Patient specific selection of lateral wall cochlear implant electrodes based on anatomical indication ranges

ObjectivesThe aim of this study was to identify anatomical indication ranges for different lateral wall cochlear implant electrodes to support surgeons in the preoperative preparation.Methods272 patients who were implanted with a FLEX20, FLEX24, FLEX28, or a custom-made device (CMD) were included in this study. The cochlear duct length (CDL) and basal cochlear diameter (length A) were measured within preoperative imaging data. The parameter A was then employed to additionally compute CDL estimates using literature approaches. Moreover, the inserted electrode length (IEL) and insertion angle (IA) were measured in postoperative CT data. By combining the preoperative measurements with the IA data, the covered cochlea length (CCL) and relative cochlear coverage (CC) were determined for each cochlea.ResultsThe measurements of the CDL show comparable results to previous studies. While CDL measurements and estimations cover similar ranges overall, severe deviations occur in individual cases. The electrode specific IEL and CCL are fairly consistent and increase with longer electrodes, but relatively wide ranges of electrode specific CC values were found due to the additional dependence on the respective CDL. Using the correlation of IEL and CCL across electrode arrays, CDL ranges for selected arrays were developed (FLEX24: 31.3–34.4, FLEX28: 36.2–40.1, FLEXSoft: 40.6–44.9).ConclusionsOur analysis shows that electrode specific CC varies due to the CDL variation. Preoperative measurement of the CDL allows for an individualized implant length selection yielding optimized stimulation and a reduced risk of intraoperative trauma. The CDL, as derived from preoperative CT imaging studies, can help the implant surgeon select the appropriate electrode array to maximize the patient’s outcomes.研究目标：本研究旨在明确不同侧壁式人工耳蜗电极的解剖学适用范围，以辅助外科医生开展术前准备工作。研究方法：本研究纳入272名分别植入FLEX20、FLEX24、FLEX28或定制式装置（custom-made device，CMD）的患者。在术前影像数据中测量了耳蜗导水管长度（cochlear duct length，CDL）与耳蜗基底直径（长度A）。随后借助已发表文献中的方法，利用参数A额外计算耳蜗导水管长度的预估数值。此外，在术后CT影像数据中测量了电极插入长度（inserted electrode length，IEL）与插入角度（insertion angle，IA）。结合术前测量数据与插入角度数据，可计算出每侧耳蜗的覆盖耳蜗长度（covered cochlea length，CCL）与相对耳蜗覆盖率（relative cochlear coverage，CC）。研究结果：本次耳蜗导水管长度的测量结果与既往同类研究相近。尽管整体上耳蜗导水管长度的测量值与预估值覆盖范围相似，但个别病例中存在显著偏差。不同电极对应的电极插入长度与覆盖耳蜗长度均较为稳定，且随电极长度增加而增大，但由于额外受个体耳蜗导水管长度的影响，不同电极对应的相对耳蜗覆盖率分布范围较广。基于不同电极阵列的电极插入长度与覆盖耳蜗长度的相关性，本研究推导了对应电极阵列的耳蜗导水管长度范围：FLEX24：31.3–34.4，FLEX28：36.2–40.1，FLEXSoft：40.6–44.9。研究结论：本研究分析表明，不同电极对应的相对耳蜗覆盖率会因耳蜗导水管长度的个体差异而有所不同。术前测量耳蜗导水管长度可实现个性化的植入电极长度选择，从而优化刺激效果并降低术中创伤风险。基于术前CT影像获取的耳蜗导水管长度，能够帮助植入外科医生选择合适的电极阵列，以最大化患者的术后获益。