Lee Sang-Yeon, Choi Byung Yoon
Department of Otorhinolaryngology-Head and Neck Surgery, Seoul National University Hospital, Seoul, Korea.
Department of Otorhinolaryngology-Head and Neck Surgery, Seoul National University Bundang Hospital, Seongnam, Korea.
Clin Exp Otorhinolaryngol. 2021 Aug;14(3):287-294. doi: 10.21053/ceo.2021.00752. Epub 2021 Jun 8.
Malformations of the inner ear account for approximately 20% of cases of congenital deafness. In current practice, straight arrays with circumferential electrodes (i.e., full-banded electrodes) are widely used in severely malformed cochleae. However, the unpredictability of the location of residual spiral ganglion neurons in such malformations argues against obligatorily using full-banded electrodes in all cases. Here, we present our experience of electrically evoked compound action potential (ECAP) and radiography-based selection of an appropriate electrode for severely malformed cochleae.
Three patients with severely malformed cochleae, showing cochlear hypoplasia type II (CH-II), incomplete partition type I (IP-I), and cochlear aplasia with a dilated vestibule (CADV), respectively, were included, and the cochlear nerve deficiency (CND) was evaluated. A full-banded electrode (CI24RE(ST)) and slim modiolar electrode (CI632) were alternately inserted to compare ECAP responses and electrode position.
In patient 1 (CH-II with CND), who had initially undergone cochlear implantation (CI) using a lateral wall electrode (CI422), revision CI was performed due to incomplete insertion of CI422 and resultant unsatisfactory performance by explanting the CI422 and re-inserting the CI24RE(ST) and CI632 sequentially. Although both electrodes elicited reliable ECAP responses with correct positioning, CI24RE(ST) showed overall lower ECAP thresholds compared to CI632; thus, CI24RE(ST) was selected. In patient 2 (IP-I with CND), CI632 elicited superior ECAP responses relative to CI24RE(ST), with correct positioning of the electrode; CI632 was chosen. In patient 3 (CADV), CI632 did not elicit an ECAP response, while meaningful ECAP responses were obtained with the CI24RE(ST) array once correct positioning was achieved. All patients' auditory performance markedly improved postoperatively.
The ECAP and radiography-based strategy to identify an appropriate electrode may be useful for severely malformed cochleae, leading to enhanced functional outcomes. The practice of sticking to full-banded straight electrodes may not always be optimal for IP-I and CH-II.
内耳畸形约占先天性耳聋病例的20%。在当前的临床实践中，带有环形电极的直列阵列（即全带电极）广泛应用于严重畸形的耳蜗。然而，在这种畸形中，残余螺旋神经节神经元位置的不可预测性表明，并非所有病例都必须使用全带电极。在此，我们介绍我们在严重畸形耳蜗中基于电诱发复合动作电位（ECAP）和影像学选择合适电极的经验。
纳入3例严重畸形耳蜗患者，分别表现为II型耳蜗发育不全（CH-II）、I型不完全分隔（IP-I）和伴有前庭扩张的耳蜗发育不全（CADV），并评估耳蜗神经缺损（CND）情况。交替插入全带电极（CI24RE(ST)）和纤细蜗轴电极（CI632），比较ECAP反应和电极位置。
患者1（CH-II合并CND）最初使用侧壁电极（CI422）进行了人工耳蜗植入（CI），由于CI422插入不完全且性能不佳，通过取出CI422并依次重新插入CI24RE(ST)和CI632进行了翻修CI。尽管两个电极在正确定位时都能引出可靠的ECAP反应，但与CI632相比，CI24RE(ST)的ECAP阈值总体较低；因此，选择了CI24RE(ST)。患者2（IP-I合并CND），在电极正确定位时，CI632相对于CI24RE(ST)引出了更好的ECAP反应；选择了CI632。患者3（CADV），CI632未引出ECAP反应，而一旦实现正确定位，CI24RE(ST)阵列获得了有意义的ECAP反应。所有患者术后听觉性能均显著改善。
基于ECAP和影像学确定合适电极的策略可能对严重畸形的耳蜗有用，可提高功能结果。对于IP-I和CH-II，一味坚持使用全带直电极的做法可能并非总是最佳选择。
