Definition

Congenital hearing loss, or congenital hearing impairment, is a hearing disorder present at birth and is often found in children. This disorder can lead to the complete or partial loss of hearing ability at birth. The condition is chronic or occurs in the long term.

The ear has the ability to convert the mechanical energy of sound vibrations into electrical energy in the nerves. The electrical signals are then transmitted to the brain. Hearing loss is categorized based on the location of the disorder, whether it occurs in the ear or in the auditory nerves and brain. This disorder is divided into conductive hearing loss, sensorineural hearing loss, and mixed hearing loss.

• Conductive hearing impairment

In conductive hearing impairment, there is a disorder in the outer ear or middle ear, preventing sound waves from entering and being processed in the inner ear. Abnormalities in the formation or development of the outer or middle ear can occur during pregnancy.

• Sensorineural hearing impairment

In sensorineural ear disorders, there is a disturbance in the inner ear, auditory nerves, or the pathway to the brain. While the outer ear can capture the mechanical energy of sound vibrations and transmit it to the inner ear, the inner ear may be unable to process or relay this vibrational sound energy to the brain.

• Mixed hearing impairment

In addition to conductive and sensorineural impairments, there is mixed hearing impairment. In this condition, there is a combination of conductive and sensorineural hearing impairments. The outer or middle ear cannot transmit sound waves to the inner ear, and the inner ear or its nerve pathways cannot process the sound message to the brain.

Congenital hearing impairments can impact the development of a child's speech and language skills. Therefore, screening examinations play a crucial role in preventing delays in a child's speech and communication abilities. Optimal development of speech and language skills can provide additional advantages in the social and emotional aspects of a child's development, ultimately enhancing their quality of life.

Causes

Genetic factors

The most common cause of congenital hearing disorders is genetic factors. Genes play a crucial role in the formation of the auditory pathways. Mutations or changes in genes can affect the development of various parts of a child's ear, ultimately leading to hearing impairments.

Infections during Pregnancy

In addition to genetics, disturbances in fetal environmental conditions, such as infections, can also cause congenital hearing impairments. These infections occur while the baby is still in the mother's womb. Some types of infectious agents commonly associated with congenital disorders include:

• Viruses: cytomegalovirus, rubella virus, herpes simplex virus (HSV), and Zika virus 
• Bacteria: Treponema pallidum (the bacteria causing syphilis) 
• Parasites: Toxoplasma gondii

Environmental Factors

Apart from infections, other environmental factors that can cause congenital hearing disorders include the use of alcohol and several medications consumed by the mother during pregnancy, jaundice, premature or low birth weight, and injuries during childbirth.

Risk Factor

Several factors can increase the risk of congenital hearing disorders, including:

1. Genetic factors 
2. Having a family history of hearing disorders from birth 
3. Infections such as viruses, bacteria, or parasites attacking the mother during pregnancy 
4. Premature baby birth, before the auditory system has fully matured 
5. Babies requiring medical intervention with a hospital stay longer than 5 days and a history of treatments that may be harmful to the auditory system.

Symptoms

The symptoms that appear can vary widely. In newborns, symptoms are often challenging to recognize, so special screening tests are needed to detect hearing impairments in infants. In older children, several symptoms may arise, including:

• Delayed or slow development of language skills in children 
• Behavioural issues 
• Frequent listening to TV or other electronic devices at high volumes 
• Tinnitus or ringing in the ears 
• Vertigo or dizziness and spinning sensations 
• Discharge from the ears
• Ear pain

Diagnosis

Establishing a diagnosis in newborns with congenital hearing disorders tends to be challenging and requires specific examinations using certain diagnostic tests. It is recommended that infants undergo screening within the first month of life. Most newborns born in hospitals with certain risk factors will be examined within a few days of birth.

Specialized examinations that can be performed include Otoacoustic Emission (OAE) and Automated Auditory Brainstem Response (aABR). In OAE, the examination is conducted by directing sound into the inner ear. This will cause the inner ear organ, known as the cochlear hair cells, to produce a soft sound called otoacoustic emission. The OAE sound is measured to determine the presence of hearing impairments. In the Automated Auditory Brainstem Response (aABR) examination, an assessment of responses to sound is measured through electrodes placed on the baby's head.

Both of these examinations, in addition to confirming the diagnosis, are also performed to screen for hearing impairments in children. In addition to using OAE and aABR, imaging examinations such as magnetic resonance imaging (MRI) and genetic testing can also be conducted.

If hearing impairment is detected in your child through these examinations, your doctor will recommend further tests based on the child's behaviour.

Management

Until now, there has been no cure for congenital hearing disorders. Early detection and intervention can prevent disruptions in a child's speech and language development. Therapies involving learning sign language and using hearing aids can help your child adapt to their environment.

Complications

Congenital hearing disorders can impact a child's speech and language development, leading to delays and difficulties in communication. Furthermore, delays in a child's speech and language abilities can contribute to disruptions in their social and emotional development, affecting their overall quality of life.

Prevention

Environmental factors leading to hearing disorders can be prevented through complete vaccination and ensuring that pregnant mothers do not consume alcohol, drugs, or medications that may impact the fetus. If infections like cytomegalovirus, rubella, herpes, Zika virus, toxoplasmosis, syphilis, or jaundice are detected during pregnancy examinations, early and thorough treatment is highly recommended.

Regular prenatal check-ups with a doctor can help detect issues early and provide appropriate therapy. Adequate treatment can prevent congenital hearing disorders in your child.

When to see a doctor?

The condition of congenital hearing impairment can be detected during pregnancy. Regular check-ups with a doctor are crucial for screening and preventing congenital hearing disorders. Make sure to have routine prenatal check-ups with your doctor. It is recommended to conduct screening tests within the first month of your child's life to identify any congenital hearing abnormalities.