Speech perception and localization with adults with bilateral sequential cochlear implants

This investigation reports measures of binaural hearing of all of our seven adults who have received sequential bilateral cochlear implants (range of time between implantation of 6 yr/8 mo and 17 yr). All subjects used both devices in everyday life. The internal array, number of channels, rate, and signal processing strategies were usually quite different between devices. Speech recognition was tested by using words in quiet and sentences in noise with the sentence stimuli presented from the front and the noise presented from the front, the right, or the left at a 90 degrees angle. Bilateral localization was tested by using an everyday sounds test with stimuli presented from one of eight loudspeakers. Results showed that all subjects received a significant bilateral improvement on at least one speech perception test compared to either implant alone. Four of seven subjects with bilateral devices demonstrated some (root-mean-square error below 30 degrees ) localization abilities. The two subjects tested unilaterally before receiving a second implant showed a bilateral improvement on localization after implantation of the second side. We conclude that sequential implants can be beneficial even after many years of monaural use and even with very different cochlear implants.