Auditory-Nerve Responses to Varied Inter-Phase Gap and Phase Duration of the Electric Pulse Stimulus as Predictors for Neuronal Degeneration
Auditory-Nerve Responses to Varied Inter-Phase Gap and Phase Duration of the Electric Pulse Stimulus as Predictors for Neuronal Degeneration
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DOI：
10.1007/s10162-013-0440-x
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发表时间：
2014-04-01
影响因子：
2.4
通讯作者：
Grolman, Wilko
中科院分区：
文献类型：
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作者：
Ramekers, Dyan;Versnel, Huib;Grolman, Wilko
在严重的毛细胞损失后，螺旋神经节细胞（SGCs）的继发性变性被阻止-这是一个渐进的过程，在人类中持续数年，但在豚鼠中只需数周。作为人工耳蜗植入的靶点，耳蜗基底节细胞的生理状态对人工耳蜗植入的有效性至关重要。对于神经状态的评估，焦点通常是其反应阈值。我们的目标是添加对SGC功能的更详细描述。为此，电诱发复合动作电位（eCAP）记录在正常听力的豚鼠和豚鼠，实验前2或6周的听力。我们评估了当双相电流脉冲的相持续时间（PD）和相间间隙（IPG）变化时eCAP特征的变化。我们将这些变化的幅度与神经变性的定量组织学测量（SGC堆积密度和SGC大小）相关联。最大eCAP振幅，来自输入-输出函数，在耳聋后降低，并且随着PD和IPG的增加而增加。聋后eCAP阈值无明显变化，随着PD和IPG的增加而降低。动态范围更广泛的6周聋动物比其他两组。IPG的兴奋性增加（输入-输出函数的斜率更陡，在半最大eCAP振幅下的刺激水平更低），但在较低程度上，与听力正常的对照组相比，听力正常的动物。6周聋动物的潜伏期短于其他两组。对于这些eCAP特征中的几个，IPG的效应量与变性的组织学测量结果具有良好的相关性，而PD的效应量则没有相关性。这些相关性取决于高电流水平的使用，这可能限制临床应用。然而，这些相关性对评估听神经状况的潜力可能对人工耳蜗植入者的临床诊断和预后非常有益。
After severe hair cell loss, secondary degeneration of spiral ganglion cells (SGCs) is observed-a gradual process that spans years in humans but only takes weeks in guinea pigs. Being the target for cochlear implants (CIs), the physiological state of the SGCs is important for the effectiveness of a CI. For assessment of the nerve's state, focus has generally been on its response threshold. Our goal was to add a more detailed characterization of SGC functionality. To this end, the electrically evoked compound action potential (eCAP) was recorded in normal-hearing guinea pigs and guinea pigs that were deafened 2 or 6 weeks prior to the experiments. We evaluated changes in eCAP characteristics when the phase duration (PD) and inter-phase gap (IPG) of a biphasic current pulse were varied. We correlated the magnitude of these changes to quantified histological measures of neurodegeneration (SGC packing density and SGC size). The maximum eCAP amplitude, derived from the input-output function, decreased after deafening, and increased with both PD and IPG. The eCAP threshold did not change after deafening, and decreased with increasing PD and IPG. The dynamic range was wider for the 6-weeks-deaf animals than for the other two groups. Excitability increased with IPG (steeper slope of the input-output function and lower stimulation level at the half-maximum eCAP amplitude), but to a lesser extent for the deafened animals than for normal-hearing controls. The latency was shorter for the 6-weeks-deaf animals than for the other two groups. For several of these eCAP characteristics, the effect size of IPG correlated well with histological measures of degeneration, whereas effect size of PD did not. These correlations depend on the use of high current levels, which could limit clinical application. Nevertheless, their potential of these correlations towards assessment of the condition of the auditory nerve may be of great benefit to clinical diagnostics and prognosis in cochlear implant recipients.