The world’s first successful cochlear implant surgery in Melbourne 46 years ago made global headlines and changed the way hearing loss was treated forever. It began a revolution in hearing for severely to profoundly deaf people and it’s estimated more than one million people have since benefitted worldwide. As advances continue to improve outcomes, Hearing Practitioner Australia (HPA) looks at what’s on the horizon.
As a boy, visionary Melbourne ENT surgeon Professor Graeme Clark, now 89, “wanted to fix ears” because he had a deaf father. His invention became one of the world’s greatest medical research breakthroughs, considered by educators and clinicians to be one of, and possibly the, most important advance in the history of the management of profound deafness.
When he started his research in 1967 on electrical stimulation of the auditory pathways, he did so against opposition from the scientific and medical community. But he persisted and the breakthrough occurred one day at the beach with his children when he examined a Turban seashell and found grass blades would go far enough around the spiral if they were flexible at the tip and stiffer at the base, according to the Graeme Clark Foundation. This mechanical principle was applied to that used for electrodes for the cochlear implant.
After initiating and leading the team that developed the first multi-channel cochlear implant at The University of Melbourne, Prof Clark implanted it in patient Mr Rod Saunders at The Royal Victorian Eye and Ear Hospital in 1978. The Bionics Institute, which he founded to continue development of the implant, states: “Professor Clark knew the operation was a success when his team developed a speech code for electrical stimulation of Saunders’ brain that enabled him to recognise some words without any help from lipreading. Prof Clark says he was so overcome with emotion he went quietly into the next-door lab and cried tears of joy.”
The subsequent Australian-founded company Cochlear established to provide the implants, says when Saunders heard speech, it was the first time anyone had shown that an artificial sensory stimulus could be interfaced to human consciousness. Prof Clark then became the driving force in seeking government funding for its industrial development.
The multi-channel implant was the first cochlear implant to reliably give speech understanding to severely and profoundly deaf people and spoken language to children born deaf. Improvements made in the years following included a smarter speech code, using implants in each ear to make it easier to localise sound and hear in noise and smaller, safer and more reliable devices.
Preserving residual hearing
The progress continues with one challenge being that the implant can damage residual hearing. Dr Christo Bester, working jointly with the Ear Science Institute Australia and University of Melbourne, specialises in cochlear electrophysiology and cochlear mechanics. He says interfering with a person’s natural level of hearing can limit cochlear implant benefits.
“People with preserved natural hearing tend to do better in complicated hearing tasks that many cochlear implant recipients find difficult – hearing in noisy environments, with multiple talkers, enjoyment of music,” he says.
“Although while 50% to 70% of cochlear implant recipients lose residual hearing, they’re usually already so far down the hearing loss journey that the implant will give them much better outcomes even if they do lose all their natural hearing, they’ll be in a better place,” he says. However, he is working with Cochlear and University of Melbourne cochlear implant surgeons Dr Claire Iseli and Professor Stephen O’Leary at The Eye and Ear to prevent this happening during surgery and to protect recipients’ hearing for the rest of their lives.
Dr Bester has sat in on dozens of cochlear implant surgeries to do this, precisely measuring inner ear function before, during and after implantation. “It’s worth it for memorable moments such as being in the room after we successfully preserve a baby’s hearing during a challenging implantation and being able to say to the parents, ‘Because of what we did today, your child will still have their natural hearing,” he says.
Trauma from the electrode can damage residual hearing as can inflammatory response that damages hair cells, and foreign body response, resulting in scarring.
“During surgery we’re informing the surgeon of changes to the condition of the patient’s hearing by playing the patient sounds and recording the ears’ electrical response to those sounds from the implant as the electrode is being put in. Measuring electrical signals produced by their ear in response to these sounds gives us a way of monitoring the health of the ear during implantation,” Dr Bester says.
“Researchers like me, and a team I’m training, sit at the end of the operating table, watch the condition of the ear and inform the surgeon if there are changes that we associate with loss of residual hearing. If the ear stops responding to us, they can pause insertion and reconsider how far in they’re placing the electrode or alter the trajectory to see if it can be modified to produce best outcomes.
“Our interventional trial at the Eye and Ear basically reversed it and went from 70% of recipients losing residual hearing to 70% having good, functional hearing post implantation”.
Dr Iseli adds: “We utilised this technology to monitor insertion and reduce trauma so we can hear what the inner and outer hair cells are doing while we’re inserting the electrode. This real time feedback has reduced the amount of hearing loss we’re losing and doubled the chance of preserving what natural hearing they have.”
Meanwhile, she says another trial has started at The Eye and Ear and in Sydney and the US of a steroid-impregnated cochlear implant which elutes the steroid post implantation. The hope is this will reduce scarring, foreign body response and inflammation. The Eye and Ear implanted the first patient with the drug-eluting array and has since done two more.
