Congenital Hearing Loss - Causes, Symptoms, Diagnosis, and Treatment

Introduction:

Congenital hearing loss is a birth defect that causes partial or complete hearing loss at birth or may develop in later stages of life. The condition arises when the person's ears cannot convert sound waves into electrical impulses in the brain. It is a common condition in babies, and therefore many countries have established a standard for early screening and diagnosis of hearing loss in children. Most of the time, newborns are born with these defects; in some cases, they carry defective genes that cause hearing impairment later in life. The condition can also become severe in some cases and leads to congenital deafness. Therefore, newborns should be screened with specific screening tests at birth for early diagnosis and prevention of this condition.

What Are the Causes of Congenital Hearing Loss?

Causes of congenital hearing loss in newborns include:

• Premature birth.

• Birth injuries.

• Maternal infections, such as herpes simplex virus and rubella.

• Childhood infections, such as measles, mumps, and meningitis.

• Low birth weight.

• Maternal diabetes.

• Use of drugs and alcohol during pregnancy.

• Preeclampsia, also recognized as high blood pressure during pregnancy, is a condition of elevated blood pressure levels.

• Rh factor and jaundice problems.

• Genetic problems cause hearing loss at birth or may develop later in life. Genetic factors cause nearly 40 percent of congenital hearing loss.

• Newborns suffering from anoxia or do not have enough oxygen supply.

Congenital hearing loss in newborns also occurs along with other genetic syndromes, such as:

• Usher Syndrome - Genetic disease that affects both vision and hearing.

• Alport Syndrome - Genetic condition that causes hearing loss, kidney diseases, and eye abnormalities.

• Down Syndrome - Commonly referred to as Trisomy 21, it causes inner ear hearing loss and middle ear disease.

• Treacher Collins Syndrome - Inherited condition that affects the facial structure and also causes hearing and vision loss.

• Pendred Syndrome - Genetic condition that causes hearing loss in children and also cause problems with balance.

• Crouzon Syndrome - Genetic mutation affecting the craniofacial structure, causing the skull to fuse abnormally. The syndrome causes conductive hearing loss in patients.

• Waardenburg Syndrome - Genetic condition causing a change in pigmentation or color of eyes, skin, and hair. The condition also causes hearing loss.

What Are the Various Types of Congenital Hearing Loss?

Congenital hearing loss is of three types. These are as follows:

• Conductive Hearing Loss - This type affects the middle or outer ear, so the sound waves cannot move properly. The condition usually arises due to improper middle or outer ear formation or an obstruction in the middle ear; mainly, fluids from infections can cause this blockage.

• Sensorineural Hearing Loss - This congenital hearing loss occurs due to an affected inner ear's bone or inner ear's auditory nerve pathways. Hearing loss can be subdivided into two:

  1. Central Hearing Loss - caused by an affected central auditory processing pathway.

  2. Sensory Hearing Loss - caused by affected hair cells inside the ear's cochlea.

• Mixed Hearing Loss - The hearing loss observed in this case combines sensorineural and conductive hearing loss elements.

• Genetic or Hereditary Hearing Loss - This type of hearing loss is brought on by genetic mutations or abnormalities that are present from birth.

• Syndromic Hearing Loss - Some congenital hearing loss is associated with genetic syndromes, where hearing loss is one of the symptoms along with other medical conditions or physical abnormalities.

• Non-syndromic Hearing Loss - This refers to congenital hearing loss that occurs without any associated medical conditions or physical abnormalities.

What Are the Signs and Symptoms of Congenital Hearing Loss?

Congenital hearing loss shows different signs and symptoms at various stages of life. Symptoms are usually very challenging to diagnose in newborns and require specific screening tests. However, symptoms of congenital hearing loss in young children include:

• Behavioral problems.

• Dizziness or vertigo, and a sensation of spinning or moving.

• Earache.

• Ringing in the ear or tinnitus.

• Delayed language skills.

• Listening to music or television at a high volume.

• Liquid discharge or drainage from the ear.

How Is Congenital Hearing Loss Diagnosed?

Congenital hearing loss should be diagnosed in newborns in the first month of life with a specific screening test. The screening tests are therefore done in the hospital in the initial few days after birth. These tests are noninvasive, and therefore, if hearing loss is detected in newborns, they have to undergo various other diagnostic tests in the future, such as genetic testing or magnetic resonance imaging (MRI).

The procedures for initial screening tests are of two types:

• AABR (Automated Auditory Brainstem Response) - In this procedure, the electrodes are placed on the newborn's head to measure the response to sound during this screening test.

• OAE (Otoacoustic Emission) - In this procedure, the sound waves are directed into the inner ear, leading to the cochlea's hair-producing sound, known as otoacoustic emissions. These sounds are then measured in the screening test, and if they are lower than normal, congenital hearing loss is suspected in a baby.

How Is Congenital Hearing Loss Treated?

Congenital hearing loss cannot be cured. Therefore, the treatment plan only focuses o preventing further loss of hearing and other therapeutic options, such as hearing aids, and prevention of language development and speech delay. After diagnosing the cause and type of congenital hearing loss, the doctor's treatment plan usually includes hearing aids, learning sign language, and cochlear implants. However, the treatment is not limited to only these options; advancement in treatment plans may involve gene therapy for hearing loss.

The healthcare providers work in a team to treat the cases of congenital hearing loss and thus include:

• Pediatrician or a child specialist.

• Otolaryngologist or an ENT.

• Speech-language pathologist.

• Audiologist or a person who specializes in hearing.

• Genetic counselors.

Conclusion:

Congenital hearing loss occurs due to environmental and genetic factors and thus has no cure. Therefore only early diagnosis and treatment of the condition can prevent speech delays and language problems in children. Hearing aids and other treatment options like cochlear implants can help a person with a congenital disability adapt to their surroundings and communicate with other people who do not have this defect.

Delayed speech issues are also resolved with these treatment plans. Therefore doctors should detect this defect as early as possible to prevent communication difficulties in children suffering from this condition. It may cause lasting psychological and emotional consequences due to depression, loneliness, and isolation.