New Scientist vol 183 issue 2462 - 28 August 2004, page 36

PHILIP Aiello has been deaf since 1943. He was just three months old when his hearing was destroyed by meningitis. More than half-a-century later, medicine had advanced to the point where a tiny device called a cochlear implant could help. The implant is no instant cure for deafness, but it can restore some degree of hearing. For Aiello, by this time 55, the chance was too good to miss.

In June 1998, he underwent surgery to have the device implanted. The first thing he heard was the soft hum of the electrodes warming up. The second was his wife Myrna saying hello.

But if the joy of hearing her voice for the first time is etched on his memory, so too are the reactions he received. While he was still learning to use the implant, Aiello went to Texas to attend a deaf congress. Aiello, from Wheaton in Maryland, recalls what happened when people started noticing the implant's distinctive wire and hearing-aid type headpiece. "They would finish the conversation to run and tell their friends," he says.

People began to keep their distance. Or they'd creep up behind him and make noises - if he didn't hear them, they'd tell their friends that the implant didn't work. Aiello felt like he no longer belonged in the deaf community.

His ostracism demonstrates just how polarised opinions are on the treatment of deafness. As cochlear implants and other devices become increasingly sophisticated (see Interview, "Blessed voices"), scientists are getting closer to "curing" deafness. But they are on a collision course with large sections of the deaf community who believe they are not sick and do not need curing. To some, it's a personal right to remain deaf.

But the current conflicts are nothing to the furore set to erupt when more effective and permanent treatments for deafness become available. Scientists believe that within the next decade or so they may be able to completely restore deaf people's hearing. Various high-tech strategies are being investigated, including gene therapy and stem cell therapy. But to some deaf people, such approaches are akin to eugenics. "We consider such research an appalling waste of money," says Paddy Ladd, a lecturer in deaf studies at the University of Bristol, who has been deaf from birth. "Do they really think we are damaged and deficient people who are simply a biological mistake?"

About 5 per cent of people in the west have significant hearing problems, and just under 1 per cent are profoundly deaf. Causes include genetics, infections in the womb or during childhood, certain drugs, chronic exposure to loud noise, or simply the ageing process.

Many people who have been profoundly deaf from an early age immerse themselves in the deaf community, where sign language is the primary communication tool. The UK signing community has long fought for official recognition of British Sign Language (BSL) as an indigenous language, arguing that about 70,000 people in the UK use it as their first or preferred form of communication. Last year they achieved this aim, when the government granted BSL official recognition. But the deaf community argues this must be translated into better provision of interpreters and video phones, and funding for teaching of BSL.

Many in the signing community reject the popular notion that they are "disabled", arguing they are simply a minority with their own rich culture and language. "These people were born deaf and they want to be deaf and the rest of us have to come to terms with that," says Pamela Morrisey, head of fund-raising for the British Deaf Association.

These battles have far-reaching implications for the way that doctors treat deafness, or whether they treat it at all. In particular, they will determine whether it is ethically defensible to restore, or refuse, hearing to a deaf child too young to decide for themselves.

In many cases of deafness, the problem lies with the cochlea, the snail-shaped cavity in the inner ear whose job is to convert sound waves into nerve impulses (see Diagram). In the functioning ear, sound waves striking the eardrum trigger movement of fluid inside the cochlea, stimulating auditory hair cells on its lining to produce electrical signals; these travel along the auditory nerve to the brain. But the hair cells are particularly vulnerable to damage, and cannot be regenerated.

A cochlear implant is an electrode that is embedded within the cochlea, where it stimulates the auditory nerve directly, bypassing the hair cells. The user wears a microphone on the back of the ear, which picks up sound waves and transmits them to the implant. To avoid passing a wire through the skin, they are transmitted via radio waves.

Cochlear implants by no means restore hearing to normal. The sounds produced have an artificial, tinny quality, and it can take months of effort for people to get used to them, with varying degrees of success. Children in particular need a lot of support. Some people never really succeed with the device. What's more, a cochlear implant can destroy any remaining natural hearing a person might have, because the surgery kills off any hair cells that are still functioning.

Despite these drawbacks, many people find the implants hugely beneficial. The device significantly improves lip-reading in most people and about 10 per cent of users end up being able to communicate through sound alone. To date, an estimated 65,000 people worldwide have had a cochlear implant.

Debate rages among deaf people about the pros and cons of the device. Many members of the signing community argue they have no need to undergo invasive surgery that yields less-than-wonderful results. "Deaf people see themselves as not in need of 'cures'," says Ladd, who is author of Understanding Deaf Culture.

Most contentious, however, is what happens with children. Nearly 90 per cent of deaf children have hearing parents, who often see implants as a logical choice. But numerous deaf associations, including ones in Britain, the US and Australia, condemn cochlear implants for children. Implants, says Ladd, "cast [deaf children] adrift in a world in which they are an inferior version of a hearing person, rather than as a first-class deaf citizen".

