The first part of this thesis focusses on the benefits of bilateral cochlear implantation. We present the results of a randomized controlled trial comparing simultaneous bilateral cochlear implantation to unilateral cochlear implantation in postlingually deafened adults. Patients in the bilateral cochlear implantation group benefit significantly in difficult everyday listening situations and were able to localize sounds, which was impossible for unilateral implanted patients. Furthermore, in the simultaneous bilateral implanted patients, we found a measurable benefit from the squelch effect, which is an important principle in binaural hearing.
In the second part of this thesis we focus on future indications for cochlear implantation. A systematic review of the existing literature shows a decrease of tinnitus after unilateral cochlear implantation. However, tinnitus may also increase or even be induced after cochlear implantation. These findings are supported by the results of a prospective study of our study group on this subject. Finally, we systematically reviewed the literature on the clinical outcome of cochlear implantation for patients with single-sided deafness of asymmetrical hearing loss. Overall, current literature suggests important benefits of cochlear implantation regarding sound localization, quality of life and tinnitus burden.