6 Signs And Causes Of Hearing Loss In Infants

Infant hearing loss, hearing impairment, or deafness refers to the complete or partial loss of the ability to hear in one or both ears. When babies experience hearing loss before developing speech and language skills, it is called prelingual hearing loss. It may negatively impact the development of the auditory centers of the brain.

Read this post to learn more about the causes, types, symptoms, diagnosis, treatment, prevention, and outcomes of hearing loss in babies.

Causes Of Hearing Loss In Babies

Some babies may have hearing loss from birth (congenital deafness), while a few may lose hearing during infancy.

Problems of the outer and middle ear cause hearing loss since they prevent the conduction of sound to the inner ear. External and middle ear problems that cause hearing loss may include (1):

• Birth defects of ear structures
• Accumulation of fluid behind the eardrum
• Ear wax buildup
• Scars on the eardrum
• Foreign objects in the ear canal
• Eardrum injuries or rupture

Some babies could have hearing loss due to inner ear problems. Damage to the nerve endings in the inner ear can be the cause of hearing loss. This can be due to:

• Genetic disorders
• Congenital infections such as toxoplasmosis, herpes, or measles
• Exposure to certain medications or toxic substances in intrauterine life or early infancy
• Brain infections, such as meningitis, encephalitis, or measles infection, damaging the hearing function of the brain
• Abnormal inner ear structure
• Kernikterus (due to extreme high bilirubin levels in the neonatal period damaging the brain)
• Tumors
• Certain medication can be toxic when the levels are too high

A family history of auditory impairment and low birth weight could increase the risk of hearing loss in many babies.

Types Of Hearing Loss

Hearing loss can be of the following types (2).

• Conductive hearing loss where something in the outer ear or middle ear prevents the sound from passing to the inner ear. Some causes of conductive hearing loss can be cured with surgeries and medications.
• Sensorineural hearing loss occurs due to issues in the inner ear or auditory (hearing) nerve.
• Mixed hearing loss is a combination of conductive hearing loss and sensorineural hearing loss.

Auditory neuropathy spectrum disorders may cause hearing loss due to damage to the hearing nerve or inner ear, leading to failed conduction of sound-related impulses to the brain. In such cases, even though the sound is conducted normally in the ear, the brain fails to understand it.

Hearing loss is classified in the following ways based on the degree of hearing loss (3).

• Mild hearing loss when someone can hear some sounds but has difficulty hearing soft or low sounds.
• Moderate hearing loss is when a person cannot hear another person’s normal voice, but they do hear loud voices.
• Severe hearing loss is when someone only hears some loud sounds and unable to hear normal sounds levels.
• Profound hearing loss in which the person does not hear any speech sounds and may hear only very loud sounds.

The degree of hearing loss depends on the sound levels (decibels) a person can hear. 10 to 15 decibel sound levels are heard in normal hearing. The sound levels that can be heard on each degree of hearing loss are listed in the table below (4).

Depending on the onset and clinical features, the hearing loss can be described in the following ways (5).

• Unilateral or bilateral hearing loss: Hearing loss affects one ear (unilateral) or both ears (bilateral)
• Progressive or sudden hearing loss: Sudden hearing loss is a rapid onset of hearing loss, whereas progressive hearing loss may occur over time.
• Pre-lingual or post-lingual hearing loss: Hearing loss before the baby learns to speak is called prelingual hearing loss, and after learning to talk is known as post-lingual hearing loss.
• Fluctuating or stable hearing loss: Hearing loss stays the same over time in stable hearing loss, and it may get better or worse in fluctuating hearing loss.
• Congenital, acquired, or delayed onset of hearing loss: Hearing loss present at birth is called congenital hearing loss, and if it occurs later, it is called acquired or delayed onset of hearing loss.
• Symmetrical or asymmetrical hearing loss: Similar loss of hearing on both ears is called symmetrical hearing loss. If there is a different degree of hearing loss level in both ears, it is called asymmetrical hearing loss.

Doctors may combine the types, degree, onset, and clinical presentation of the hearing loss to name the hearing loss in your baby. These terms may help to understand the type and cause of hearing loss in the baby.

Signs And Symptoms Of Hearing Loss In Babies

The following signs and symptoms may indicate a hearing loss in babies (6).

1. Newborn lacking Moro reflex (not startled by loud noises)
2. No reaction (no smile) if you speak to older babies
3. May not achieve speech milestones such as saying single words by 15 months and two-word sentences by age two
4. Not turning their head or responding to sounds
5. Not making cooing or babbling sounds
6. Unable to follow basic commands

Many children are diagnosed with hearing loss during school-age even if they had congenital hearing loss. So noticing the signs of hearing loss at an early age could be beneficial since babies can develop their speech and language skills at a natural pace after the repair in many cases.

Diagnosis Of Hearing Loss In Babies

Doctors may look at a baby’s ear using an otoscope to identify any abnormalities, wax, or foreign objects that cause hearing loss. The following tests are performed to determine the presence of a hearing loss in babies (7).

• Auditory brainstem response (ABR) test is done using electrodes to see the response of the auditory nerve to sounds.
• Otoacoustic emissions (OAE) test by placing microphones in babies ears to evaluate the presence of sound Hearing loss can be diagnosed if there is no echo of sound in the ear canal.
• Visual response audiometry or play audiometry can help evaluate the hearing loss in older babies by noticing their response to sounds through play. 

Treatment Of Hearing Loss In Babies

Treatment may begin as early as by six months of age since this could help the baby develop speech and language skills at a normal pace. Depending on the cause of hearing loss and general health status, any of the following treatment options are given (8).

• Cochlear implant for profound sensorineural hearing loss
• Medications to treat infections
• Ear tube placement in babies with recurrent ear infections
• Removal of tumors
• Surgical correction of structural anomalies

Speech and language therapies could improve the baby’s communication skills affected by hearing loss. Even though hearing cannot be restored in some babies, early speech therapy and sign language training could improve their life quality.

Prognosis Of Hearing Loss In Babies

Middle ear or outer ear problems causing hearing loss can be cured with surgery or medications in many cases. There is no treatment for some inner ear problems and nerve damages.

The outcome depends on the severity and type of hearing loss. Babies with profound hearing loss have positive outcomes after cochlear implants. Advanced hearing aids and speech therapy may help babies develop normal speech and language skills as their peers without hearing problems. 

Prevention Of Hearing Loss In Babies

All cases of hearing loss in babies cannot be prevented. Maternal vaccination and avoiding exposure to toxins and medications that may damage the baby’s hearing could reduce the risk of congenital hearing loss.

Immunization of your baby, as per recommendation, could prevent some of the infections that may lead to hearing issues. You may also ensure that your baby is not exposed to loud noises since this may result in noise-induced hearing loss.

Treating brain infections and ear infections on time may reduce the risk of hearing loss in some babies. Seeking genetic counselling may also help the couple plan a pregnancy if they have a family history of hearing loss.

References

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Dr. Elna GibsonMBChB, MMed, Paeds

 

Dr. Elna Gibson is a general pediatrician. She did her MBChB and specialization as a pediatrician in South Africa at the University of Pretoria. She obtained MMed Pediatrics (masters) with distinction in 1993.As a young specialist, Dr.

Read full bio of Dr. Elna Gibson