Auditory measures: Results of a retrospective comparative study between perimodiolar and straight electrodes in cochlear implanted children.
MP Tuset (MD), C. Benoit (MD), N. Noel-Petroff (MD), N. Teissier (MD, PhD), T. Van Den Abbeele (MD, PhD).
Service d’ORL et chirurgie cervico-faciale pédiatrique, Hôpital Universitaire Robert Debré, GHU Paris Nord, APHP, DHU I2D2, Université de Paris, France.
Objectives : The design of the electrode array is one of the main factors likely to influence hearing performance in cochlear implanted patients. Perimodiolar electrodes positioned close to the modiolus seem to provide more specific electrical stimulation with lower intensity. This retrospective study of a pediatric population of 64 cochlear implanted children compares the Cochlear perimodiolar CI632/532 and straight CI622/522 electrode arrays.
Methods:
The inclusion criteria were cochlear implantation with a Cochlear® implant with a CI632/532 perimodiolar electrode or a CI622/522 straight electrode, all causes of hearing loss combined. Hearing thresholds in pure tone audiometry, impedances, T-C thresholds as well as NRT (Neural Response Telemetry) immediately post-implantation, at 6 months and at 1 year were analyzed. The angular depth of insertion (aDOI), the electrode array diameters and intracochlear position index (ICPI) were measured for each patient by analyzing postoperative Stenvers digital radiographs and preoperative CT-scan with Stenvers reconstructions.
Résultats:
Sixty-four patients were included and received 82 cochlear implants (42 CI622/CI522, 40 CI532/CI632) between 2016 and 2021. The ICPI values demonstrated a significant wrapping effect of perimodiolar electrodes (0.74± 0.06) as compared with straight ones (0.98 ± 0.07, P<0.0001).However, the measurement of aDOI in the CI632/CI532 group (360+23 ± 44 degrees) was not significantly different from that of the CI622/CI522 group (360+39 ± 56 degrees). However, NRT measurements at 6 months were lower in the perimodiolar group (p<0.05). A significant difference was also found when measuring the impedances between these two groups (p<0.01). The measurements of the average thresholds (500 to 4000 Hz) in tonal audiometry immediately postoperatively (69±15 dB), improved significantly at 6 months (40±13 dB, +27 dB, p<0.0001) in patients implanted with perimodiolar electrodes. This difference was lower for straight electrodes (+17 dB) but also significant. The 6-month analysis did not reveal any significant difference between the two groups. The T-C adjustment thresholds at 0, 6 and 12 months were comparable in the two groups.
Conclusions: Our study found significant differences in objective and subjective auditory measures between children wearing perimodiolar and straight electrodes. Perimodiolar electrodes were constantly measured closer to the modiolus and the depth of insertion were found comparable. Improvement in hearing thresholds seems higher in the perimodiolar group during the first 6 months, suggesting accelerated progression for these children. A long-term comparative effects need to be investigated.

**Auditory measures: Results of a retrospective comparative study between perimodiolar and straight electrodes in cochlear implanted children.**
**MP Tuset (MD), C. Benoit (MD), N. Noel-Petroff (MD), N. Teissier (MD, PhD), T. Van Den Abbeele (MD, PhD).**
**Service d’ORL et chirurgie cervico-faciale pédiatrique, Hôpital Universitaire Robert Debré, GHU Paris Nord, APHP, DHU I2D2, Université de Paris, France.**
**Objectives :** The design of the electrode array is one of the main factors likely to influence hearing performance in cochlear implanted patients. Perimodiolar electrodes positioned close to the modiolus seem to provide more specific electrical stimulation with lower intensity. This retrospective study of a pediatric population of 64 cochlear implanted children compares the Cochlear perimodiolar CI632/532 and straight CI622/522 electrode arrays.
**Methods:**
The inclusion criteria were cochlear implantation with a Cochlear® implant with a CI632/532 perimodiolar electrode or a CI622/522 straight electrode, all causes of hearing loss combined. Hearing thresholds in pure tone audiometry, impedances, T-C thresholds as well as NRT (Neural Response Telemetry) immediately post-implantation, at 6 months and at 1 year were analyzed. The angular depth of insertion (aDOI), the electrode array diameters and intracochlear position index (ICPI) were measured for each patient by analyzing postoperative Stenvers digital radiographs and preoperative CT-scan with Stenvers reconstructions.
**Résultats:**
Sixty-four patients were included and received 82 cochlear implants (42 CI622/CI522, 40 CI532/CI632) between 2016 and 2021. The ICPI values demonstrated a significant wrapping effect of perimodiolar electrodes (0.74± 0.06) as compared with straight ones (0.98 ± 0.07, P<0.0001).However, the measurement of aDOI in the CI632/CI532 group (360+23 ± 44 degrees) was not significantly different from that of the CI622/CI522 group (360+39 ± 56 degrees). However, NRT measurements at 6 months were lower in the perimodiolar group (p<0.05). A significant difference was also found when measuring the impedances between these two groups (p<0.01). The measurements of the average thresholds (500 to 4000 Hz) in tonal audiometry immediately postoperatively (69±15 dB), improved significantly at 6 months (40±13 dB, +27 dB, p<0.0001) in patients implanted with perimodiolar electrodes. This difference was lower for straight electrodes (+17 dB) but also significant. The 6-month analysis did not reveal any significant difference between the two groups. The T-C adjustment thresholds at 0, 6 and 12 months were comparable in the two groups.
**Conclusions:** Our study found significant differences in objective and subjective auditory measures between children wearing perimodiolar and straight electrodes. Perimodiolar electrodes were constantly measured closer to the modiolus and the depth of insertion were found comparable. Improvement in hearing thresholds seems higher in the perimodiolar group during the first 6 months, suggesting accelerated progression for these children. A long-term comparative effects need to be investigated.

Auditory measures: Results of a retrospective comparative study between perimodiolar and straight electrodes in cochlear implanted children.

It is with great pleasure and enthusiasm, that on behalf of the Cochlear Implant centers of the Radboud UMC in Nijmegen and Erasmus MC Sophia Children’s Hospital in Rotterdam to invite you to attend the 16th European Symposium on Pediatric Cochlear Implantation to Rotterdam, the Netherlands in 2023.

Yours sincerely, on behalf of the CI Centers at Radboud UMC and Erasmus MC,