Stronks H Christiaan, Briaire Jeroen J, Frijns Johan H M
Department of Otorhinolaryngology, Leiden University Medical Center, Leiden, The Netherlands.
Leiden Institute for Brain and Cognition, Leiden University, Leiden, The Netherlands.
Audiol Neurootol. 2022;27(1):75-82. doi: 10.1159/000515210. Epub 2021 Apr 13.
Contralateral routing of signals (CROS) can be used to eliminate the head shadow effect. In unilateral cochlear implant (CI) users, CROS can be achieved with placement of a microphone on the contralateral ear, with the signal streamed to the CI ear. CROS was originally developed for unilateral CI users without any residual hearing in the nonimplanted ear. However, the criteria for implantation are becoming progressively looser, and the nonimplanted ear can have substantial residual hearing. In this study, we assessed how residual hearing in the contralateral ear influences CROS effectiveness in unilateral CI users.
In a group of unilateral CI users (N = 17) with varying amounts of residual hearing, we deployed free-field speech tests to determine the effects of CROS on the speech reception threshold (SRT) in amplitude-modulated noise. We compared 2 spatial configurations: (1) speech presented to the CROS ear and noise to the CI ear (SCROSNCI) and (2) the reverse (SCINCROS).
Compared with the use of CI only, CROS improved the SRT by 6.4 dB on average in the SCROSNCI configuration. In the SCINCROS configuration, however, CROS deteriorated the SRT by 8.4 dB. The benefit and disadvantage of CROS both decreased significantly with the amount of residual hearing.
CROS users need careful instructions about the potential disadvantage when listening in conditions where the CROS ear mainly receives noise, especially if they have residual hearing in the contralateral ear. The CROS device should be turned off when it is on the noise side (SCINCROS). CI users with residual hearing in the CROS ear also should understand that contralateral amplification (i.e., a bimodal hearing solution) will yield better results than a CROS device. Unilateral CI users with no functional contralateral hearing should be considered the primary target population for a CROS device.
信号对侧路由（CROS）可用于消除头部阴影效应。在单侧人工耳蜗（CI）使用者中，可通过在对侧耳放置麦克风并将信号传输至CI耳来实现CROS。CROS最初是为非植入耳无残余听力的单侧CI使用者开发的。然而，植入标准越来越宽松，非植入耳可能有大量残余听力。在本研究中，我们评估了对侧耳的残余听力如何影响单侧CI使用者的CROS效果。
在一组残余听力程度不同的单侧CI使用者（N = 17）中，我们采用自由声场言语测试来确定CROS对调幅噪声中言语接受阈（SRT）的影响。我们比较了两种空间配置：（1）言语呈现给CROS耳，噪声呈现给CI耳（SCROSNCI）和（2）相反情况（SCINCROS）。
与仅使用CI相比，在SCROSNCI配置中，CROS平均使SRT提高了6.4 dB。然而，在SCINCROS配置中，CROS使SRT恶化了8.4 dB。CROS的益处和弊端均随残余听力量的增加而显著降低。
CROS使用者在CROS耳主要接收噪声的聆听条件下，需要仔细了解潜在的弊端，特别是如果他们对侧耳有残余听力。当CROS设备位于噪声侧（SCINCROS）时应关闭。CROS耳有残余听力的CI使用者也应明白，对侧放大（即双耳聆听解决方案）将比CROS设备产生更好的效果。非植入耳无功能性听力的单侧CI使用者应被视为CROS设备的主要目标人群。
