Etiological Work-up in Referrals From Neonatal Hearing Screening: 20 Years of Experience

Background: Confirmation of permanent hearing loss in a newborn should be followed by a search for an underlying etiology because this may impact hearing loss management and counselling. Methods: Retrospective chart review of all newborns seen at a tertiary referral center after referral from newborn hearing screening over a 20-year period. The changes in the diagnostic protocol over the years are outlined and the most recent protocol includes targeted next-generation sequencing using a panel for known hearing loss causing genes, in all cases of bilateral sensorineural hearing loss (SNHL). Results: Permanent hearing loss was confirmed in 235 of 1,002 neonates. A complete etiological work-up was performed in 138 cases of SNHL (77 bilateral and 61 unilateral), with the underlying cause found in 77.9% and in 67.2% of patients respectively. Genetic causes explained 55 (58.4%) of bilateral cases and in 17 a genetic cause was identified by the gene panel. Pathogenic variants in GJB2 and MYO15A explained most cases of nonsyndromic SNHL. Waardenburg syndrome was the most frequent syndromic cause. Cochlear nerve deficiency and congenital cytomegalovirus infection accounted for the majority of unilateral SNHL. Other causes of congenital hearing loss were conductive hearing loss (n = 12) and auditory neuropathy/dyssynchrony (n = 9). Conclusion: Implementation of targeted next-generation sequencing in the etiological work-up improves the diagnostic yield in congenital SNHL, leaving only about 20% of bilateral and 30% of unilateral cases unsolved.