nerve cells responsible for hearing; Increased attention to conditions in the work environment has greatly decreased the chances of work-related hearing loss. See: Occupational hearing loss

Other:

• Acoustic neuroma
• Meniere's disease
• Sudden hearing loss without a known cause (idiopathic hearing loss)

Temporary hearing loss can be caused by:

• Allergies
• 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 medications such as aminoglycosides, chloroquine, quinidine
• Scarred or perforated eardrum

Baloh RW. Hearing and Equilibrium. In: Goldman L, Ausiello D, eds. Cecil Medicine. 23rd ed. Philadelphia, PA : Saunders Elsevier; 2007: chap 454.

Wrightson AS. Universal newborn hearing screening. Am Fam Physician. 2007; 75(9):1349.