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Genetic Hearing Loss in Children - Symptoms to Watch For
Fifty percent of hearing loss present at birth, also known as congenital hearing loss, is caused by a genetic defect. Genes are cells inside the body that instruct it how to work and grow. They tell the body how to make specific proteins that affect everything from blood sugar, collagen production or hair and eye color. Scientists have identified eight different genes that are the most likely the cause of genetic hearing loss in children. Genetic hearing loss is typically autosomal dominant, autosomal recessive or X-linked.
Autosomal dominant hearing loss occurs when one parents has the dominant gene for hearing loss and usually suffers from hearing loss themselves. This gene is then passed on to the child. If one parent has the hearing loss gene there is at least a 50% chance the child will have it as well. If both parents or both grandparents on one side have the gene there is an even greater chance the child will experience hearing loss. However, just because a person has a dominant gene for hearing loss does not mean they will experience hearing loss in their lifetime. That is why it is possible for two deaf parents to give birth to a child who can hear.
Autosomal recessive hearing loss occurs when both parents carry a recessive gene for hearing loss. Because the gene is recessive, neither parents will suffer from hearing loss, therefore they may not know they even have the gene. When this occurs, the child born has a 25% chance of experiencing genetic hearing loss. However, as long as neither parents or any family members suffer from hearing loss, there is no expectation that the child will experience hearing loss.
In some cases the mother can carry the recessive gene for hearing loss on the sex chromosome. The X and Y chromosomes determine the sex of the child. Men carry both X and Y chromosomes while women carry two X chromosomes. The hearing loss gene is recessive and occurs on the X chromosome from the mother. If she passes this chromosome onto her child, only a boy will experience hearing loss. If she passes it onto her daughter she will be a carrier for the trait, but will not experience it herself. Only 3% of genetic hearing loss occurs because of a recessive gene in the X chromosome.
Of the 50% of genetic hearing loss cases, genetic syndromes cause 30%. These can range from Down syndrome, Usher syndrome, Trencher Collins syndrome, Crouzon syndrome and Alport syndrome. Today, most hospitals perform a hearing test a few hours after a child is born, which has allowed for early diagnosis and intervention for genetic hearing loss. Signs of hearing loss are speech delays, poor performance in school, frequent ear infections, responding inconsistently to sounds, talking in a very soft or very loud voice and continuously studying a person’s face while they are talking.
If any of these symptoms are present, parents should raise their concerns with their child’s pediatrician. Many city health departments typically offer free screenings a few times a year for those who do not have a regular family doctor. The earlier a diagnosis is made, the more quickly parents can begin to help their children adapt to hearing loss. This can include teaching them sign language, enrolling them in special programs or joining support groups for themselves. Living with hearing loss can be difficult, especially for young children; however with the proper support and education from family, friends and teachers, these children can and do thrive and live full, productive lives.