Hearing Preservation Outcomes with Different Cochlear Implant Electrodes: Nucleus® Hybrid™-L24 and Nucleus Freedom™ CI422

Abstract

Objectives: In recent years, it has been possible to preserve hearing after cochlear implantation in patients with significant amounts of low-frequency residual hearing. Due to the dimensions and characteristics of the cochlear implants (CIs) Nucleus® Hybrid™-L24 and Nucleus Freedom™ CI422, both can be used to preserve residual hearing. The aim was to investigate the degree and progression of hearing preservation over a longitudinal postoperative period in a large consecutive cohort of implanted patients with preoperative residual hearing who received either the Nucleus Hybrid-L24 or the Nucleus Freedom CI422 implant. The intention was to examine potential characteristics and triggers of resulting postoperative hearing loss which may support a differentiation of CI candidacy criteria for a certain implant type. Methods: A retrospective data analysis of patient files on consecutively implanted subjects presenting with a severe-to-profound sensorineural hearing loss at frequencies >1,500 Hz and substantial residual hearing at frequencies ≤1,500 Hz, implanted with a Nucleus Hybrid-L24 (n = 97) or a CI422 implant (n = 100), was undertaken. A single-subject repeated-measure design comparing the mean threshold shift for pure-tone thresholds under headphones up to 24 months after implantation was used. Results: Hearing preservation is observed in the majority of subjects with either implant (250-1,500 Hz frequency range). Hybrid-L24 patients exhibited a median hearing loss of 10 dB at initial fitting (n = 97) and of 15 dB after 24 months (n = 51). A 14.4-dB decrease in median hearing loss at initial fitting (n = 100) and a 30-dB decrease after 24 months (n = 28) was observed with the CI422 electrode. At initial fitting, 54.6% of the Hybrid-L24 (n = 97) and 49.0% of the CI422 (n = 100) subjects showed a mean threshold shift <15 dB. After 24 months, 58.8% (Hybrid-L24, n = 51) and 28.6% (CI422, n = 28) of the patients showed a mean threshold shift <15 dB. Conclusions: The results indicate that residual hearing was preserved for the majority of implanted patients with the Hybrid-L24 and the CI422 implant. Patients implanted with the Hybrid-L24 implant demonstrate greater stability and less median hearing loss over time than those with the CI422 implant. Assessments of onset and stability of hearing loss prior to implantation are important factors to consider during candidacy evaluation for electrode selection to potentially maximize the performance outcome for each patient.

Hearing Preservation Outcomes With a Mid-Scala Electrode in Cochlear Implantation

“…After implantation, 78.6%, 57.1%, and 75% of patients had preserved aidable hearing at activation, 6-months, and 12-months, respectively. These rates are comparable with previously published reports with the FLEXsoft and Freedom CI422 (23).…”

“…Similarly, Roland et al (22) reported the results of the U.S. clinical trial for the Hybrid-L; though they did not report mean or median threshold elevation data, they reported that 66.6% of patients retained aidable hearing postoperatively (lowfrequency thresholds 85 dB HL). Comparable to our Recognizing that the mean threshold elevation is between 15 and 20 dB for long electrodes following CI, if patients begin with thresholds around 80 dB HL, we must assume they will not have aidable hearing preserved postoperatively (17)(18)(19)23,24). Thus, we analyzed a subgroup of patients who had preoperative thresholds at 250 Hz at 65 dB HL or better.…”

“…reported outcomes(Table 2), Jurawitz et al(23) retrospectively looked at 53 patients implanted with the CI422 electrode at 6 months and reported median differences of 15, 25, and 20 dB at 250, 500, and 1000 Hz, respectively.…”

Cochlear Implant – State of the Art

“…The outcome clearly depends on the length of the electrode as well as the size of the individual cochlea. Insertion depths of less than 18 mm show significantly better hearing preservation than higher insertion depths [40]. The use of local or systemic steroids may also have a protective effect.…”

Hearing Preservation with the Slim Modiolar Electrode Nucleus CI532® Cochlear Implant: A Preliminary Experience

“…According to Jurawitz et al [2014], the degree of HL at each interval can be divided into the following 3 groups: pure tone average (PTA) shifts < 15 dB, > 15 to 30 dB, and PTA shift > 30 dB. Additionally, in our study, the percentage of subjects with some measurable postoperative hearing was documented.…”