“Similar previous trials involved bulky electrodes and not surprisingly, most people were losing hearing because even if it was preserved in surgery, they lost it in the first three months because of fibrosis,” Dr Iseli says. “But now that we’re combining the drug with a slimmer electrode, there is potential for the steroids to be hearing preserving and stop swelling, avoiding that secondary loss. It’s a unique opportunity to preserve hearing.”
Robotics is another area of interest. “A steady hand is much kinder on the tissues and no-one’s as steady as a robot,” Dr Iseli says. “In the US they’re doing cochlear implants from start to finish just with a robot but it’s much slower and they were having complications with different anatomies. While that hasn’t taken off, what has is the process of putting the electrode in using a robot and we’ve applied for an insertion robot in Melbourne which is in the process of being approved.”
The robot will be part of Dr Bester’s trial and will be informed by him and his team on insertion so it knows the condition of the ear during cochlear implantation surgery.
“A robot inserts a lot slower than a human; it’s hard to move very slowly to push 22 millimetres in two minutes which is the recommendation,” Dr Iseli says. “The structures are so delicate that the faster you hit them, the more likely they are to be traumatised.”
She predicts the next phase could be gene therapy where implants are an intracochlear delivery method for genetic material to ears that are missing that genetic makeup in people with genetic deafness. “If we became really good at genetic treatment, we might even avoid hearing aids and cochlear implants in people with genetic deafness,” she adds.
Implantable microphone
The microphone remains one of the largest barriers to adopting a fully internalised cochlear implant but US researchers announced in July 2024 that they’d developed an implantable microphone that could lead to fully internal cochlear implants. They claim it performs as well as external hearing aid microphones.
The tiny microphone is a sensor produced from biocompatible piezoelectric material that generates an electric charge when compressed or stretched and measures miniscule movements on the underside of the ear drum. The triangular 3x3mm motion sensor UmboMic comprises two layers of piezoelectric material sandwiched on either side of a flexible printed circuit board, forming a microphone the size of a grain of rice and twice as thick as an average human hair.
To maximise performance, the team from MIT, Massachusetts Eye and Ear, Harvard Medical School and Columbia University, developed a low-noise amplifier that enhances the signal while minimising noise from the electronics.
Most fully implantable devices in development sense sound under the skin or motion of middle ear bones but can struggle to capture soft sounds and wide frequencies. UmboMic targets the umbo which vibrates unidirectionally, making it easier to sense simple movements. The goal is to implant it with the cochlear implant and an internalised processor.
Tests in cadaver human ear bones found it had robust performance in the intensity and frequency range of human speech and the microphone and amplifier together had a low noise floor so very quiet sounds could be distinguished. Results showed the necessary broad-band response and low noise needed to act as an acoustic sensor. Researchers are planning animal studies.
Trials of Cochlear’s totally implantable cochlear implant prototype have occurred at the Eye and Ear, says the hospital’s cochlear implant audiologist Dr Jaime Leigh and it’s likely there’ll be more in future. The version includes an implanted microphone, rechargeable battery and sound processor, as well as an external sound processor which also charges the internal battery. Patients choose between using the external sound processor or taking it off.
She says they enjoyed ‘invisible hearing’ – being able to hear without the external processor – but challenges include battery life and the microphone being under the skin which can potentially muffle the signal. Optimising microphone placement and technology is one future design challenge to prevent an inferior signal.
The hospital has partnered with community audiology providers at 28 Victorian sites involving 36 audiologists to provide services in their local community, training and upskilling them in cochlear implant counselling, protocols and clinical competencies. This model will continue in future and more audiologists will become involved. “The technology will improve, become more automated but how clients apply that is where support from audiologists will continue and increase in future,” Dr Leigh adds.
Growing nerve fibres
In Sydney, a trial will test if neurotrophin growth factors inserted during cochlear implant surgery can stimulate auditory nerve fibres in the cochlea to regrow towards the electrode array.
The Cochlear Implant Neurotrophin Gene Therapy Trial will evaluate safety and efficacy of neurotrophin gene therapy after animal studies showed improvement in cochlear implant performance. The fibres grew towards the electrode, “closing the neural gap” and improving the interface between the prosthesis and the cochlear nerve, says the Passe & Williams Foundation which is assisting with funds.
Leading the trial are Professor Gary Housley and his team from UNSW, The University of Sydney, The Bionics Institute, Macquarie University, Cochlear and NextSense, whose cochlear implant program medical director Clinical Professor Catherine Birman OAM will conduct the surgery.
The trial website says 15 patients will receive the gene therapy and 15 will have standard implants to see if benefits to hearing seen in pre-clinical studies translate to humans. Prof Birman will insert the gene delivery array into the cochlea delivering one drop of DNA solution. A few brief electrical pulses passed between the electrodes will drive the DNA into target cells.
