What is Congenital Hearing Loss?
Congenital hearing loss, also called congenital deafness is a physical defect that is present at the time of birth. Experts opine that nearly 50% of all general to complicated hearing problems are congenital in nature. Congenital hearing loss is gained in two different ways. The most obvious one is hereditary, but there are other congenital hearing loss issues that may be non-hereditary in nature. Sometimes doctors find it difficult to diagnose the actual cause of congenital hearing loss, as it may be due to a combination of two recessive genes that a newly born baby has received from both the parents or it may be due to a troublesome incident during birth.
What are the Causes of Congenital Hearing Loss?
Depending on the type of congenital hearing loss – hereditary or non-heriditary the causes would vary. Let us see the causes of congenital hearing loss caused by each type.
Non-hereditary Causes of Congenital Hearing Loss:
Two primary causes of non-hereditary hearing loss are as follows:
- Teratogenic Drugs: Teratogenic drugs are unsafe for the fetus. If the mother is exposed to one or more of these drugs, like Quinine, Reticonic, and Thalidomide, etc. during early days of development of the fetus, there remains a chance of birth defects including congenital hearing loss.
- Viral Infections: Some kinds of viral infections like rubella, syphilis, herpes simplex, cytomegalovirus, and toxoplasmosis during any stages of pregnancy can be very damaging for the fetus. Congenital hearing loss in the fetus can occur if any of these virus infections occur during the inner ear development in the fetus. Virus infection just after the childbirth, such as Neonatal Septicemia or Meningitis can be damaging for the ear too.
Other visible factors of non-hereditary congenital hearing loss include the following:
- Premature birth of the baby or below standard weight
- Injuries during birth
- Diabetes of the mother during pregnancy
- Jaundice in the baby
- Alcohol consumption during birth
- Lack of oxygen or anoxia in the baby.
Hereditary Causes of Congenital Hearing Loss:
Hearing loss due to genetic defect can be detected at birth or it can develop later as the child grows with age. Hereditary hearing loss can be either autosomal recessive or autosomal dominant.
- Autosomal Recessive Hearing Loss: The genes are carried by both the parents and they pass it to the child. In more than 70% of hereditary congenital hearing loss, this is the primary cause.
- Autosomal Dominant Hearing Loss: It occurs when any one of the parents pass on an abnormal gene while the other parent passes on a normal matching gene. In this case, the abnormal gene becomes dominant gene. Over 15% of hereditary congenital hearing loss is due to this reason.
Some rare hereditary congenital hearing loss problem occurs due to defective sex chromosome or defective mitochondrial constitution.
Epidemiology of Congenital Hearing Loss
The occurrence of hereditary congenital hearing loss is more pervasive in developing and underdeveloped countries than in the developed nations. More than 30,000 babies are born with this problem every year in China. In the USA, 1 to 6 newborns in every 1000 born with this disease and approximately 6 children in every 10000 in the USA show several symptoms of early hearing loss. It is found that the problem worsens between the age of 2 to 5 years, so any hearing issue in infants and children should be taken seriously and needs proper treatment.
No clear statistics is available on congenital hearing loss in the world due to poor infrastructure and lack of scientific methodologies in registering the cases in the developing and underdeveloped countries yet.
Diagnosis of Congenital Hearing Loss
Generally, an ENT specialist treats a child with a hearing problem. The doctor thoroughly investigates the issue with the child's medical history and physical diagnosis. Some important physical investigation process includes the following:
A pneumatic otoscope is used to check external auditory canal for any abnormality or presence of any foreign body and the mobility of tympanic membrane against pressure changes.
If necessary, the specialist may undertake Weber's test which can differentiate between conductive and sensorineural hearing losses.
Rinne test is conducted to ensure whether the problem is present in both ears or it is a unilateral hearing loss.
Besides, other modern diagnostic methods like audiography are undertaken if necessary. Apart from these diagnostic processes, the attending doctor may also do speech test and examine the neck, head, and cranial nerves.
Doctors consider the following high-risk indicators while detecting congenital hearing loss of any nature and determining whether it is hereditary or non-hereditary in nature:
- Congenital hearing loss within the first month of birth:
- Birth related abnormalities
- Family history
- Viral infection of the mother during pregnancy
- Physical features of the infant
- Presence of any syndrome that is associated with congenital hearing loss
- Congenital Hearing Loss within the second month of birth
- Reports from the caregiver or parents
- Family history of congenital hearing loss in childhood
- Presence of any other genetic syndrome that can cause congenital hearing loss or physical abnormality
- Head injury of any kind
- Neurological disorders like Hunter's syndrome.
Treatment of Congenital Hearing Loss
Congenital hearing loss in a child should be treated as early as possible. The research has revealed that early diagnosis and treatment can help a child in developing communication skills. Several types of treatment procedures are available but the following factors are considered before initiating a treatment for congenital hearing loss:
- The age of the child
- The level of hearing loss
- The personality of the child
- Presence of any other issues
- Economic condition of the family
It is always feasible to take expert opinion before selecting a treatment procedure. Certain treatment depends on the age and personality of the child while some other treatment procedures can be applied to any children with congenital hearing loss. With the advancement of technology, treatment for this issue is improving with time. Some congenital hearing loss can be treated with hearing aid. A hearing aid amplifies the sound and makes it audible for the patients who are unable to accept normal frequencies. Besides, children are also trained scientifically to understand symbols and speak accordingly. These days, Cochlear implants are also suggested for babies who are 12 months of age.
Congenital hearing loss is not a rare disease but it is not rampant either. Detection of the issues as early as possible is important for the overall health of the infant or child; hence, any sort of abnormality in a child's behavior should be informed to the pediatrician. It is also necessary that sufficient precautions are taken during pregnancy. Use of any medication should only be according to the advice of a medical practitioner. Congenital hearing loss is a difficult disease as a child cannot communicate properly and express their needs. With the right treatment and training, the problem can be eliminated to a large extent.