Influence of cochlear implant insertion depth on performance: A prospective randomized trial

Objective: The purpose of the present study was to assess the influence of electrode insertion length on cochlear implant (CI) performance.

Study Design: Prospective randomized allocation of CI patients to receive either a standard (26.4 mm)-or medium (20.9 mm)-length electrode array. The processing strategy and electrode insertion number were held constant. The postoperative testing audiologist was blinded to the map details and array.

Setting: Tertiary referral center.

Patients: Thirteen adult CI candidates randomized to receive the standard-(n = 7) or medium-length (n = 6) electrode array. Intervention(s): Unilateral CI using standard-or medium length array from the same implant system.

Main Outcome Measures(s): Speech perception was assessed with HINT sentences in quiet and steady-state noise (SNR, +10) and CNC words in quiet at defined intervals. Quality of life was assessed using the Hearing Device Satisfaction Survey and the Abbreviated Profile of Hearing Aid Benefit (APHAB). Music perception was assessed using the Musical Sounds In Cochlear implants (MuSIC) test. Postoperative electrode insertion angle was assessed using reconstructed computed tomographic images.

Results: Interim analysis necessitated discontinuation of subject enrollment by the institutional review board. There was a trend (p = 0.07) for improved speech perception performance among standard array patients. This difference was significant when the standard array group was increased retrospectively. Quality of life and music perception differences were not apparent between groups.

Conclusion: Longer electrode insertions (and greater insertion angles) appear to offer better speech perception performance in the early postactivation period when using the same implant system.