Objectives: Recently, we identified three novel mutations of the GJB2 gene in Japanese families with autosomal-recessive non-syndromic deafness.1 Seven of 11 mutated chromosomes (63.6%) contained a 233delC allele, suggesting that the 233delC mutation is the most common mutation of the GJB2 gene in the Japanese population. After it was recognized that cochlear implantation (CI) is of benefit to children with prelingual deafness, we have had a number of prelingual pediatric CI patients. Because children carrying the homozygous 233delC mutation show bilateral prelingual profound deafness, they could be enrolled in the CI program at Osaka University Graduate School of Medicine. The purposes of this study were 1) to analyze the occurrence of the GJB2 mutations in our 15 prelingual pediatric CI patients in whom the cause of non-syndromic deafness was unknown, and 2) to evaluate the auditory function and postoperative speech perception with CI of those GJB2-related deaf subjects.
Study design: Retrospective analysis.
Methods: Mutation analysis of the GJB2 gene by direct sequencing was performed with genomic DNA from 15 children born profoundly deaf as a result of unknown causes and implanted with CI. Intraoperative electrically evoked auditory brainstem response (EABR) and intra-/postoperative EAP were measured. The speech perception was evaluated with Infants and Toddlers Meaningful Auditory Integration Scale (IT-MAIS).
Results and conclusions: We identified 4 CI patients (26.7%) out of 15 children carrying the homozygous 233delC mutation. Intra- and postoperative evaluation of the auditory system revealed almost intact cochlear and retrocochlear auditory function in these 4 patients. Postoperative auditory testing indicates that their speech perception had become significantly higher in comparison with that of other prelingual CI patients. These results suggest that prelingual deaf children carrying the homozygous 233delC mutation of the GJB2 gene can benefit from CI.