Hearing loss in children can be sensorineural, conductive, congenital, acquired (after birth), fluctuating, or permanent and caused by genetic or environmental factors.

Sensorineural Hearing Loss

Sensorineural hearing loss (SNHL) is by far the most common type of hearing loss present at birth (congenital). It can occur as a result of a lack of development or damage to either the auditory nerve or the delicate hair cells in the inner ear (cochlea). About 25% of congenital SNHL cases are caused by acquired risk factors. Although SNHL is generally irreversible, an evaluation is important to:

Track progression of hearing loss in the affected ear and the unaffected ear in unilateral hearing loss

• Diagnose associated physical conditions
• Identify other family members at risk
• Get adequate treatment and therapy
• Counsel parents and children (when they’re old enough)

Conductive Hearing Loss

Conductive hearing loss is caused by blockage or damage to a child’s outer ear, ear canal, or middle ear, making it difficult for sounds to pass from their outer ear to their middle ear. In newborns, fluid in the middle ear space makes it difficult for sound to pass to the inner ear. In infants and children, fluid in the middle ear is usually secondary to an ear infection. Impacted earwax or a foreign body can also completely block a child’s ear canal. Once the fluid, earwax, or foreign body is resolved, the child's hearing typically returns to normal.

A small number of children are born with abnormal middle ear bones, so they don’t vibrate normally in response to sound. Other children are born with a condition called aural atresia, which results in partial development of their ear canal, eardrum, and tiny bones in one or both ears. These conditions can usually be repaired surgically.

Congenital Hearing Loss

Although prematurity and low birth weight are associated with congenital hearing loss, the precise mechanism involved is unclear. About 30% of congenital hearing loss is syndromic, which means it’s related to an existing syndrome, while 70% is non-syndromic, with hearing loss the only disability.

Despite thorough evaluations, the cause of an estimated 25–45% of SNHL cases is unknown. Either genetic or environmental (acquired) causes are responsible for all other cases. Hearing loss risk factors are often classified by periods of child development.

Prenatal (During Pregnancy)

• Syndromes associated with hearing loss
• Family history of permanent childhood SNHL
• Craniofacial anomalies
• Toxoplasmosis, other agents, rubella (German measles), cytomegalovirus, and herpes simplex (known together as TORCH infections)

Perinatal (One to Four Weeks Post-Birth)

• Being in the neonatal ICU for more than 48 hours
• Jaundice
• Ototoxic medications (drugs that cause hearing damage)
• Meningitis

Early Childhood

• Persistent pulmonary hypertension requiring ventilation
• Conditions requiring ECMO (a type of prolonged cardiac and respiratory support)
• Syndromes associated with progressive hearing loss
• Pediatric neurodegenerative disorders
• Head trauma
• Recurrent/persistent otitis media for more than three months

Middle Childhood and Adolescence

• Noise exposure
• Drug/chemical exposure
• Head trauma
• Otosclerosis

A large number of late-onset SNHL cases are caused by congenital cytomegalovirus infection not detected during neonatal screenings. Research indicates about 30–60% of children with SNHL have co-occurring visual impairments or cognitive, motor, emotional, behavioral, or other problems. About 40–60% of children with hearing loss also have visual impairments.

Cytomegalovirus (CMV) is a common virus related to herpes that typically doesn’t cause symptoms in people with healthy immune systems. Congenital CMV is the most common infection impacting unborn infants. Although it’s more prevalent in low- and middle-income countries, CMV affects people from all backgrounds and geographic locations. During pregnancy, an unborn infant can be infected after the mother has a primary infection or recurrence of an existing infection or reinfection.

CMV is the leading cause of non-genetic congenital SNHL in children. Experts don’t know why the virus causes hearing impairment in some children and not others. Symptoms vary from mild to severe, with hearing loss often delayed in onset and progressive. Less than 50% of infants born with congenital CMV show symptoms at birth, which complicates hearing loss diagnosis. In children with congenital symptomatic CMV, hearing loss has been reported in up to 75% of cases. Children with asymptomatic CMV have a 10–15% chance of developing hearing loss. Other long-term symptoms include mental and developmental disabilities and impaired vision.

