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Cochlear Implantation in Cases of Unilateral Hearing Loss: Initial Localization Abilities

Dillon, Margaret T.1; Buss, Emily1; Anderson, Meredith L.1; King, English R.2; Deres, Ellen J.2; Buchman, Craig A.3; Brown, Kevin D.1; Pillsbury, Harold C.1

doi: 10.1097/AUD.0000000000000430
Research Articles
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Objectives: The present study evaluated early auditory localization abilities of cochlear implant (CI) recipients with normal or near-normal hearing (NH) in the contralateral ear. The goal of the study was to better understand the effect of CI listening experience on localization in this population.

Design: Twenty participants with unilateral hearing loss enrolled in a prospective clinical trial assessing outcomes of cochlear implantation (ClinicalTrials.gov Identifier: NCT02203305). All participants received the MED-EL Standard electrode array, were fit with an ear-level audio processor, and listened with the FS4 coding strategy. Localization was assessed in the sound field using an 11-speaker array with speakers uniformly positioned on a horizontal, semicircular frame. Stimuli were 200-msec speech-shaped noise bursts. The intensity level (52, 62, and 72 dB SPL) and sound source were randomly interleaved across trials. Participants were tested preoperatively, and 1, 3, and 6 months after activation of the audio processor. Performance was evaluated in two conditions at each interval: (1) unaided (NH ear alone [NH-alone] condition), and (2) aided, with either a bone conduction hearing aid (preoperative interval; bone conduction hearing aid + NH condition) or a CI (postoperative intervals; CI + NH condition). Performance was evaluated by comparing root-mean-squared (RMS) error between listening conditions and between measurement intervals.

Results: Mean RMS error for the soft, medium, and loud levels were 66°, 64°, and 69° in the NH-alone condition and 72°, 66°, and 70° in the bone conduction hearing aid + NH condition. Participants experienced a significant improvement in localization in the CI + NH condition at the 1-month interval (38°, 35°, and 38°) as compared with the preoperative NH-alone condition. Localization in the CI + NH condition continued to improve through the 6-month interval. Mean RMS errors were 28°, 25°, and 28° in the CI + NH condition at the 6-month interval.

Conclusions: Adult CI recipients with normal or near-normal hearing in the contralateral ear experienced significant improvement in localization after 1 month of device use, and continued to improve through the 6-month interval. The present results show that binaural acclimatization in CI users with unilateral hearing loss can progress rapidly, with marked improvements in performance observed after only 1 month of listening experience.

1Department of Otolaryngology/Head & Neck Surgery, University of North Carolina at Chapel Hill, Chapel Hill, North Carolina, USA; 2Department of Audiology, UNC Healthcare, Chapel Hill, North Carolina, USA; and 3Department of Otolaryngology/Head & Neck Surgery, Washington University, Saint Louis, Missouri, USA.

Received July 5, 2016; accepted January 30, 2017.

The clinical trial discussed in this manuscript was supported by MED-EL Corporation (ClinicalTrials.gov Identifier: NCT02203305).

E.R.K. is on the MED-EL Audiology Advisory Board; H.C.P. is on the MED-EL Surgical Advisory Board; M.T.D. and M.L.A. are supported by a research grant from MED-EL Corporation.

This study was approved by the study site’s Institutional Review Board, and is part of a US FDA Investigational Device Exemption study.

M.T.D., C.A.B., and H.C.P. contributed to the study design, acquisition of the data, and analysis and interpretation of the data. E.B. contributed to the study design, and analysis and interpretation of the data. M.L.A., E.R.K., E.J.D., and K.D.B. contributed to the acquisition of the data. All authors discussed the results and implications, and commented on the manuscript.

Address for correspondence: Margaret T. Dillon, Department of Otolaryngology/Head & Neck Surgery, University of North Carolina at Chapel Hill, 170 Manning Drive, Physician Office Building G-190, CB#7070, Chapel Hill, NC 27516, USA. E-mail: mdillon@med.unc.edu

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