Impact of cochlear tonotopy on electrically evoked compound action potentials (ECAPs)

Abstract

Background: A wide range of cochlear implant electrode designs exists. Lateral wall electrodes may be favored for their potential to preserve residual hearing by virtue of being thin and delicate; whereas perimodiolar electrodes may have advantages in case of profound hearing loss, due to electrode positioning in close proximity to the auditory nerve fibers.

Aim: The aim of this study was to investigate the impact of these two array designs on the interaction between electrodes and the auditory nerve in different tonotopic regions of the cochlea.

Patients and methods: A retrospective study of both adult and pediatric cochlear implant recipients (CI24RE/CI512 or CI422, Cochlear®) was undertaken. The differences of threshold Neural Response Telemetry (tNRT) acquired 12 months after surgery were analyzed with respect to the tonotopic location.

Results: The results of 168 implants showed that perimodiolar arrays had lowest thresholds in the basal region whereas straight arrays had lowest thresholds in the apex. Highest thresholds for both array types were encountered in the medial parts.

Conclusions and Significance: tNRTs differ depending on electrode type and location inside the cochlea. This should be considered pre implantation when choosing the electrode array type and post-implantation when mapping the CI program.

Chinese abstract

背景：耳蜗植入电极设计各种各样。侧壁电极由于薄而精致而具有保留残余听力的潜力, 因此会受到青睐；而颧周电极由于电极位置靠近听神经纤维而对严重听力损失具有优势。

目的：本研究旨在探讨这两种设计对耳蜗不同张力区的电极与听神经相互作用的影响。

患者和方法：对成年和儿童人工耳蜗植入者（CI24RE/CI512或CI422, Cochlear®）进行回顾性研究。分析术后12个月阈值神经反应遥测（tNRT）在眼压定位方面的差异。

结果：168个植入体的结果显示颧周阵列在基底区域具有最低的阈值, 而直阵列在顶部具有最低的阈值。两种阵列类型的最高阈值在中部出现。

结论和意义：tNRTs的不同取决于耳蜗内电极的类型和位置。在植入前选择电极阵列类型时, 以及植入后在制作CI程序图时, 都应该考虑这一点。

Keywords:

• CI
• cochlear implant
• ECAP
• NRT
• electrode
• array
• tonotopy
• perimodiolar
• hearing loss

Disclosure statement

No potential conflict of interest was reported by the authors.