New hope for the profoundly deaf
An electronic implant placed directly into part of the brain's sound-processing centre could soon offer people suffering from profound deafness a chance to regain their hearing. Background The human hearing apparatus is delicate and complex. Damage to different structures in the ear can cause partial or complete deafness. Since 1984, more than 25,000 people world-wide have benefited from cochlear implants, electronic devices that transmit sounds directly into the inner ear. Vast improvements in implant technology have been made since then, but even the most sophisticated cochlear device cannot restore hearing in someone whose nerve connection between the ear and the brain has been severed. What could help is a device implanted directly in the cochlear nucleus, the region of the brainstem that translates electrical signals from the auditory nerve into the sensation of sound. By connecting the device to a small external processor which is currently used in conjunction with cochlear implants, sound from the outside world could be channelled directly into the brain to restore the sense of hearing. Description, impact and results The project partners have already developed implants that sit on the surface of the cochlear nucleus in the brainstem. These have been trialled in nine European countries in 49 patients with neurofibromatosis type II, a condition in which nerve tumours form sporadically around the body. Tumours that grow on the auditory nerve cause deafness and often become life threatening. Auditory implants were put in place during the operation to remove the tumours and some degree of hearing has been restored in 47 of the 49 people. To try to improve the quality of sound perceived, the University Clinic of Navarra team has been mapping the three-dimensional structure of the cochlear nucleus since autumn 1998. Now, Cochlear UK has the criteria to design an implant with several angled `pins' that penetrate the brainstem, rather than just sitting on it.The length and angle of the pins will be designed to interact with distinct areas of the cochlear nucleus to allow sounds of different frequencies to be more accurately processed. Within three years, patients could have access to a device that can provide a much better quality of hearing. Working partnerships Since 1992, Cochlear (UK) Ltd, an international biotechnology company with a special interest in developing electronic auditory protheses, has been collaborating with researchers at the University Clinic of Navarra in Spain to develop tiny electrodes that can be used as brainstem implants. In 1997, the partners decided to formalise their relationship with the help of one of the partners of the CENEO Innovation Relay Centre in Spain. Contracts and technology transfer agreements signed in autumn 1998 set out the research strategy that will enable the University Clinic to develop their knowledge of the cochlear nucleus and to work with Cochlear UK Ltd to develop and test a new generation of implants.