Meanwhile, US biotechnology company Sound Pharmaceuticals (SPI) will trial giving its new investigational drug to cochlear implant recipients to see if it prevents and/or treats loss of residual hearing during and after implantation. It received FDA notification in May 2024 that it may proceed with a phase two trial of SPI-1005 (ebselen) anti-inflammatory compound which mimics and induces the activity of Glutahione Peroxidase, an enzyme critical to hearing and balance.
“Ebselen has shown safety and efficacy in three different forms of acquired sensorineural hearing loss in adults including loud sound exposure or acute noise-induced hearing loss, Meniere’s disease, and antibiotic or aminoglycoside induced ototoxicity,” SPI says. The trial with MED EL will enrol 40 adults scheduled to receive a cochlear implant who have moderate to severely impaired residual low frequency hearing at risk of being lost after implantation. They’ll be randomised to six months of oral ebselen or placebo starting two days before surgery.
Lesser hearing loss and more remote fitting
Mr Chris Rehn, chief executive of NextSense, Australia’s largest cochlear implant program with 22 centres nationwide performing around 400 implants annually, says more children with moderate to severe hearing loss rather than just severe to profound deafness are being implanted and he predicts this will increase. Campaigns are also needed to encourage more adults to come forward, he adds.
“We do about 300 implants annually in adults but thousands more could benefit,” he says.
“Our nuture program in the community is one way of introducing the public to hearing loss so there’s a higher level of consciousness of the need to look at cochlear implants if they’re not getting benefits from hearing aids and it also recommends exploring hearing aids through a hearing aid provider if there’s untreated hearing loss.
“Anecdotally, we’re seeing children with profound hearing loss and cochlear implants do better in outcomes than some kids with lesser hearing loss and hearing aids which challenges us to work out what level of hearing loss works best for a cochlear implant. More cochlear implants are already being done in kids with lesser hearing loss as well as people with single sided deafness,” Rehn says.
“We need to continue building centres where people live. When we opened our Newcastle site we thought we’d get a trickle but we got an avalanche. Removing distance as an impediment to hearing services is important. Manufacturers are also looking at newer and more innovative ways of enhancing technology to interface with people’s complex lives. Already, implants are Bluetooth accessible and work with other assistive listening devices.”
The LOCHI study from Hearing Australia and the National Acoustic Laboratories follows children with hearing impairment and involves NextSense and other organisations.
NextSense head of Cochlear Implant Services, audiologist Ms Eleanor McKendrick, says technology is providing amazing outcomes and proving earlier implantation is better, with the LOCHI study showing babies implanted at six-month-olds achieve better outcomes than later implantation.
“Sound processors worn on the external part of the ear are usually upgraded every five to seven years and that’s where we’re also seeing huge changes in terms of what they can do and aesthetics – they’ve gone from the size of a mobile phone to the size of a hearing aid,” she says.
“Signal processing within the sound processor is always improving and the fitting software is becoming more focussed on remote service delivery so in future, we’ll see more access to remote technology and remote fitting, and remote services will be far more streamlined.”
Dr Leigh, The Eye and Ear’s cochlear implant audiologist, adds it’ll be easier for patients to manipulate their own programs through their mobile phone and while this is happening, it isn’t yet the full suite of services. “They’ll have more control over how their implant and sound processor work and future sound processors will have better aesthetics, be smaller and may proceed to where there’s no visible external or in ear device,” she says.
Dr Iseli concludes: “We now recognise how critical healthy aging is and cochlear implants and hearing aids are going to have an increasing importance and recognition in our ability to keep patients cognitively healthy as well as socially connected so I don’t see cochlear implants going away anytime soon; in fact, I think we’re growing and the future is exciting.”
THE BIONICS INSTITUTE AWARDS VISIONARY AWARD TO PROFESSOR GRAEME CLARK
The Bionics Institute has awarded its Visionary Award to cochlear implant pioneer Laureate Professor Graeme Clark AC for his enormous contributions to the field. Her Excellency, Professor, the Honourable Margaret Gardner AC, Governor of Victoria, presented the award on 2 July 2024 at a celebration at Government House of the 46th anniversary of the successful implantation of the first multi-channel cochlear implant. She thanked Prof Clark for transforming the lives of people with hearing loss; about 15,000 Australians have cochlear implants and more than one million people worldwide have received the implants.
“I feel very honoured to receive the award and am pleased the Bionics Institute is expanding our work to other areas,” Prof Clark said. “I am also excited the University of Melbourne has created the Graeme Clark Institute of Biomedical Engineering to integrate research across disciplines to help people with disabilities, and it is good the Graeme Clark Foundation is raising funds to help poor and disadvantaged people in Australia and overseas.”
Bionics Institute CEO Mr Robert Klupacs said the institute’s journey began with development of the cochlear implant which positively impacted the lives of so many people. He thanked Prof Clark for being such an inspiration.