Oral valganciclovir (antiviral medication) for six months is the gold standard therapy for newborns diagnosed with congenital symptomatic CMV. Studies show this therapy preserves normal hearing or prevents the progression of hearing loss in infants, and also results in improved long-term neurodevelopmental outcomes.

Otitis media, an inflammation in the middle ear affects 75% of children at least once by age 3. It is more common in children because their Eustachian tube is smaller and horizontal, which can make it prone to fluid buildup. The Eustachian tube links the back of the nose to the middle ear. Hearing loss caused by otitis media is typically conductive and temporary. Three tiny bones in the middle ear carry sound vibrations from the eardrum to the inner ear. When fluid accumulates, vibrations aren’t transmitted efficiently, and sound becomes muffled or inaudible. Recurrent infections can damage a child’s eardrum, bones of the ear, or auditory nerve, resulting in permanent SNHL.

Genes are responsible for 50–60% of cases of children born with hearing loss, yet about 90% of newborns with inherited forms of hearing loss are born to parents with normal hearing. Experts have identified more than 120 independent genes for deafness and at least 400 known genetic syndromes that include hearing loss as a symptom. Mutations in a single gene called GJB2, which is tied to inner ear cells, are thought to account for almost 50% of hereditary non-syndromic SNHL cases.

Select Syndromes Linked to Genetic Hearing Loss

• Alport syndrome
• Branchiootorenal syndrome
• Jervel and Lange Nielsen syndrome
• Mohr-Tranebjaerg syndrome
• Neurofibromatosis 2
• Pendred syndrome
• Refsum disease
• Stickler syndrome
• Usher syndrome (all three types)
• Waardenburg syndrome

Hearing is an essential component of a child’s social, emotional, and cognitive development. Even mild hearing loss can impact a child's ability to develop proper speech, language, and social skills. The early years of childhood, from birth to age 3, are thought to deeply affect lifelong health, and this also applies to hearing. Some studies have shown that profoundly deaf children have language and academic levels equivalent to fourth grade students with normal hearing when they graduate high school.

• Many childhood studies have found that better vocabulary and other language outcomes are related to the absence of additional disabilities, lesser degrees of hearing loss, having a parent who is deaf or hard of hearing, and higher maternal education. Even with early identification, it’s challenging for hearing impaired children older than 18 months to keep up with their peers.

Being aware of key speech and hearing milestones can help you determine if your child has a potential hearing problem. Hearing milestones in infants and babies include:

• Startling or “jumping” to sudden loud noises (newborns)
• Recognizing your voice (3 months)
• Turning eyes or head toward a sound (6 months)
• Imitating some sounds and saying a few words (6 to 12 months)

Signs of Hearing Loss in Toddlers

• Limited, poor, or no speech
• Frequently inattentive
• Difficulty learning
• Needing higher TV volume
• Not responding to conversation-level speech
• Responding inappropriately to speech
• Not responding to their name
• Showing frustration when there's a lot of background noise

The American Speech-Language-Hearing Association (ASHA) offers more in-depth milestones, classified by age.

Children with permanent childhood hearing loss should receive treatment as soon as possible after diagnosis. Hearing treatment/rehabilitation includes selection, fitting, and evaluation of technology; and a family-centered, interdisciplinary, and comprehensive early intervention program. When selecting a treatment approach, it’s important that your family's goals, preferences, values, beliefs, culture, and language background are taken into consideration.

• ASHA recommends follow-up appointments for a child every three months during the first two years of using amplification and every four to six months thereafter, with more frequent visits if there are concerns.

Early diagnosis and treatment of hearing loss are essential to giving your child a good start in life. Universal newborn hearing screening programs help ensure that children with congenital and early-onset hearing loss receive prompt diagnosis and support in their first months of life to develop language skills later. Children at risk of late-onset hearing loss should be closely monitored, even after passing a screening test. This ensures identification as early as possible, prevents delays in treatment and unnecessary costs, and helps avoid added parental stress.