The DFNB1 subtype of autosomal recessive, nonsyndromic hearing impairment, caused by mutations affecting the GJB2 (connection-26) gene, is highly prevalent in most populations worldwide. DFNB1 hearing impairment is mostly severe or profound and usually appears before the acquisition of speech (prelingual onset), though a small number of hypomorphic missense mutations result in mild or moderate deafness of postlingual onset. We identified a novel GJB2 splice-site mutation, c. -22-2A>C, in three siblings with mild postlingual hearing impairment that were compound heterozygous for c. -22-2A>C and c.35delG. Reverse transcriptase-PCR experiments performed on total RNA extracted from saliva samples from one of these siblings confirmed that c. -22-2A>C abolished the acceptor splice site of the single GJB2 intron, resulting in the absence of normally processed transcripts from this allele. However, we did isolate transcripts from the c. -22-2A>C allele that keep an intact GJB2 coding region and that were generated by use of an alternative acceptor splice site previously unknown. The residual expression of wild-type connection-26 encoded by these transcripts probably underlies the mild severity and late onset of the hearing impairment of these subjects.
Objective: To evaluate the hearing preservation (HP) in cochlear implant (CI) recipients who did not fulfill the criteria for electric acoustic stimulation (EAS). Study Design: Prospective study Setting: Tertiary academic hospital. Patients: Adults undergoing CI with deep insertion electrode arrays who had measurable residual hearing (RH) before surgery. Intervention: Demographic data, surgical technique, pure-tone average, and radiological findings were evaluated. Main Outcome Measure: Pre- and postoperative pure-tone audiometry. A preservation study was therefore performed for the whole range of frequencies (THP), and for low frequencies (LFHP). Results: From the total 25 patients who underwent the surgical procedure, 6 of them (26.08%) did not retain any RH and 17 of them (73.91%) had some degree of HP. A clear association was observed between the use of the atraumatic technique (AT) and the percentage of some degree of HP. In patients who underwent the AT, LFHP was 72.79% and THP was 70.40%. In patients who did not undergo the technique, LFHP was 31.48% (p: 0.003) and THP was 23.50% (p: 0.002). LFHP was complete or partial (more than 25% of initial RH) in 92.3% of patients who underwent AT and in 50% of those who did not. Radiological findings showed that complete insertion is not associated with poorer HP. Conclusion: If the appropriate technique is used, preservation of RH is feasible after cochlear implant surgery with deep insertion electrode arrays.
The DFNB1 subtype of autosomal recessive, nonsyndromic hearing impairment, caused by mutations affecting the GJB2 (connection-26) gene, is highly prevalent in most populations worldwide. DFNB1 hearing impairment is mostly severe or profound and usually appears before the acquisition of speech (prelingual onset), though a small number of hypomorphic missense mutations result in mild or moderate deafness of postlingual onset. We identified a novel GJB2 splice-site mutation, c. -22-2A>C, in three siblings with mild postlingual hearing impairment that were compound heterozygous for c. -22-2A>C and c.35delG. Reverse transcriptase-PCR experiments performed on total RNA extracted from saliva samples from one of these siblings confirmed that c. -22-2A>C abolished the acceptor splice site of the single GJB2 intron, resulting in the absence of normally processed transcripts from this allele. However, we did isolate transcripts from the c. -22-2A>C allele that keep an intact GJB2 coding region and that were generated by use of an alternative acceptor splice site previously unknown. The residual expression of wild-type connection-26 encoded by these transcripts probably underlies the mild severity and late onset of the hearing impairment of these subjects.
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