Nehmé Antoine, El Zir Elie, Moukarzel Nabil, Haidar Hassan, Vanpoucke Filiep, Arnold Laure
Cochlear Implants Int. 2014 Jan;15(1):53-60. doi: 10.1179/1754762813Y.0000000039. Epub 2014 Jan 6.
To investigate electrically evoked compound action potentials (eCAPs) measured with the neural response imaging (NRI) 'SmartNRI' algorithm. NRI thresholds and slopes were examined according to three aspects: (1) site along the cochlea, (2) development of responses over time, and (3) influence of age/duration of deafness.
Thirty-four individuals implanted with the Advanced Bionics HiRes 90K(TM) device were included. The eCAP recordings were made from four electrodes along the array at first fitting and at frequent intervals up to at least 2 years. Slope and threshold (tNRI) of the amplitude growth function were measured and a range of explanatory variables were tested for significant effects on these measures using multi-factorial analysis of variance.
Electrode position emerged as a significant effect for the tNRI measure, with lowest thresholds at the apical end of the array. Mean slope was greatest for the most apical electrode, but not significantly. Slope was significantly influenced by onset of deafness, with congenital hearing loss associated with steeper slopes than acquired hearing loss. There was also a highly significant effect of duration of device use, with a gradual increase in slope over the 2 years following device activation.
The observed effects of electrode position are consistent with a model in which eCAP threshold is governed primarily by an effect of distance between electrode and neural interface (which is shorter towards the apex of the cochlea) and in which slope is governed primarily by density of surviving neural elements.
研究采用神经反应成像（NRI）“智能NRI”算法测量的电诱发复合动作电位（eCAP）。根据三个方面检查NRI阈值和斜率：（1）沿耳蜗的部位；（2）反应随时间的发展；（3）年龄/耳聋持续时间的影响。
纳入34名植入Advanced Bionics HiRes 90K（TM）设备的个体。在初次调试时以及之后至少2年的频繁间隔时间，从阵列上的四个电极记录eCAP。测量幅度增长函数的斜率和阈值（tNRI），并使用多因素方差分析测试一系列解释变量对这些测量值的显著影响。
电极位置对tNRI测量有显著影响，阵列顶端的阈值最低。最顶端电极的平均斜率最大，但不显著。斜率受耳聋起始的显著影响，先天性听力损失比后天性听力损失的斜率更陡。设备使用时长也有高度显著影响，在设备激活后的2年中斜率逐渐增加。
观察到的电极位置效应与一个模型一致，在该模型中，eCAP阈值主要由电极与神经界面之间的距离效应决定（朝向耳蜗顶端距离较短），而斜率主要由存活神经元的密度决定。
