Molecular study in Brazilian cochlear implant recipients

Abstract

The most common form of non-syndromic autosomal recessive deafness (NSRD) is caused by mutations in the GJB2 gene. Recently, a deletion truncating the GJB6 gene, called del(GJB6-D13S1,830) has also been described normally accompanying mutations in another allele of the GJB2 gene. Among all the mutations described to date, 35delG in the GJB2 gene is the most common. Preliminary data suggest that pathologic changes due to GJB2 mutations do not affect the spiral ganglion cells, which are the site of stimulation of the cochlear implant. Besides, the survival of the spiral ganglion cells is believed to be an important determinant of the outcome after surgery. Therefore, we have studied 49 non-syndromic deaf patients with unknown etiologies in order to determine the prevalence of GJB2 and GJB6 gene mutations in patients undergoing cochlear implantation surgery. Also, the molecular studies were performed using polymerase chain reaction amplification and direct sequencing. As a result, we found 19 individuals with GJB2 mutation including one new mutation (K168R), one patient homozygous for the del(GJB6-D13S1,830). These results establish that genetic screening can provide an etiologic diagnosis, and may help with prognosis after cochlear implantation, as has been hypothesized in previous studies.

DFNB1-associated deafness in Portuguese cochlear implant users: Prevalence and impact on oral outcome

“…This high proportion of CI individuals with mutations in DFNB1 is consistent with previous studies [9,12], highlighting the relevance of the DFNB1-associated deafness in the Portuguese deaf population.…”

“…However, it has been documented that the contribution of these factors to speech perception explains less than 50% of the variability observed [11], the remaining being related to other factors. One of these factors is thought to be the cause of deafness [1,9,12]. Since GJB2 mutations do not affect the spiral ganglion cells which are the site of stimulation of the cochlear implant, we could assume that individuals with GJB2-associated deafness might have a better performance after CI than individuals whose deafness is associated with neural and/or central damage to the auditory system [10].…”

A novel missense mutation p.L76P in the GJB2 gene causing nonsyndromic recessive deafness in a Brazilian family

“…The c.35delG is particularly common in many populations, especially in the Mediterranean region (6), where it accounts for approximately 60% of GJB2 mutated alleles. In Brazil, it represents near 50% of the GJB2 mutations (7).…”

Clinical Application of Screening for GJB2 Mutations before Cochlear Implantation in a Heterogeneous Population with High Rate of Autosomal Recessive Nonsyndromic Hearing Loss

“…Correct selection of the matched controls for any deduction is emphasized in the works of other authorities [ 15 ]. More recent studies have been cautious in making any suggestion regarding the superiority of genetic deafness over controls for the CI outcome [ 16 ]. In 2008, a study on Taiwanese patients reported the same positive effect for genetic cases of hearing loss on the outcome of the CI.…”