Low-Frequency Hearing Preservation With Long Electrode Arrays: Inclusion of Unaided Hearing Threshold Assessment in the Postoperative Test Battery

Purpose: The goal of this work was to evaluate the low-frequency hearing preservation of long electrode array cochlear implant (CI) recipients. Method: Twenty-five participants presented with an unaided hearing threshold of <= 80 dB HL at 125 Hz pre-operatively in the ear to be implanted. Participants were implanted with a long (31.5-mm) electrode array. The unaided hearing threshold at 125 Hz was compared between the preoperative and postoperative intervals (i.e., initial CI activation, and 1, 3, 6, 9, and 12 months after activation). Results: Eight participants maintained an unaided hearing threshold of <= 80 dB HL at 125 Hz postoperatively. The majority (n = 5) demonstrated aidable low-frequency hearing at initial activation, whereas 3 other participants experienced an improvement in unaided low-frequency hearing thresholds at subsequent intervals. Conclusions: CI recipients can retain residual hearing sensitivity with fully inserted long electrode arrays, and low-frequency hearing thresholds may improve during the postoperative period. Therefore, unaided hearing thresholds obtained within the initial weeks after surgery may not reflect later hearing sensitivity. Routine measurement of postoperative unaided hearing thresholds-even for patients who did not demonstrate aidable hearing thresholds initially after cochlear implantation-will identify CI recipients who may benefit from electric-acoustic stimulation.