J Am Acad Audiol 2019; 30(03): 235-242
DOI: 10.3766/jaaa.17117
Thieme Medical Publishers 333 Seventh Avenue, New York, NY 10001, USA.

Contralateral Routing of Signal Yields Significant Speech in Noise Benefit for Unilateral Cochlear Implant Recipients

Robert T. Dwyer
*   Department of Hearing and Speech Sciences, Vanderbilt University Medical Center, Nashville, TN
David Kessler
*   Department of Hearing and Speech Sciences, Vanderbilt University Medical Center, Nashville, TN
Iliza M. Butera
†   Vanderbilt Brain Institute, Vanderbilt University, Nashville, TN
René H. Gifford
*   Department of Hearing and Speech Sciences, Vanderbilt University Medical Center, Nashville, TN
‡   Department of Otolaryngology, Vanderbilt University Medical Center, Nashville, TN
› Author Affiliations
Further Information

Publication History

Publication Date:
26 May 2020 (online)



Bilateral cochlear implantation is the standard of care for individuals with moderate sloping-to-profound sensorineural hearing loss who do not receive benefit from appropriately fit hearing aids. Because of financial, insurance, or medical reasons, some unilateral cochlear implant (CI) recipients are unable to obtain a second CI. Here, we evaluated the first clinically available solution for individuals who have been unilaterally implanted and who do not or cannot use technology (e.g., hearing aid or CI) on the non-implanted ear.


We aimed to investigate how the addition of a contralateral routing of signal (CROS) device could provide objective and/or subjective benefit to adult CI recipients with moderate-to-profound hearing loss in the non-implanted ear.

Research Design:

Single-center prospective study using a within-subjects repeated-measures design.

Study Sample:

Participants included ten experienced unilateral CI recipients with severe-to-profound (n = 9) or moderate-to-profound (n = 1) sensorineural hearing loss in the non-implanted ear. At the time of study enrollment, participants did not use any technology on the non-implanted ear. No other exclusion criteria were used.


Individuals were tested with and without a CROS device worn on the non-implanted ear.

Data Collection and Analysis:

We obtained measures of speech understanding in quiet (50 and 65 dBA) and in noise (+5-dB signal-to-noise ratio with a 65-dBA speech signal) both with and without the CROS device in an acute listening condition. Subjective benefit was assessed via the Speech, Spatial and Qualities 12-item questionnaire before CROS fitting and after two weeks of continuous use. A mixed-model, repeated-measures analysis of variance was completed with three talker locations and three presentation levels included as within-subjects factors and the presence or absence of a CROS device as a between-subjects factor.


There was an 11% improvement in speech understanding in noise with the addition of the CROS device when speech was located at 0° azimuth. Subjective benefit in the speech domain of the SSQ was also observed.


Use of CROS provided both subjective and objective speech recognition benefit for unilateral CI recipients who do not have access to bilateral cochlear implantation.

This research was supported by NIDCD DC009404 as well as a grant from Advanced Bionics, LLC (Valencia, CA) which provided CROS devices to the ten study participants.


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