Department of Otorhinolaryngology, Hanover Medical School, Hannover, Germany.
Cluster of Excellence 'Hearing4all,' Hanover, Germany.
Ear Hear. 2020 Jul/Aug;41(4):868-882. doi: 10.1097/AUD.0000000000000807.
The aim of this study was to determine electric-acoustic masking in cochlear implant users with ipsilateral residual hearing and different electrode insertion depths and to investigate the influence on speech reception. The effects of different fitting strategies-meet, overlap, and a newly developed masking adjusted fitting (UNMASKfit)-on speech reception are compared. If electric-acoustic masking has a detrimental effect on speech reception, the individualized UNMASKfit map might be able to reduce masking and thereby enhance speech reception.
Fifteen experienced MED-EL Flex electrode recipients with ipsilateral residual hearing participated in a crosssover design study using three fitting strategies for 4 weeks each. The following strategies were compared: (1) a meet fitting, dividing the frequency range between electric and acoustic stimulation, (2) an overlap fitting, delivering part of the frequency range both acoustically and electrically, and (3) the UNMASKfit, reducing the electric stimulation according to the individual electric-on-acoustic masking strength. A psychoacoustic masking procedure was used to measure the changes in acoustic thresholds due to the presence of electric maskers. Speech reception was measured in noise with the Oldenburg Matrix Sentence test.
Behavioral thresholds of acoustic probe tones were significantly elevated in the presence of electric maskers. A maximum of masking was observed when the difference in location between the electric and acoustic stimulation was around one octave in place frequency. Speech reception scores and strength of masking showed a dependency on residual hearing, and speech reception was significantly reduced in the overlap fitting strategy. Electric- acoustic stimulation significantly improved speech reception over electric stimulation alone, with a tendency toward a larger benefit with the UNMASKfit map. In addition, masking was significantly inversely correlated to the speech reception performance difference between the overlap and the meet fitting.
(1) This study confirmed the interaction between ipsilateral electric and acoustic stimulation in a psychoacoustic masking experiment. (2) The overlap fitting yielded poorer speech reception performance in stationary noise especially in subjects with strong masking. (3) The newly developed UNMASKfit strategy yielded similar speech reception thresholds with an enhanced acoustic benefit, while at the same time reducing the electric stimulation. This could be beneficial in the long-term if applied as a standard fitting, as hair cells are exposed to less possibly adverse electric stimulation. In this study, the UNMASKfit allowed the participants a better use of their natural hearing even after 1 month of adaptation. It might be feasible to transfer these results to the clinic, by fitting patients with the UNMASKfit upon their first fitting appointment, so that longer adaptation times can further improve speech reception.
本研究旨在确定具有同侧残余听力的人工耳蜗植入患者的电声掩蔽情况，并探讨其对言语感知的影响。比较不同的拟合策略（相遇、重叠和新开发的掩蔽调整拟合（UNMASKfit））对言语感知的影响。如果电声掩蔽对言语感知有不利影响，那么个体化的 UNMASKfit 图可能能够减少掩蔽，从而提高言语感知。
15 名经验丰富的 MED-EL Flex 电极接受者参与了一项交叉设计研究，使用三种拟合策略，每种策略持续 4 周。比较了以下策略：（1）相遇拟合，将电刺激和声刺激的频率范围分开；（2）重叠拟合，以声电的方式传递部分频率范围；（3）UNMASKfit，根据个体的电声掩蔽强度减少电刺激。使用心理声学掩蔽程序测量由于存在电掩蔽而导致的声学探测音阈值的变化。使用奥登堡矩阵句子测试测量噪声中的言语感知。
当电刺激和声刺激的位置频率相差约一个倍频程时，电掩蔽达到最大值。存在电掩蔽时，声学探针音的行为阈值显著升高。重叠拟合策略下，言语感知得分和掩蔽强度与残余听力有关，言语感知显著降低。电声刺激显著提高了言语感知，而 UNMASKfit 图的效果更大。此外，掩蔽与重叠拟合和相遇拟合之间的言语感知性能差异呈显著负相关。
（1）本研究在心理声学掩蔽实验中证实了同侧电声刺激的相互作用。（2）重叠拟合在固定噪声中导致言语感知性能下降，尤其是在掩蔽较强的受试者中。（3）新开发的 UNMASKfit 策略产生了相似的言语感知阈值，并增强了声刺激的益处，同时减少了电刺激。如果将其作为标准拟合应用，可能会有益于长期应用，因为毛细胞受到的潜在不利电刺激会减少。在这项研究中，UNMASKfit 允许参与者在适应 1 个月后更好地利用他们的自然听力。可以将这些结果转化为临床实践，在患者首次就诊时就使用 UNMASKfit 进行拟合，以便更长的适应时间可以进一步提高言语感知。
