When a baby is born, parents are often anxious to see who the baby resembles – does she have daddy’s eyes, mommy’s nose, grandpa’s ears? Even more questions arise when the baby is born with a medical problem, such as hearing loss. Parents often wonder whether or not they did something that could’ve caused the abnormality, or whether it just happened due to genetic factors.
While some cases of hearing loss can be traced back to prenatal causes, such as exposure to an environmental toxin, or maternal use of drugs, other cases have more of a genetic origin. Sometimes, finding the cause is helpful in determining the course of treatment. It can also provide valuable information for the parents in case they decide to have more children in the future.
Congenital versus acquired hearing loss
When hearing loss, or any other abnormality, is discovered, it can generally be categorized as either congenital or acquired. Congenital hearing loss means that it is present at birth, whereas acquired hearing loss occurs over time. Research has shown that about 50% of all congenital hearing loss cases arise from genetic causes, while 25% are from non-genetic factors. The remaining cases stem from unknown causes.
Genetic hearing loss basics
Genes are the building blocks of what makes up each individual including their health, their looks, and their personality. Half of an individual’s genes come from each parent. The traits that result from this gene combination are determined by whether or not the genes are recessive or dominant.
- Autosomal recessive inheritance – Autosomal recessive hearing loss results from both parents having a recessive gene for hearing loss. They each pass on a copy of this “bad” gene to their child. The newborn child experiences hearing loss because she has two affected copies of this gene. The parents themselves, however, usually have normal hearing because they each only have one version of the recessive mutated gene.
- Autosomal dominant inheritance – Sometimes, only one mutated gene is needed to cause hearing loss. This is referred to as autosomal dominant hearing loss. Therefore, if only one parent passes on a copy of this gene, the child will experience hearing loss. Since the gene is dominant, the parent who is a carrier will also have some degree of hearing impairment, with or without the presence of other abnormalities.
Syndromes that cause genetic hearing loss
Sometimes hearing loss occurs without any other abnormalities being present – this is known as non-syndromic hearing loss. Other times, however, the hearing impairment actually coincides with and is caused by another disorder. A few of the known genetic syndromes that cause hearing loss include:
- Alport Syndrome
- Goldenhar’s Syndrome
- Norrie Disease
- Stickler Syndrome
- Usher Syndrome
How to diagnose genetic hearing loss
It can be a time-consuming, and sometimes frustrating, process to identify the genetic cause of hearing loss, either in an infant or in an older adult. Working with a team of healthcare practitioners such as a geneticist, audiologist, otolaryngologist, and/or a genetics counselor can help speed the process. Using this team-based approach may even reduce the amount of diagnostic testing that must be done.
In general, your medical team will have the following roles:
- Otolaryngologist (ENT) – Complete a physical, go through a detailed medical history with you, and refer you to other specialists as needed.
- Audiologist – Complete a thorough hearing evaluation and audiology workup.
- Geneticist/ Genetic Counselor – Utilize testing results from the other professionals to rule out certain genetic causes, then perform genetic testing as needed to aid in diagnosis.
In summary, working hand in hand with health professionals can help you make informed decisions about the diagnosis and treatment of hearing loss, whether it’s present at birth or occurs later in life. There’s no reason to let it go untreated!
