Predicting sequential bilateral cochlear implantation performance in postlingually deafened adults; A retrospective cohort study

Objective: To identify which preoperative patient characteristics influence sequential bilateral cochlear implantation performance and to create a statistical model that predicts benefit. Design: Multicentre retrospective cohort study. Setting: All patients were operated in four academic teaching hospitals in Perth, Australia, and followed up by audiologists of the Ear Science Institute Australia. Participants: A total of 92 postlingually deafened adult patients who had undergone sequential cochlear implantations between 19 June 1990 and 14 March 2016 were included. Patients were excluded if the 12-month follow-up consonant-nucleus-consonant (CNC) phoneme score was missing. Main outcome measure: The effect of 18 preoperative factors on the CNC phoneme score in quiet (at 65 dB SPL) with the second cochlear implant (CI2) one year after implantation. Results: Two factors were positively correlated to speech understanding with CI2: Wearing a hearing aid (HA) before receiving CI2 (r = 0.46, P = 0.00) and the maximum CNC phoneme score with the first CI (CI1) (r = 0.21, P = 0.05). Two factors were negatively correlated: the length of hearing loss before CI2 in the second implanted ear (r = −0.25, P = 0.02) and preoperative pure tone average (PTA) (0.5, 1, 2 kHz) before CI2 in the second implanted ear (r = −0.27, P = 0.01). The following model could be created: predicted CNC phoneme score with CI2 (%) = 16 + (44 * HA use before CI2 (yes)) − (0.22 * length of hearing loss before CI2 (years)) + (0.23 * CNC phoneme score with CI1 (%)). Because the effect of HA use before implantation played such a major role, we also created a model after exclusion of the HA factor: Predicted CNC phoneme score with CI2 (%) = 82 − (0.17 * length of hearing loss before CI2 (years)) − (0.27 * PTA in second implanted ear before CI2 (0.5, 1, 2 kHz)) + (0.20 * CNC phoneme score with CI1 (%)). Conclusion: Advanced age or a long interval between implantations does not necessarily lead to poor CI2 results. Patients who are successful HA users before CI2, who have a low PTA before CI2, a high CNC phoneme score with CI1 and a limited length of hearing loss before CI2, are likely to be successful CI2 recipients.