[Restoration of hearing--comparing auditory brainstem implant to cochlear implant]

Restorative neurosurgery proceeds in the two ways, through biological means or through nerve-computer interface technology. Stem cells are now expected to repair the injured spinal cord and cochlear implants have already restored hearing in many patients. These examples represent each of these methodologies, respectively. The auditory brainstem implant is an extension of the technology of the cochlear implant. In this review article, the author summarizes the present status of auditory brainstem implant (ABI), comparing it to cochlear implant (CI). CI restores hearing by stimulating the cochlear nerve in the cochlea for patients whose deafness has been caused by inner ear disease; ABI does it by stimulating the cochlear nucleus of the brainstem for those deaf due to bilateral cochlear nerve dysfunction. In the world, up until now, more than 700 patients, almost all of whom are neurofibromatosis type 2, have undergone ABI and had hearing restored. Hearing performance by ABI, however, is not so good as that by CI. To improve the quality of hearing by ABI, new techniques such as advanced coding strategies and depth electrodes are now being introduced.