What are the diagnostic and management steps for a 6-year-old boy with right unilateral sensorineural hearing loss?

Causes of Right Unilateral Sensorineural Hearing Loss in a 6-Year-Old Boy

The most common causes of unilateral sensorineural hearing loss in a 6-year-old include congenital inner ear malformations, congenital cytomegalovirus (CMV) infection, genetic mutations, and acquired causes such as viral labyrinthitis, meningitis, or temporal bone trauma. 1, 2

Congenital Causes

Inner Ear Malformations

• Bony labyrinth abnormalities are the most frequently identified structural causes and include cochlear dysplasia, enlarged vestibular aqueduct syndrome, and Mondini deformity 3, 2
• These malformations may be isolated or associated with genetic syndromes 2
• High-resolution CT is the preferred imaging modality to identify otic capsule dysplasias and bony labyrinth abnormalities 2

Congenital Infections

• Congenital CMV infection is the leading non-genetic cause of congenital sensorineural hearing loss and can present with unilateral or progressive hearing loss 1
• CMV testing should be performed early in the diagnostic evaluation, though by age 6, serologic testing may have limited utility 1

Genetic Causes

• Genetic mutations account for approximately 50-60% of congenital sensorineural hearing loss cases 1
• Connexin 26 (GJB2) mutations are the most common genetic cause 1
• Genetic evaluation should be offered to all children with confirmed sensorineural hearing loss 4, 1

Acquired Causes

Infectious Etiologies

• Bacterial meningitis can cause profound bilateral or unilateral sensorineural hearing loss through labyrinthitis ossificans 2
• Viral labyrinthitis from mumps, measles, or other viral infections can cause sudden unilateral hearing loss 2

Traumatic Causes

• Temporal bone fractures involving the otic capsule can result in immediate sensorineural hearing loss 3, 2
• Perilymphatic fistula from head trauma may present with fluctuating or progressive hearing loss 2

Neoplastic Causes (Less Common in Children)

• While rare in pediatric populations, vestibular schwannomas and other cerebellopontine angle tumors must be excluded, particularly with unilateral or asymmetric hearing loss 3

Diagnostic Approach

Immediate Audiological Assessment

• Comprehensive audiologic evaluation by a pediatric audiologist is mandatory and should include air-conduction and bone-conduction pure tone thresholds, speech reception thresholds, and word recognition testing 4
• At age 6, conventional audiometry is appropriate using a fail criterion of >20 dB HL at one or more frequencies (500,1000,2000,4000 Hz) 4
• Ear-specific testing with insert earphones is essential to accurately characterize unilateral hearing loss 4

Auditory Brainstem Response Testing

• ABR testing should be performed to confirm sensorineural hearing loss and rule out auditory neuropathy/dyssynchrony, particularly if behavioral audiometry results are inconsistent 4
• ABR can provide frequency-specific information and differentiate conductive from sensorineural components 4

Imaging Studies

• High-resolution CT of the temporal bones (unenhanced) is the first-line imaging study to evaluate for congenital otic capsule dysplasias, temporal bone fractures, and bony labyrinth abnormalities 2
• Contrast-enhanced MRI of the internal auditory canals and brain is indicated for any unilateral or asymmetric sensorineural hearing loss to exclude retrocochlear pathology such as vestibular schwannoma, inflammatory processes, or brain stem lesions 3, 2

Laboratory and Genetic Testing

• Genetic consultation and testing should be offered to all families of children with confirmed sensorineural hearing loss 4, 1
• Consider CMV testing if not previously performed, though interpretation may be limited at age 6 1

Ophthalmologic Evaluation

• Comprehensive eye examination by a pediatric ophthalmologist is required, as many syndromes causing hearing loss also affect vision 4

Management Considerations

Hearing Amplification

• Hearing aid fitting should occur within 1 month of confirmed hearing loss diagnosis if the family chooses amplification 4
• Even unilateral hearing loss can significantly impact speech perception in noise, sound localization, and binaural processing 4
• Children with unilateral hearing loss are at risk for speech and language delays and academic difficulties 4

Early Intervention Services

• All children with unilateral sensorineural hearing loss should be considered eligible for early intervention services, as approximately one-third experience significant language and academic delays 4
• Services should be provided by professionals with expertise in hearing loss, including educators of the deaf, speech-language pathologists, and audiologists 4

Monitoring and Follow-Up

• Regular audiological reevaluations at 6-month intervals are essential to monitor for progression or changes in hearing function 5
• Developmental monitoring should occur at regular intervals using norm-referenced instruments 4

Critical Pitfalls to Avoid

• Do not assume unilateral hearing loss is benign or requires no intervention; these children are at significant risk for developmental and academic difficulties 4
• Do not delay imaging studies in cases of unilateral or asymmetric sensorineural hearing loss, as retrocochlear pathology must be excluded 3, 2
• Do not rely solely on tympanometry or otoacoustic emissions to assess hearing; behavioral pure-tone audiometry remains the gold standard 4
• Do not postpone amplification while awaiting additional diagnostic testing; hearing aid fitting should proceed within 1 month of diagnosis if chosen by the family 4