Insertion depth impacts speech perception and hearing preservation for lateral wall electrodes

• Published in: The Laryngoscope 2017-10, Vol.127 (10), p.2352-2357
• Main Authors: O'Connell, Brendan P., Hunter, Jacob B., Haynes, David S., Holder, Jourdan T., Dedmon, Matt M., Noble, Jack H., Dawant, Benoit M., Wanna, George B.
• Format: Article
• Language: English
• Subjects: Adult; Aged; Aged, 80 and over; audiologic outcomes; Cochlear implant; Cochlear Implantation - methods; Cochlear Implants; electrode location; Electrodes; Female; Flex 24; Flex 28; Hearing - physiology; Hearing Loss, Unilateral - physiopathology; Hearing Loss, Unilateral - rehabilitation; Hearing Tests; Humans; Male; Middle Aged; Retrospective Studies; Scala Tympani - diagnostic imaging; Scala Tympani - surgery; scalar translocation; Speech; speech perception; Speech Perception - physiology; Tomography, X-Ray Computed; Transplants & implants; Treatment Outcome
• ISSN: 0023-852X; 1531-4995
• DOI: 10.1002/lary.26467

Objectives 1) Examine angular insertion depths (AID) and scalar location of Med‐El (GmbH Innsbruck, Austria) electrodes; and 2) determine the relationship between AID and audiologic outcomes controlling for scalar position. Study Design Retrospective review. Methods Postlingually deafened adults undergoing cochlear implantation with Flex 24, Flex 28, and Standard electrode arrays (Med‐El) were identified. Patients with preoperative and postoperative computed tomography scans were included so that electrode location and AID could be determined. Outcome measures were 1) speech perception in the cochlear implant (CI)‐only condition, and 2) short‐term hearing preservation. Results Forty‐eight implants were included; all electrodes (48 of 48) were positioned entirely within the scala tympani. The median AID was 408° (interquartile [IQ] range 373°–449°) for Flex 24, 575° (IQ range 465°–584°) for Flex 28, and 584° (IQ range 368°–643°) for Standard electrodes (Med‐El). The mean postoperative CNC score was 43.7% ± 21.9. A positive correlation was observed between greater AID and better CNC performance (r = 0.48, P < 0.001). Excluding patients with postoperative residual hearing, a strong correlation between AID and CNC persisted (r = 0.57, P < 0.001). In patients with preoperative residual hearing, mean low‐frequency pure‐tone average (PTA) shift was 27 dB ± 14. A correlation between AID and low‐frequency PTA shift at activation was noted (r = 0.41, P = 0.04). Conclusion Favorable rates of scala tympani insertion (100%) were observed. In the CI‐only condition, a direct correlation between greater AID and CNC score was noted regardless of postoperative hearing status. Deeper insertions were, however, associated with worse short‐term hearing preservation. When patients without postoperative residual hearing were analyzed independently, the relationship between greater insertion depth and better performance was strengthened. Level of Evidence 4. Laryngoscope, 127:2352–2357, 2017