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Your child’s hearing loss may be genetic, even if no other people in your family have hearing loss. We offer answers to your frequently asked questions.
At least half of all children with inner ear (sensorineural) hearing loss have a genetic cause of their hearing loss. More than 100 genes tell the ear how to hear. Mutations (changes) in any one of those genes may cause hearing loss. Nerve-based hearing loss is likely to be genetic if:
Genetic hearing loss is related to the passage of genes that cause hearing loss through the family. Your child’s hearing loss may be genetic, even if no other people in your family have hearing loss.
A gene is a packet of information that tells our bodies to do a specific job. Many genes work together to tell the ear to hear. Genes are made of a chemical called DNA (deoxyribonucleic acid). There are about 20,000-25,000 genes in our bodies. At least 100 of these genes play a role in hearing. In our bodies, genes come in pairs. One member of each pair is inherited from a child’s mother, and one from a child’s father. Most of the time, both genes within a pair are nearly identical. Sometimes, a small change occurs within a gene that may be harmful. A change in one of the many genes that control the functioning of the ear may lead to hearing loss.
A carrier of a genetic disorder is someone who has a change in one of his or her genes without showing symptoms of the disorder. When two people carry a genetic disorder they can pass the disorder on to their children. So, it is possible to have a child with genetic hearing loss, even when parents are hearing and have no family history of hearing loss.
Hearing loss may also be passed along in a family as X-linked recessive or mitochondrially inherited traits. Your genetic counselor can explain these in more depth.
Genetic testing is the complex process by which the more common genes related to hearing loss are analyzed in the laboratory. A small sample of blood (or other tissue) is needed for analysis. Cincinnati Children’s tests for 23 genes associated with hearing loss. About 80 percent of the genetic causes of hearing loss are identified by these tests.
We believe that all children with inner ear hearing loss may benefit from genetic evaluation and testing. Genetic test results may:
The ear has three main parts: outer, middle and inner.
The outer ear (the part you can see) opens into the ear canal. The eardrum separates the ear canal from the middle ear. Small bones in the middle ear help transfer sound to the inner ear. The inner ear contains several channels of fluid and specialized cells that detect fluid motion. These cells are connected to the auditory (hearing) nerve, which leads to the brain.
Any source of sound sends vibrations or sound waves into the air. These funnel through the ear opening, down the ear, canal, and strike your eardrum, causing it to vibrate. The vibrations are passed to the small bones of the middle ear, which transmit them to the fluid of the inner ear. Here, the fluid vibrations become nerve impulses and go directly to the brain, which interprets the impulses as sound (music, voice, a car horn).
If a problem arises in the outer or middle portion of the ear, a conductive (or mechanical) hearing loss (CHL) is present. Common causes of CHL are fluid in the middle ear from ear infections or an ear plug. If the inner ear or hearing nerve is damaged, a sensorineural hearing loss (SNHL) develops. The common forms of SNHL are from genetic (hereditary) factors or infections (i.e., meningitis). In general, CHL can be corrected with medicine or surgery, while SNHL is usually not reversible.
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