Simultaneous vs Sequential CI: Bimodal Hearing and Second Implant Timing

Introduction: Deciding between sequential versus simultaneous cochlear implantation (CI) can be challenging for adults with continued aidable hearing in the second ear. This study aims to: 1) compare speech recognition outcomes between sequential and simultaneous CI adult users and 2) investigate the impact of bimodal hearing and timing to second CI.

Methods: Retrospective chart review identified adults who underwent bilateral CI, either simultaneously or sequentially, at a high-volume center between 2012-2022. Sequential patients were further delineated based on the second ear being aidable, defined as contralateral AzBio testing in quiet >60%, as well as continued hearing aid use, after initial CI.

Results: Of 135 bilateral CI patients, 118 and 17 underwent sequential (aided: 23, unaided: 95) and simultaneous implantation, respectively. Age, duration and etiology of hearing loss, and CI usage at all follow-ups were similar between all three groups. Preoperatively, the aided sequential group had significantly lower PTA and higher speech scores in the 1st and 2nd ear than the unaided and simultaneously implanted groups (p < 0.005). The aidable sequential group had a longer time interval to second CI than the unaided sequential group (37 vs 17 mo, p< 0.0001). Controlling for preoperative scores, aidable contralateral hearing predicted higher postoperative CI-only and bimodal performance at 1 and 3 months. At 6 and 12 months, datalogging was the only variable that predicted speech performance. There was no significant difference in CI-only performance improvement between the simultaneous versus sequential unaided ears at any time point.

Conclusions: Our findings indicate that an initial period of contralateral acoustic hearing for individuals with aidable hearing may be beneficial for adaptation to CI and improve early performance. Datalogging was the strongest predictor of performance at 6 and 12 months. Both simultaneous and sequential implantation proved to be similarly effective in improving hearing performance.