Department of Otolaryngology-Head and Neck Surgery, NYU School of Medicine, New York, New York, USA.
Ear Hear. 2021 Mar/Apr;42(2):475-486. doi: 10.1097/AUD.0000000000000949.
There are many potential advantages to combined electric and acoustic stimulation (EAS) with a cochlear implant (CI), including benefits for hearing in noise, localization, frequency selectivity, and music enjoyment. However, performance on these outcome measures is variable, and the residual acoustic hearing may not be beneficial for all patients. As such, we propose a measure of spectral resolution that might be more predictive of the usefulness of the residual hearing than the audiogram alone. In the following experiments, we measured performance on spectral resolution and speech perception tasks in individuals with normal hearing (NH) using low-pass filters to simulate steeply sloping audiograms of typical EAS candidates and compared it with performance on these tasks for individuals with sensorineural hearing loss with similar audiometric configurations. Because listeners with NH had similar levels of audibility and bandwidth to listeners with hearing loss, differences between the groups could be attributed to distortions due to hearing loss.
Listeners with NH (n = 12) and those with hearing loss (n = 23) with steeply sloping audiograms participated in this study. The group with hearing loss consisted of 7 EAS users, 14 hearing aid users, and 3 who did not use amplification in the test ear. Spectral resolution was measured with the spectral-temporal modulated ripple test (SMRT), and speech perception was measured with AzBio sentences in quiet and noise. Listeners with NH listened to stimuli through low-pass filters and at two levels (40 and 60 dBA) to simulate low and high audibility. Listeners with hearing loss listened to SMRT stimuli unaided at their most comfortable listening level and speech stimuli at 60 dBA.
Results suggest that performance with SMRT is significantly worse for listeners with hearing loss than for listeners with NH and is not related to audibility. Performance on the speech perception task declined with decreasing frequency information for both listeners with NH and hearing loss. Significant correlations were observed between speech perception, SMRT scores, and mid-frequency audiometric thresholds for listeners with hearing loss.
NH simulations describe a "best case scenario" for hearing loss where audibility is the only deficit. For listeners with hearing loss, the likely broadening of auditory filters, loss of cochlear nonlinearities, and possible cochlear dead regions may have contributed to distorted spectral resolution and thus deviations from the NH simulations. Measures of spectral resolution may capture an aspect of hearing loss not evident from the audiogram and be a useful tool for assessing the contributions of residual hearing post-cochlear implantation.
联合电声刺激（EAS）和人工耳蜗植入（CI）具有许多潜在的优势，包括改善噪声下的听力、定位、频率选择性和音乐享受。然而，这些结果测量的性能是可变的，并且残余听力可能对所有患者都没有益处。因此，我们提出了一种光谱分辨率的测量方法，它可能比听力图更能预测残余听力的有用性。在以下实验中，我们使用低通滤波器模拟典型 EAS 候选者陡峭的听力图，测量了具有正常听力（NH）的个体在光谱分辨率和语音感知任务上的表现，并将其与具有相似听力配置的感音神经性听力损失个体在这些任务上的表现进行了比较。由于具有 NH 的听众与听力损失的听众具有相似的可听度和带宽水平，因此两组之间的差异可以归因于听力损失引起的失真。
本研究纳入了具有 NH（n=12）和陡峭听力图的听力损失（n=23）的个体。听力损失组包括 7 名 EAS 用户、14 名助听器用户和 3 名在测试耳中不使用放大设备的用户。通过光谱-时间调制纹波测试（SMRT）测量光谱分辨率，在安静和噪声中使用 AzBio 句子测量语音感知。具有 NH 的听众通过低通滤波器并在两个水平（40 和 60 dBA）下收听刺激，以模拟低和高声级。具有听力损失的听众在最舒适的听力水平下不使用辅助设备收听 SMRT 刺激，并在 60 dBA 下收听语音刺激。
结果表明，与具有 NH 的听众相比，听力损失的听众在 SMRT 上的表现明显更差，且与可听度无关。对于具有 NH 和听力损失的听众，随着频率信息的减少，语音感知任务的表现下降。对于听力损失的听众，观察到语音感知、SMRT 评分和中频听力阈值之间存在显著相关性。
NH 模拟描述了听力损失的“最佳情况”，其中可听度是唯一的缺陷。对于听力损失的听众，听觉滤波器的可能变宽、耳蜗非线性的丧失以及可能的耳蜗死区可能导致光谱分辨率失真，从而偏离 NH 模拟。光谱分辨率的测量方法可能会捕捉到听力图中不明显的听力损失方面，并成为评估耳蜗植入后残余听力的有用工具。
