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Pediatric Deafness
Normal hearing requires that all parts of the auditory pathway are working correctly. This pathway includes the external ear, middle ear, inner ear, auditory nerve, and the connection between the auditory nerve and the brain. The exact location and nature of the problem in the auditory pathway determines the type and severity of a person's hearing loss.
Some causes of hearing loss occur before a baby is born. These include genetic disorders (such as Waardenburg syndrome or Crouzon syndrome) and infections (such as congenital rubella or congenital syphilis).
Genetic Factors
About half of all cases of hearing loss among children are thought to result from genetic factors. Sometimes these children have a syndrome of which hearing loss is only one feature. However, in most children with hearing loss that is due to a genetic cause, the hearing loss is not part of a syndrome. A variant of the connexin 26 gene is responsible for much of the hearing loss in this latter group of children.
Postpartum Factors
Problems during or soon after birth can also be risk factors for developing hearing loss. These include hypoxia (where the baby does get not enough oxygen), bleeding in the brain, and hyperbilirubinemia (severe jaundice). Children who are born early or at low birth weight are more likely to have problems that may lead to hearing loss. However, children who are normal birth weight can have hearing loss.
Other Factors
Hearing loss can also occur later in a child's or adult's life. Causes during this time include infection (such as meningitis, chronic middle ear infections, or measles), injuries (such as head injury), or certain drugs (such as the antibiotic gentamycin). High noise levels (such as from firecrackers or loud rock concerts) can also damage a person's hearing. About 30 million workers are exposed to dangerous noise levels on their jobs. Another nine million are at risk of hearing loss as a result of working with certain metals or solvents.
Some causes of hearing loss can be prevented. For example, vaccines can prevent certain infections, such as H-flu meningitis or measles, that can cause hearing loss.
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