Congenital hearing loss
The term congenital hearing loss implies that the hearing loss is present at birth.
Congenital hearing loss can include hereditary hearing loss or hearing loss due to other factors present either in utero (prenatal) or at the time of birth.
Genetic factors are thought to cause more than 50% of all incidents of congenital hearing loss in children. In autosomal dominant hearing loss, one parent who carries the dominant gene for hearing loss and typically has a hearing loss passes it on to the child. In this case there is at least a 50% probability that the child will also have a hearing loss. The probability is higher if both parents have the dominant gene (and typically both have a hearing loss) or if both grandparents on one side of the family have hearing loss due to genetic causes. Because at least one parent usually has a hearing loss, there is prior expectation that the child may have a hearing loss.
In autosomal recessive hearing loss, both parents who typically have normal hearing, carry a recessive gene. In this case the probability of the child having a hearing loss is 25%. Because both parents usually have normal hearing, and because no other family members have hearing loss, there is no prior expectation that the child may have a hearing loss. Approximately 80% of inherited hearing loss is autosomal recessive.
In X-linked hearing loss, the mother carries the recessive trait for hearing loss on the sex chromosome and passes it on to males, but not to females. This kind of hearing loss is rare, accounting for only about 2% of hereditary hearing losses.
There are some genetic syndromes where hearing loss is one of the known characteristics. Some examples are Down syndrome (abnormality on a gene), Usher syndrome (autosomal recessive), Treacher Collins syndrome (autosomal dominant), Fetal alcohol syndrome (genetic abnormality), Crouzon syndrome (autosomal dominant), and Alport syndrome (X-linked).
Other causes of congenital hearing loss that are not hereditary in nature include prenatal infections, illnesses, or conditions occurring at the time of birth or shortly thereafter. These conditions typically cause sensorineural hearing loss ranging from mild to profound in degree. Examples include:
- Intrauterine infections including rubella, cytomegalovirus, and herpes simplex virus
- Complications associated with the Rh factor in the blood
- Prematurity
- Maternal diabetes
- Toxaemia during pregnancy
- Lack of oxygen (anoxia)
- Syphilis
- Malformation of ear structures
- Acquired hearing loss
Read more about acquired hearing loss.
[Error in plugin $$ContentFooter;, details in event log]