Apelian Cochlear Implant Center, Long Island Jewish Medical Center, New Hyde Park, New York, USA.
Ear Hear. 2011 Feb;32(1):104-13. doi: 10.1097/AUD.0b013e3181ec5d95.
Since the introduction of neural response telemetry (NRT) for the Nucleus 24 cochlear implant (CI24), researchers and clinicians have investigated the feasibility of using the electrically evoked compound action potential (ECAP) threshold to objectively predict psychophysical measurements that are used in the programming of the speech processor. The ability to substitute objective for behavioral measurements, particularly measurements made at the time of surgery, would greatly facilitate programming the MAP for young children and other individuals who are not able to provide reliable behavioral data required for MAP programming. There have been a number of studies that have examined characteristics of the ECAP measured at the time of surgery and postoperatively; however, all the available published data are based on the CI24. With the introduction of the Nucleus Freedom device, an automated NRT (AutoNRT) program became available, which was capable of measuring ECAP thresholds at lower levels than was previously possible with NRT software associated with the CI24 device. It was hypothesized that the enhancements to the NRT program may improve the predictability of postoperative measurements from intraoperatively recorded ECAP thresholds. The purpose of this study was to track ECAP thresholds obtained using AutoNRT as a function of time and electrode position.
ECAP thresholds were recorded from 71 children and adults implanted with the Nucleus Freedom device using the AutoNRT test protocol. ECAP thresholds were obtained at the time of surgery, at initial stimulation, and 3 mos poststimulation. Five electrodes located at basal, middle, and apical positions in the cochlea were tested at each time interval and thresholds were compared.
Significant differences were found in ECAP thresholds measured with AutoNRT as a function of both time and electrode position. Basal electrodes had higher ECAP thresholds than apical electrodes and that relationship was consistent for each time period. Thresholds for all electrodes decreased between surgery and initial stimulation and remained relatively stable at 3 mos poststimulation. ECAP thresholds were consistently lower for children compared with adults at each time point. Mid-array electrodes (11 and 16) showed the least amount of change over time.
AutoNRT thresholds demonstrated significant change over time, limiting the ability to use intraoperatively recorded ECAP thresholds to predict postoperative measurements. In this study, electrodes 11 and 16 showed the least amount of change in ECAP threshold over time and therefore would be the best choices for estimating postoperative ECAP thresholds. Although not an ideal solution, mid-array ECAP thresholds obtained intraoperatively may prove to be helpful in creating a first MAP when no other behavioral or electrophysiological data are available.
自从神经反应遥测（NRT）被引入 Nucleus 24 人工耳蜗（CI24）以来，研究人员和临床医生一直在研究使用电诱发复合动作电位（ECAP）阈值来客观预测言语处理器编程中使用的心理物理测量值的可行性。能够用客观测量值代替行为测量值，特别是在手术时进行的测量值，这将极大地促进对 MAP 编程，特别是对无法提供 MAP 编程所需的可靠行为数据的儿童和其他个体的编程。已经有许多研究检查了手术时和术后测量的 ECAP 的特征；然而，所有可用的已发表数据都是基于 CI24。随着 Nucleus Freedom 设备的引入，一种自动 NRT（AutoNRT）程序变得可用，该程序能够测量比以前与 CI24 设备相关联的 NRT 软件更低的 ECAP 阈值。假设该 NRT 程序的增强功能可能会提高从手术期间记录的 ECAP 阈值预测术后测量值的可预测性。本研究的目的是跟踪使用 AutoNRT 获得的 ECAP 阈值随时间和电极位置的变化。
使用 AutoNRT 测试方案，对植入 Nucleus Freedom 设备的 71 名儿童和成人进行 ECAP 阈值记录。在手术时、初始刺激时和刺激后 3 个月时获得 ECAP 阈值。在每个时间间隔测试位于耳蜗基底、中间和顶端位置的五个电极，并比较阈值。
AutoNRT 测量的 ECAP 阈值随时间和电极位置的不同而有显著差异。基底电极的 ECAP 阈值高于顶端电极，这种关系在每个时间段都保持一致。所有电极的阈值在手术和初始刺激之间降低，并在刺激后 3 个月时保持相对稳定。在每个时间点，儿童的 ECAP 阈值均低于成人。中数组电极（11 和 16）随时间的变化最小。
AutoNRT 阈值随时间显著变化，限制了使用手术期间记录的 ECAP 阈值来预测术后测量值的能力。在本研究中，电极 11 和 16 在 ECAP 阈值随时间的变化最小，因此是估计术后 ECAP 阈值的最佳选择。虽然不是理想的解决方案，但在没有其他行为或电生理数据可用时，术中获得的中数组 ECAP 阈值可能有助于创建第一个 MAP。
