Congenital Hearing Loss
The term Congenital hearing loss is used for babies who are born with a hearing loss. Either genetic (Hereditary) or non-genetic factors are responsible for Congenital hearing loss.
Non-genetic factors accounts for about quarter of all babies who are born with some kind of hearing impairment (congenital hearing loss). Non-genetic factors which causes congenital hearing loss are:
- Infection to mothers (cytomegalovirus, rubella or German measles etc.)
- Premature or early birth
- Low weight at the time of birth
- Injuries at the time of birth
- Consumption of toxins such as alcohol, tobacco or other drugs during the pregnancy
- Diabetes to the mother
- Toxemia/Toxaemia during pregnancy
- Anoxia - Lack of oxygen
Genetic factors (Hereditary)
Genetic factors (Hereditary cause) are considered to account for over half of all congenital hearing impairment . Hearing loss due to genetic factors can be present at the time of birth or it can even develop at a later stage in life. Most of the genetic hearing loss can be described under the following three categories:
1. Autosomal Recessive Hearing Loss
In autosomal recessive hearing loss, both parents carry one copy of the altered (recessive) gene and pass it along to their baby. Parents of babies with autosomal recessive hearing loss are often surprised to find about the condition as they themselves are not aware of the fact that they are carrying a recessive/altered gene. This type of inheritance pattern accounts for almost 3 quarters of all hereditary related hearing loss. The embedded video explains what is autosomal recessive hearing loss in more details.
2. Autosomal Dominant Hearing Loss
An autosomal dominant hearing loss occurs when any one of the parent is carrying an abnormal gene which is passed onto the baby and cause hearing loss (the hearing loss is cause due to abnormal gene of only one parent and the other parent's matching gene is normal). The parent who is carrying the abnormal (dominant) gene may also have hearing impairment. About 15% of all hereditary related hearing loss cases are due to autosomal dominant pattern.
3. X-Linked Recessive Hearing Loss
In X-Linked hearing loss (also know as mitochondrial inheritance patterns), the mother carries the altered (recessive) gene for hearing loss on the sex chromosome. Mother can pass on the gene to both males and female children, but usually only male children are affected (as female children has 2 X chromosome and the other one is a normal one. Genetic syndromes generally have a combination of signs and symptoms that together indicate a specific condition/disease.
There are many genetic disorders which have hearing impairment as one of the many symptoms. some of the examples includes:
- Usher syndrome
- Down syndrome
- Crouzon syndrome
- Alport syndrome
- Treacher Collins syndrome
- Waardenburg syndrome
Hearing Loss Prevention
For any child who is diagnosed with a congenital hearing loss, treatment should start by the time they reach 6 month of age. Studies indicates that children who receive treatment at early stage are more likely to develop communication skills (using spoken or sign language) that are as good as those of hearing peers. Experts in the field of hearing (ENT specialist, audiologist, a speech-language therapist etc.) should design the treatment plan for the child. This plan can changed/altered as the child grow older.
Hearing aids can help children as young as 4 weeks old who has hearing problems. These devices help by amplifying (increasing the volume of) sound, which make it possible for many children to hear spoken words and develop language. For young children, a behind-the-ear hearing aid is more suitable as it is safer and easier to fit. This can also be adjusted as the child grows. However, hearing aid may not be sufficient/suitable for some children who have severe to profound hearing loss. For such children Cochlear Implants may be recommended as it is implanted inside head and provide hearing signals directly to hearing nerves.