Auditory outcome after cochlear implantation in patients with congenital nonsyndromic hearing loss: influence of the GJB2 status.

OBJECTIVE: To compare the audiologic outcome after cochlear implantation between 2 groups of patients with congenital nonsyndromic sensorineural hearing loss. STUDY DESIGN: Retrospective cohort study. SETTING: Department of Otorhinolaryngology, University hospital (tertiary referral center). PATIENTS: From a bigger pool of implanted patients, 2 groups, each numbering 30 were enrolled. The patients from the first group were diagnosed with a Connexin 26 mutation (GJB2), whereas all of the patients from the second cohort were with a wild type genotype. Both groups were age matched, 1 to 7 years old at the age of implantation, with diagnosed congenital nonsyndromic sensorineural hearing loss. MAIN OUTCOME MEASURES: Both groups were evaluated with the help evaluation of auditory responses to speech/EARS/test battery - LiP test (Listening Progress Profile), MTP tests 3,6,12 (Monosyllabic-Trochee-Polysyllabic Test), GASP test (Glendonald Auditory Screening Procedure), and others. Follow-up period was at least 36 months. RESULTS: Mean test scores were compared at the 1st, 6th, 12th, 24th, and 36th month. LiP outcome was significantly better (p < 0.05) for the GJB2-related cohort for the whole follow-up period except at the first month. MTP3, 6, and 12 tests displayed the same statistically significant outcome in favor of the first group. In the open-set test GASP, the difference was apparent: 1.22, 2.40, 5.59, and 7.40 mean scores at the 6th, 12th, 24, and 36th months for the first cohort versus 0.00, 0.07, 0.81, and 1.74 for the GJB2-unrelated patients. CONCLUSION: The results from our study suggest that children with GJB2-related deafness show better auditory performance after cochlear implantation than age-matched children with GJB2-nonrelated sensorineural hearing loss.

Prevalence of GBJ2 mutations in patients with severe to profound congenital nonsyndromic sensorineural hearing loss in Bulgarian population.

Objective of the study is to assess the prevalence of Connexin 26 (GJB2) mutation in patients with congenital nonsyndromic sensorineural hearing loss in Bulgarian population. Study design is done prospectively. Patient inclusion criteria for this study were diagnosis of congenital nonsyndromic hearing loss, and absence of potential sibling relationships between patients included in the study (anamnestic pedigree for at least three generations). Patients were excluded from the study group if one of the following conditions were present: secondary hearing loss (cytomegalovirus, rubella, meningo-encephalitis, mastoiditis, other infections, posterior fossa tumors, etc.), exposure to drugs or other prenatal or perinatal etiology of deafness, and congenital syndromic hearing loss. Genomic DNA samples from whole blood were tested with sequence analysis for mutations in the coding region of the GJB2. Results state that 51 patients were analyzed for GJB2 mutations. Twenty of the patients (39%) with mutant alleles were homozygous for the c.35delG mutation (c.35delG/c.35delG) and four patients (8%) presented as heterozygotes (c.35delG/WT). In one patient, who carried a heterozygous mutation c.35delG, a second mutation was found-312del114. Additionally, in two other patients were discovered the mutations Trp24X (W24X) and, respectively, Arg127His(R127H), both in heterozygous states. From the whole study group there was only one patient with compound heterozygous genotype-p.Leu90Pro(L90P)/p.Ile121Asn. The latter one has never been reported in the literature so far. In conclusion, this study determines the importance of connexin 26 mutations in Bulgarian children with severe to profound congenital nonsyndromic sensorineural hearing loss, the prevalence of the different mutation variants and their relationship with the ethnical background of the patients. In addition, we report for the first time a novel mutation in the GJB2 gene.