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Genetic Testing Is Appropriate for Some Pediatric Patients with Unilateral Hearing Loss or Single-Sided Deafness

by Armine Kocharyan, MD, Amanda M. Schaefer, MS, LGC, Richard J. H. Smith, MD, and Marlan R. Hansen, MD •

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BACKGROUND

Pediatric unilateral hearing loss (UHL), defined as hearing loss in one ear and normal hearing in the contralateral ear, can range in severity from mild to profound, with profound UHL referred to as single-sided deafness (SSD). Unilateral hearing loss, which can be congenital or acquired, occurs at an estimated incidence of 0.6–0.7 in 1,000 live births in the United States, with increasing incidence (2.5%–6%) in school-age children (CDC database)

A growing body of evidence points to the detrimental effects of pediatric SSD on speech development, social interactions, and academic performance. Increased cognitive effort and reliance on monoaural hearing with poor spatial hearing and impaired speech understanding in noise can make cognitively demanding tasks more challenging, affecting attention, executive function, working memory and cognitive performance.

Although there is increasing evidence on the predictive importance of etiologic diagnosis in UHL and SSD, the optimal diagnostic pathways that can guide rehabilitative interventions and follow-up remain controversial. Rehabilitation strategies that depend, in part, on etiology are emerging. For example, cochlear implantation may have a questionable outcome for children with SSD due to significant labyrinthine malformation or cochlear nerve deficiency (CND), but may be strongly considered in cases where the contralateral ear is at risk for progressive hearing loss. Some support the use of imaging, and some question its importance over genetic testing; thus, the assessment of these patients tends to be somewhat physician dependent.

BEST PRACTICE

As a best practice, a sequential approach is recommended in the evaluation of UHL or SSD. Given the etiologic profile of UHL and SSD, magnetic resonance imaging (MRI), and congenital cytomegalovirus (cCMV) testing (limited in its time of application) are recommended to rule out labyrinthine abnormalities, CND and cCMV infection. In cases when the MRI is negative or consistent with abnormalities that will warrant further investigation, CT can be used as a complementary imaging modality to detect bony structural abnormalities. Routine and initial use of genetic testing is not recommended if there are no imaging or physical exam findings consistent with syndromic features or a family history of hearing loss. Genetic testing should be considered when the most common nongenetic causes (cCMV, negative imaging for structural inner ear, or cochlear nerve abnormality) are ruled out as subtle phenotypic manifestations of syndromic hearing loss and incomplete penetrance occur, and some UHL will further progress to bilateral.