Cochlear implant research
The development of more effective cochlear implant devices and services is one of the main priorities of Deafness Research UK. To date, Deafness Research UK has contributed over £400,000 to implant development in the UK.
Research has included the development of improved assessment and rehabilitation processes, a trial of a 'through the skin' connector made of a new material, and a device with electrodes positioned on the outside wall of the cochlea which could offer special benefits to certain groups, including those with some residual hearing.
More recently, Deafness Research UK announced a £200,000 study to improve cochlear implantation services for children. The research, supported by The National Lottery Charities Board, is comparing the long-term progress of deaf children who have received an implant with those who have not, providing invaluable information about which children stand to gain the most. The research will also help to shape future cochlear implant services in this country, maximising the benefits of this remarkable technology for deaf children and their families.
Modiolus Hugging
A potentially major technological advance currently undergoing clinical testing is called the "modiolus hugging" electrode array.
The aim of the implant is to use an electrode to excite the 'spiral ganglion cells' and, in principle, the closer the electrode can get to these cells, the better. Put simply, the new technique should enable electrode arrays to 'wrap' themselves around the central hub of the cochlear where the spiral ganglion cells are located. Each of the major manufacturers is working on such an array, although the "hugging" is achieved in different ways.
Neural response telemetry
One of the latest cochlear implantation systems can measure the activity of the auditory nerve in the vicinity of each electrode shortly after a stimulating electric pulse is delivered. In principle, this allows clinicians to check that each electrode is actually stimulating the auditory nervous system and should help improve the ability to tune the device to suit the patients' needs. An objective measure such as this is particularly useful when tuning an implant for a young child.
Bilateral implants
A handful of patients around the world have now received two implants. Bilateral implantation has been shown to have additional advantages, such as locating where sounds are coming from and thus establishing who is talking. In the UK, one multi-centre study to investigate the benefits of bilateral implants has been completed, and the results are expected soon.
Short electrode arrays
Researchers are working on the development of techniques which can provide high-frequency hearing via an implant while allowing conventional amplification (such as that provided by a hearing aid) to provide low-frequency hearing. Such a technique could be beneficial for many millions of hearing-impaired people who are affected by poor high-frequency hearing while retaining good low-frequency hearing. For the foreseeable future, this option is likely to be available only through private health care because of the high cost involved.
Looking to the future
A small number of researchers are currently pursuing the exciting possibilities now being opened by the use of combined acoustic and electrical stimulation. In a few cases, people with considerable hearing sensitivity at low frequencies, but a total loss of hearing at high frequencies, have received a modified cochlear implant in which the electrode array is much shorter than usual. The short electrode stimulates only those regions of the cochlea that are normally responsive to high-frequency sounds. Improved surgical techniques employed when the electrode is inserted may reduce the likelihood that damage will occur to the low-frequency regions of the cochlea where that most hearing sensitivity remains.
Although this research is too new for definite conclusions to be drawn at this time, it does appear feasible to implant an electrode while substantially preserving existing hearing. If continuing research confirms the benefits of combining acoustic and electric hearing in this way, the number of potential cochlear implant recipients may grow dramatically.
