The Relationship Between Insertion Angles, Default Frequency Allocations, and Spiral Ganglion Place Pitch in Cochlear Implants.
The Relationship Between Insertion Angles, Default Frequency Allocations, and Spiral Ganglion Place Pitch in Cochlear Implants.
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DOI：
10.1097/aud.0000000000000163
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发表时间：
2015-09
期刊：
影响因子：
3.7
通讯作者：
Svirsky M
中科院分区：
文献类型：
--
作者：
Landsberger DM;Svrakic M;Roland JT Jr;Svirsky M
市售的耳蜗植入系统试图传递下降到几百Hz的频率信息，但是电极阵列没有被设计成到达对应于这些低频的耳蜗的最顶端区域。这可能导致由耳蜗植入电极阵列呈现的频率与在正常听力耳蜗中的对应位置处表示的频率之间的失配。在以下研究中，针对美国最常用的耳蜗植入系统，检查了在给定耳蜗角度处呈现的频率与声学听力耳朵在相应角度处预期的频率之间的不匹配。根据X射线估计四个不同电极阵列（MED-EL Standard、MED-EL Flex28、Advanced Bionics HiFocus 1 J和Cosmopar Contour Advance）上每个电极的角度插入。对于每个电极阵列上的每个电极的角位置，估计预测的螺旋神经节频率。将预测的螺旋神经节频率与使用制造商的默认频率-电极分配的相应电极提供的中心频率进行比较。对于低于650 Hz的频率，在刺激位置观察到器械之间的差异。较长的电极阵列（即MED-EL标准和Flex28）与其他电极阵列相比，与螺旋神经节图的偏差较小。对于高达约270°的插入角，在给定位置处呈现的频率通常比螺旋神经节频率图预期的频率低约一个倍频程，而对于比270°更深的角度，偏差更大。对于高于650 Hz的频率，频率与角度的关系在所有四种电极型号中是一致的。在所有电极阵列上的每个电极提供的预测频率和默认频率之间观察到不匹配。可以通过改变默认频率分配、将电极更深地插入耳蜗或允许人工耳蜗用户适应失配来减少失配。需要进一步的研究来充分评估频率失配的临床意义。
Commercially available cochlear implant systems attempt to deliver frequency information going down to a few hundred Hz, but the electrode arrays are not designed to reach the most apical regions of the cochlea which correspond to these low frequencies. This may cause a mismatch between the frequencies presented by a cochlear implant electrode array and the frequencies represented at the corresponding location in a normal hearing cochlea. In the following study, the mismatch between the frequency presented at a given cochlear angle and the frequency expected by an acoustic hearing ear at the corresponding angle is examined for the cochlear implant systems that are most commonly used in the United States. The angular insertion of each of the electrodes on four different electrode arrays (MED-EL Standard, MED-EL Flex28, Advanced Bionics HiFocus 1J, and Cochlear Contour Advance) was estimated from x-rays. For the angular location of each electrode on each electrode array, the predicted spiral ganglion frequency was estimated. The predicted spiral ganglion frequency was compared with the center frequency provided by the corresponding electrode using the manufacturer’s default frequency-to-electrode allocation. Differences across devices were observed for the place of stimulation for frequencies below 650 Hz. Longer electrode arrays (i.e. the MED-EL Standard and Flex28) demonstrated smaller deviations from the spiral ganglion map than the other electrode arrays. For insertion angles up to approximately 270°, the frequencies presented at a given location were typically approximately an octave below what would be expected by a spiral ganglion frequency map, while the deviations were larger for angles deeper than 270°. For frequencies above 650 Hz, the frequency to angle relationship was consistent across all four electrode models. A mismatch was observed between the predicted frequency and default frequency provided by every electrode on all electrode arrays. The mismatch can be reduced by changing the default frequency allocations, inserting electrodes deeper into the cochlea, or allowing cochlear implant users to adapt to the mismatch. Further studies are required to fully assess the clinical significance of the frequency mismatch.