Baumhoff Peter, Rahbar Nikoukar Laya, de Andrade José Santos Cruz, Lenarz Thomas, Kral Andrej
Department of Experimental Otology & Institute of AudioNeuroTechnology (VIANNA), ENT Clinics, Hannover Medical School, Hannover, Germany.
Department of Otorhinolaryngology and Head and Neck Surgery, Federal University of São Paulo (UNIFESP), São Paulo, Brazil.
Ear Hear. 2023;44(1):118-134. doi: 10.1097/AUD.0000000000001259. Epub 2022 Jul 27.
Cochlear implantation criteria include subjects with residual low-frequency hearing. To minimize implantation trauma and to avoid unwanted interactions of electric- and acoustic stimuli, it is often recommended to stop cochlear implantation before the cochlear implant (CI) reaches the cochlear partition with residual hearing, as determined by an audiogram. For this purpose, the implant can be used to record acoustically evoked signals during implantation, including cochlear compound action potentials (CAP), cochlear microphonics (CMs), and summating potentials (SPs). The former two have previously been used to monitor residual hearing in clinical settings.
In the present study we investigated the use of intracochlear, bipolar SP recordings to determine the exact cochlear position of the contacts of implanted CIs in guinea pig cochleae (n = 13). Polarity reversals of SPs were used as a functional marker of intracochlear position. Micro computed tomography (µCT) imaging and a modified Greenwood function were used to determine the cochleotopic positions of the contacts in the cochlea. These anatomical reconstructions were used to validate the SP-based position estimates.
The precision of the SP-based position estimation was on average within ± 0.37 octaves and was not impaired by moderate hearing loss caused by noise exposure after implantation. It is important to note that acute hearing impairment did not reduce the precision of the method. The cochleotopic position of CI accounted for ~70% of the variability of SP polarity reversals. Outliers in the dataset were associated with lateral CI positions. Last, we propose a simplified method to avoid implantation in functioning parts of the cochlea by approaching a predefined frequency region using bipolar SP recordings through a CI.
Bipolar SP recordings provide reliable information on electrode position in the cochlea. The position estimate remains reliable after moderate hearing loss. The technique presented here could be applied during CI surgery to monitor the CI approach to a predefined frequency region.
人工耳蜗植入标准包括有残余低频听力的受试者。为了将植入创伤降至最低并避免电刺激和声刺激的不必要相互作用，通常建议在人工耳蜗（CI）到达由听力图确定的具有残余听力的蜗隔板之前停止人工耳蜗植入。为此，植入物可用于在植入过程中记录声诱发信号，包括耳蜗复合动作电位（CAP）、耳蜗微音电位（CMs）和总和电位（SPs）。前两者此前已用于临床环境中监测残余听力。
在本研究中，我们调查了在豚鼠耳蜗（n = 13）中使用耳蜗内双极SP记录来确定植入的CI电极触点的确切耳蜗位置。SP的极性反转被用作耳蜗内位置的功能标记。使用微型计算机断层扫描（µCT）成像和改良的格林伍德函数来确定耳蜗中电极触点的蜗轴位置。这些解剖重建用于验证基于SP的位置估计。
基于SP的位置估计精度平均在± 0.37倍频程内，并且不受植入后噪声暴露引起的中度听力损失的影响。需要注意的是，急性听力损伤并未降低该方法的精度。CI的蜗轴位置约占SP极性反转变异性的70%。数据集中的异常值与CI的外侧位置相关。最后，我们提出了一种简化方法，通过使用CI的双极SP记录接近预定义的频率区域，避免在耳蜗的功能部分进行植入。
双极SP记录提供了关于耳蜗中电极位置的可靠信息。在中度听力损失后，位置估计仍然可靠。这里介绍的技术可应用于CI手术期间，以监测CI接近预定义频率区域的情况。