Equally, deaf parents who reject implants for their deaf children also draw flak. One deaf couple recently came under heavy fire when they took this a step further and deliberately conceived a deaf child through IVF (see "Designing Deafness").

The decision on whether to give a child a cochlear implant cannot be put off for long. The first six years of life are crucial for language acquisition. Many centres advocate carrying out the surgery on children of two, or even younger. Recent research seems to support this approach. For example, a study published in May in the journal Otology & Neurotology followed 10 congenitally deaf infants fitted with implants between the ages of 6 and 18 months. Within one to four months of the surgery, the previously silent babies started babbling - the first stage of speech development. The younger they were when the device was implanted, the sooner this occurred.

The debate has been muddied by concerns that the implants raise the risk of the potentially fatal brain infection meningitis, perhaps due to the surgery or simply the presence of a foreign object in the inner ear. Worldwide there have been 91 known cases of meningitis in people with implants, including 17 deaths. New implant recipients are now vaccinated, but passions on this issue run high. At a Manchester conference on cochlear implants two years ago, members of a group called the Deaf Liberation Front staged a protest with banners saying "Better deaf than dead".

If controversy surrounds cochlear implants, what would happen if a complete cure for deafness became available? Many groups of scientists around the world are investigating other strategies to restore hearing, including gene therapy and stem cell therapy. The research is still at an early stage, but few doubt that eventually a cure will emerge.

In the late 1980s, researchers found that unlike mammals, birds can regenerate auditory hair cells. The new hair cells are derived from cells in the cochlea called supporting cells, which have a maintenance role.

In the developing embryo, both supporting cells and hair cells are descendants of the same precursor cells. The ones that are destined to become hair cells start expressing a gene called Math1, whose protein product turns on a suite of other genes characteristic of hair cells.

Researchers at the University of Michigan have used gene therapy to turn supporting cells into hair cells in mammals (The Journal of Neuroscience, vol 23, p 4395). They introduced the Math1 gene into guinea pigs' supporting cells. Within two months they looked like hair cells. "They started changing their identity," says Yehoash Raphael, who led the research. The team is now seeing if the new hair cells can transmit signals to the auditory nerve.

But gene therapy is not the only possible approach. Last year, researchers at Harvard Medical School found that small numbers of stem cells exist in the inner ear of adult mice. Unfortunately these were in the balance organs of the inner ear, not the cochlea. But the balance organs contain hair cells that are very similar to those in the cochlea.

The team showed that when prodded with two biological signalling molecules, the stem cells gave rise to what appeared to be new hair cells, both in the test tube and when put into the developing cochleae of chicken embryos. The researchers' next goals are to repeat the feat in mice embryos, then adult animals, and assess if the new cells function properly. "That's the ultimate test," says cell biologist Stefan Heller, who leads the team.

The finding has galvanised researchers in the field, for three reasons. First, it is possible that inner ear stem cells could be taken from people who donate organs after death. Second, studying inner ear stem cells in the lab should make it much easier to work out how to push embryonic stem cells along the road to becoming hair cells. Third, it suggests that stem cells could also be present in the cochlea itself. Perhaps with the right chemical cues, they could be persuaded to form new hair cells without the need for any invasive surgery. "That's the hope of the whole field," says Heller. "To find a drug that brings back hearing."

Unsurprisingly, members of the signing community are less than impressed. "Scientists are patronising the deaf by assuming they need 'curing'," says Lori Fuller, a deaf advocate for the campaigning group Deaf Empowerment, based in Wisconsin in the US. "It's hearing people who have a problem with hearing loss, not deaf people."

Ladd slates the scientists involved in this research. "They do not care about us, only about their own salaries or careers," he says. "None of these people has any sustained contact with deaf communities."

Not all deaf people feel the same way of course. The research is welcomed by Richard Roehm, a leading deaf activist based in Irvine, California, although he acknowledges that "the majority of the adult deaf would perceive this as some sort of genocide".

Few would argue that adults have the right to decide for themselves if they want medical treatment, but as with cochlear implants, the fiercest battles are likely to be fought over children. When the day eventually comes, as it surely will, that a safe cure for deafness becomes available, many hearing parents of deaf children will want to use it. To the deaf community, this is a challenge to their very right to exist, and must be resisted.

It's a viewpoint that most hearing people find hard to understand. Deaf people "have to accept that there are now real treatments", says Heller. But to those who are sceptical of the deaf community's viewpoint, Ladd suggests the following thought experiment: "Had [gene therapy] emerged in the 1950s, there would have been immense social pressure to use this technology to remove homosexuality," he says. "Fifty years later, we can imagine the magnitude of the crime that would have been committed in society's name."