Cochlear implants have been in use for almost half a century. Since the first multi-channel implant in Vienna in 1977, the number of people with implants has steadily climbed towards the one million mark. Sixty years of research are on the verge of a new breakthrough: gene therapy is supposed to ‘cure’ deafness, but only genetic deafness, and even then only a certain proportion, and only under certain conditions will this proportion achieve so-called ‘normal’ hearing with speech understanding and development. We have summarised the articles on the first successful experiments in 2024 and take a critical look at the topic from a deaf perspective.
As with cochlear implants, deaf people are concerned that members of the community could be removed from the community. Every implanted child is potentially one who does not learn sign language, or who is hard of hearing instead of deaf and may therefore end up at a hearing school without hearing aids. It is a justified fear that is difficult to measure, as the sign language factor is not recorded in the statistics – only the disability. According to WHO figures, around 80,000 people in Germany should be deaf, but only around 50,000 are recorded, namely those who have a disability card with the sign ‘deaf’. How many of them are culturally deaf, i.e. use sign language as their main form of communication, is not known. The ‘deaf’ sign is also often retained, even if hearing aids or prostheses enable almost normal hearing and acoustic participation. Conversely, it is also unlikely that manufacturers will provide reliable statistics or even state when an implantation has been unsuccessful. Here too, it is primarily the ‘installed’ devices that are counted. So even if the hearing aids gather dust in a drawer with an empty battery, they are a success for the statistics.
What remains are subjective truths and personal impressions. It is also a topic that is or can be very emotional for both sides of the hearing curve.
When it is now announced that gene therapy could cure deafness, fear is mixed with hope. Fear on the part of the community that deafness could be injected everywhere like a vaccination, hope among hearing people that deafness in relatives and children will no longer be a burden for them, or that they themselves will one day find a cure, even if it is not possible with the current new method.
As is so often the case, a closer look reveals that this is a solution that is only an option for a small group of hearing-impaired people.
The CRISPR method, also known as ‘gene scissors’, is a way of specifically splitting DNA strands and inserting new genetic information, hence the name ‘scissors’ – the DNA is split lengthwise. This works via certain proteins. The cell in which the DNA is located then attempts to repair these separated strands. The material for this repair is previously introduced, so-called ‘therapeutic’ DNA. The result is specially adapted DNA.
Of over 200 gene mutations that lead to deafness, the ‘Otoferlin defect’ is the one that was chosen for the CRISPR test run. A success was reported at the Children’s Hospital in Philadelphia, USA, in January 2024, but it was only technically a success. An eleven-year-old boy could hear again. In the ‘Otoferlin defect’, the mutation ensures that a certain messenger substance is not produced. Rapidly simplified: just as serotonin is the neurotransmitter for feelings of happiness, otoferlin is the relevant neurotransmitter for hearing. If the cells are taught to produce this neurotransmitter again using gene therapy, so to speak, hearing will also work again, at least if, as in this case, all other components of the auditory system such as the ears and cochlea are intact.
This therapy is only of limited use for two reasons. Firstly because the area of application is so limited, and secondly for somewhat more complicated reasons.
The fact that the area of application is limited is simply due to the numbers. A good ten to 30 children are born with the ‘Otoferlin defect’ in Germany every year. With a good 700,000 children born in Germany every year, this is a proportion of 0.004%, which is vanishingly small. In comparison: there are around 700-2,100 children born deaf or hard of hearing every year, which is 0.1-0.3%.
Back to genetic deafness: In addition to Otoferlin deafness, there are 200 other forms of deafness that are genetically determined. However, even if the right genes are changed, these can no longer be influenced using the Otoferlin method, because if a gene has changed the inner ear, for example, this change has already occurred by the time a child is born and the deafness is diagnosed. The gene scissors are therefore a much smaller threat to deafness than cochlear implants, even if all genetically caused deafness could be destroyed in this way.
However, the 11-year-old boy who can hear with gene therapy has missed the window of opportunity in which he could have learnt a language – whether spoken or sign language. Although he can hear, he cannot do anything with the signals because his brain was not stimulated during the relevant period. The Apotheken-Rundschau interviewed Dr Kristin Rak from the University Hospital of Würzburg, who confirmed that the therapy could also work after implantation, but also recommended that the areas of the brain responsible for language should be stimulated. Although Rak’s medical position is fast-tracked for cochlear implants, her statement also applies to sign language learning and the bilingual approach: ‘We advise parents […] not to wait for the approval of gene therapy so that the centres of the brain responsible for hearing and speech can develop at an early stage.’
This raises the question: So why have this method tested on a boy who has not been encouraged linguistically? Could it be that they wanted to test to be on the safe side whether the therapy also affects speech ability? In terms of research ethics, it would be a very questionable procedure.
The bottom line is that there is still a risk of misjudgement: deafness is curable, we don’t need to set about preserving the speech centre in any way, i.e. promoting any language in the child, whether signed or spoken. This means that the child’s linguistic development falls by the wayside.
In fact, gene therapy is also fuelling a combination with cochlear implants: researchers in Göttingen want to use the findings to advance the development of optical cochlear implants, a technology that has been under development there since 2008 and is said to allow better hearing than previous electrical implants. The gene therapy is not intended to correct mutations, but rather to ensure that light-sensitive proteins are produced in the ears, which in turn, together with the optical implants, enable better hearing.
It is hard to imagine how much money is being invested in this research compared to the non-existent promotion of sign language and deaf culture – in a practical sense.
Author: Wille Felix Zante (manua)