基底及耳蜗外位点电刺激的声学掩蔽

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中文摘要

背景： 具有残余低频听力的耳蜗植入（CI）候选者越来越多地接受保留听力的电极阵列，以实现电-声联合刺激（EAS）。然而，评估新生儿和幼儿的极低频听力仍然困难。既往研究表明，当刺激位点在空间上分离时，声学刺激可以掩蔽电诱发的听觉感知。当电刺激在耳蜗插入前于圆窗（RW）附近传递时，是否也会发生这种掩蔽仍不清楚。本研究在12名植入短电极阵列或部分插入电极阵列、具有残余低频听力的EAS使用者中，研究了同侧声学掩蔽对传递至顶转、基底及近RW位点电刺激的影响。方法：采用心理物理学范式，测量同时声学刺激期间电脉冲串的阈值升高。电刺激施加于耳蜗外RW位置以及耳蜗内基底和顶转电极，同时系统改变刺激参数。结果：在个体化优化参数下，近RW电刺激在12名参与者中的8名中可靠地诱发了听觉感知且无副作用，尽管最佳刺激参数和掩蔽强度在参与者之间存在差异。顶转刺激始终观察到强声学掩蔽，而基底和RW刺激则出现较弱但可测量的掩蔽。耳蜗集总参数模型表明，RW处传递的电流约5%可到达顶转区域，这解释了低频声调所观察到的掩蔽。掩蔽强度仅与顶转刺激的残余听力相关。结论：这些发现表明，顶转电刺激的声学掩蔽与残余听力相关，有潜力作为术后评估低频听力的诊断工具。在RW和基底刺激期间均检测到掩蔽是一个有希望的结果，表明这些刺激范式可以产生可量化的效应。鉴于参与者之间观察到的相当大的变异性，需要进一步研究以确定掩蔽测量在多大程度上反映残余听力或听力损失。尽管如此，这些结果为基底及耳蜗外电刺激相关的听觉感知和副作用提供了新见解，为未来优化该方法以进行低频听力评估提供了信息。

英文摘要

Cochlear implant (CI) candidates with residual low-frequency hearing increasingly receive hearing-preserving electrode arrays to enable electric-acoustic stimulation (EAS). However, assessing very low-frequency hearing in newborns and young children remains difficult. Previous work has shown that acoustic stimulation can mask electrically evoked auditory percepts when stimulation sites are spatially separated. Whether such masking also occurs when electric stimulation is delivered near the round window (RW), prior to cochlear insertion, remains unclear. This study investigated ipsilateral acoustic masking of electric stimulation delivered at apical, basal, and near-RW sites in 12 EAS users with residual low-frequency hearing implanted with short or partially inserted electrode arrays. Using a psychophysical paradigm, threshold elevations of electric pulse trains were measured during simultaneous acoustic stimulation. Electric stimulation was applied at extra-cochlear RW locations and intra-cochlear basal and apical electrodes, while stimulation parameters were systematically varied. With Individually optimized parameters, electric stimulation near the RW reliably evoked auditory percepts without side effects in 8 of 12 participants, though optimal stimulation parameters and masking strength varied across participants. Strong acoustic masking was consistently observed for apical stimulation, whereas weaker but measurable masking occurred for basal and RW stimulation. A cochlear lumped-parameter model indicated that approximately 5% of current delivered at the RW can reach apical regions, explaining the observed masking by low-frequency acoustic tones. Masking strength correlated with residual hearing for apical stimulation only. These findings indicate that acoustic masking of apical electric stimulation, which correlated with residual hearing, holds potential as a diagnostic tool for assessing low-frequency hearing post-operatively. The detection of masking during both RW and basal stimulation represents a promising result, indicating that these stimulation paradigms can produce quantifiable effects. Given the considerable variability observed among participants, further investigation is required to establish the extent to which masking measures reflect residual hearing or hearing loss. Nonetheless, these results provide novel insight into auditory perception and side effects associated with basal and extra-cochlear electric stimulation, informing future efforts to optimize this approach for low-frequency hearing assessment.