Hearing loss is the total or partial inability to hear sound in one or both ears. This article focuses on hearing loss in infants.

About 2 - 3 infants out of every 1,000 live births will have some degree of hearing loss at birth. Hearing loss can also develop in children who had normal hearing as infants. The loss can occur in one or both ears, and may be mild, moderate, severe, or profound. Profound hearing loss is what most people call deafness.

Some cases of hearing loss are progressive (they get worse over time). Other cases of hearing loss stay stable and do not get worse.

Risk factors for infant hearing loss include:

• Family history of hearing loss
• Infection with some viruses and bacteria
• Low birth weight
• Problems with the structure of the skull bones

There are four types of hearing loss:

• Conductive hearing loss (CHL)
• Sensorineural hearing loss (SNHL)
• Mixed hearing loss
• Central hearing loss

Conductive hearing loss results from a problem in the outer or middle ear, such as wax buildup, rupture of the eardrum, or repeated infections. It is usually possible to treat conductive hearing loss with medication or surgery.

Causes of conductive hearing loss in infants include:

• Abnormalities in the structure of the ear canal or middle ear
• Buildup of ear wax
• Ear infections (especially repeated infections)
• Foreign objects in the ear
• Injury
• Rupture of the eardrum
• Tumors

Sensorineural hearing loss results from a problem with the inner ear. The inner ear is responsible for sending signals to the auditory (hearing) nerve. There is no cure for sensorineural hearing loss. People with this type of hearing loss may benefit from hearing aids or a cochlear implant.

Causes of sensorineural hearing loss include:

• Exposure to certain toxic chemicals or medications while in the womb or after birth
• Genetic changes or conditions, such as Down syndrome
• Infection before birth, including cytomegalovirus infection, or infection with German measles during the early stages of pregnancy
• Infections after birth, such as bacterial meningitis
• Problems with the structure of the inner ear

Mixed hearing loss is hearing loss that results from a combination of conductive and sensorineural problems. Causes of mixed hearing loss can include any combination of the above SNHL and CHL causes.

Central hearing loss results from damage to the auditory nerve itself, or the brain pathways that lead to the nerve. Central hearing loss is rare in infants and children.

Causes of central hearing loss include:

• Diseases that affect the protective coating (myelin sheath) around nerve cells
• Tumors