ABSTRACT: Importance:Pediatric-onset unilateral and asymmetric sensorineural hearing loss (SNHL) is a common condition, but in most patients, the cause remains unclear; thus, determination of the hearing outlook is difficult. Objective:To analyze the etiologic and audiologic characteristics of pediatric-onset unilateral and asymmetric SNHL. Design, Setting, and Participants:In this retrospective cohort study performed from January 1, 2008, through December 31, 2016, patients at a tertiary referral center who were diagnosed with pediatric-onset unilateral or asymmetric SNHL were divided into 3 groups according to their hearing levels: unilateral hearing loss with scaled-out levels (UHL-SO), unilateral hearing loss with residual hearing (UHL-RH), and asymmetric hearing loss (AHL). Main Outcomes and Measures:Basic demographic data, family and medical histories, audiologic results, imaging findings, and genetic results were ascertained and compared among patients of the 3 groups. Results:A total of 133 patients (mean [SD] age, 9.1 [10.9] years; 63 [47.4%] male and 70 [52.6%] female), including 50 with UHL-SO, 42 with UHL-RH, and 41 with AHL, were enrolled for analyses. Of 50 patients with UHL-SO, 49 (98.0%) had stable hearing levels with time, whereas 10 of 42 patients with UHL-RH (23.8%) and 18 of 41 patients with AHL (43.9%) revealed progressive or fluctuating hearing loss. Inner ear malformations detected with temporal bone high-resolution computed tomography, particularly cochlear aperture stenosis, were detected at higher rates in patients with UHL-SO (9 of 31 [29.0%]) and UHL-RH (6 of 24 [25.0%]) than in those with AHL (1 of 30 [3.3%]). In contrast, screening for mutations in 3 common deafness genes-GJB2, SLC26A4, and MTRNR1-achieved definite diagnosis in a higher percentage of patients with AHL (10 of 37 [27.0%]) than patients with UHL-SO (0 of 33) and UHL-RH (1 of 25 [4.0%]). Conclusions and Relevance:The UHL-SO and UHL-RH conditions share a common or similar etiopathogenesis different from that of AHL. Imaging studies and genetic testing might be prioritized during the respective general etiologic workups for patients with UHL and AHL. Regular hearing checkups are warranted for patients with UHL and AHL because a certain proportion of patients might sustain progression in SNHL.
