Walia Amit, Shew Matthew A, Lefler Shannon M, Kallogjeri Dorina, Wick Cameron C, Holden Timothy A, Durakovic Nedim, Ortmann Amanda J, Herzog Jacques A, Buchman Craig A
Department of Otolaryngology-Head and Neck Surgery, Washington University School of Medicine in St. Louis, St. Louis, MO, United States.
Front Neurosci. 2022 Jul 22;16:915302. doi: 10.3389/fnins.2022.915302. eCollection 2022.
Electrocochleography (ECochG) recordings during cochlear implantation have shown promise in estimating the impact on residual hearing. The purpose of the study was (1) to determine whether a 250-Hz stimulus is superior to 500-Hz in detecting residual hearing decrement and if so; (2) to evaluate whether crossing the 500-Hz tonotopic, characteristic frequency (CF) place partly explains the problems experienced using 500-Hz.
Multifrequency ECochG comprising an alternating, interleaved acoustic complex of 250- and 500-Hz stimuli was used to elicit cochlear microphonics (CMs) during insertion. The largest ECochG drops (≥30% reduction in CM) were identified. After insertion, ECochG responses were measured using the individual electrodes along the array for both 250- and 500-Hz stimuli. Univariate regression was used to predict whether 250- or 500-Hz CM drops explained low-frequency pure tone average (LFPTA; 125-, 250-, and 500-Hz) shift at 1-month post-activation. Postoperative CT scans were performed to evaluate cochlear size and angular insertion depth.
For perimodiolar insertions ( = 34), there was a stronger linear correlation between the largest ECochG drop using 250-Hz stimulus and LFPTA shift ( = 0.58), compared to 500-Hz ( = 0.31). The 250- and 500-Hz CM insertion tracings showed an amplitude peak at two different locations, with the 500-Hz peak occurring earlier in most cases than the 250-Hz peak, consistent with tonotopicity. When using the entire array for recordings after insertion, a maximum 500-Hz response was observed 2-6 electrodes basal to the most-apical electrode in 20 cases (58.9%). For insertions where the apical insertion angle is >350 degrees and the cochlear diameter is <9.5 mm, the maximum 500-Hz ECochG response may occur at the non-apical most electrode. For lateral wall insertions ( = 14), the maximum 250- and 500-Hz CM response occurred at the most-apical electrode in all but one case.
Using 250-Hz stimulus for ECochG feedback during implantation is more predictive of hearing preservation than 500-Hz. This is due to the electrode passing the 500-Hz CF during insertion which may be misidentified as intracochlear trauma; this is particularly important in subjects with smaller cochlear diameters and deeper insertions. Multifrequency ECochG can be used to differentiate between trauma and advancement of the apical electrode beyond the CF.
人工耳蜗植入术中的电耳蜗图（ECochG）记录在评估对残余听力的影响方面已显示出前景。本研究的目的是：（1）确定在检测残余听力减退方面，250Hz刺激是否优于500Hz刺激；如果是这样；（2）评估跨越500Hz的音频定位、特征频率（CF）位置是否部分解释了使用500Hz时遇到的问题。
在插入过程中，使用包含250Hz和500Hz刺激的交替、交错声学复合体的多频ECochG来诱发耳蜗微音电位（CMs）。确定最大的ECochG下降（CM下降≥30%）。插入后，使用沿阵列的各个电极测量250Hz和500Hz刺激的ECochG反应。使用单变量回归来预测250Hz或500Hz的CM下降是否能解释激活后1个月时低频纯音平均听阈（LFPTA；125Hz、250Hz和500Hz）的变化。术后进行CT扫描以评估耳蜗大小和角向插入深度。
对于蜗轴周围植入（n = 34），与500Hz刺激（r = 0.31）相比，使用250Hz刺激时最大的ECochG下降与LFPTA变化之间的线性相关性更强（r = 0.58）。250Hz和500Hz的CM插入轨迹在两个不同位置显示出一个振幅峰值，在大多数情况下，500Hz的峰值比250Hz的峰值出现得更早，这与音频定位一致。插入后使用整个阵列进行记录时，在20例（58.9%）中，在最顶端电极基底2 - 6个电极处观察到最大500Hz反应。对于顶端插入角度>350度且耳蜗直径<9.5mm的情况，最大500Hz的ECochG反应可能出现在非最顶端电极处。对于侧壁植入（n = 14），除1例以外，所有病例中最大的250Hz和500Hz的CM反应都出现在最顶端电极处。
在植入过程中使用250Hz刺激进行ECochG反馈比500Hz更能预测听力保留情况。这是因为电极在插入过程中经过500Hz的CF，这可能被误识别为耳蜗内创伤；这在耳蜗直径较小和插入较深的受试者中尤为重要。多频ECochG可用于区分创伤和顶端电极超出CF的推进情况。
