[Екатерина-Челябинск] If we know we carry the GJB gene, can we plan for the birth of a hearing child? IVF?
IVF does not allow choosing an embryo with the right genotype – the failure rate with analysing just the one available cell is way too high. With IVF, at 10-12 weeks of pregnancy, you can undergo genetic diagnostics. If the genotype of the foetus has two mutations, the hearing impairment will be in place, but we cannot forecast the severity. You are the ones making the decision as you take your family’s situation into account. The parents’ decision must not be influenced by anyone.
[Lilit – Yerevan] L. Balabekyan is asking whether the deafness of the child’s great-grandmother means that the child is deaf for reasons of genetics? Can removal of two teeth during pregnancy cause deafness in a child?
Samples should be submitted and tested, the impairment may as well be genetic. The teeth are likely not at fault.
[Роман г.Владикавказ] Can a birthing trauma cause damage to the gene?
When we speak of tooth removal or of birth circumstances, we must realize neither of them entail changes in the genes. However, they may combine with the genetic factors. It is proven that the age of the common 35delG mutation in the connexin 26 gene is more than 10,000 years old. We suggest ruling out the coincidence of acquired and hereditary risk factors, through a genetic analysis.
[Oleg Zyabrikov-Moscow] Does a mutation of the GJB2 gene affect only the auditory nerve, or the cilia as well? We are planning to have our child implanted, so it matters that the nerve is be functional.
A mutation in the GJB2 gene does not cause damage to the nerve itself. The stereocilia are also morphologically intact, but without the connexin canals they can’t function properly. Normally they should convert the sound wave into an electric signal, which is then passed on to the nerve fibers of the hearing nerve. In case of a pathology of connexin channels, sound perception is compromised, and information does not reach the auditory nerve.
[Monika Lehnhardt] What is the percentage of newborns undergoing audiological screening in Russia?
Universal audiological screening is conducted nationwide. The data differs across regions – there are those where the coverage is 95%, 80% or lower. The total rate for 2012 is 70%.
In certain maternity hospitals the screening is absent. Even in Moscow there are clinics where OAE are not measured. In this case the parents must find a polyclinic where they can have the tests at 1 month of the baby’s age.
[Vera Lyubomudrova – Moscow] Does this mutation affect any other organs? Are there other conditions characteristic of persons with the mutation?
In most cases there are no other pathologies involved in addition to the hearing loss. An accompanying pathology is possible, just like for any other child. We often find hemangiomas in persons with a flawed connexin 26 gene. But this needs in-depth investigation, I cannot provide any data now.
A completely different subject are dominant mutations in the connexin 26 gene, which manifest themselves in hearing loss and skin conditions, but on the whole this is very rare.
[Екатерина-Челябинск] Does a CI affect the heart, or sight? A friend’s family noticed that four years after implantation, the child started losing sight and started experiencing heart murmur.
I would recommend a genetician’s consultation. First, a syndrome must be eliminated. Every situation should be treated individually; however, this is unlikely to be connected with the implant.