A comparative study of hearing loss in two microdeletion syndromes: Velocardiofacial (22q11.2 Deletion) and Williams (7q11.23 Deletion) Syndromes

Objective: To comprehensively assess auditory impairments in velocardiofacial syndrome (VCFS) and Williams syndrome (WS). Study design: Audiologic measurements were conducted with 62 subjects with VCFS and 44 subjects with WS, as well as two control groups consisting of 22 subjects with idiopathic developmental disability and 23 typically developing controls. An association between severity of hearing loss in VCFS and the ¹⁵⁸Val/Met polymorphism of the catechol-O-methyltransferase gene (COMT) was explored. Results: Hearing was significantly more impaired in the VCFS and WS groups compared with the developmental disability and typically developing groups. Audiologic abnormalities identified in both the VCFS and WS groups included high-tone hearing loss (predominantly sensorineural or mixed type), loss of acoustic reflex, and middle ear pathologies. In both the VCFS and WS groups, hearing loss severity was positively correlated with age. In the VCFS group, hearing loss was more severe in the subgroup carrying the COMT Val allele compared with the subgroup carrying the COMT Met allele. Conclusions: Hearing impairments, including sensorineural hearing loss and acoustic reflex dysfunction, are very common in both VCFS and WS. Hearing loss is less severe in subjects with the COMT Met allele, possibly due to the protective effect of dopamine on the hearing system.