Congenital Hearing Loss
January is National Birth Defects Prevention Month. In recognition this week, we’re answering the question: can hearing loss be inherited?
What genes have to do with it
Between 50-60 percent of children have hearing loss due to a genetic condition alone, while others have hearing difficulties due to a combination of genes and environmental factors.
Our genes contain the instructions that make our bodies’ cells work. They determine everything from how tall you’re meant to grow to whether your eyes will be blue or brown. Sometimes, a genetic defect will cause a malfunction that leads to incorrect instructions being relayed. These errors can be minor or very serious, and can be passed down from generation to generation. Genetic mutations can be dominant, meaning it is more likely for you to inherit it from one or both parents, or recessive, in which case you may still carry the defect and be able to pass it to your offspring even if you are personally unaffected by it. This is why if you see an audiologist about hearing concerns, one of the things they will ask you is whether your parents, siblings, or other close relatives have hearing loss.
Hereditary hearing loss
A genetic disorder has the potential to affect the development of your cochlea or other part of your ear, auditory brain stem, or cerebral cortex by causing physical abnormalities that interfere with hearing (conductive hearing loss or central auditory dysfunction). Alternately, a genetic problem may only cause hearing difficulties without visible physical deformities (sensorineural hearing loss). Hearing loss may be present at birth or it may not develop until you are older, yet still be caused or at least influenced by, an inherited condition. For some, genetic malfunctions result in mixed hearing loss (a combination of conductive and sensorineural).
Syndromic hearing impairment
Syndromic (due to physical malformation) genetic disorders account for up to 30 percent of children being born with hearing loss. These conditions, of which approximately 400 have been identified, include the following:
- Waardenburg syndrome―most common type. Children born with this condition are identified by the presence of a patch of white hair and other pigmentary abnormalities. Can also cause sensorineural hearing loss.
- Branchiooterenal syndrome―second most common, it is often characterized by significant malformation of the outer ear. Can cause conductive, sensorineural, or mixed hearing loss.
- Stickler syndrome―associated with cleft palate and osteoarthritis, and in some cases severe nearsightedness. Causes progressive sensorineural hearing loss.
- Neurofibromatosis 2―usually does not cause hearing difficulties until a child is three-years-old and is associated with the growth of tumors that can sometimes be removed to restore hearing.
Nonsyndromic hearing conditions
Nonsyndromic (no outward malformation) genetic defects are responsible for approximately 70 to 80 percent of cases of genetic hearing loss. Some children are born with immediate hearing difficulties, while others might not be affected until much later in life. Scientists have identified more than 30 genes that can be associated with nonsyndromic hearing problems, most of which relate to the development and function of the cochlea. While all babies should have their hearing tested shortly after birth, if hearing loss “runs in your family” this testing is particularly important, as there may be no outward evidence of a problem otherwise.
If you know your parents, grandparents, or others in your family lost their hearing at any point in their lives, you should take extra care to avoid environmental causes of hearing loss (such as exposure to loud noise without hearing protection). Even if your hearing is currently perfect, you may be prone to losing it over time due in part to genetics, so you don’t want to compound the risk. Also, make sure to mention any inherited hearing difficulties to your doctor when getting prescriptions, so that they take extra care to avoid giving you potentially ototoxic (hearing damaging) medications.
Whether or not you have hearing problems due to your genes, your environment, or both, hearing aids might still be able to help restore at least some of your hearing. If you have any questions or concerns about your hearing, make an appointment with your hearing care professional for a full workup.
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