Etiology of unilateral hearing loss in a national hereditary deafness repository

PurposeThe aim of this study was to characterize the genetic, audiologic, and epidemiologic characteristics of unilateral hearing loss (HL) in a national hereditary deafness repository.Materials and MethodsThis is a prospective clinical study involving 34 subjects identified in a national hereditary deafness repository. Clinical data and family history of HL were obtained on enrollment. Candidate deafness genes were screened by single-stranded conformation polymorphism, and mutations were confirmed with sequencing.ResultsThirty-four subjects (19 males, 15 females) with unilateral HL were identified, ranging in age from 2 months to 36 years. The mean age at diagnosis was 7 years, and the left ear was affected in 62% of the cases. The racial distribution of our sample was 62% white, 23% African American, and 15% Hispanic. Imaging results were available in 47%, and most (69%) were considered normal. Nineteen percent had enlarged vestibular aqueducts, 2 had ipsilateral Mondini dysplasia, and 1 had a common cavity deformity. Twenty subjects (59%) had a family history of HL, with 26% specifically reporting familial unilateral HL. Mutational screening revealed sequence variants in the GJB2 (connexin 26), GJB3 (connexin 31), TECTA, and COCH genes. Two novel mutations were detected in COCH and TECTA.ConclusionsSequence variants in known deafness genes were detected in more than one-third of our study population, suggesting that gene/gene or gene/environmental interactions may indeed play a role in the etiology of some cases of unilateral deafness. Further prospective studies including congenital cytomegalovirus screening at birth and molecular screening of deafness genes in children with congenital unilateral HL will be required to establish the etiology of unilateral deafness with certainty.