Genetic Testing for Hearing Loss

Frequently Asked Questions (FAQs)

The Ear and Hearing Center at Cincinnati Children's Hospital Medical Center provides these responses to commonly asked questions.

Is my child's hearing loss genetic?

At least half (50%) 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:

Hearing loss is present at birth or in early childhood
Hearing loss is related with other problems in the child
Hearing loss affects both ears
Hearing loss is severe to profound
There is a family history of hearing loss

How can my child's hearing loss be genetic if no one else in the family has hearing loss?

Genetic hearing loss is related to the passage of genes which 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.

How Hearing Loss Is Genetic

Genes are a packet of information that tell our bodies to do the things they are suppose to do (i.e., for an 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 which may be harmful. A change in one of the many genes which control the functioning of the ear may lead to hearing loss.

Common Patterns of Inheritance of Hearing Loss

Autosomal Recessive Inheritance (AR)

Most genetic hearing loss in childhood is inherited as an AR condition. AR conditions arise when both members of a gene pair fail to work properly. In these families, a child inherits a change which causes hearing loss from each parent. The parents are hearing because they have both the functioning gene, as well as a change in the other gene which causes hearing loss. These parents are described as carriers of hearing loss. In these families, each child has a one-in-four (25%) chance of 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. People who carrier a genetic disorder 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.

Autosomal Dominant Inheritance (AD)

In some families, parents or other relatives do have hearing loss. Most genetic hearing loss that occurs in adolescence or adulthood is inherited as an AD condition. AD conditions arise when a single member of a gene pair fails to function properly. In these families, a child inherits a change which causes hearing loss from only one parent. Typically, that parent has hearing loss as well. In these families, each child has a one-in-two (50%) chance of hearing loss, and a 50% chance of hearing.

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.

What is genetic testing?

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.

The genes which are currently tested in our laboratory include:

About 60% of the genetic causes of hearing loss are identified by these tests.

What are the benefits of genetic testing for my child?

We believe that all children with inner ear hearing loss may benefit from genetic evaluation and testing.

Genetic test results may:

Determine the exact cause of your child's hearing loss.
Reduce or eliminate the need for other invasive and costly medical tests.
Provide you with information about your child's future hearing and other potential medical complications.
Help you and your child's physician to determine the best treatment and long-term medical management for your child.
Provide you with information about your chance of having another child with hearing loss.

How does my ear produce hearing?

The ear has three main parts:

Outer Ear
Middle Ear
Inner Ear

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, etc.).

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.

Do you offer medical consultation and genetic counseling services?

Complete medical consultation and genetic counseling is available through the combined efforts of the Ear and Hearing Center and the Division of Human Genetics (513-636-4760, option 1) at Cincinnati Children's. For questions please contact the Ear and Hearing Center administrative office.