Purpose: Changes in auditory thresholds following cochlear mplantation are generally assumed to be due to damage to neural elements. Theoretical studies have suggested that placement of a cochlear implant can cause a conductive hearing loss. Identification of a conductive component following cochlear implantation could guide improvements in surgical techniques or device designs. The purpose of this study is to characterize new-onset conductive hearing losses after cochlear implantation.
Method: In a prospective study, air- and bone-conduction audiometric testing were completed on cochlear implant recipients. An air–bone gap equal to or greater than 15 dB HL at 2 frequencies determined the presence of a conductive component.
Results: Of the 32 patients with preoperative boneconduction hearing, 4 patients had a new-onset conductive component resulting in a mixed hearing loss, with air-conduction thresholds ranging from moderate to profound and an average air–bone gap of 30 dB HL. One had been implanted through the round window, 2 had an extended round window, and 1 had a separate cochleostomy.
Conclusions: Loss of residual hearing following cochlear implantation may be due in part to a conductive component. Identifying the mechanism for this conductive component may help minimize hearing loss. Postoperative hearing evaluation should measure both air- and bone-conduction thresholds.